Review of Unit 2

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Review of Unit 2

• EQ 1 -15

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• Prokaryotes thrive almost everywhere
• Including places too acidic, too salty, too cold,
  or too hot for most other organisms

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• Prokaryotic cells have a variety of shapes
• The three most common of which are spheres
  (cocci), rods (bacilli), and spirals

Figure 27.2ac
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• Using a technique called the Gram stain
• Scientists can classify many bacterial species
  into two groups based on cell wall composition,
  Gram-positive and Gram-negative

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Reproduction and Adaptation

• Prokaryotes reproduce quickly by binary fission
• And can divide every 13 hours
• Horizontal gene transfer
• Bacterial Sex
• Conjugation

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• Examples of all four models of nutrition
• Photoautotrophy
• Energy Light, Carbon CO2
• Chemoautotrophy
• Energy Inorganic Chemicals, Carbon CO2
• Photoheterotrophy
• Energy Light, Carbon Organic Compounds
• Chemoheterotrophy
• Energy Inorganic Chemicals, Carbon Organic
  Compounds

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• Extreme halophiles, ARCHEABACTERIA
• Live in high saline environments

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Chemical Recycling

• Prokaryotes play a major role
• In the continual recycling of chemical elements
  between the living and nonliving components of
  the environment in ecosystems
• BioRemediation
• Make inorganic nitrogen fixed into organic
  nitrogen.

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Symbiotic Relationships

• Many prokaryotes
• Live with other organisms in symbiotic
  relationships such as mutualism and commensalism

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LE 6-2
10 m
Human height
1 m
Length of some nerve and muscle cells
Unaided eye
0.1 m
Chicken egg
1 cm
Frog egg
1 mm
Measurements 1 centimeter (cm) 102 meter (m)
0.4 inch 1 millimeter (mm) 103 m 1 micrometer
(µm) 103 mm 106 m 1 nanometer (nm) 103
µm 109 m
100 µm
Most plant and animal cells
Light microscope
10 µm
Nucleus
Most bacteria
Mitochondrion
1 µm
Electron microscope
Smallest bacteria
100 nm
Viruses
Ribosomes
10 nm
Proteins
Lipids
1 nm
Small molecules
Atoms
0.1 nm
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• Prokaryotic cells have no nucleus
• In a prokaryotic cell, DNA is in an unbound
  region called the nucleoid
• Prokaryotic cells lack membrane-bound organelles

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Overview Life at the Edge

• The plasma membrane is the boundary that
  separates the living cell from its nonliving
  surroundings
• The plasma membrane exhibits selective
  permeability, allowing some substances to cross
  it more easily than others

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LE 7-2
WATER
Hydrophilic head
Hydrophobic tail
WATER
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LE 7-3
Hydrophilic region of protein
Phospholipid bilayer
Hydrophobic region of protein
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LE 7-5a
Lateral movement (107 times per second)
Flip-flop ( once per month)
Movement of phospholipids
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LE 7-5c
Cholesterol
Cholesterol within the animal cell membrane
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LE 7-7
Fibers of extracellular matrix (ECM)
Glycoprotein
Carbohydrate
Glycolipid
EXTRACELLULAR SIDE OF MEMBRANE
Cholesterol
Peripheral proteins
Microfilaments of cytoskeleton
Integral protein
CYTOPLASMIC SIDE OF MEMBRANE
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Transport Proteins

• Transport proteins allow passage of hydrophilic
  substances across the membrane
• Some transport proteins, called channel proteins,
  have a hydrophilic channel that certain molecules
  or ions can use as a tunnel
• Channel proteins called aquaporins facilitate the
  passage of water

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• Other transport proteins, called carrier
  proteins, bind to molecules and change shape to
  shuttle them across the membrane
• A transport protein is specific for the substance
  it moves

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Concept 7.3 Passive transport is diffusion of a
substance across a membrane with no energy
investment

• Diffusion is the tendency for molecules to spread
  out evenly into the available space
• Although each molecule moves randomly, diffusion
  of a population of molecules may exhibit a net
  movement in one direction
• At dynamic equilibrium, as many molecules cross
  one way as cross in the other direction

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LE 7-11a
Molecules of dye
Membrane (cross section)
WATER
Net diffusion
Net diffusion
Equilibrium
Diffusion of one solute
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• Substances diffuse down their concentration
  gradient, the difference in concentration of a
  substance from one area to another
• No work must be done to move substances down the
  concentration gradient
• The diffusion of a substance across a biological
  membrane is passive transport because it requires
  no energy from the cell to make it happen

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LE 7-11b
Net diffusion
Net diffusion
Equilibrium
Net diffusion
Net diffusion
Equilibrium
Diffusion of two solutes
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Effects of Osmosis on Water Balance

• Osmosis is the diffusion of water across a
  selectively permeable membrane
• The direction of osmosis is determined only by a
  difference in total solute concentration
• Water diffuses across a membrane from the region
  of lower solute concentration to the region of
  higher solute concentration

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LE 7-12
Lower concentration of solute (sugar)
Higher concentration of sugar
Same concentration of sugar
H2O
Selectively permeable mem- brane sugar
mole- cules cannot pass through pores, but water
molecules can
Osmosis
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Water Balance of Cells Without Walls

• Tonicity is the ability of a solution to cause a
  cell to gain or lose water
• Isotonic solution solute concentration is the
  same as that inside the cell no net water
  movement across the plasma membrane
• Hypertonic solution solute concentration is
  greater than that inside the cell cell loses
  water
• Hypotonic solution solute concentration is less
  than that inside the cell cell gains water

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• Animals and other organisms without rigid cell
  walls have osmotic problems in either a
  hypertonic or hypotonic environment
• To maintain their internal environment, such
  organisms must have adaptations for
  osmoregulation, the control of water balance
• The protist Paramecium, which is hypertonic to
  its pond water environment, has a contractile
  vacuole that acts as a pump

Video Chlamydomonas
Video Paramecium Vacuole
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Facilitated Diffusion Passive Transport Aided by
Proteins

• In facilitated diffusion, transport proteins
  speed movement of molecules across the plasma
  membrane
• Channel proteins provide corridors that allow a
  specific molecule or ion to cross the membrane
• Carrier proteins undergo a subtle change in shape
  that translocates the solute-binding site across
  the membrane

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LE 7-15a
EXTRACELLULAR FLUID
Solute
Channel protein
CYTOPLASM
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LE 7-15b
Carrier protein
Solute
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Concept 7.4 Active transport uses energy to move
solutes against their gradients

• Facilitated diffusion is still passive because
  the solute moves down its concentration gradient
• Some transport proteins, however, can move
  solutes against their concentration gradients

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The Need for Energy in Active Transport

• Active transport moves substances against their
  concentration gradient
• Active transport requires energy, usually in the
  form of ATP
• Active transport is performed by specific
  proteins embedded in the membranes
• The sodium-potassium pump is one type of active
  transport system

Animation Active Transport
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LE 7-16
EXTRACELLULAR FLUID
Na
Na high K low
Na
Na
Na
Na
Na
Na
Na
ATP
Na low K high
P
Na
P
CYTOPLASM
ADP
Phosphorylation causes the protein to
change its conformation, expelling Na to the
outside.
Cytoplasmic Na bonds to the
sodium-potassium pump
Na binding stimulates phosphorylation by
ATP.
K
K
K
K
K
P
K
P
Extracellular K binds to the protein,
triggering release of the phosphate group.
Loss of the phosphate restores the
proteins original conformation.
K is released and Na sites are receptive
again the cycle repeats.
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• Catabolic pathways release energy by breaking
  down complex molecules into simpler compounds
• Anabolic pathways consume energy to build complex
  molecules from simpler ones
• Bioenergetics is the study of how organisms
  manage their energy resources

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• Kinetic energy is energy associated with motion
• Heat (thermal energy) is kinetic energy
  associated with random movement of atoms or
  molecules
• Potential energy is energy that matter possesses
  because of its location or structure
• Chemical energy is potential energy available for
  release in a chemical reaction
• Energy can be converted from one form to another

Animation Energy Concepts
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LE 8-2
On the platform, the diver has more
potential energy.
Diving converts potential energy to kinetic
energy.
Climbing up converts kinetic energy of muscle
movement to potential energy.
In the water, the diver has less potential
energy.
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The Laws of Energy Transformation

• Thermodynamics is the study of energy
  transformations
• A closed system, such as that approximated by
  liquid in a thermos, is isolated from its
  surroundings
• In an open system, energy and matter can be
  transferred between the system and its
  surroundings
• Organisms are open systems

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The First Law of Thermodynamics

• According to the first law of thermodynamics, the
  energy of the universe is constant
• Energy can be transferred and transformed
• Energy cannot be created or destroyed
• The first law is also called the principle of
  conservation of energy

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The Second Law of Thermodynamics

• During every energy transfer or transformation,
  some energy is unusable, often lost as heat
• According to the second law of thermodynamics,
  every energy transfer or transformation increases
  the entropy (disorder) of the universe

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LE 8-6a
Reactants
Amount of energy released (?G lt 0)
Energy
Free energy
Products
Progress of the reaction
Exergonic reaction energy released
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LE 8-6b
Products
Amount of energy required (?G gt 0)
Free energy
Energy
Reactants
Progress of the reaction
Endergonic reaction energy required
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LE 8-8
Adenine
Phosphate groups
Ribose
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LE 8-9
P
P
P
Adenosine triphosphate (ATP)
H2O

P
P
P
Energy

i
Adenosine diphosphate (ADP)
Inorganic phosphate
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The Regeneration of ATP

• ATP is a renewable resource that is regenerated
  by addition of a phosphate group to ADP
• The energy to phosphorylate ADP comes from
  catabolic reactions in the cell
• The chemical potential energy temporarily stored
  in ATP drives most cellular work

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LE 8-12
ATP
Energy for cellular work (endergonic,
energy- consuming processes)
Energy from catabolism (energonic,
energy- yielding processes)
P
ADP

i
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LE 8-13
Sucrose C12H22O11
Glucose C6H12O6
Fructose C6H12O6
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LE 8-14
A
B
C
D
Transition state
EA
A
B
Free energy
C
D
Reactants
A
B
DG lt O
C
D
Products
Progress of the reaction
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LE 8-15
Course of reaction without enzyme
EA without enzyme
EA with enzyme is lower
Reactants
Free energy
Course of reaction with enzyme
DG is unaffected by enzyme
Products
Progress of the reaction
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LE 8-16
Substrate
Active site
Enzyme-substrate complex
Enzyme
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LE 8-17
Substrates enter active site enzyme changes
shape so its active site embraces the substrates
(induced fit).
Substrates held in active site by
weak interactions, such as hydrogen bonds
and ionic bonds.

• Active site (and R groups of
• its amino acids) can lower EA
• and speed up a reaction by
• acting as a template for
• substrate orientation,
• stressing the substrates
• and stabilizing the
• transition state,
• providing a favorable
• microenvironment,
• participating directly in the
• catalytic reaction.

Substrates
Enzyme-substrate complex
Active site is available for two
new substrate molecules.
Enzyme
Products are released.
Substrates are converted into products.
Products
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Effects of Local Conditions on Enzyme Activity

• An enzymes activity can be affected by
• General environmental factors, such as
  temperature and pH
• Chemicals that specifically influence the enzyme

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Effects of Temperature and pH

• Each enzyme has an optimal temperature in which
  it can function
• Each enzyme has an optimal pH in which it can
  function

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LE 8-19
Substrate
A substrate can bind normally to the active site
of an enzyme.
Active site
Enzyme
Normal binding
A competitive inhibitor mimics the substrate,
competing for the active site.
Competitive inhibitor
Competitive inhibition
A noncompetitive inhibitor binds to the enzyme
away from the active site, altering
the conformation of the enzyme so that its active
site no longer functions.
Noncompetitive inhibitor
Noncompetitive inhibition
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Allosteric Regulation of Enzymes

• Allosteric regulation is the term used to
  describe cases where a proteins function at one
  site is affected by binding of a regulatory
  molecule at another site
• Allosteric regulation may either inhibit or
  stimulate an enzymes activity

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LE 9-7
Enzyme
Enzyme
ADP
P
Substrate
ATP

Product
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Concept 9.2 Glycolysis harvests energy by
oxidizing glucose to pyruvate

• Glycolysis (splitting of sugar) breaks down
  glucose into two molecules of pyruvate
• Glycolysis occurs in the cytoplasm and has two
  major phases
• Energy investment phase
• Energy payoff phase

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LE 9-8
Energy investment phase
Glucose
2 ATP
2 ADP 2 P
used
Citric acid cycle
Glycolysis
Oxidative phosphorylation
Energy payoff phase
formed
4 ADP 4 P
4 ATP
ATP
ATP
ATP
2 NAD 4 e 4 H
2 H
2 NADH
2 Pyruvate 2 H2O
Net
2 Pyruvate 2 H2O
Glucose
2 ATP
4 ATP formed 2 ATP used
2 NADH 2 H
2 NAD 4 e 4 H
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Concept 9.5 Fermentation enables some cells to
produce ATP without the use of oxygen

• Cellular respiration requires O2 to produce ATP
• Glycolysis can produce ATP with or without O2 (in
  aerobic or anaerobic conditions)
• In the absence of O2, glycolysis couples with
  fermentation to produce ATP

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Types of Fermentation

• Fermentation consists of glycolysis plus
  reactions that regenerate NAD, which can be
  reused by glycolysis
• Two common types are alcohol fermentation and
  lactic acid fermentation

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• In alcohol fermentation, pyruvate is converted to
  ethanol in two steps, with the first releasing
  CO2
• Alcohol fermentation by yeast is used in brewing,
  winemaking, and baking

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LE 9-17a
P
2 ADP 2
2 ATP
i
Glucose
Glycolysis
2 Pyruvate
2 NADH
2 NAD
CO2
2
2 H
2 Acetaldehyde
2 Ethanol
Alcohol fermentation
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• In lactic acid fermentation, pyruvate is reduced
  to NADH, forming lactate as an end product, with
  no release of CO2
• Lactic acid fermentation by some fungi and
  bacteria is used to make cheese and yogurt
• Human muscle cells use lactic acid fermentation
  to generate ATP when O2 is scarce

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LE 9-17b
P
2 ADP 2
2 ATP
i
Glucose
Glycolysis
2 NADH
2 NAD
CO2
2
2 H
2 Pyruvate
2 Lactate
Lactic acid fermentation
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The Evolutionary Significance of Glycolysis

• Glycolysis occurs in nearly all organisms
• Glycolysis probably evolved in ancient
  prokaryotes before there was oxygen in the
  atmosphere

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• Photosynthesis
• Occurs in plants, algae, certain other protists,
  and some prokaryotes

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Tracking Atoms Through Photosynthesis Scientific
Inquiry

• Photosynthesis is summarized as

6 CO2 12 H2O Light energy ? C6H12O6 6 O2
6 H2 O
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The Splitting of Water

• Chloroplasts split water into
• Hydrogen and oxygen, incorporating the electrons
  of hydrogen into sugar molecules

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The Two Stages of Photosynthesis A Preview

• Photosynthesis consists of two processes
• The light reactions
• The Calvin cycle

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• The light reactions
• Occur in the grana
• Split water, release oxygen, produce ATP, and
  form NADPH

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• The Calvin cycle
• Occurs in the stroma
• Forms sugar from carbon dioxide, using ATP for
  energy and NADPH for reducing power

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• An overview of photosynthesis

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Photosynthetic Pigments The Light Receptors

• Pigments
• Are substances that absorb visible light

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• Reflect light, which include the colors we see

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• The spectrophotometer
• Is a machine that sends light through pigments
  and measures the fraction of light transmitted at
  each wavelength

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Excitation of Chlorophyll by Light

• When a pigment absorbs light
• It goes from a ground state to an excited state,
  which is unstable

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• Produces NADPH, ATP, and oxygen

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• A mechanical analogy for the light reactions

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• In cyclic electron flow
• Only photosystem I is used
• Only ATP is produced

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• The Calvin cycle

Phase 1 Carbon fixation
Phase 3Regeneration ofthe CO2 acceptor(RuBP)
Phase 2Reduction
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The Importance of Photosynthesis A Review

• A review of photosynthesis