Transcript The Cell Membrane

Essentials of Anatomy & Physiology, 4th Edition
Martini / Bartholomew
3
Cell Structure
and Function
PowerPoint® Lecture Outlines
prepared by Alan Magid, Duke University
Slides 1 to 102
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Studying Cells
Cell Theory: Four Basic Concepts
• Basic building blocks of all
animals and plants
• Smallest functional units of life
• Products of cell division
• Basic homeostatic units
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Studying Cells
The Diversity of Cells in the Human Body
Figure 3-1
Studying Cells
Cytology
Study of structure and function of cells
Cytology depends on seeing cells
• Light microscope (LM)
• Electron Microscope (EM)
• Scanning EM (SEM)
• Transmission EM (TEM)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Studying Cells
Overview of Cell Anatomy
• Extracellular fluid
• Also called interstitial fluid
• Cell Membrane
• Lipid barrier between outside
and inside
• Cytoplasm (intracellular fluid)
• Around nucleus
• Cytosol + organelles
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Studying Cells
Anatomy of a
Representative
Cell
Figure 3-2
The Cell Membrane
Functions of the plasma membrane
• Physical isolation
• Regulation of exchange with the
environment
• Sensitivity
• Structural support
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The Cell Membrane
Membrane Structure
• Phospholipid bilayer
• Molecular components
• Lipids
• Proteins
• Carbohydrates
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The Cell Membrane
The Cell Membrane
Figure 3-3
The Cell Membrane
Functions of Membrane Proteins
•
•
•
•
•
•
Receptors
Channels
Carriers
Enzymes
Anchors
Identifiers
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The Cell Membrane
Table 3-2
The Cell Membrane
Membrane Transport
• Selective permeability
• Permeability factors
• Molecular size
• Electrical charge
• Molecular shape
• Lipid solubility
PLAY
Doors and Channels
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The Cell Membrane
Membrane Transport Processes
• Passive transport
• Diffusion
• Filtration
• Carrier-Mediated transport
• Facilitated transport
• Active transport
PLAY
Membrane Transport: Cell Membrane Barrier
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The Cell Membrane
Membrane Transport Definitions
• Diffusion
Random movement down a
concentration gradient (from higher to
lower concentration)
• Osmosis
Movement of water across a membrane
down a gradient in osmotic pressure
(from lower to higher osmotic pressure)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Diffusion
PLAY
Membrane Transport: Diffusion
Figure 3-4
The Cell Membrane
Diffusion Across Cell Membranes
Figure 3-5
PLAY
Membrane Transport: Fat- and Water-Soluble Molecules
The Cell Membrane
Osmosis
Figure 3-6
The Cell Membrane
Key Note
Things tend to even out, unless
something—like a cell membrane—
prevents this from happening. Across
a freely permeable or water permeable
membrane, diffusion and osmosis will
quickly eliminate concentration
gradients.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Osmotic Effects of Solutions on Cells
• Isotonic—Cells maintain normal size and
shape
• Hypertonic—Cells lose water osmotically
and shrink and shrivel
• Hypotonic—Cells gain water osmotically
and swell and may burst.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Membrane
Osmotic
Flow across
a Cell
Membrane
Figure 3-7
The Cell Membrane
Facilitated Diffusion
Figure 3-8
PLAY
Membrane Transport: Facilitated Diffusion
The Cell Membrane
The SodiumPotassium
Exchange Pump
Figure 3-9
PLAY
Membrane
Transport:
Active
Transport
The Cell Membrane
Vesicular Transport
• Membranous vesicles
• Transport in both directions
• Endocytosis
• Movement into cell
• Receptor-mediated
• Pinocytosis
• Phagocytosis
• Exocytosis
• Movement out of cell
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Exocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Vesicles fuse with lysosomes.
Ligands are removed and absorbed
into the cytoplasm.
Lysosome
Ligands
removed
Fused vesicle
and lysosome
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The membrane containing the
receptor molecules separates from
the lysosome.
The vesicle returns to the surface.
Figure 3-10
1 of 8
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Ligands
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Ligand
receptors
CYTOPLASM
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Figure 3-10
2 of 8
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Ligands
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
CYTOPLASM
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Figure 3-10
3 of 8
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-10
4 of 8
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Vesicles fuse with lysosomes.
Lysosome
Fused vesicle
and lysosome
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-10
5 of 8
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Vesicles fuse with lysosomes.
Ligands are removed and absorbed
into the cytoplasm.
Lysosome
Fused vesicle
and lysosome
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-10
6 of 8
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Vesicles fuse with lysosomes.
Ligands are removed and absorbed
into the cytoplasm.
Lysosome
Ligands
removed
The membrane containing the
receptor molecules separates from
the lysosome.
Fused vesicle
and lysosome
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-10
7 of 8
Ligands
EXTRACELLULAR
Ligands binding
FLUID
to receptors
Receptor-Mediated Endocytosis
Target molecules (ligands) bind to
receptors in cell membrane.
Endocytosis
Exocytosis
Ligand
receptors
Areas coated with ligands form
deep pockets in membrane surface.
Pockets pinch off, forming vesicles.
CYTOPLASM
Coated
vesicle
Vesicles fuse with lysosomes.
Ligands are removed and absorbed
into the cytoplasm.
Lysosome
Ligands
removed
Fused vesicle
and lysosome
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The membrane containing the
receptor molecules separates from
the lysosome.
The vesicle returns to the surface.
Figure 3-10
8 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Lysosomes fuse with the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
This fusion activates digestive
enzymes.
CYTOPLASM
EXTRACELLULAR FLUID
Undissolved
residue
The enzymes break down the
structure of the phagocytized
material.
Residue is then ejected from the
cell by exocytosis.
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Figure 3-11
1 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
EXTRACELLULAR FLUID
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Figure 3-11
2 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
EXTRACELLULAR FLUID
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Figure 3-11
3 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
EXTRACELLULAR FLUID
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
4 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Lysosomes fuse with the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
EXTRACELLULAR FLUID
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
5 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Lysosomes fuse with the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
This fusion activates digestive
enzymes.
EXTRACELLULAR FLUID
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
6 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Lysosomes fuse with the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
CYTOPLASM
EXTRACELLULAR FLUID
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
This fusion activates digestive
enzymes.
The enzymes break down the
structure of the phagocytized
material.
Figure 3-11
7 of 8
Phagocytosis
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact
with the foreign object and sends
pseudopodia (cytoplasmic
extensions) around it.
The pseudopodia approach one
another and fuse to trap the
material within the vesicle.
The vesicle moves into the
cytoplasm.
Vesicle
Lysosomes fuse with the vesicle.
Foreign
object
Pseudopodium
(cytoplasmic
extension)
This fusion activates digestive
enzymes.
CYTOPLASM
EXTRACELLULAR FLUID
Undissolved
residue
The enzymes break down the
structure of the phagocytized
material.
Residue is then ejected from the
cell by exocytosis.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-11
8 of 8
The Cytoplasm
Cytoplasm
All the “stuff” inside a cell, not
including the cell membrane
and nucleus.
The “stuff”:
• The cytosol
• The organelles
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The Cytoplasm
The Cytosol contains:
• Intracellular fluid
• Dissolved nutrients and
metabolites
• Ions
• Soluble proteins
• Structural proteins
• Inclusions
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The Cytoplasm
Organelles
• Membranous organelles
• Isolated compartments
• Nucleus
• Mitochondria
• Endoplasmic reticulum
• Golgi apparatus
• Lysosomes
• Peroxisomes
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The Cytoplasm
Organelles
• Nonmembranous organelles
• Cytoskeleton
• Microvilli
• Centrioles
• Cilia
• Flagella
• Ribosomes
• Proteasomes
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The Cytoplasm
Organelles: The Cytoskeleton
• Cytoplasmic strength and form
• Main components
• Microfilaments (actin)
• Intermediate filaments (varies)
• Microtubules (tubulin)
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The Cytoplasm
The Cytoskeleton
Figure 3-12
The Cytoplasm
Nonmembranous Organelles
• Centrioles—Direct chromosomes in mitosis
• Microvilli—Surface projections increase
external area
• Cilia—Move fluids across cell surface
• Flagella—Moves cell through fluid
• Ribosome—Makes new proteins
• Proteasome—Digests damaged proteins
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cytoplasm
Membranous Organelles
• Endoplasmic reticulum—Network of
intracellular membranes for molecular
synthesis
• Rough ER (RER)
• Contains ribosomes
• Supports protein synthesis
• Smooth ER (SER)
• Lacks ribosomes
• Synthesizes proteins, carbohydrates
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cytoplasm
The Endoplasmic
Reticulum
Figure 3-13
The Cytoplasm
Membranous Organelles
• Golgi apparatus
• Receives new proteins from RER
• Adds carbohydrates and lipids
• Packages proteins in vesicles
• Secretory vesicles
• Membrane renewal vesicle
• Lysosomes
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Endoplasmic reticulum
EXTRACELLULAR
CYTOSOL FLUID
Lysosomes
Cell
membrane
Secretory
vesicles
Transport
vesicle
Golgi apparatus
(a)
Membrane renewal
vesicles
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(b) Exocytosis
Vesicle
Incorporation in
cell membrane
Figure 3-14
1 of 7
EXTRACELLULAR
CYTOSOL FLUID
Endoplasmic reticulum
Cell
membrane
Transport
vesicle
(a)
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Figure 3-14
2 of 7
Endoplasmic reticulum
EXTRACELLULAR
CYTOSOL FLUID
Cell
membrane
Transport
vesicle
Golgi apparatus
(a)
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Figure 3-14
3 of 7
Endoplasmic reticulum
EXTRACELLULAR
CYTOSOL FLUID
Lysosomes
Transport
vesicle
Cell
membrane
Golgi apparatus
(a)
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Figure 3-14
4 of 7
Endoplasmic reticulum
EXTRACELLULAR
CYTOSOL FLUID
Lysosomes
Transport
vesicle
Golgi apparatus
(a)
Membrane renewal
vesicles
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Cell
membrane
Vesicle
Incorporation in
cell membrane
Figure 3-14
5 of 7
Endoplasmic reticulum
EXTRACELLULAR
CYTOSOL FLUID
Lysosomes
Cell
membrane
Secretory
vesicles
Transport
vesicle
Golgi apparatus
(a)
Membrane renewal
vesicles
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Vesicle
Incorporation in
cell membrane
Figure 3-14
6 of 7
Endoplasmic reticulum
EXTRACELLULAR
CYTOSOL FLUID
Lysosomes
Cell
membrane
Secretory
vesicles
Transport
vesicle
Golgi apparatus
(a)
Membrane renewal
vesicles
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
(b) Exocytosis
Vesicle
Incorporation in
cell membrane
Figure 3-14
7 of 7
The Cytoplasm
Membranous Organelles
• Lysosomes
• Packets of digestive enzymes
• Defense against bacteria
• Cleaner of cell debris
• Hazard for autolysis
• “Suicide packets”
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cytoplasm
Key Note
Cells respond directly to their
environment and help maintain
homeostasis at the cellular level.
They can also change their internal
structure and physiological functions
over time.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cytoplasm
Membranous Organelles
• Mitochondria
• 95% of cellular ATP supply
• Double membrane structure
• Outer membrane very permeable
• Inner membrane very impermeable
Folded into cristae
Filled with matrix (fluid)
Studded with ETS complexes
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cytoplasm
Mitochondria
Figure 3-15
The Cytoplasm
Key Note
Mitochondria provide most of the
energy needed to keep your cells
(and you) alive. They consume
oxygen and organic substrates,
and they generate carbon dioxide
and ATP.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Nucleus
Properties of the Nucleus
• Exceeds other organelles in size
• Controls cellular operations
• Determines cellular structure
• Directs cellular function
• Nuclear envelope separates cytoplasm
• Nuclear pores penetrate envelope
• Enables nucleus-cytoplasm exchange
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Nucleus
The Nucleus
Figure 3-16
The Nucleus
Chromosome Structure
• Location of nuclear DNA
• Instructions for protein synthesis
• 23 pairs of human chromosomes
• Histones
• Principal chromosomal proteins
• DNA-Histone complexes
• Chromatin
• DNA and associated proteins
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Nucleus
Chromosome
Structure
Figure 3-17
The Nucleus
Key Note
The nucleus contains DNA, the genetic
instructions within chromosomes. The
instructions tell how to synthesize the
proteins that determine cell structure
and function. Chromosomes also
contain various proteins that control
expression of the genetic information.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Nucleus
The Genetic Code
• Triplet code
• Comprises three nitrogenous
bases
• Specifies a particular amino acid
• A Gene
• Heredity carried by genes
• Sequence of triplets that codes
for a specific protein
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Nucleus
Protein Synthesis
• Transcription—the production of
RNA from a single strand of DNA
• Occurs in nucleus
• Produces messenger RNA (mRNA)
• Triplets specify codons on mRNA
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DNA
RNA
polymerase
Codon
1
Codon
2
Triplet 1
1
Triplet 2
2
Triplet 3
3
Gene
Complementary
triplets
Promoter
Triplet 4
mRNA
strand
Codon
1
2
4
Codon
3
Codon 4
(stop signal)
RNA
nucleotide
KEY
Adenine
Guanine
Cytosine
Uracil (RNA)
Thymine
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Figure 3-18
1 of 5
DNA
Gene
KEY
Adenine
Guanine
Cytosine
Uracil (RNA)
Thymine
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Figure 3-18
2 of 5
DNA
RNA
polymerase
Triplet 1
1
Triplet 2
2
Triplet 3
3
Gene
Triplet 4
Complementary
triplets
Promoter
2
4
KEY
Adenine
Guanine
Cytosine
Uracil (RNA)
Thymine
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Figure 3-18
3 of 5
DNA
RNA
polymerase
Triplet 1
1
Triplet 2
2
Triplet 3
3
Gene
Triplet 4
Complementary
triplets
Promoter
Codon
1
2
4
RNA
nucleotide
KEY
Adenine
Guanine
Cytosine
Uracil (RNA)
Thymine
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Figure 3-18
4 of 5
DNA
RNA
polymerase
Codon
1
Codon
2
Triplet 1
1
Triplet 2
2
Triplet 3
3
Gene
Complementary
triplets
Promoter
Triplet 4
mRNA
strand
Codon
1
2
4
Codon
3
Codon 4
(stop signal)
RNA
nucleotide
KEY
Adenine
Guanine
Cytosine
Uracil (RNA)
Thymine
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-18
5 of 5
The Nucleus
Protein Synthesis
• Translation—the assembling of a
protein by ribosomes, using the
information carried by the mRNA
molecule
• tRNAs carry amino acids
• Anticodons bind to mRNA
• Occurs in cytoplasm
PLAY
Protein Synthesis: tRNA
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
NUCLEUS
The mRNA strand binds to the small
ribosomal subunit and is joined at the
start codon by the first tRNA, which
carries the amino acid methionine.
Binding occurs between complementary base pairs of the codon and
anticodon.
mRNA
The small and large ribosomal
subunits interlock around the mRNA
strand.
Amino acid
Small
ribosomal
subunit
KEY
Adenine
tRNA
Anticodon
tRNA binding sites
Guanine
Cytosine
Uracil (RNA)
Thymine
Start codon
A second tRNA arrives at the
adjacent binding site of the
ribosome. The anticodon of the
second tRNA binds to the next
mRNA codon.
mRNA strand
The first amino acid is detached from
its tRNA and is joined to the second
amino acid by a peptide bond. The
ribosome moves one codon farther
along the mRNA strand; the first
tRNA detaches as another tRNA
arrives.
Large
ribosomal
subunit
The chain elongates until the stop
codon is reached; the components
then separate.
Small ribosomal
subunit
Peptide bond
Completed
polypeptide
Stop
codon
Large
ribosomal
subunit
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Figure 3-19
1 of 6
NUCLEUS
mRNA
The mRNA strand binds to the small
ribosomal subunit and is joined at the
start codon by the first tRNA, which
carries the amino acid methionine.
Binding occurs between complementary base pairs of the codon and
anticodon.
Amino acid
KEY
Adenine
Small
ribosomal
subunit
tRNA
Anticodon
tRNA binding sites
Guanine
Cytosine
Uracil (RNA)
Thymine
Start codon
mRNA strand
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-19
2 of 6
NUCLEUS
mRNA
The mRNA strand binds to the small
ribosomal subunit and is joined at the
start codon by the first tRNA, which
carries the amino acid methionine.
Binding occurs between complementary base pairs of the codon and
anticodon.
The small and large ribosomal
subunits interlock around the mRNA
strand.
Amino acid
KEY
Adenine
Small
ribosomal
subunit
tRNA
Anticodon
tRNA binding sites
Guanine
Cytosine
Uracil (RNA)
Thymine
Start codon
mRNA strand
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Large
ribosomal
subunit
Figure 3-19
3 of 6
NUCLEUS
The mRNA strand binds to the small
ribosomal subunit and is joined at the
start codon by the first tRNA, which
carries the amino acid methionine.
Binding occurs between complementary base pairs of the codon and
anticodon.
mRNA
The small and large ribosomal
subunits interlock around the mRNA
strand.
Amino acid
Small
ribosomal
subunit
KEY
Adenine
tRNA
Anticodon
tRNA binding sites
Guanine
Cytosine
Uracil (RNA)
Thymine
Start codon
mRNA strand
Large
ribosomal
subunit
A second tRNA arrives at the
adjacent binding site of the
ribosome. The anticodon of the
second tRNA binds to the next
mRNA codon.
Stop
codon
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-19
4 of 6
NUCLEUS
The mRNA strand binds to the small
ribosomal subunit and is joined at the
start codon by the first tRNA, which
carries the amino acid methionine.
Binding occurs between complementary base pairs of the codon and
anticodon.
mRNA
The small and large ribosomal
subunits interlock around the mRNA
strand.
Amino acid
Small
ribosomal
subunit
KEY
Adenine
tRNA
Anticodon
tRNA binding sites
Guanine
Cytosine
Uracil (RNA)
Thymine
Start codon
A second tRNA arrives at the
adjacent binding site of the
ribosome. The anticodon of the
second tRNA binds to the next
mRNA codon.
mRNA strand
Large
ribosomal
subunit
The first amino acid is detached from
its tRNA and is joined to the second
amino acid by a peptide bond. The
ribosome moves one codon farther
along the mRNA strand; the first
tRNA detaches as another tRNA
arrives.
Peptide bond
Stop
codon
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-19
5 of 6
NUCLEUS
The mRNA strand binds to the small
ribosomal subunit and is joined at the
start codon by the first tRNA, which
carries the amino acid methionine.
Binding occurs between complementary base pairs of the codon and
anticodon.
mRNA
The small and large ribosomal
subunits interlock around the mRNA
strand.
Amino acid
Small
ribosomal
subunit
KEY
Adenine
tRNA
Anticodon
tRNA binding sites
Guanine
Cytosine
Uracil (RNA)
Large
ribosomal
subunit
Thymine
Start codon
A second tRNA arrives at the
adjacent binding site of the
ribosome. The anticodon of the
second tRNA binds to the next
mRNA codon.
mRNA strand
The first amino acid is detached from
its tRNA and is joined to the second
amino acid by a peptide bond. The
ribosome moves one codon farther
along the mRNA strand; the first
tRNA detaches as another tRNA
arrives.
The chain elongates until the stop
codon is reached; the components
then separate.
Small ribosomal
subunit
Peptide bond
Completed
polypeptide
Stop
codon
Large
ribosomal
subunit
PLAY
Transcription and Translation
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-19
6 of 6
The Nucleus
Key Note
Genes are the functional units of DNA
that contain the instructions for making
one or more proteins. The creation of
specific proteins involves multiple
enzymes and three types of RNA.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Life Cycle
Cell division—The reproduction of
cells
Apoptosis—Genetically programmed
death of cells
Mitosis—The nuclear division of
somatic cells
Meiosis—The nuclear division of sex
cells
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Life Cycle
The Cell Life
Cycle
• Highly Variable
•Interphase
duration
•Mitotic
frequency
Figure 3-20
The Cell Life Cycle
DNA Replication
Figure 3-21
The Cell Life Cycle
Mitosis—A process that separates and
encloses the duplicated chromosomes
of the original cell into two identical
nuclei
• Four phases in mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Life Cycle
Cytokinesis
Division of the cytoplasm
to form two identical
daughter cells
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Life Cycle
Mitotic Phases
• Prophase
• Chromosomes condense
• Chromatids connect at centromeres
• Metaphase
• Chromatid pairs align at metaphase plate
• Anaphase
• Daughter chromosomes separate
• Telophase
• Nuclear envelopes reform
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Interphase
Nucleus
Early prophase
Mitosis
begins
Spindle
fibers
Centrioles
(two pairs)
Metaphase
Late prophase
Centromeres
Anaphase
Chromosome
with two
sister chromatids
Telophase
Separation
Daughter
chromosomes
Cytokinesis
Metaphase
plate
Cleavage
furrow
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Daughter
cells
Figure 3-22
1 of 8
Interphase
Nucleus
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Figure 3-22
2 of 8
Interphase
Nucleus
Mitosis
begins
Early prophase
Spindle
fibers
Centrioles
(two pairs)
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Figure 3-22
3 of 8
Interphase
Nucleus
Mitosis
begins
Centrioles
(two pairs)
Early prophase
Late prophase
Spindle
fibers
Centromeres
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Chromosome
with two
sister chromatids
Figure 3-22
4 of 8
Interphase
Nucleus
Mitosis
begins
Centrioles
(two pairs)
Early prophase
Late prophase
Spindle
fibers
Centromeres
Chromosome
with two
sister chromatids
Metaphase
Metaphase
plate
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-22
5 of 8
Interphase
Nucleus
Early prophase
Mitosis
begins
Spindle
fibers
Centrioles
(two pairs)
Metaphase
Late prophase
Centromeres
Chromosome
with two
sister chromatids
Anaphase
Daughter
chromosomes
Metaphase
plate
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-22
6 of 8
Interphase
Nucleus
Early prophase
Mitosis
begins
Spindle
fibers
Centrioles
(two pairs)
Metaphase
Late prophase
Centromeres
Anaphase
Chromosome
with two
sister chromatids
Telophase
Daughter
chromosomes
Metaphase
plate
Cleavage
furrow
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 3-22
7 of 8
Interphase
Nucleus
Early prophase
Mitosis
begins
Spindle
fibers
Centrioles
(two pairs)
Metaphase
Late prophase
Centromeres
Anaphase
Chromosome
with two
sister chromatids
Telophase
Separation
Daughter
chromosomes
Cytokinesis
Metaphase
plate
Cleavage
furrow
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Daughter
cells
Figure 3-22
8 of 8
The Cell Life Cycle
Key Note
Mitosis is the separation of
duplicated chromosomes into
two identical sets and nuclei in
the process of somatic cell
division.
PLAY
Interphase, Mitosis, and Cytokinesis
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Life Cycle
Cell Division and Cancer
• Abnormal cell growth
• Tumors (also called, neoplasm)
• Benign
• Encapsulated
• Malignant
• Invasive
• Metastasis
• Cancer—Disease that results from
unchecked cellular division
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
The Cell Life Cycle
Key Note
Cancer results from mutations that
disrupt the control mechanism that
regulates cell growth and division.
Cancers most often begin where
cells are dividing rapidly, because
the more chromosomes are copied,
the greater the chances of error.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Cell Diversity and Differentiation
Somatic Cells
• All have same genes
• Some genes inactivate during
development
• Cells thus become functionally
specialized
• Specialized cells form distinct tissues
• Tissue cells become differentiated
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings