Chapter 3 cells

Chapter 3: Cells
© 2013 John Wiley & Sons, Inc. All rights reserved.

Cells
 A GENERALIZED VIEW OF THE CELL
 THE PLASMA MEMBRANE
 TRANSPORT ACROSS THE PLASMA
MEMBRANE
 CYTOPLASM
 NUCLEUS
 GENE ACTION: PROTEIN SYNTHESIS
 SOMATIC CELL DIVISION
 CELLULAR DIVERSITY
 AGING AND CELLS

A Generalized View of the Cell
 Cells vary greatly in size, shape and function,
but all cells have common features and
components
 All cells have three main regions
 Nucleus
 Cytoplasm – cytosol and organelles
 Plasma membrane

A Generalized View of the Cell

Anatomy Overview:
You must be connected to the internet to run this animation.
• Cell Structure and Function

The Plasma Membrane
 Selectively permeable – permits some
substances to cross more easily than others
 Primarily lipid barrier that surrounds and
contains the cytoplasm of a cell
 Lipid barrier consists of two back to back
phospholipid layers
 Lipid bilayer contains numerous proteins
 Integral proteins extend through membrane
 Peripheral proteins found on one surface
 Membrane proteins function as channels,
receptors and cell identity markers

The Plasma Membrane

Anatomy Overview:
• Plasma Membrane Structure

Transport Across the Plasma
Membrane
 Membrane transport – substance movement
into or out of the cell
 Two general methods of transport
 ____ transport – no energy required
 ____ transport – cell must use energy (ATP)
 The plasma membrane allows some
substances to move into and out of the cell but
restricts the passage of other substances
 This property of membranes is called _____

Membrane
 Membrane transport – substance movement
into or out of the cell
 Two general methods of transport
 Passive transport – no energy required
 Active transport – cell must use energy (ATP)
 The plasma membrane allows some
substances to move into and out of the cell but
restricts the passage of other substances
 This property of membranes is called selective
permeability

Membrane
 ____ (ICF) – fluid in body cells
 ____ (ECF) – fluid outside body cells
 ____ fluid – ECF between cells in tissues
 ____ – ECF in blood vessels
 ____ – ECF in lymphatic vessels
 ____ – any material dissolved in a fluid
 ____ – fluid that dissolves materials

Membrane
 Intracellular fluid (ICF) – fluid in body cells
 Extracellular fluid (ECF) – fluid outside body
cells
 Interstitial fluid – ECF between cells in tissues
 Plasma – ECF in blood vessels
 Lymph – ECF in lymphatic vessels
 Solute – any material dissolved in a fluid
 Solvent – fluid that dissolves materials

Membrane – Diffusion
 The selective permeability of the plasma membrane supports the existence
of concentration gradients, differences in the concentration of chemicals
between one side of the membrane and the other.
 Diffusion is the movement of substances due to their kinetic energy. In net
diffusion, substances move from an area of higher concentration to an area
of lower concentration until equilibrium is reached. At equilibrium the
concentration is the same throughout the solution.
 In simple diffusion, lipid-soluble substances move through the lipid bilayer.
In facilitated diffusion, substances cross the membrane with the
assistance of ion channels and carriers.

Membrane – Osmosis
 Osmosis is the movement of water molecules through a
selectively permeable membrane from an area of higher water
concentration to an area of lower water concentration. In an
isotonic solution, red blood cells maintain their normal
shape; in a hypotonic solution, they gain water and undergo
hemolysis; in a hypertonic solution, they lose water and
undergo crenation.

Membrane – Vesicular Transport
 Transport in vesicles includes both endocytosis
(phagocytosis and bulk-phase endocytosis [pinocytosis])
and exocytosis. Phagocytosis is the ingestion of solid
particles. It is an important process used by some white blood
cells to destroy bacteria that enter the body. Bulk-phase
endocytosis is the ingestion of extracellular fluid. Exocytosis
involves movement of secretory or waste products out of a
cell by fusion of vesicles within the cell with the plasma
membrane.

Membrane – Passive Processes
 Diffusion – particles
distribute
themselves evenly
(homogenously)
within a solution
moving from high
concentration to low
concentration

Transport Across the Plasma Membrane

Membrane – Active Processes
 Active processes are required when materials
are unable to pass through the cell
membrane by diffusion
 e.g. too large, unable to dissolve in the fat core of
the membrane, or have to move up a
concentration gradient

Membrane – Active Processes

Animation:
• Transport Across the Plasma Membrane

Transport
Across the
Plasma
Membrane –
Active
Processes

Cytoplasm
 Cytoplasm includes all the cellular contents between the
plasma membrane and nucleus; it consists of cytosol and
organelles.
 Organelles are specialized cellular structures with
characteristic shapes and specific functions.

Cytoplasm – Cytoskeleton
 The cytoskeleton is a network of several kinds of
protein filaments that extend throughout the cytoplasm;
they provide a structural framework for the cell and
generate movements. Components of the cytoskeleton
include microfilaments, intermediate filaments, and
microtubules.

Cytoplasm –
Cytoskeleton
 Provides a
framework for
cellular shape and
organization
 Functions in
internal and
external cellular
movement

Cytoplasm – Centrosome
 The centrosome is an organelle that
consists of two centrioles and pericentriolar
material. The centrosome serves as a center
for organizing microtubules in interphase
cells and the mitotic spindle during cell
division.

Cytoplasm – Centrosome
 Forms a
scaffold
essential for
duplication of
cellular DNA
during cellular
division

Cytoplasm – Ribosomes
 Ribosomes, composed of ribosomal RNA
and ribosomal proteins, consist of two
subunits and are the sites of protein
synthesis.

Cytoplasm –
Ribosomes
 Synthesize all
_______

Cytoplasm –
Ribosomes
 Synthesize all
proteins

Cytoplasm – Endoplasmic Reticulum
 Endoplasmic reticulum (ER) is a network of membranes that
extends from the nuclear envelope throughout the cytoplasm.
Rough ER is studded with ribosomes. Proteins synthesized
on the ribosomes enter the ER for processing and sorting.
The ER is also where glycoproteins and phospholipids form.
 Smooth ER lacks ribosomes. It is the site where fatty acids
and steroids are synthesized. Smooth ER also participates in
releasing glucose from the liver into the bloodstream,
inactivating or detoxifying drugs and other potentially harmful
substances, and storing and releasing calcium ions that
trigger contraction in muscle cells.

 ______ER –
studded with
ribosomes to
synthesize proteins
embedded in
membranes
 ______ER –
involved in calcium
regulation, lipid
synthesis &
detoxification

 Rough ER –
studded with
ribosomes to
synthesize proteins
embedded in
membranes
 Smooth ER –
involved in calcium
regulation, lipid
synthesis &
detoxification

Cytoplasm – Golgi Complex
 The Golgi complex consists of flattened sacs called cisterns
that receive proteins synthesized in the rough ER. Within the
Golgi cisterns the proteins are modified, sorted, and packaged
into vesicles for transport to different destinations.
 Some processed proteins leave the cell in secretory vesicles,
some are incorporated into the plasma membrane, and some
enter lysosomes.

Cytoplasm – Golgi Complex
 Modifies
proteins
 Forms
secretory
vesicles

Cytoplasm – Mitochondria
 Mitochondria consist of a smooth outer
membrane, an inner membrane containing
folds called mitochondrial cristae, and a
fluid-filled cavity called the matrix. They are
called “powerhouses” of the cell because
they produce most of a cell’s ATP.

Cytoplasm –
Mitochondria
 Powerhouses of
the cell that form
most cellular ___

Cytoplasm –
Mitochondria
 Powerhouses of
the cell that form
most cellular ATP

Cytoplasm – Lysosomes, Peroxisomes,
and Proteasomes
 Lysosomes are membrane-enclosed vesicles that contain digestive
enzymes. They function in digestion of worn-out organelles (autophagy)
and even in digestion of their own cell (autolysis).
 Peroxisomes are similar to lysosomes but smaller. They oxidize various
organic substances.
 Proteasomes contain proteases that continually degrade unneeded,
damaged, or faulty proteins.

Cytoplasm

Nucleus
 The nucleus consists of a double nuclear envelope; nuclear pores, which control the
movement of substances between the nucleus and cytoplasm; nucleoli, which produce
ribosomes; and genes arranged on chromosomes.
 Most body cells have a single nucleus; some (red blood cells) have none, and others
(skeletal muscle cells) have several.
 Genes control cellular structure and most cellular functions.
 Master control center
of the cell that
contains hereditary
genetic material
(DNA)

Gene Action – Protein Synthesis

Gene Action –
Protein Synthesis
 ___________ –
process by which a
RNA copy
(messenger RNA
or mRNA) of a
DNA gene is
produced

Gene Action –
Protein Synthesis
 Transcription –
process by which a
RNA copy
(messenger RNA
or mRNA) of a
DNA gene is
produced

 Translation – process by which a messenger
RNA is “read” in order to manufacture the
corresponding protein

Gene Action –
Protein
Synthesis

 Most of the cellular machinery is devoted to protein synthesis.
 Cells make proteins by transcribing and translating the
genetic information encoded in the sequence of four types of
nitrogenous bases in DNA.
 In transcription, genetic information encoded in the DNA
base sequence (base triplet) is copied into a complementary
sequence of bases in a strand of messenger RNA (mRNA)
called a codon. Transcription begins on DNA in a region
called a promoter.

 Translation is the process in which mRNA associates
with ribosomes and directs synthesis of a protein,
converting the nucleotide sequence in mRNA into a
specific sequence of amino acids in the protein.
 In translation, mRNA binds to a ribosome, specific amino
acids attach to transfer RNA (tRNA), and anticodons
of tRNA bind to codons of mRNA, bringing specific
amino acids into position on a growing protein.
 Translation begins at the start codon and terminates at
the stop codon.

Animation:
• Protein Synthesis

Somatic Cell Division
 Cell division is the process by which cells reproduce themselves. Cell
division that results in an increase in the number of body cells is called
somatic cell division; it involves a nuclear division called mitosis plus
division of the cytoplasm, called cytokinesis.
 Cell division that results in the production of sperm and oocytes is called
reproductive cell division.
 The cell cycle is an orderly sequence of events in somatic cell division in
which a cell duplicates its contents and divides in two. It consists of
interphase and a mitotic phase.
 During interphase, the DNA molecules, or chromosomes, replicate
themselves so that identical chromosomes can be passed on to the next
generation of cells. A cell that is between divisions and is carrying on every
life process except division is said to be in interphase.

Somatic Cell Division
 Mitosis is the replication and distribution of two sets of
chromosomes into separate and equal nuclei; it consists of
prophase, metaphase, anaphase, and telophase.
 During cytokinesis, which usually begins late in anaphase and
ends in telophase, a cleavage furrow forms and progresses
inward, cutting through the cell to form two separate identical
cells, each with equal portions of cytoplasm, organelles, and
chromosomes.

Somatic
Cell
Division

Cellular Diversity
 The different types of cells in the body vary considerably
in size and shape.
 The sizes of cells are measured in micrometers. One
micrometer (µm) equals 10-6
m (1/25,000 of an inch).
Cells in the body range from 8 µm to 140 µm in size.
 A cell’s shape is related to its function.

Cellular
Diversity

Aging and Cells
 Aging is a normal process accompanied by progressive
alteration of the body’s homeostatic adaptive responses.
 Many theories of aging
have been proposed,
including genetically
programmed cessation of
cell division, shortening of
telomeres, addition of glucose
to proteins, buildup of free radicals, and an intensified
autoimmune response.

End of Chapter 3
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Chapter 3 cells

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