Chapter 3: The Cellular Level of Organization

1
Chapter 3 The Cellular Level of Organization
2
Cellular Organization

• Cell smallest living unit
• Performs all life functions

Figure 31
3
Two Categories of Cells

• Sex cells (germ cells)
• reproductive cells
• male sperm
• female oocytes (eggs)
• Somatic cells (soma body)
• all body cells except sex cells

4
Cellular Organization

• Different cells have different shapes
• Unique morphology is related to function
• All cells surrounded by plasma membrane
• Separates cells from the environment
• Plasma membrane holds in the cytoplasm
• Cytoplasm consists of cytosol (fluid) and
  organelles (structures)
• Body cells surrounded by interstitial fluid
• Interstitial fluid fluid outside the membrane

5
Organelle Functions
Table 31 (1 of 2)
6
Organelle Functions
Table 31 (2 of 2)
7
The structures and functions of the cell
membrane.
8
1. The Plasma (Cell) Membrane
- Mostly phospholipid bilayer - Interface between
cell and environment
Figure 32
9
Functions of Plasma (Cell) Membrane

• Physical barrier
• Maintain homeostasis
• Separates intracellular fluid from extracellular
  fluid, different conditions in each
• Regulates exchange with environment
• ions and nutrients enter
• waste and cellular products released
• Monitors the environment
• extracellular fluid composition
• Cell communication and signaling
• Structural support
• anchors cells and tissues

10
Plasma Membrane Components

• Phospholipid bilayer
• Cholesterol resist osmotic lysis
• Carbohydrates
• Proteins

11
Plasma Membrane Components

• 1. Phospholipid Bilayer
• hydrophilic headstoward watery environment, both
  sides
• hydrophobic fatty-acid tailsinside membrane
• barrier to ions and water soluble compounds
• 2. Cholesterol resist osmotic lysis

12
Plasma Membrane Components

• 3. Carbohydrates
• Membrane Carbohydrates including
• Proteoglycans, glycoproteins, and glycolipids
• extend outside cell membrane
• form sticky carb layer or sugar coat called the
  glycocalyx

13
Functions of Membrane Carbohydrates

• Lubrication and protection
• Anchoring and locomotion
• Specificity in binding
• Acts as receptors
• Recognition
• Self recognition
• immune response

14
Plasma Membrane Components

• 4. Protein
• ½ mass of membrane
• Integral proteins span width of membrane
• within the membrane
• Peripheral proteins
• Adhere to inner or outer surface of the membrane

15
6 Functions of Membrane Proteins

• Anchoring proteins (stabilizers)
• attach to inside or outside structures
• Recognition proteins (identifiers)
• Self identification by immune system
• Label cells normal or abnormal
• Enzymes
• catalyze reactions in cytosol in extra cellular
  fluid
• Receptor proteins
• bind and respond to ligands (ions, hormones) or
  signaling, or import/export
• Carrier proteins
• transport specific solutes through membrane
• Channels
• regulate water flow and solutes through membrane

16
Which component of the cell membrane is primarily
responsible for the membranes ability to form a
physical barrier between the cells internal and
external environments?
A. phospholipid bilayer B. glycocalyx C.
peripheral proteins D. proteoglycans
17
Which type of integral protein allows water and
small ions to pass through the cell membrane?
A. receptor proteins B. carrier proteins C.
channel proteins D. recognition proteins
18
How things get in and out of cells.
19
Overcoming the Cell Barrier

• The cell membrane is a barrier, but
• nutrients must get in
• products and wastes must get out
• Permeability determines what moves in and out of
  a cell
• A membrane that
• lets nothing in or out is impermeable
• lets anything pass is freely permeable
• restricts movement is selectively permeable

20
Selective Permeability

• Cell membrane is selectively permeable
• allows some materials to move freely
• restricts other materials
• Restricts materials based on
• size
• electrical charge
• molecular shape
• lipid solubility

21
Transport

• Transport through a cell membrane can be
• active (requiring energy and ATP)
• passive (no energy required)
• 3 Categories of Transport
• Diffusion (passive)
• Carrier-mediated transport (passive or active)
• Vesicular transport (active)

22
Solutions

• All molecules are constantly in motion
• Molecules in solution move randomly
• Random motion causes mixing

23
Concentration Gradient

• Concentration is the amount of solute (glucose)
  in a solvent (e.g. H20)
• Concentration gradient
• more solute in 1 part of a solvent than another
• Function Diffusion
• molecules mix randomly
• solute spreads through solvent
• eliminates concentration gradient
• Solutes move down a concentration gradient
• From high concentration to low concentration

24
Factors Affecting Diffusion Rates

• Distance the particle has to move
• Molecule size
• smaller is faster
• Temperature
• more heat, faster motion
• Gradient size
• the difference between high and low concentration
• Electrical forces
• opposites attract, like charges repel

25
Diffusion and the Cell Membrane

• Diffusion can be simple or channel-mediated

Figure 315
26
Simple Diffusion

• Materials which diffuse through cell membrane
• lipid-soluble compounds (alcohols, fatty acids,
  and steroids)
• dissolved gases (oxygen and carbon dioxide)

27
Channel-Mediated Diffusion

• Materials which pass through transmembrane
  proteins (channels)
• are water soluble compounds
• are ions
• Passage depends on
• size
• charge
• interaction with
• the channel

28
Osmosis

• Osmosis is the diffusion of water across the cell
  membrane

Figure 316
29
How Osmosis Works

• More solute molecules, lower concentration of
  water molecules
• Membrane must be freely permeable to water,
  selectively permeable to solutes
• Osmosis Water Movement
• Water molecules diffuse across membrane toward
  solution with more solutes
• Volume increases on the side with more solutes
• Osmotic Pressure
• Is the force of a concentration gradient of water
• Equals the force (hydrostatic pressure) needed to
  block osmosis

30
Osmotic Pressure
31
Isotonic

• A solution that does not cause osmotic flow of
  water in or out of a cell
• iso same, tonos tension
• The osmotic effect of a solute on a cell
• 2 fluids may have equal osmolarity

Figure 317a
32
Cells and Hypotonic Solutions

• hypo below
• Has less solutes
• Loses water through osmosis
• A cell in a hypotonic solution
• gains water
• ruptures (hemolysis of red blood cells)

Lysis
Figure 317b
33
Cells and Hypertonic Solutions

• hyper above
• Has more solutes
• Gains water by osmosis
• A cell in a hypertonic solution
• loses water
• shrinks (crenation of red blood cells)

Crenation
Figure 317c
34
KEY CONCEPT

• Concentration gradients tend to even out
• In the absence of membrane, diffusion eliminates
  concentration gradients
• When different solute concentrations exist on
  either side of a selectively permeable membrane,
  osmosis moves water through the membrane to
  equalize the concentration gradients

35
How would a decrease in the concentration of
oxygen in the lungs affect the diffusion of
oxygen into the blood?

1. decrease in molecule size results in decreased
   diffusion
2. decrease in distance results in increased
   diffusion
3. increase in electrical forces results in
   increased diffusion
4. decrease in gradient size results in decreased
   speed of diffusion

36
Some pediatricians recommend the use of a 10
salt solution to relieve congestion for infants
with stuffy noses. What effect would such a
solution have on the cells lining the nasal
cavity, and why?
A. Cells will lose water because this is a
hypertonic solution. B. Cells will lose water
because this is a hypotonic solution. C. Cells
will gain water because this is a hypertonic
solution. D. Cells will gain water because this
is a hypotonic solution.
37
Carrier-Mediated Transport

• Carrier-mediated transport of ions and organic
  substrates
• facilitated diffusion (No energy needed)
• active transport (Energy is needed)

38
Characteristics of Carrier-Mediated Transport

• Specificity
• 1 transport protein, 1 set of substrates
• Saturation limits
• rate depends on transport proteins, not substrate
  (same as enzymatic reactions)
• Regulation
• cofactors such as hormones

39
Carrier-Mediated Transport

• Cotransport
• 2 substances move in the same direction at the
  same time
• Countertransport
• 1 substance moves in while another moves out

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Facilitated Diffusion

• Passive, Carrier mediated
• Carrier proteins transport molecules too large to
  fit through channel proteins (glucose, amino
  acids)
• molecule binds to receptor site on carrier
  protein
• protein changes shape, molecules pass through
• receptor site is specific to certain molecules

Figure 318
41
Active Transport

• Active transport proteins
• move substrates against concentration gradient
• require energy, such as ATP
• ion pumps move ions (Na, K, Ca, Mg2)
• exchange pump countertransports 2 ions at the
  same time

42
Active Transport, Carrier Mediated

• E.g. Sodium-Potassium Exchange Pump
• 3 Na out
• 2 K in
• 1 ATP Moves 3 Na
• 40 cell ATP

43
Secondary Active Transport

• Na concentration gradient drives glucose
  transport
• ATP energy pumps Na back out

Cotransport
Countertransport
Figure 320
44
Transport Vesicles

• Also called bulk transport
• Vesicles
• endocytosis (endo into)
• active transport using ATP
• receptor-mediated
• pinocytosis
• phagocytosis
• exocytosis (exo out of)

45
Receptor-Mediated Endocytosis
Figure 321
46
Receptor-Mediated Endocytosis

• Receptors (glycoproteins) bind target molecules
  (ligands)
• Coated vesicle (endosome) carries ligands and
  receptors into the cell

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Pinocytosis

• Pinocytosis (cell drinking)
• Endosomes drink extracellular fluid and enclose
  it in membranous vesicles at the cell surface
• Similar to the steps in receptor-mediated
  endocytosis, except that ligand binding is not
  the trigger

Figure 322a
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Phagocytosis

• Phagocytosis (cell eating)
• pseudopodia (psuedo false, podia feet)
• engulf large objects in phagosomes

Figure 322b
49
Exocytosis

• Is the reverse of endocytosis

Figure 37b
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Summary

• The 7 methods of transport

Table 33
51
Transmembrane potential
52
Electrical Charge

• Selective permeability of membrane allows
  different concentrations of molecules in/outside
  cells
• Cell membrane
• Inside cell slightly negative
• due to the abundance of proteins
• Outside cell slightly positive
• due to cations in extracellular fluids
• Phospholipids hold charges apart creating a
  transmembrane potential
• Unequal charge across the cell membrane
• Resting potential ranges from
• 10 mV to 100 mV, depending on cell type

53
During digestion in the stomach, the
concentration of hydrogen ions (H) rises to many
times that in cells of the stomach. Which
transport process could be responsible?
A. facilitated diffusion B. osmosis C. active
transport D. endocytosis
54
During digestion in the stomach, the
concentration of hydrogen ions (H) rises to many
times that in cells of the stomach. Which
transport process could be responsible?
A. facilitated diffusion B. osmosis C. active
transport D. endocytosis
55
If the cell membrane were freely permeable to
sodium ions (Na), how would the transmembrane
potential be affected?
A. it would move closer to zero B. it would
become more positive C. it would become more
negative D. it would become unstable
56
When they encounter bacteria, certain types of
white blood cells engulf the bacteria and bring
them into the cell. What is this process called?
A. pseudocytosis B. exocytosis C.
pinocytosis D. phagocytosis
57
Increase Surface Area Microvilli

• Surface area of membrane can be increased by
  microvilli
• For absorption or secretion
• Microvilli fingers of cell membrane containing
  a web of microfilaments and cytoplasm, anchored
  to cytoskeleton

58
2. Cytoplasm

• Material enclosed by plasma membrane
• Occupies space between plasma membrane and
  nuclear membrane
• Components
• cytosol (fluid)
• High K, low Na
• Colloid Solution proteins and enzymes
• Nutrient Reserves carbohydrates, lipids, and
  amino acids
• Inclusions
• Type and number varies with cell
• E.g. glycogen, melanin, steroids, etc.
• organelles
• Carry out cellular functions
• Each has separate function
• Some have membranes
• Some free in cytosol

59
Cell organelles and their functions
60
Types of Organelles

• Nonmembranous organelles
• no membrane
• direct contact with cytosol
• Membranous organelles
• covered with plasma membrane
• isolated from cytosol

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Nonmembranous Organelles

• 6 types of nonmembranous organelles
• cytoskeleton
• Microvilli
• centrioles
• cilia
• ribosomes
• proteasomes

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3. The Cytoskeleton

• Structural proteins for shape and strength
  (Internal Framework)
• 4 types of filaments
• Microfilaments
• Intermediate filaments
• Thick filaments
• Microtubules

Figure 33a
63
A. Microfilaments

• Thin filaments (lt6nm diameter)
• Composed of the protein actin
• Usually at periphery of the cell
• Functions
• provide additional strength by attaching the
  membrane to the cytoplasm
• Attach integral proteins to cytoskeleton
• Pairs with thick filaments of myosin for muscle
  movement

64
Intermediate Filaments Thick Filaments

• B. Intermediate Filaments
• 7-11 nm diameter
• Mid-sized between microfilaments and thick
  filaments
• Durable, type varies with cell (collagen,
  elastin, keratin)
• Functions
• strengthen cell and maintain shape
• stabilize position of organelles
• stabilize the cell relative to other cells
• C. Thick Filaments
• 15 nm diameter
• Composed of myosin
• Muscle cells only
• Function
• Interact with actin to produce movement

65
D. Microtubules

• Large (25nm diameter), hollow tubes
• Composed of tubulin protein
• Originate from centrosome
• Functions
• Foundation of the cytoskeleton
• Allows the cell to change shape and assists in
  mobility
• Involved in transport
• Molecular motors travel along microtubule
  tracks
• move vesicles within cell
• Makes up the spindle apparatus for nuclear
  division (mitosis)
• The structural part of some organelles
• Centrioles, cilia, flagella

66
4. Centrioles in the Centrosome

• Centrioles form spindle apparatus during cell
  division
• Centrosome cytoplasm surrounding centriole near
  the nucleus
• Consists of matrix and paired centrioles
• Functions as microtubule organizing center
• Responsible for assembling spindle apparatus
  during mitosis

Figure 34a
67
5. Cilia and Flagella

• Hair like projections
• Contain a microtubule core with cytoplasm covered
  in plasma membrane
• Anchored in the cytosol by basal bodies
• Cilia Short, numerous
• Function sweep substances over cell surface
• Flagella Long, singular
• Function propel cell through environment

Figure 34b,c
68
6. Ribosomes

• Site of protein synthesis (polypeptide formation)
• Two subunits composed of rRNA protein
• free ribosomes in cytoplasm
• Manufacture proteins for use in cytoplasm
• fixed ribosomes attached to Endoplasmic
  reticulum
• Manufacture proteins for export or use in membrane

69
Cells lining the small intestine have numerous
fingerlike projections on their free surface.
What are these structures, and what is their
function?
A. microvilli move substances across cell
surface B. microvilli increase cells surface
area and absorptive ability C. cilia increase
cells surface area and absorptive ability D.
cilia move substances across cell surface
70
Membranous Organelles

• 5 types of membranous organelles
• endoplasmic reticulum (ER)
• Golgi apparatus
• lysosomes
• peroxisomes
• mitochondria

71
7. Endoplasmic Reticulum (ER)
Location - Attached to the Nuclear
Envelope
Figure 35a
72
Endoplasmic Reticulum (ER)

• endo within, plasm cytoplasm, reticulum
  network
• Cisternae are storage chambers within membranes
• Function
• Synthesis of proteins, carbohydrates, and lipids
• Storage of synthesized molecules and materials
• Transport of materials within the ER
• Detoxification of drugs or toxins

73
Smooth Endoplasmic Reticulum (SER)

• No ribosomes attached
• Tubular Membrane
• Functions
• Lipid metabolism (synthesis, breakdown,
  transport)
• Synthesis of steroid hormones (reproductive
  system)
• Detoxification of drugs
• Breakdown of glycogen (storage in muscles) to
  glucose
• Store ions (e.g. Ca2)

74
Rough Endoplasmic Reticulum (RER)

• Surface covered with ribosomes
• Ribosomes synthesize proteins and feed them into
  RER cisternae to be modified
• E.g. carbs glycoprotein
• Modified proteins are put into transport vesicles
  to go to Golgi
• These proteins for exocytosis or use in membrane

• Surface covered with ribosomes
• Ribosomes synthesize proteins and feed them into
  RER cisternae to be modified
• E.g. carbs glycoprotein
• Modified proteins are put into transport vesicles
  to go to Golgi
• These proteins for exocytosis or use in membrane

75
Golgi Apparatus

• Stack of cisternae with associated transport
  vesicles
• Near nucleus but not attached
• Function
• Modify, concentrate, and sort export proteins

Figure 36a
76
Golgi Apparatus

• Transport vesicles from RER dock on cis (forming)
  face of golgi and release contents into golgi
• Proteins (and glycoproteins) are modified
• Phosphate, carbs, or lipids attached
• Proteins transit between cisternae via vesicles
  from cis face (forming) to trans face (maturing)

77
Vesicles of the Golgi Apparatus

• At trans face, proteins are packaged into
• Secretory vesicles
• modify and package products for exocytosis
• Membrane renewal vesicles
• Carry products to membrane
• Lysosomes
• Membrane bound sacs of digestive enzymes

78
Exocytosis

• Ejects secretory products and wastes

Figure 37b
79
9. Lysosomes

• Powerful enzyme-containing vesicles
• lyso dissolve, soma body
• Digestion centers for large molecules or
  structures
• Endosomes or phagosomes containing endocytosed
  things, and organelles targeted for destruction
  are fused with lysosome and broken down
• Some solutes diffuse into cytoplasm for use,
  remaining debris are exocytosed

Figure 38
80
Lysosome Structures and Function

• Primary lysosome
• formed by Golgi and inactive enzymes
• Secondary lysosome
• lysosome fused with damaged organelle
• digestive enzymes activated
• toxic chemicals isolated
• Functions
• Clean up inside cells
• break down large molecules
• Attack bacteria
• recycle damaged organelles
• ejects wastes by exocytosis

81
Autolysis

• Self-destruction of damaged cells
• auto self, lysis break
• lysosome membranes break down
• digestive enzymes released
• cell decomposes
• cellular materials recycle

82
Tay Sachs Disease

• Caused by lysosomes that fail to break down
  glycolipids in nerve cells
• Accumulation of glycolipids disrupts nerve
  function
• Progressive mental retardation
• Death by age 18 months

83
10. Peroxisomes

• Are enzyme-containing vesicles
• break down fatty acids
• Membrane sacs containing oxidases and catalases
  to neutralize free radicals that are formed
  during catabolism of organic molecules
• produce hydrogen peroxide (H2O2)
• Peroxisomes not made by golgi
• appear to self replicate

84
11. Proteasomes

• Cylindrical structure composed of protein
  digesting enzymes (proteases)
• Disassemble damaged proteins for recycling
• E.g. degrade proteins tagged with ubiquitin to
  recycle amino acids

85
KEY CONCEPT

• Cells basic structural and functional units of
  life
• respond to their environment
• maintain homeostasis at the cellular level
• modify structure and function over time

86
12. Mitochondrion Structure

• Sausage-shaped with double membrane
• Outer membrane Smooth
• Inner membrane folded into cristae
• Center matrix

Figure 39a
87
Mitochondrial Function Power House of the Cell

• Aerobic respiration occurs on surface of cristae
• takes chemical energy from food (glucose)
• With the use of oxygen, Glucose is catabolized
  creating CO2 waste to convert ADP into ATP
• Mitochondria supply most of cells energy
• Have their own DNA (maternal)
• Can replicate independent of the cell

glucose oxygen ADP carbon dioxide
water ATP
Figure 39b
88
KEY CONCEPT

• Mitochondria provide cells with energy for life
• require oxygen and organic substrates
• generate carbon dioxide and ATP

89
Certain cells in the ovaries and testes contain
large amounts of smooth endoplasmic reticulum
(SER). Why?
A. to produce large amounts of proteins B. to
digest materials quickly C. to store large
amounts of hormones D. to produce large amounts
of steroid hormones
90
What does the presence of many mitochondria imply
about a cells energy requirements?
A. a high demand for energy B. a low demand for
energy C. fluctuating energy needs requiring
flexibility D. number of mitochondria provides
no implication of energy needs
91
How the nucleus controls the cell
92
13. The Nucleus

• Is the cells control center
• Contains DNA genetic material
• Most cells have one, exceptions
• Skeletal muscle (many), RBCs (none)

Figure 310a
93
Structure of the Nucleus

• Nucleus
• largest organelle
• Nuclear envelope
• double membrane around the nucleus, connected to
  ER
• Nuclear pores with regulator proteins
• Control exchange of materials between cytoplasm
  and nucleus

94
Within the Nucleus

• Nucleoplasm
• fluid containing ions, proteins (enzymes), DNA,
  RNA, and nucleoli
• Nucleoli Dark areas
• site of rRNA synthesis and packaging into
  ribosomal subunits
• In non-dividing cells DNA is loose
• Called chromatin

95
Organization of DNA

• DNA in chromatin is organized into Nucleosomes
• DNA coiled around histones
• During Nuclear Division, Chromatin is tightly
  coiled into visible chromosomes (23 pairs in
  humans)
• Chromosomes
• tightly coiled DNA (cells dividing)

Figure 311
96
The Genetic Code
97
DNA and Genes

• DNA contains genes
• instructions for every protein in the body
• Gene functional units of heredity
• DNA instructions for a product RNA or protein
• Humans have 30-75 thousand potential genes (only
  1.5 of total DNA)
• Remainder is involved with control of genes or
  appear to be junk (25)
• Noncoding parts of DNA (non-genes) is highly
  variable from one person to the next
• Variability allows for identification of an
  individual by DNA fingerprinting

98
Gene Activation

• In order for a gene to be expressed (used to make
  a product) it must be unwound from the histone
  proteins so it can be read
• Disassembly of the nucleosomes and unwinding of
  the DNA is called gene activation

99
Genetic Code

• The chemical language of DNA instructions
• Read off a gene in order to assemble a protein
• sequence of bases (A, T, C, G)
• triplet code
• 3 bases of DNA 1 amino acid (codon)
• A gene all the codons for all the amino acids
  in one protein in the correct order

100
Gene Structure and Expression

• Structure
• Expression
• (original) (copy)
  (product)
• DNA RNA Protein
• Transcription Translation

Open Reading Frame
Promoter
Terminator
Stop Codon
Start Codon
101
KEY CONCEPT

• The nucleus contains chromosomes
• Chromosomes contain DNA
• DNA stores genetic instructions for proteins
• Proteins determine cell structure and function

102
How DNA instructions become proteins
103
Protein Synthesis

• Transcription
• copies instructions from DNA to mRNA (in nucleus)
• Translation
• ribosome reads code from mRNA (in cytoplasm)
• assembles amino acids into polypeptide chain
• Processing
• by RER and Golgi apparatus produces protein

104
mRNA Transcription

• A DNA gene is transcribed to mRNA in 3 steps
• gene activation
• DNA to mRNA
• RNA processing

105
mRNA Transcription
106
Step 1 Gene Activation

• Uncoils DNA, removes histones
• Start (promoter) and stop codes on DNA mark
  location of gene
• coding strand is code for protein
• template strand used by RNA polymerase molecule

107
Step 2 DNA to mRNA

• Enzyme RNA polymerase transcribes DNA
• binds to promoter (start) sequence
• reads DNA code for gene
• binds nucleotides to form messenger RNA (mRNA)
• mRNA duplicates DNA coding strand, uracil
  replaces thymine

108
Step 3 RNA Processing

• At stop signal, mRNA detaches from DNA molecule
• code is edited (RNA processing)
• unnecessary codes (introns) removed
• good codes (exons) spliced together
• triplet of 3 nucleotides (codon) represents one
  amino acid

109
Codons
Table 32
110
Key Concept

• The timing of gene activation (transcription) for
  any gene is controlled by signals from outside
  the nucleus, either from within the cell or in
  response to external cues
• E.g. Hormones

111
Translation

• Making a protein using the mRNA blueprint
• Occurs in the cytoplasm on free ribosomes or on
  fixed ribosomes on the RER
• mRNA moves
• from the nucleus
• through a nuclear pore

Figure 313
112
Translation

• tRNA delivers amino
• acids to mRNA

113
Translation
114
Genetic Code
115
Examples using the Genetic Code

• Coding Strand DNA
• ATgCAgTTTACgCAgAAgATCAgTTAg
• Template strand DNA complement A-T, C-G
• TACgTCAAATgCgTCTTCTAgTCAATC
• Transcription to form mRNA
• complementary base pairing to template, U
  replaces T
• AUgCAgUUUACgCAgAAgAUCAgUUAg
• Translation to form protein read codons from
  genetic code
• e.g. AUg Met/Start (start codon)
• Aug/CAg/UUU/ACg/CAg/AAg/AUC/AgU/UAg
• Met-Gln-Phe-Thr-Glu-Lys-Ile-Ser
• UAg stop codon (no tRNA, no amino acid)

116
Mutations

• Most non-infectious disease, conditions, and
  disorders are due to mutations in the DNA that
  change the amino acids in the protein
• E.g. sickle cell anemia
• Point mutation in DNA A ? T
• Changes on codon GAG ? GTG
• Changes one amino acid
• Glutamic acid (-charge) ? valine (neutral)
• This alters the 3D shape of the whole hemoglobin
  protein globular ? fibrous
• Which changes the shape of the red blood cell
• Disc ? crescent
• Which prevents the RBC from carrying oxygen, and
  causes it to block capillaries

117
Mutations

• Point mutations change in 1 base of DNA can be
  a silent mutation if the amino acids is not
  changed
• common at the 3rd base in a codon
• Insertion mutation addition of a base which
  changes the reading framewhole protein after the
  mutation is wrong
• Deletion Mutation removal of a base, alter
  reading frame, protein wrong.

118
KEY CONCEPT

• Genes
• are functional units of DNA
• contain instructions for 1 or more proteins
• Protein synthesis requires
• several enzymes
• ribosomes
• 3 types of RNA
• Mutation is a change in the nucleotide sequence
  of a gene
• can change gene function
• Causes
• exposure to chemicals
• exposure to radiation
• mistakes during DNA replication

119
How does the nucleus control the activities of a
cell?
A. through nuclear pores B. through the nuclear
matrix C. through DNA D. through RNA
120
What process would be affected by the lack of the
enzyme RNA polymerase?
A. nothing would be affected DNA polymerase
would take over B. cells ability to duplicate
DNA C. cells ability to translate DNA D.
cells ability to transcribe RNA
121
How cells reproduce
122
Cell Life Cycle

• Life span of cell depends on type of cell
• All cells eventually die
• Apoptosis controlled cell death, lysosomes are
  defused
• Some cells must divide to make cells to replace
  dying cells function of stem cells
• To divide, DNA must be replicated and equally
  distributed between the stem cell and new
  daughter cell

Figure 33
123
Interphase

• Most of a cells life is spent in a nondividing
  state (interphase)
• Period of time that a cell performs its normal
  functions
• The nondividing period
• G-zero phasespecialized cell functions only
• If a cell never divides
• Cells preparing for dividing, will go through 3
  stages
• G1 phasecell growth, organelle duplication,
  protein synthesis, synthesizes enough cytoplasm
  for 2 cells
• S phaseDNA replication and histone synthesis
• G2 phasefinishes protein synthesis and centriole
  replication

124
3 Stages of Cell Division

• Body (somatic) cells divide in 3 stages
• DNA replication duplicates genetic material
  exactly
• Mitosis divides genetic material equally
• Cytokinesis divides cytoplasm and organelles into
  2 daughter cells

125
DNA Replication
126
DNA Replication

• DNA helicases unwind the DNA and separates the
  strands
• DNA polymerase bind to the DNA and synthesizes
  complementary antiparallel strands
• DNA polymerase only add to the 3 end of the
  molecule
• Leading strand synthesized continuously
• Lagging strand synthesized in pieces called
  Okasaki fragments
• Okasaki fragments are attached end to end into
  one strand by DNA Ligase
• DNA rewinds into double helix molecules
• New molecules contains one strand of the original
  DNA and one newly synthesized strand

Figure 324
127
Overview of Cell Life Cycle
128
Mitosis

• Mitosis (nuclear division) divides duplicated DNA
  into 2 sets of chromosomes
• DNA coils tightly into chromatids
• chromatids connect at a centromere
• protein complex around centromere called the
  kinetochore
• Followed by cytokinesis
• Separation of the cells

129
Stage 1 Prophase

• Nucleoli disappear
• Centriole pairs move to cell poles
• Microtubules (spindle fibers) extend between
  centriole pairs
• Nuclear envelope disappears
• Spindle fibers attach to kinetochore

Figure 325 (Stage 1)
130
Stage 2 Metaphase

• Chromosomes align in a central plane (metaphase
  plate)

Figure 325 (Stage 2)
131
Stage 3 Anaphase

• Microtubules pull chromosomes apart
• Daughter chromosomes groups near centrioles

Figure 325 (Stage 3)
132
Stage 4 Telophase

• Nuclear membranes reform
• Chromosomes uncoil
• Nucleoli reappear
• Cell has 2 complete nuclei

Figure 325 (Stage 4, 1 of 2)
133
Overview of Mitosis
134
KEY CONCEPT

• Mitosis duplicates chromosomes in the nucleus for
  cell division

135
Stage 4 Cytokinesis

• Division of the cytoplasm
• Cleavage furrow around metaphase plate
• Membrane closes, producing daughter cells

Figure 325 (Stage 4, 2 of 2)
136
What regulates cell division
137
Mitotic Rate and Life Span

• Rate of cell division
• slower mitotic rate means longer cell life
• cell division requires energy (ATP)
• Cell Life Span
• Muscle cells, neurons rarely divide
• Exposed cells (skin and digestive tract) live
  only days or hours

138
Regulating Cell Life

• Normally, cell division balances cell loss
• Increases cell division
• internal factors (MPF)
• extracellular chemical factors (growth factors)
• Decreases cell division
• repressor genes (faulty repressors cause cancers)
• worn out telomeres (terminal DNA segments)

139
Chemicals Controlling Cell Division
Table 34
140
A cell is actively manufacturing enough
organelles to serve two functional cells. This
cell is probably in which phase of its life cycle?
A. S B. G1 C. G2 D. M
141
During DNA replication, a nucleotide is deleted
from a sequence that normally codes for a
polypeptide. What effect will this deletion have
on the amino acid sequence of the polypeptide?
A. no effect, deletion will be skipped B. no
effect, deletion will be automatically
repaired C. amino acid sequence will
disintegrate D. the amino acid sequence would be
altered
142
What would happen if spindle fibers failed to
form in a cell during mitosis?
A. centromeres would not appear B. nuclear
membrane would not disintegrate C. chromosomes
would not separate D. chromatin would not
condense
143
Cancer

• Cell division controlled by internal and
  external factors
• In adult cell growth cell death
• If growth exceeds death a tumor can form
• Cancer
• illness that disrupts cellular controls
• produces malignant cells

144
Cancer

• Benign tumors
• grow in a connective tissue capsule and remain
  in one place
• Malignant tumor ignore growth control mechanisms
• spread into surrounding tissues (invasion)
• start new tumors (metastasis)
• Cancer develops in steps
• 1. abnormal cell 3. metastasis
• 2. primary tumor 4. secondary tumor

145
Cancer

• Cancer caused by mutation in a growth control
  gene (oncogene mutated genes that cause cancer)
• 1 tumor cells grow uncontrolled
• 2 tumor cells metastasize in blood and lymph to
  establish new growth elsewhere
• Tumors trigger growth of blood vessels to support
  the cells
• In order for diffusion to bring nutrients and
  remove wastes all cells have to be within 125µm
  of a vessel
• Eventually the tumor will crowd out normal
  tissues causing organ failure

Figure 326
146
KEY CONCEPT

• Mutations disrupt normal controls over cell
  growth and division
• Cancers often begin where stem cells are dividing
  rapidly
• More chromosome copies mean greater chance of
  error

147
Cell Differentiation
148
What is cell differentiation?

• Cells specialize or differentiate
• All somatic cells in the body have the same DNA
  but different sizes, shapes, and functions
• As cells specialize to become a specific cell
  type many genes get turned off permanently, cells
  are considered differentiated
• Differentiated cells only express genes related
  to their function
• Stem cells are undifferentiated
• Embryonic stem cells can express all of their
  genes and become any cell type
• Other stem cells can express most of their genes
• All stem cells do not show many specialized
  functions and can differentiate into many types
  of tissue

149
KEY CONCEPT

• All body cells, except sex cells, contain the
  same 46 chromosomes
• Differentiation depends on which genes are active
  and which are inactive

150
SUMMARY

• Structures and functions of human cells
• Structures and functions of membranous and
  nonmembranous organelles
• ATP, mitochondria, and the process of aerobic
  cellular respiration
• Structures and functions of the nucleus
• control functions of nucleic acids
• structures and replication of DNA
• DNA and RNA in protein synthesis

151
SUMMARY

• Structures and chemical activities of the cell
  membrane
• diffusion and osmosis
• active transport proteins
• vesicles in endocytosis and exocytosis
• electrical properties of plasma
• Stages and processes of cell division
• DNA replication
• mitosis
• cytokinesis
• Links between cell division, energy use, and
  cancer

152
Homework

• Lecture
• Study Chapter 1, 2, and 3 for Exam 1
• Complete Homework 1
• Laboratory