The Cell

1. PNUR 113 – Module #3
1
The Cell

2. Overview
 In a multicellular organism such as the human
body, cells make up all tissues
 All the activities of the human body, which is
composed of trillions of cells, result from the
activities of individual cells
 Cells produce all the materials manufactured
within the body
 Understanding the functioning of a basic body
cell enables the student to understand the
structure and function of all body tissues, organs
and systems
2

3. Learning Outcomes
 Upon successful completion of this module, you will be
able to:
 Describe the structure and functions of the plasma (cell) membrane
 List the components of the cytoplasm
 List the major organelles of the cell and describe their structure and
function
 List the organelles involved in protein synthesis and describe the two
steps involved in protein synthesis including where they occur and the
molecules involved.
 Define and distinguish between the two types of cell division and give
examples.
 Describe the different types of transport across cell membranes and
give examples for each.
 Describe different types of solutions and explain the effect of osmosis
on cells
 Discuss the concept of cell aging and the concept of cancer
 Discuss strategies to promote the health of cells
3
Answer in your own words
using complete sentences

4. Cell Structure: Plasma (Cell) Membrane
 Encloses the cell contents
 Participates in cellular
activities
 Regulates what enters and
leaves the cell and therefore is
described as semi-permeable
(not everything freely crosses
it)
1. Phospholipid bilayer is the
main structure with phospholipids
as the most prevalent molecule
2. Proteins within it can act as
specific transporters or channels
3. Cholesterol strengthens
4

5. Plasma Membrane Components
Table 3-1 Proteins in the Plasma Membrane and Their Functions
Type of Protein Function
Channels Pores in the membrane that allow passage of
specific substances
Transporters Shuttle substances across membrane
Receptors Allow for attachment of substances to membrane;
used for cell-to-cell signaling
Enzymes Participate in chemical reactions at membrane
surface
Linkers Help stabilize the plasma membrane and attach
cells together
Cell identity markers Proteins unique to a person’s cells; important in
the immune system and in transplantation of tissue
from one person to another
Learn all of theses basic functions of proteins in the plasma membrane

6. Cytoplasm
 Activities of the cell
mainly occur in
cytoplasm
 Consists of:
 fluid (cytosol) or water
with suspended or
dissolved substances
such as enzymes,
glucose, electrolytes
like sodium ions
 organelles or “little
organs” of the cell that
perform specific
functions such as the
nucleus and
ribosomes
6

7. Overview of Cell Parts
Name Description Function
PLASMA MEMBRANE Outer layer of the cell; composed mainly of lipids and
proteins
Encloses the cell contents; regulates what enters and
leaves the cell; participates in many activities, such
as growth, reproduction, and interactions between
cells
Microvilli Short extensions of the plasma membrane Absorb materials into the cell
NUCLEUS Large, membrane-bound, dark-staining organelle near
the center of the cell
Contains the chromosomes, the hereditary structures
that direct all cellular activities
Nucleolus Small body in the nucleus Makes ribosomes
CYTOPLASM Colloid that fills the cell from the nuclear membrane to
the plasma membrane
Site of many cellular activities; consists of cytosol
and organelles
Cytosol The fluid portion of the cytoplasm; contains water,
enzymes, nutrients, and other substances
Surrounds the organelles; site of many chemical
reactions and nutrient storage
Endoplasmic reticulum
(ER)
Network of membranes within the cytoplasm. Rough
ER has ribosomes attached to it; smooth ER does
not
Rough ER modifies, folds, and sorts proteins; smooth
ER participates in lipid synthesis
Ribosomes Small bodies free in the cytoplasm or attached to the
ER; composed of RNA and protein
Manufacture proteins
Golgi apparatus Layers of membranes Further modifies proteins; sorts and prepares
proteins for transport to other parts of the cell or
out of the cell
Mitochondria Large organelles with internal folded membranes Convert energy from nutrients into ATP
Lysosomes Small sacs of digestive enzymes Digest substances within the cell
Peroxisomes Membrane-enclosed organelles containing enzymes Break down harmful substances
Proteasomes Barrel-shaped organelles Destroy improperly synthesized proteins
Vesicles Small membrane-bound sacs in the cytoplasm Store materials and move materials into or out of the
cell in bulk
Centrioles Rod-shaped bodies (usually two) near the nucleus Help separate the chromosomes during cell division
SURFACE PROJECTIONS Structures that extend from the cell Move the cell or the fluids around the cell
Cilia Short, hairlike projections from the cell Move the fluids around the cell
Flagellum Long, whiplike extension from the cell Moves the cell

8. 1. Nucleus
 Control centre of the cell
 Contains genetic material
called chromosomes
which are composed of
DNA
 Specific sequences of DNA
functions as genes that
code for specific proteins
 Involved in cell
reproduction
 The nucleus is enclosed in
nuclear membrane
 Contains nucleolus where
ribosomes are made
(required for protein
synthesis)
8

9. 2. Ribosomes
 Composed of protein and
RNA only
 Not a membranous
organelle
 Produced in the
nucleolus but leaves the
nucleus for the cytoplasm
 Involved in protein
synthesis
 Found free in cytoplasm
or bound to rough
endoplasmic reticulum
9

10. 3. Endoplasmic Reticulum
 Network of membranes
 Various functions
 Rough endoplasmic
reticulum (ER) contains
ribosomes and is the site
of protein synthesis
 Smooth ER is important
for
1. making more
membranes (i.e. for
plasma membrane and
organelles)
2. detoxifying substances
3. In muscle it stores
calcium ions and is
called the sarcoplasmic
reticulum 10

11. 4. Mitochondria
 Tiny organelles (although drawn large in this figure)
 Possess folded internal membranes that create
separate compartments with different enzymes and
functions
 Involved in aerobic cellular respiration
 In the presence of oxygen convert glucose to energy for use by the
cell - ATP
11

12. 5. Endoplasmic Reticulum (ER)
 System of membranes
found extensively
throughout cells
 Two types:
 Rough ER which has
embedded ribosomes
 Important production of
proteins to be released
from cells, embedded in
membranes or stored in
vesicles (lysosomes)
 Smooth ER lacking
ribosomes
 Lipid synthesis
 Detoxification
 Liver cells have lots
12

13. 6. Golgi Apparatus
 Layers of membranous
sacs
 Receiving, processing
and packaging area for
proteins made at
ribosomes
 Creates the final
functional protein for
use by the cell or
release from the cell
(i.e. mucous or
hemoglobin found in
red blood cells)
13

14. 7. Lysosomes and Peroxisomes
 Contain
digesting
enzymes
 Important for
recycling worn
out organelles,
self-destruction
of a cell, or
detoxification of
drugs
14

15. 8. Centrioles
 Rod-shaped
bodies composed
of microtubule
proteins
 Usually 2
centrioles per cell
 Function in cell
division by helping
separate the
chromosomes so
that each daughter
cell gets the proper
number
15

16. 9. Organelles Responsible for Locomotion
 Cilia and flagella are both
composed of
microtubules
 Cilia
 Many small hair-like
projections on a cell
 Wave back and forth to
move mucous trapped
particles (airways) or ovum
(uterine tubes)
 Flagellum
 A single, long whip-like
extension on a
spermatozoa (sperm) used
for locomotion
16

17. 17
Review the
structures we
have covered in
the previous
slides
Table 3-2

18. DNA Molecules (Deoxyribonucleic Acid)
 DNA is found in nucleus
 DNA makes up the 23 pairs
of chromosomes in
humans
 It’s main structure is a
double helix (twisting
ladder shape)
 It is composed of 4 types of
nucleotides/nitrogenous
bases
18

19. 19
 Distinct regions of the DNA of a chromosome make up
genes
 Or sequence of nucleotides that code for a protein
 Variations in genes determine hereditary traits or genetic
diseases such as sickle-cell anemia and cystic fibrosis
Genes

20. 20
RNA versus DNA
 RNA is similar to DNA and is involved in protein synthesis
 It is made in the nucleus and leaves the nucleus to go to
ribosomes in the cytoplasm
 RNA is single stranded, has a different sugar and although it
consists of 4 nucleotides, 1 is different from DNA
Table 3-6

21. Discussion
 For this discussion topic find a website or YouTube video
that would be useful for learning about cells and briefly
summarize it in your own words!
 Include the link for the source of your information
 Try to ensure it is of a similar level of depth to your textbook
 If someone has already posted what you found, find
another!
 Post your website or YouTube video link and summary to the
Moodle Forum: Discussion Module 3 - Cell Websites and
YouTube Videos
 Try out some of the sites and videos your classmates have
posted and comment on them if you like them!
21
You can’t open the quiz
until you have posted
to this forum!

22. Cell Functions
 Protein Synthesis
 Two steps required to take information
from a gene and make a protein
product
1. Transcription – DNA to mRNA
2. Translation – mRNA to protein
 Cell Division – two types
 Cell Transport
22

23. Protein Synthesis - Transcription
 Review the organelles involved: ribosomes, rough
endoplasmic reticulum and Golgi Apparatus
 Genes, composed of DNA nucleotides coding for a specific
protein, are copied in the nucleus
23

24. Protein Synthesis - Transcription
 DNA is used as a template to make messenger RNA or
mRNA from free nucleotides suspended in the nucleus
 mRNA leaves the nucleus (DNA cannot)
24
mRNA

25. Protein Synthesis - Translation
 mRNA which left the nucleus, binds to ribosomes in the
cytoplasm or on rough endoplasmic reticulum
 A specific transfer RNA or tRNA molecule reads the mRNA
nucleotide sequence and brings the correct amino acid to the
mRNA on the ribosome
 As the sequence is read by more tRNA’s amino acids are joined
together eventually forming a long protein chain
25

26. Cell Division
 Before any cell division, the DNA in the nucleus is
precisely copied (this is when mutations can
occur)
 Mitosis is important for growth and repair
 Meiosis is important for the formation of gametes
(egg/ovum or sperm) with half the number of
chromosomes
 Upon fertilization of the egg by the sperm, the full
number of chromosomes is restored
26

27. Cell Division
 Mitosis
parent cell divides once
gives rise to two genetically identical
daughter cells
 Meiosis
Parent cell divides twice
Gives rise to 4 genetically different/unique
gametes
Uniqueness of each is due to the mixing of
genes from the two separate sets of
chromosomes the individual inherited from
their parents 27

28. Cell Division, cont.
 4 stages of mitosis:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
 Cytoplasm divides to produce two identical
daughter cells with original number of
chromosomes
 The same stages are seen with meiosis except
that the cell divides twice in a row!
 How many chromosomes would be in these
daughter cells? 28

29. Figure 3-15 The stages of mitosis.
If the original cell shown has 46 chromosomes, how many
chromosomes will each new daughter cell have?
Cell Division (cont.)

30. Cell Transport
30
 Movement of substances across the plasma membrane
 plasma membrane is semi-permeable or selectively
permeable due to the phospholipid bilayer
 Based on size and charge of molecules

31. Cell Transport, cont.
31
 membrane proteins allow substances that normally cannot
cross to cross
 Passive transport across the plasma membrane
 Substances cross following their concentration gradients
(from high concentration to low concentration)
 Ex. Diffusion, facilitated diffusion, osmosis, filtration
 Active Transport across the plasma membrane
 Energy (ATP) required to move substances
 Against concentration gradient
 or for movement of large molecules
 Vesicular Transport
 phagocytosis, pinocytosis, exocytosis

32. 1. Diffusion
 Diffusion is the constant movement of molecules from an
area of high concentration to an area of low concentration
to achieve equilibrium
 Diffusion occurs with or without a plasma membrane
 Example of diffusion without a plasma membrane – sugar
cube dissolving in coffee
32

33. 1. Diffusion, cont.
 Substances can move down their concentration gradients across a
semi-permeable membrane (no energy required)
 permit some solutes (dissolved substances) to cross, but not others
 Water-soluble substances cannot cross (proteins, glucose)
 Fat-soluble substances can (lipids, alcohol)
 Also water, carbon dioxide and oxygen can cross
 i.e. oxygen exchange in the lungs and nutrient exchange between
blood capillaries and tissues
33

34. 2. Facilitated Diffusion
 movement of solutes down their concentration
gradient with the help of transporter proteins that
act as channels
 No energy required
 charged, water-soluble substances
 Glucose, amino acids
 electrolytes such as sodium ions
34

35. 3. Osmosis
 movement of water across a
semi-permeable membrane
when solutes can’t move
 water molecules move from a
solution of low solutes (high
water) to a solution of high
solutes (low water) to
achieve equilibrium
 i.e. if a cell containing solutes is
placed in pure water, water will
move into the cell to achieve
equilibrium
 Osmotic pressure is the
force needed to stop the flow
of water by osmosis 35

36. 4. Filtration
 Mechanical force pushes a substance through a membrane
 The membrane limits which particles can pass through
 Pores in the membrane can permit larger molecules through
 Small particles go through and appear in the filtrate
 Ex. movement of substances out of blood capillaries due to
high blood pressure
 Ex. filtration of blood at kidney nephrons – urine formation
36

37. 5. Active Transport
 The movement of small, solute particles in or
out of the cell against the concentration gradient
 Requires energy (ATP)
 Requires a protein pump (active transporter)
 Important for muscle contraction and neuron
function – creates resting membrane potential
 Active transport pumps produce high concentrations
of sodium ions outside cells and potassium ions
inside cells
 Results in potential energy like a charged battery as
the solutes (electrolytes) will move back down the
gradient if permitted 37

38. 6. Vesicular Transport
A. Phagocytosis
 The plasma membrane
engulfs large particles from
its surroundings and brings
them into the cell
 Ex. White blood cells
phagocytize bacteria
B. Pinocytosis
 The plasma membrane
engulfs small droplets of
liquid from its surroundings
and brings it into the cell
38
What organelle would likely help to destroy a particle taken
in by phagocytosis?

39. C. Exocytosis
 Materials are moved out of
the cell through the
creation of membrane-
bound vesicles
 Often protein based
substances produced by
ribosomes and package by
Golgi complex
 ex. mucous secretion from
cells lining upper airways
 ex. release of
neurotransmitters at ends of
neurons 39
6. Vesicular Transport, cont.

40. Osmosis Effect on Cells
 Another way to think about osmosis is in
terms of solute concentration.
Water Follows the Salt
Low solute
High water
High solute
Low waterOsmosis

41. Osmosis Effect on Cells, cont.
 Solutions are composed of solutes (dissolved
substances) and a solvent (liquid - water)
 When cells are placed in solutions with different
concentrations of solutes, osmosis can have an effect
 Types of Solutions and their effect on a cell
 Isotonic Solution
 Same concentration as the fluid within the cell - No change
 Hypotonic Solution
 Cytosol more concentrated than the surrounding solution –
water moves into the cell causing it to swell and perhaps bursts
(hemolysis with red blood cells)
 Hypertonic Solution
 cytosol less concentrated than the surrounding solution – water
moves out of the cell and it shrinks (crenation) 41

42. What would happen to red blood cells in the body if blood
lost through injury were replaced with pure water?
Osmosis Effect on Cells, cont.

43. Osmosis, cont.
Table 3-3 Solutions and Their Effects on
CellsSolution Description Examples Effect on Cells
Isotonic Has the same
concentration of dissolved
substances as the fluid in
the cell
0.9% salt
(normal saline);
5% glucose
None
Hypotonic Has a lower concentration
of dissolved substances
than fluid in the cell
Less than 0.9%
salt or 5%
glucose
Cell takes in water
and may burst
(lysis)
Hypertonic Has a higher concentration
of dissolved substances
than fluid in the cell
Higher than
0.9% salt or 5%
glucose
Cell loses water
and shrinks
(crenation)

44. Membrane Transport Overview
Process Definition Example
Do not require cellular energy (passive)
Diffusion Random movement of particles down the
concentration gradient (from higher concentration to
lower concentration)
Movement of gases through the membrane,
ions through an ion channel, or nutrients
via transporters
Osmosis Diffusion of water through a semipermeable
membrane
Movement of water across the plasma
membrane through aquaporins
Filtration Movement of materials through a membrane down a
pressure gradient
Movement of materials out of the blood
under the force of blood pressure
Require cellular energy
Active transport (pumps) Movement of materials through the plasma membrane
against the concentration gradient using transporters
Transport of ions (e.g., Na+
, K+
, and Ca2+
) in
neurons
Bulk transport Movement of large amounts of material through the
plasma membrane using vesicles; also called
vesicular transport
Endocytosis Transport of bulk amounts of materials into the cell
using vesicles
Phagocytosis—intake of large particles, as
when white blood cells take in waste
materials; also pinocytosis (intake of fluid),
and receptor-mediated endocytosis,
requiring binding sites in the plasma
membrane
Exocytosis Transport of bulk materials out of the cell using
vesicles
Release of neurotransmitters from neurons

45. Cell Aging
As cells multiply, changes occur that may lead to their
damage or death
Free radical injury
 Free radicals are highly reactive, destructive compounds
produce during cellular activities
 They can damage lysosomes which then release their
destructive enzymes causing further cell injury
 Could result in gene mutations that could lead to cancer
Slowing cell activity
Apoptosis – preprogrammed cell death
 Note that apoptosis is also a normal process for replacing
some types of cells that experience a lot of wear-and-tear
such as stomach lining cells
45

46. Cells and Cancer
 Certain mutations may cause changes in cells
leading to uncontrolled reproduction – cancer!
 Cancer cells form tumours, crowding out normal cells and
interfere with normal organ function
 Cancer cells can spread to other areas of the body -
metastasize
 Risk factors for cancer include:
 Heredity – breast cancer, colon cancer
 Chemicals that are carcinogens – cigarette smoke
 Ionizing radiation such as x-rays and UV-rays
 Diets high in fat and calories and also low in fibre, fruits
and vegetables
 Viruses – some leukemias, cervical cancer (human
papilloma virus) 46

47. Discussion
 This discussion topic asks “How can we promote the
health of our cells?”
 Apply what you have learned in this topic
 Read the suggestions that have already been posted
(unless of course you are the first to post a
suggestions, then the topic is wide open!)
 Then try to post a new response to this question
 Post to the Moodle Forum Discussion Module 3:
Promoting Health of Cells
 Check back to the discussion topic latter in the course
to get some ideas to improve the health of your cells
47
You can’t open the quiz
until you have posted
to this forum!