general-biology-1-discussion-and-practice-materials.pdf

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General Biology 1 - discussion and practice materials
Biological Sciences (Don Mariano Marcos Memorial State University)
Studocu is not sponsored or endorsed by any college or university
General Biology 1 - discussion and practice materials
Biological Sciences (Don Mariano Marcos Memorial State University)
Downloaded by KENNEDY VAGAY (kennedy.vagay@deped.gov.ph)
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1 | g r a c e a n c h e t a h o l t @ g m a i l . c o m
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INTRODUCTION
Cells are the basic building blocks of all living things. They are the structural, functional,
and biological units of all living beings. A cell can replicate itself
independently. Hence, they are known as the building blocks of life. The
human body is composed of trillions of cells. They provide structure for the
body, take in nutrients from food, convert those nutrients into energy, and
carry out specialized functions. These cell organelles perform specialized
functions to carry out life processes. Cells also contain the body’s hereditary
material and can make copies of themselves. Each cell contains a fluid
called the cytoplasm, which is enclosed by a membrane. Also present in the cytoplasm are several
biomolecules like proteins, nucleic acids and lipids. Moreover, cellular structures called cell
organelles are suspended in the cytoplasm.
So to appreciate life as we know it, let’s go very microscopic today. It is a different world
visible to us and a world that we did not even know existed before the 17th century. It opened a can
of wonder and helped us understand what we all are made up of even to the smallest of details.
This module is divided into six important lessons about cells which are going to be tackled
in seven weeks. Formative assessments, textbook and online resources are incorporated in the
module and are found every after a topic or lesson. For queries, you may email me or give me a
ring.
So now let’s do one thing, let us dive into this amazing microscopic wonder! Let’s see what
makes it so special and understand the structures and the functions of different cells.
LEARNING OBJECTIVES
At the end of this learning module, you are expected to:
 Explain the postulates of the cell theory
 Describe the structure and function of major and subcellular organelles
 Describe some cell modifications that lead to adaptation to carry out specialized functions (e.g.,
microvilli, root hair)
 Explain transport mechanisms in cells (diffusion osmosis, facilitated transport, active
transport)
 Characterize the phases of the cell cycle and their control points
 Describe the stages of mitosis/meiosis given 2n=6
 Explain the significance or applications of mitosis/meiosis
 Identify disorders and diseases that result from the malfunction of the cell during the cell cycle
 Explain coupled reaction processes and describe the role of ATP in energy coupling and
transfer
 Explain the importance of chlorophyll and other pigments
 Describe the patterns of electron flow through light reaction events
 Describe the significant events of the Calvin cycle
 Differentiate aerobic from anaerobic respiration
 Explain the major features and sequence the chemical events of cellular respiration
 Distinguish major features of glycolysis, Krebs cycle, electron transport system, and
chemiosmosis
 Describe reactions that produce and consume ATP
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 Describe the role of oxygen in respiration and describe pathways of electron flow in the
absence of oxygen
 Explain the advantages and disadvantages of fermentation and aerobic respiration
INSTRUCTIONAL MATERIALS AND RESOURCES
General Biology 1 textbook, Internet (interactive presentations, off-site activities, images)
ESTIMATED TIME: 5 weeks
CONCEPTS IN A BUBBLE
The following will be the focus of our first learning module. Study the parts of the cell
because these will be the emphasis of our lessons in terms of the cellular processes and activities.
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DISCUSSION
A. ATTENTION-GETTER
Lesson 1: The Cell Theory
The discovery of cells was made possible by the development of the microscope in the 17th
century. In 1665, the English scientist Robert Hooke used a microscope to examine a thin slice of
cork. Hooke described it as consisting of “a great many little boxes.” These “little boxes” reminded
him of the cubicles or “cells” in which monks lived, so he called them cells. What Hooke had
observed were actually the remains of dead plant cells.
The first person to observe living cells was a Dutch trader, Anton van Leeuwenhoek. Although van
Leeuwenhoek’s microscope was rather simple, in 1673 it was powerful enough to enable him to
view the world of microscopic organisms
which had never before been seen.
About 150 years passed before
scientists began to organize the
observations begun by Hooke and van
Leeuwenhoek into a unified theory known
as the cell theory.
Matthias Schleiden and Theodor
Schwann proposed spontaneous generation
as the method for cell origination, but
spontaneous generation (also called
abiogenesis) was later disproven. Rudolf
Virchow famously stated “Omnis cellula e
cellula”. “All cells only arise from pre-
existing cells.”
The expanded version of the cell theory can also include:
 Cells carry genetic material passed to daughter cells during cellular division
 All cells are essentially the same in chemical composition
 Energy flow (metabolism and biochemistry) occurs within cells
Lesson 2: Cell Structure and Functions
The Cell Factory
Didn’t you know that our cell works like a factory? Cells comprise several cell organelles
that perform specialized functions to carry out life processes. Every organelle has a specific
structure. Discovery of cells is one of the remarkable advancements in the field of science. It helped
us know that all the organisms are made up of cells, and these cells help in carrying out various life
processes. The structure and functions of cells helped us to understand life in a better way.
Characteristics of Cells
Cells provide structure and support to the body of an organism.
The cell interior is organised into different individual organelles
surrounded by a separate membrane.
The nucleus holds genetic information necessary for reproduction and
cell growth.
Every cell has one nucleus and membrane-bound organelles in the
Rudolf Virchow
-Matthias Schleiden
& TheodorSchwann
Robert Hooke
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cytoplasm.
Mitochondria, a double membrane-bound organelle is mainly responsible for the energy
transactions vital for the survival of the cell.
Lysosomes digest unwanted materials in the cell.
Endoplasmic reticulum plays a significant role in the internal organisation of the cell by
synthesizing selective molecules and processing, directing and sorting them to their
appropriate locations.
(https://byjus.com/biology/cells/)
Study the diagram below. This compares the organelles present in plants and animals. I
want you to take note of the common organelles and the ones which are exclusive to each cell type.
https://www.pngkit.com/view/u2w7q8u2r5r5w7q8_this-illustration-shows-a-typical-eukaryotic-animal-
microfilaments/
Anatomically, cells vary with respect to their classification, therefore, prokaryotic cells and
eukaryotic cells differ from each other quite drastically. Since the cell can be likened to a factory, it
has a network of organelles that play an important role in relation to the protein production and
delivery. The Endomembrane system is a membranous component of the eukaryotic cell.
https://www.google.com.ph/search?q=endomembrane+system
***You may also read your General Biology 1 textbook for additional information on this lesson.
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Lesson 3: Specialized Structures and Cellular Modifications
https://www.infoplease.com/specialized-cell-structure-and-function-modifications-and-adaptive-functions
Advancements in structure and function created complex life-supporting systems that are
more versatile and allow the organisms’ greater freedom for colonization and survival.
Photosynthesis, respiration, and protein synthesis are typical examples of complex chemical
phenomena that occur around and within us constantly.
Apical Modifications
 Specialized structures found on the surface of the cell
(https://www.slideshare.net/magaoaykevin/lesson-4-cell-modifications)
Exercise: A group of scientists from the Berlin Institute of Health discovered that certain
progenitor cells in the bronchi are mainly responsible for producing the coronavirus receptors.
These progenitor cells normally develop into respiratory tract cells lined with hair-like projections
called cilia that sweep mucus and bacteria out of the lungs. How will knowledge of the target cells
of coronavirus help us in combating SARS-CoV-2?
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
_______________________________________________________________
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Basal Modifications
 Specialized structures found on the basal surface (basement) of the cell
Lateral Modifications
 Specialized structures which join adjacent cells within the epithelium
Lesson 4: Substance Transport
Objective: explain how cells make use of different mechanisms for substance transport in
communicating with neighboring cells and sustaining their life activities
The Cell Membrane
The cell membrane is the outermost layer of the cell that surrounds all the components of a
cell, including different organelles. The cell membrane acts as a boundary separating the cellular
contents with the outside environment. It consists of a phospholipid bilayer with integral proteins
that provides a pathway for the movement of molecules across the membrane. The membrane
allows only a certain molecules to pass through it because of the hydrophobic lipids present. It is
found in both plant cell and animal cells. However, the plant cells have a cell wall that surrounds
the cell membrane.
Cell Membrane vs Plasma Membrane
Are these two organelles the same or different? Plasma membrane and cell membrane are
often confused to be similar terms. However, they are quite different from each other. Read on to
know what distinguishes the two.
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Cell Membrane Plasma Membrane
It surrounds the entire components of the cell. It surrounds only the cell organelles.
It regulates the tonicity of the cell. It does not regulate the tonicity of the cell.
Cell membrane can be transformed to stimulate
movement and feeding in organisms such as
Paramecium.
Plasma membrane cannot be modified.
It contains initial receptors for signal transduction and is
the first step in cell signalling.
It is not the first step in cell signalling.
However, it is involved in the process.
Always protects the cell from bacteria and viruses. Does not always protect the cell from outside
invaders.
Plays an important role in cytokinesis during cell
division.
Do not play a key role in cytokinesis during
cell division.
Cilia are present and are involved in feeding and
movement.
Cilia are absent.
byjus.com
The Structure of the Cell Membrane: Fluid Mosaic Model
The cell membrane is a semi-permeable membrane composed of lipids and proteins. The
selective permeability is a special feature that provides systematic movement of macro and micro
molecules. Below is an example of the fluid mosaic model of the cell membrane.
The main functions of the cell membrane include:
 protecting the integrity of the interior cell.
 providing support and maintaining the shape of the cell.
 helping in regulating cell growth through endocytosis and exocytosis.
 cell signalling and communication.
 allowing the entry of only selected substances into the cell.
How do substances get into and out of the cell?
Cells make use of several transport mechanisms in order to move substances into and out
of the cell. The main difference lies in the presence or absence of ATP, the energy currency of the
cell, in the movement of substances. Active and passive transport are the two main biological
processes that play a crucial role in supplying nutrients, oxygen, water, and other essential
molecules to the cells along with the elimination of waste products. Both active and passive
transport works for the same cause, but with different movement.
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PASSIVE TRANSPORT
♥ NO ATP required
♥ a physical process
♥ moves along the concentration gradient- from higher to lower
concentration
♥ transports all the soluble molecules which include oxygen, water,
carbon dioxide, lipids, sex hormones, monosaccharides, etc.
♥ maintains equilibrium inside the cell
♥ partly non-selective and is a slow process
♥ NOT influenced by temperature, level of oxygen, and metabolic
inhibitors
♥ Types of Passive Transport (Pearson Education, Inc.)
SIMPLE
DIFFUSION
*the net flow of
solutes down a
concentration
gradient until
equilibrium is
reached
*rate of diffusion
is influenced by:
-temperature
-size of solute
-surface area of
the
membrane
-distance across
which the
solute
must travel
FACILITATED
DIFFUSION
with Carrier Protein
*the net flow of solutes
down a concentration
gradient or an
electrochemical
gradient until
equilibrium is reached
*carrier protein binds
to a molecule (higher
concentration) and
transports it across
membrane through a
conformational (shape)
change; molecule is
then released on the
other side (lower
concentration)
FACILITATED
DIFFUSION
with Channel Protein
*the net flow of solutes
down a concentration
gradient or an
electrochemical
gradient until
equilibrium is reached
*channel proteins
provide corridors and
pathways that allow a
specific molecule or ion
to cross the membrane
*open or closes in
response to a change in
membrane potential
OSMOSIS
Aquaporin
*the tendency of
water to pass through
a semi-permeable
membrane into a
solution where the
solvent concentration
is lower and the
solute concentration
is higher
*movement of water
is affected by the
amount of substances
dissolved in water
*the mammalian
kidney is a good
example of how
osmosis works
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Cell Tonicity
The ability of an extracellular solution to make water move into or out of a cell by osmosis
is known as its tonicity. A solution's tonicity is related to its osmolarity, which is the total
concentration of all solutes in the solution. A solution with low osmolarity has fewer solute
particles per liter of solution, while a solution with high osmolarity has more solute particles per
liter of solution. When solutions of different osmolarities are separated by a membrane permeable
to water, but not to solute, water will move from the side with lower osmolarity to the side with
higher osmolarity (study the image below).
Image credit: OpenStax Biology
In considering a cell’s tonicity, we take note only of the solutes that cannot cross the membrane.
 If the extracellular fluid has lower osmolarity than the fluid inside the cell, it’s said to be
hypotonic—hypo means less than—to the cell, and the net flow of water will be into the cell.
 In the reverse case, if the extracellular fluid has a higher osmolarity than the cell’s
cytoplasm, it’s said to be hypertonic—hyper means greater than—to the cell, and water will
move out of the cell to the region of higher solute concentration.
 In an isotonic solution—iso means the same—the extracellular fluid has the same
osmolarity as the cell, and there will be no net movement of water into or out of the cell.
Tonicity in Living Systems
 Animal Cells
o CRENATION: If placed in a hypertonic solution, water will leave the cell, and the
cell will shrink.
o CYTOLYSIS: When a cell is placed in a hypotonic environment, water will enter the
cell, and the cell will swell or burst.
o In an isotonic environment, the relative concentrations of solute and water are
equal on both sides of the membrane. There is no net water movement, so there is
no change in the size of the cell.
Observe what
happened to the red
blood cells…
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 Plant Cells
o PLASMOLYSIS: When water leaves the plant cells, this results in a loss of turgor
pressure, which you have likely seen as wilting. Under hypertonic conditions, the
cell membrane may actually detach from the wall and constrict the cytoplasm.
o TURGIDITY: Water will enter a cell until its internal pressure—turgor pressure—
prevents further influx. The plasma membrane can only expand to the limit of the
rigid cell wall, so the cell won't burst, or lyse.
Image credit: OpenStax Biology, modification of work by Mariana Ruiz Villareal
For a more detailed discussion, you may check your General Biology 1 textbook and/or visit the
Khan Academy/ Byjus.com website.
ACTIVE TRANSPORT
♥ requires ATP
♥ circulates AGAINST the concentration gradient- from an area of lower concentration to a
region of higher concentration
♥ transports molecules such as proteins, large cells, complex sugars, ions, etc.
♥ it is a dynamic and highly selective process
♥ influenced by temperature, level of oxygen, and metabolic inhibitors
Types of Active Transport
I. Primary Active Transport
 directly dependent on ATP
 moves ions across a membrane and creates a difference in charge across that membrane
 Sodium-Potassium Pump
o maintains the electrochemical gradient of living cells by moving sodium in and
potassium out of the cell
o check on the steps to understand better
Don’t let your plants
dry up huh…
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 Carrier-Mediated Transport
o membrane adaption for active transport
o three types:
II. Secondary Transport
 dependent on primary transport
 a molecule is moved down its electrochemical gradient as another is moved up its
concentration gradient
 CO-TRANSPORT: ATP is not directly coupled to the molecule of interest. Instead, another
molecule is moved up its concentration gradient, which generates an electrochemical
gradient.
carries one specific ion
or molecule
carries two different ions
or molecules, both in the
same direction
carries two different ions
or molecules, but in
different directions
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III. Vesicular Transport
 Bulk transport using vesicles and vacuoles that fuse with the cell membrane may be utilized
to release or transport chemicals out of the cell or to allow them to enter a cell
 ENDOCYTOSIS
o takes up particles into the cell by invaginating the cell membrane, resulting in the
release of the material inside of the cell
o it can be:
 Phagocytosis: cell-eating, taking in food/large particles
 Pinocytosis: cell-drinking, taking in extracellular fluid
 Potocytosis: uses a coating protein, called caveolin, on the cytoplasmic side
of the plasma membrane to bring in smaller molecules during transcytosis
 Receptor-mediated: material to be transported binds to certain specific
molecules in the membrane
https://www.google.com.ph/search?q=endocytosis+example
 EXOCYTOSIS
o It is the release of substances out of a cell by the
fusion of a vesicle with the cell membrane.
o The contents of the vesicle are excreted/
expelled into the extracellular fluid
o This is a significant process to the cells of
organs that secrete hormones
o Study the process of exocytosis in the diagram:
https://www.google.com.ph/search?q=exocytosis
4. POTOCYTOSIS
(protein-mediated)
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Lesson 5: Biological Macromolecules
The Synthesis of Biological Molecules
Biological macromolecules are important cellular components and perform a wide array of
functions necessary for the survival and growth of living organisms. These non-living molecules
are the actual foot-soldiers in the battle for sustenance of life. Many critical nutrients are biological
macromolecules. The term “macromolecule” was first coined in the 1920s by Nobel laureate
Hermann Staudinger. Staudinger was the first to propose that many large biological molecules are
built by covalently linking smaller biological molecules together.
Biological macromolecules play a critical role in cell structure and function. Most (but not
all) biological macromolecules are polymers, which are any molecules constructed by linking
together many smaller molecules, called monomers. Typically all the monomers in a polymer tend
to be the same, or at least very similar to each other, linked over and over again to build up the
larger macromolecule. Biological macromolecules all contain carbon in ring or chain form, which
means they are classified as organic molecules. They usually also contain hydrogen and oxygen, as
well as nitrogen and additional minor elements. (byjus.com)
DEHYDRATION SYNTHESIS
♥ Dehydration synthesis can be defined as the synthesis reactions which involve the
formation of a new compound with the elimination of water molecule.
♥ Here in dehydration synthesis reactions, since water molecule eliminates during the
reaction, therefore, they are also a type of condensation reactions.
♥ This is because during the condensation reaction two molecules condense to form a large
molecule with loss of water molecule.
HYDROLYSIS
♥ It means “to split water,” a reaction in which a water is used to breakdown polymers into
monomers.
♥ Hydrolysis reactions break bonds and release energy.
♥ If the components are ionized after the split, one part gains two hydrogen atoms and a
positive charge, the other part gains an oxygen atom and a negative charge.
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Organic compounds are those that have carbon atoms. In living systems, large organic
molecules, called macromolecules, can consist of hundreds or thousands of atoms. Complex
molecules can be formed by stringing carbon atoms together in a straight line or by connecting
carbons together to form rings. The presence of nitrogen, oxygen, and other atoms adds variety to
these carbon molecules. There are four important classes: carbohydrates, proteins, lipids, and
nucleic acids. (https://www.cliffsnotes.com/study-guides/chemistry-basics/organic-molecules)
TYPES OF CARBOHYDRATES
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STRUCTURE OF PROTEINS
Protein structure depends on its amino acid sequence and local, low-energy chemical bonds
between atoms in both the polypeptide backbone and in amino acid side chains. It plays a key role
in its function; if a protein loses its shape at any structural level, it may no longer be functional.
There are four orders or structures:
1. Primary structure is the amino acid sequence.
2. Secondary structure is local interactions between stretches of a polypeptide chain and
includes α-helix and β-pleated sheet structures.
3. Tertiary structure is the overall the three-dimension folding driven largely by interactions
between R groups.
4. Quaternary structure is the orientation and arrangement of subunits in a multi-subunit
protein.
https://courses.lumenlearning.com/introchem/chapter/protein-structure/
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FUNCTIONS OF PROTEINS
https://microbenotes.com/lipids-properties-structure-classification-and-functions/
CLASSIFICATION OF LIPIDS
THE FAT FACTS!
Exercise 3c: Determine what function is represented in the
given examples.
_______________________a. lowering/increasing
blood sugar level
_______________________b. egg yolk
_______________________c. skin flexibility and
elasticity
_______________________d. bicep flexing
_______________________e. B helper cells making
antibodies
_______________________f. salivary amylase in the
mouth
_______________________g. oxygen transport to the
brain
_______________________h. secretion of pepsin in
the stomach
_______________________i. elongation of nail plate
_______________________j. raising the arm via the
deltoid muscle
PROPERTIES OF LIPIDS
 either liquids or non-crystalline solids at
room temperature
 Pure fats and oils: colorless, odorless, and
tasteless
 energy-rich organic molecules
 insoluble in water but soluble in organic
solvents like alcohol, chloroform, acetone,
benzene, etc.
 No ionic charges
 Solid triglycerols (Fats) have high
proportions of saturated fatty acids
 Liquid triglycerols (Oils) have high
proportions of unsaturated fatty acids
A. Based on Composition
1. Simple Lipids: esters of fatty acids
Ex. Fats (Saturated/Unsaturated) and Waxes
2. Complex Lipids: esters of fatty acids, alcohol and other
groups
Ex. Phospholipids, Lipoproteins, Glycolipids
3. Derived Lipids: composed of hydrocarbon rings and long
hydrocarbon chains
Ex. Sterol, Glycerol, Terpenes, Vitamins, Menthol
B. Based on Function
1. Storage Lipids
Ex. Fats and Oils
2. Structural Lipids
Ex. Phospholipids
3. Signals, Co-factors, Pigments
Ex. Steroid hormones,
Carotenoids
*lowers rates of cardiovascular diseases
*lowers bad cholesterol & triglyceride levels
*provides essential fats
*increases risk of cardiovascular
diseases
*raises levels of bad cholesterol
*increases risk of cardiovascular
diseases
*raises levels of bad cholesterol
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BIOLOGICAL ROLES OF LIPIDS
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https://www.google.com.ph/search?q=DNA+VS+RNA&hl/nucleotide
http://fig.cox.miami.edu/~cmallery/150/gene/chargaff.htm
Lesson 6: The Cell Cycle
The cell cycle is the ordered sequence of events that occur in a cell in preparation for cell
division. It is a four-stage process in which the cell:
 increases in size (gap 1, or G1, stage)
 copies its DNA (synthesis, or S, stage)
 checks for nourishment (gap 2, or G2, stage), and
 divides (mitosis/ meiosis, or M, stage).
The stages G1, S, and G2 make up interphase, which accounts for the span between cell
divisions. On the basis of the stimulatory and inhibitory messages a cell receives, it “decides”
whether it should enter the cell cycle and divide.
Cells in the body replace themselves over the lifetime of a person. For example, the cells
lining the gastrointestinal tract must be frequently replaced when constantly “worn off” by the
movement of food through the gut. But what triggers a cell to divide, and how does it prepare for
and complete cell division?
The 5-carbon sugar and the
phosphate group of
each nucleotide attaches to form
the backbone of DNA and RNA.
CHARGAFF’S RULE OF BASE-
PAIRING
A with T: the purine adenine (A) always pairs
with the pyrimidine thymine (T)
C with G: the pyrimidine cytosine (C) always
pairs with the purine guanine (G)
The rules of base pairing explain the
phenomenon that whatever the amount of
adenine (A) in the DNA of an organism, the
amount of thymine (T) is the same (Chargaff's
rule). Similarly, whatever the amount of guanine
(G), the amount of cytosine (C) is the same.
The C+G: A+T ratio varies from
organism to organism among the
prokaryotes), but within (particularly the
limits of experimental
error, A = T and C = G.
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Professor Gene and His Interactive Cell
 To help you in understanding what the cell cycle is, follow the link below for a guided
discussion of the lesson through a PowerPoint Presentation and audio explanation. The
presentation is interactive and you can hover over each specific phase to learn more about
it.
 You may also want to read Lesson 3.1 to 3.3 on pp. 75-83 of your ELTS General Biology 1
textbook.
 For this part, I want you to focus only on the Interphase sub-stages
 Take note of the significant events in order to comprehensively answer the next exercises
 The link also appears in your Google Classroom
http://webmedia.unmc.edu/eLearning_open/UBEATS/Genetics1/CellDivision/story_html5.html
INTERPHASE: The Resting Stage
What happens during Gap 0?
 From Professor Gene’s discussion, how did he describe this phase? Do all types of cells
proceed to Gap 0 or are there selected cells that proceed to such given the circumstances of
their maturity or cell integrity?
 Study the clipped information below (https://slideplayer.com/slide/9841216/APbiology/regulationofcell ):
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 Cells use special proteins and checkpoint signaling systems to ensure that the cell cycle
progresses properly.
 If DNA damage or abnormalities in spindle formation are detected at these checkpoints, the
cell is forced to undergo programmed cell death, or apoptosis.
 The cell cycle and its checkpoint systems can be sabotaged by defective proteins or genes
that cause malignant transformation of the cell, which can lead to cancer.
o For example, mutations in a protein called p53, which normally detects
abnormalities in DNA at the G1 checkpoint, can enable cancer-causing mutations to
bypass this checkpoint and allow the cell to escape apoptosis.
(https://www.britannica.com/science/cell-cycle)
Regulation of the Cell Cycle
 Internal Factors
o Come from inside the cell
 Kinase: enzyme that transfers a phosphate group from one molecule to a
specific target molecule (almost always present in the cell)
 Cyclins: group of proteins that are rapidly made and destroyed at certain
points in the cell cycle
 External Factors
o Trigger internal factors which affect the cell cycle
o Include physical and chemical signals
o Many cells release chemical signals (growth factors) that trigger cell growth
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Mitosis
DIVIDE AND CONQUER
The mitotic phase is a multi-step process during which the duplicated chromosomes are
aligned, separated, and move into two new, identical daughter cells. The M phase of the cell
typically takes between 1 and 2 hours depending on the cell type. During this phase, a cell
undergoes two major processes. The first portion of the mitotic phase is called karyokinesis, or
nuclear division during which the contents of the nucleus are equitably pulled apart and
distributed between its two halves. Mitosis is divided into four major stages that take place after
interphase and in the following order: prophase, metaphase, anaphase, and telophase. The second
portion of the mitotic phase, called cytokinesis, is the physical separation of the cytoplasmic
components into the two daughter cells.
Is it too complex to handle? Hmmm…Don’t worry because I will help you in this mitotic
mission! Do you remember Professor Gene? I want you to check with him again in his interactive
presentation, this time focus on his Mitosis discussion. Follow the link below:
You may also check Lesson 3.4 in pages 84-96 of your ELTS General Biology 1 textbook.
The figure in the right shows you the whole Cell
Cycle. Focusing on the boxed area, you can see the
stages of M phase or Mitosis.
a. Karyokinesis
Prophase
Metaphase
Anaphase
Telophase
b. Cytokinesis
The cell typically spends most of its time in
Interphase and only a little portion for Mitosis.
You must recall too that a cell spends more time in
Interphase in order to prepare itself prior to the
greater task of dividing into two identical cells. I
want you to also make sure that you can easily
remember how Professor Gene described each of
these stages in his interactive presentation.
http://legacy.hopkinsville.kctcs.edu/instructors/Jason-
Arnold/VLI/Module%202/m2celldivision/m2celldivision_print.html
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Are you excited to know what differentiates each stage of Mitosis? Let’s take a look at this
table that was lifted from https://courses.lumenlearning.com/biology1/chapter/the-cell-cycle/
and study the stages.
Mitosis Gone Wrong
Good Cells Gone Bad
There are several phases of both the cell cycle and mitosis. All of these
phases must be completed without errors in order to ensure the health of the cells.
Sometimes, however, mitosis goes wrong, and can lead to negative consequences
for the cell or the body as a whole.
If the process of mitosis goes wrong, it usually happens in a middle phase
of mitosis called metaphase, in which the chromosomes move to the center of the cell and align in
an area called the metaphase plate. If they do not align correctly, they cannot move individually to
opposite poles in the later phases of mitosis, and the result will be one cell with extra chromosomes
and a daughter cell with missing chromosomes. These mutations can lead to harmful results such
as cell death, organic disease or cancer.
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***You may also read Lesson 3-5-3.6 in pages 89-96 of your ELTS General Biology 1 textbook for
additional explanation.
Meiosis
Gametogenesis
Homologous Chromosomes
Do you have a sibling? If yes, maybe you can pinpoint a few physical traits that are very
similar while others show resemblance to some degree. In the same way, our chromosomes also
exhibit certain similarities in structure and composition. These are called homologous
chromosomes.
https://www.slideshare.net/SusanShaji/ks4-chromosomes-genes-and-dna
What differentiates Meiosis from Mitosis?
Animals and plants practice sexual reproduction, with parents passing chromosomes to
their offspring. Because each offspring receives unique combinations of chromosomes from the
parents, each offspring differs from the parents. Meiosis is the process of cell division that
produces the special cells that are needed for sexual reproduction. But, what are these special cells?
How does meiosis ensure that the correct number of chromosomes is passed on to the offsprings?
Let’s see.
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Sex Cell Production through Meiosis
Meiosis is a type of division done by sex cells or gametes. It is divided into two successive
cell divisions. The first part, Meiosis I, is often called reductional division since it reduces the
number of chromosomes from diploid (2n) to haploid (n) number. The second part, Meiosis II, is
similar to mitosis, thus called equational division since the chromosome number remains to be
haploid. Both meiosis I and meiosis II are further divided into four stages.
Now, to give you an interactive view of how sex cells are produced through the different
stages of meiosis, I want you to go back to Professor Gene’s discussion. Focus on his explanation of
the two stages of meiosis, visit the link below. If you are having trouble connecting to the web, you
may instead read Lesson 4.3-4.6 on pages 111-122 of your ELTS General Biology 1 textbook.
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Meiosis I
 Key features
o Reduction of chromosome number [from diploid to haploid]
o Synapsis (pairing of homologous chromosomes)
o Crossing-over of homologous chromosomes (for genetic exchange and variability)
o Formation of two un-identical haploid daughter cells
https://www.google.com.ph/search?q=meiosis+1&tbm=isch&ved=meiosis
Meiosis II
 Key features
o Events are the same as mitosis
o Retention of the number of chromosomes [from haploid to haploid]
o Formation of four un-identical haploid daughter cells
A Closer Look at Prophase 1
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 Daughter cells are no longer the same as the parent cell during Meiosis I
 In some species, cells enter a brief interphase, or interkinesis, before entering meiosis II.
o Interkinesis lacks an S phase, so chromosomes are not duplicated.
o The two cells produced in meiosis I go through the events of meiosis II in synchrony.
o During meiosis II, the sister chromatids within the two daughter cells separate,
forming four new haploid gametes.
o The mechanics of meiosis II is similar to mitosis, except that each dividing cell has
only one set of homologous chromosomes. Therefore, each cell has half the number
of sister chromatids to separate out as a diploid cell undergoing mitosis.
Spermatogenesis
Meiosis in Males
How are sperm cells produced in the testes? Study the schematic diagram.
(https://www.slideshare.net/opkholwad/spermatogenesis)
Three Phases of
Spermatogenesis
1. Mitosis
-Spermatocytogenesis
-stem cells divide to produce
cells that begin differentiation
2. Meiosis
-primary spermatocytes go
through meiotic division to
produce secondary
spermatocytes
-these haploid cells are now
called spermatids
3. Spermeiogenesis
- metamorphosis of spherical
spermatids into elongated
spermatozoa
-formation of acrosome,
flagellum, mitochondrial content
-spermatozoa stay in the
epididymis for maturation
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Anatomy of a Sperm Cell
Once spermatozoa mature and await release, they are temporarily stored in the epididymis.
In here, the sperm cells are properly nourished and trained to swim and survive. What makes up a
healthy and normal sperm cell? Let’s check.
You may refer to Lesson 4.4 of your ELTS General Biology 1 textbook, pages 114-118, for additional
information.
Oogenesis
Meiosis in Females
Oogenesis or egg development begins before birth while the female is still in the womb of
her mother. In any one human generation, 8 to 20 weeks after the fetus has started to grow, cells
that are to become mature ova have been multiplying, and by the time that the female is born, all
of the egg cells that the ovaries will release during the active reproductive years of the female are
already present in the ovaries. The primary ova remain dormant until just prior to ovulation, when
an egg is released from the ovary. Some egg cells may not mature for 40 years; others degenerate
and never mature.
So, are you curious now as to how egg cells are produced in the ovaries? Check Lesson 4.4
of your ELTS General Biology 1 textbook, pages 114-118 or you may study this schematic diagram.
Three Phases of Oogenesis
1. Multiplication
-primordial germinal cells divide repeatedly to form the
oogonia
-oogonia multiply via mitosis and form the primary oocytes
-happens before birth
2. Growth
-longer than the growth phase of spermatogenesis
-the size of the primary oocyte increases enormously
-nucleus becomes large due to the increased amount of the
nucleoplasm and is called germinal vesicle
3. Maturation
- cytoplasm of the oocyte divides unequally to form a single
large-sized haploid egg and three small haploid polar
bodies
-unequal divisions allow one cell out of the four daughter
cells to contain most of the cytoplasm and reserve food
material which is sufficient for the developing embryo
-completed during fertilization of the egg by the sperm cell
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Egg Cell Arrest
C. WRAP UP AND INDEPENDENT PRACTICE
Genetic Disorders Associated with Meiosis
Many human genetic disorders result from unbalanced chromosome abnormalities, in
which there is a net gain or loss of genetic material. Such imbalances often disrupt large numbers
of dosage-sensitive, developmentally important genes and result in specific and complex
phenotypes. Alternately, some chromosomal syndromes may be caused by a deletion or
duplication of a single gene with pleiotropic effects.
How does the egg cell get arrested?
At the time of birth, all future eggs are in the
prophase stage. At adolescence, anterior pituitary hormones
cause the development of a number of follicles in an ovary.
This results in the primary oocyte finishing the first meiotic
division. The cell divides unequally, with most of the cellular
material and organelles going to one cell, called a secondary
oocyte, and only one set of chromosomes and a small amount
of cytoplasm going to the other cell. This second cell is called
a polar body and usually dies. A secondary meiotic arrest
occurs, this time at the metaphase II stage. At ovulation, this
secondary oocyte will be released and travel toward the
uterus through the oviduct. If the secondary oocyte is
fertilized, the cell continues through the meiosis II,
completing meiosis, producing a second polar body and a
fertilized egg containing all 46 chromosomes of a human
being, half of them coming from the sperm.
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What are some of these disorders resulting from failed Meiosis?
Will a person with XXY
syndrome be able to
reproduce?
Why is there higher risk of
babies with Down’s syndrome
when a woman gets pregnant at
an older age?
Explain why a woman with XO syndrome is not able to
bear a child.
Why would a baby with trisomy 18 not live longer?
Why do women with triple X syndrome experience
amenorrhea?
Suppose you found out that you have high susceptibility to
having a child with Patau’s syndrome, will you still pursue
having a baby? Justify.
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INTRODUCTION
All living organisms need energy to grow and reproduce, maintain their structures, and
respond to their environments. Metabolism is the set of life-sustaining chemical processes that
enables organisms transform the chemical energy stored in molecules into energy that can be used
for cellular processes. Animals consume food to replenish energy; their metabolism breaks down
the carbohydrates, lipids, proteins, and nucleic acids to provide chemical energy for these
processes. Plants convert light energy from the sun into chemical energy stored in molecules
during the process of photosynthesis.
Scientists use the term bioenergetics to discuss the concept of energy flow through living
systems such as cells. Cellular processes such as the building and breaking down of complex
molecules occur through step-by-step chemical reactions. Some of these chemical reactions are
spontaneous and release energy, whereas others require energy to proceed. All of the chemical
reactions that take place inside cells, including those that use energy and
those that release energy, are the cell’s metabolism.
This module is divided into two important lessons about how our
cells produce and utilize energy. Formative assessments, textbook and
online resources are incorporated in the module and are found every after
a topic or lesson. For queries, you may email me or give me a ring.
Let’s capture those photons and radiate your inner genius!
LEARNING OBJECTIVES
At the end of this learning module, you are expected to:
 Explain coupled reaction processes and describe the role of ATP in energy coupling and
transfer
 Explain the importance of chlorophyll and other pigments
 Describe the patterns of electron flow through light reaction events
 Describe the significant events of the Calvin cycle
 Differentiate aerobic from anaerobic respiration
 Explain the major features and sequence the chemical events of cellular respiration
 Distinguish major features of glycolysis, Krebs cycle, electron transport system, and
chemiosmosis
 Describe reactions that produce and consume ATP
 Describe the role of oxygen in respiration and describe pathways of electron flow in the
absence of oxygen
 Explain the advantages and disadvantages of fermentation and aerobic respiration
INSTRUCTIONAL MATERIALS AND RESOURCES
General Biology 1 textbook, Internet (interactive presentations, off-site activities, images)
ESTIMATED TIME: 2 weeks
 Photosynthesis
 Cellular Respiration
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CONCEPTS IN A BOX
The following will be the focus of our second learning module- interplay between the
production of energy via Photosynthesis and the utilization of energy via Cellular Respiration.
DISCUSSION
A. ATTENTION-GETTER
Lesson 1: Photosynthesis
All living organisms on earth consist of one or more cells. Each cell runs on the chemical
energy found mainly in carbohydrate molecules (food), and the majority of these molecules are
produced by one process: photosynthesis. Through photosynthesis, certain organisms convert
solar energy (sunlight) into chemical energy, which is then used to build carbohydrate molecules.
The energy used to hold these molecules together is released when an organism breaks down food.
Cells then use this energy to perform work, such as cellular respiration.
Question 1a: What are the raw materials in the process?
___________________________________________________
1b: What are the end-products?
______________________________________
1c: What are the by-products?
_______________________________________
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B. Direct Instruction and Guided Practice
Photosynthetic Pathways
The assimilation of carbon dioxide, water, and the use of sunlight for the process of
photosynthesis and then converting it to glucose (energy) in synthesizing different product are the
key differences between the three pathways of photosynthesis.
1. C3 Pathway
 cool season or temperate
plants (85% of flora);
optimum temperature
between 65 to 750F
 show less efficiency at high
temperatures
 produces G3P (3-PGA:
phosphoglyceric acid) from
CO2
 RuBisCo/RuBPcase
(Ribulose biphosphate
carboxylase) catalyzes the
process
2. C4 Pathway
 aka Hatch and Slack
Pathway
 used by plants in the
tropical areas (ex.
sugarcane, maize)
 PEPc
(Phosphoenolpyruvate
carboxylase) carries out
the conversion of CO2 into
oxaloacetate
 RuBisCo/RuBPcase
(Ribulose biphosphate
carboxylase) converts
oxaloacetate into malate
3. CAM (Crassulacean Acid
Metabolism) Pathway
 used by plants in semi-arid
regions (ex. cacti, pineapple,
orchids)
 PEPc works in the dark;
RuBisCo works in daylight
o at night, CAM plants open
their stomata, allowing CO2
to diffuse into the leaves
o in daylight, CAM plants
don’t open their stomata
and use stored organic acid
in their vacuole to perform
photosynthesis
 avoids photorespiration and
is water-efficient
 Chlorophyll is the pigment molecule, which is the
principal photoreceptor in the chloroplasts of most
green plants.
 Photosynthetic pigments are the molecules involved in
absorbing electromagnetic radiation, transferring the
energy of the absorbed photons to the reaction center,
resulting in photochemical reactions in the organisms
capable of photosynthesis.
 In addition to chlorophyll, photosynthetic systems also
contain another pigment, phaeophytin
(bacteriopheophytin in bacteria), which plays a crucial
role in the transfer of electrons in photosynthetic
systems.
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What are Photosystems?
Photosystems, large complexes of proteins and pigments (light-absorbing molecules) that
are optimized to harvest light, play a key role in the light reactions. There are two types of
photosystems: photosystem I (PSI) and photosystem II (PSII).
Both photosystems contain many pigments that help collect light energy, as well as a
special pair of chlorophyll molecules found at the core (reaction center) of the photosystem. The
special pair of photosystem I is called P700, while the special pair of photosystem II is called P680.
Photosynthetic pigments, such as chlorophyll a, chlorophyll b, and carotenoids, are light-
harvesting molecules found in the thylakoid membranes of chloroplasts. Each photosystem has
light-harvesting complexes that contain proteins, chlorophylls, and other pigments. When a
pigment absorbs a photon (light energy units), it is raised to an excited state, meaning that one of
its electrons is boosted to a higher-energy orbital. (khanacademy.org.)
 a type of plastid—a round,
oval, or disk-shaped
 distinguished from other
types of plastids by their
green colour, which
results from the presence
of two
pigments, chlorophyll a a
nd chlorophyll b.
 they absorb light energy
 occur in all green tissues,
though they are
concentrated particularly
in the parenchyma cells of
the leaf mesophyll
 made up of:
o thylakoid
o granum
o stroma
 thylakoid membrane
houses chlorophylls and
different protein complex
es specialized for light-
dependent photosynthesis
 Photosystem I
 Photosystem II
Key Differences
 Special Pairs
 PSII: P680
 PSI: P700
 Primary Acceptor
 PSII: pheophytin (organic
molecule resembling Chl)
 PSI: A0
7,8 (chlorophyll/Chl)
 Source of Electrons
 PSII: from water
 PSI: from electron transport
chain flowing from PSII
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Stages of Photosynthesis
https://cnx.org/contents/GFy_h8cu@9.85:W7ctJeSI@8/Overview-of-Photosynthesis
Light Dependent Reactions
1. Chlorophyll Photoactivation
 chlorophyll absorbs high energy, short-wavelength light, which excites the electrons
present inside the thylakoid membrane
 excitation of electrons now initiates the transformation of light energy into chemical energy
 P680 donates a pair of electrons after absorbing light energy, resulting in an oxidized form
of P680
2. Photolysis
 an enzyme catalyzes the splitting of a water molecule into 2 electrons, 2 hydrogen ions, and
oxygen molecules
 oxidized form of P700 then accepts an electron from photosystem II, restring back to its
initial stage
3. Photophosphorylation
 electrons from photosystem I are then passed in a series of redox reactions through the
protein ferredoxin
 electrons finally reach NADP+, reducing them to NADPH
 energized electrons also fuel ADP by adding one phosphate group to form ATP (Adenosine
Tri-Phosphate)
1. Chl Photoactivation
2. Photolysis
3. Photophosphorylation
1. Carbon Fixation
2. Reduction
3. Regeneration
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Calvin Cycle/ Light Independent Reactions
https://microbenotes.com/photosynthesis/
Factors Affecting Photosynthesis
Carbon Fixation
 plants capture the carbon
dioxide from the atmosphere
through stomata; fixation of
CO2 into G3P/PGA
 one CO2 molecule is
covalently attached to a five-
carbon compound, RuBP,
catalyzed by the enzyme
RuBisCo
 attachment results in the
formation of an unstable six-
carbon compound that is then
cleaved to form two molecules
of G3P/PGA
Reduction
 conversion of G3P to PGAL
 NADPH donates electrons
 ATP releases one phosphate
group
 some of the PGAL are
o used to build the backbone of
glucose
o converted to starch in the
chloroplast and stored for
later use
o exported to the cytosol
o converted to sucrose for
transport to growing regions
of the plant
 most PGA will be used to
replenish RuBP
Regeneration
 the G3P/PGA formed in the
previous steps are then
converted into RuBP through
a series of transformations
with intermediates of three-,
four,-, five-, six-, and seven-
carbon sugar
 rearrangement results in the
starting molecule, RuBP
 a G3P molecule contains
three fixed carbon atoms, so
it takes 2 G3Ps to build a 6-
carbon glucose molecule.
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Lesson 2: Cellular Respiration
Cellular respiration is one of the most elegant, majestic, and fascinating metabolic
pathways on earth. At the same time, it’s also one of the most complicated. Organisms harvest
energy from food, but this energy cannot be directly used by cells. Cells convert the energy stored
in nutrients into a more usable form: adenosine triphosphate (ATP). ATP stores energy in chemical
bonds that can be quickly released when needed. Cells produce energy in the form of ATP through
the process of cellular respiration. Although much of the energy from cellular respiration is
released as heat, some of it is used to make ATP.
Cellular respiration is the process by which organisms combine oxygen with foodstuff
molecules, diverting the chemical energy in these substances into life-sustaining activities and
discarding, as waste products, carbon dioxide and water. Organisms that do not depend on oxygen
degrade foodstuffs in a process called fermentation. (https://www.britannica.com/science/cellular-
respiration)
https://link.springer.com/chapter/10.1007/978-3-662-57996-1_4
https://www.britannica.com/science/cellular-respiration
General Equation
A common fuel molecule for cellular respiration is glucose. Cellular respiration is the
reverse reaction of Photosynthesis. This is a catabolic process since it involves the breakdown of
glucose and the release of energy.
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Anaerobic Pathway
STAGESOF CELLULARRESPIRATION
1. Glycolysis
 Occurs in the cytoplasm
 Splitting of glucose molecule into two pyruvic acids/pyruvate (G3P)
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2. Transition Reaction
 Occurs in the mitochondrion
 Also called “Grooming Stage” or “Link Reaction”
 Pyruvate oxidation: G3P becomes Acetyl CoA (acetyl coenzyme A)
3. Krebs’ Cycle
 Occurs in the matrix of the mitochondrion
 Also called “Citric Acid Cycle” or “Tricarboxylic Acid Cycle”
4. Electron Transport Chain
 a series of electron transporters embedded in the inner mitochondrial membrane that shuttles
electrons from NADH and FADH2 to molecular oxygen
 protons are pumped from the mitochondrial matrix to the intermembrane space, and oxygen is
reduced to form water
Endof Quarter1: First Half General Biology1 Module
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