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Cell Membranes,
Transport &
Communication
1
Cell Membrane
Most often seen in books
Real cell membrane
(electron microscope)
Cell Membrane Structure
Basic Structure
Phospholipid
Cell Membrane Structure
But wait, there’s more...
Cell Membrane Structure
Carbohydrates
FUNCTION: cell-cell
recognition



Within membrane
Attached to proteins
(glycoproteins)
Attached to lipids
(glycolipids)
Cell Membrane Structure
Cholesterol
FUNCTION: Membrane
fluidity


High temp (37°C):
makes membrane less
fluid
Lowers temp required for
membrane to solidify by
disrupting packing of
phospholipid tails
Cholesterol and membrane fluidity

Remember lipid structure
 Saturated
fats = no double bonds, straight tails, pack
tightly
 Unsaturated fats = double bonds, kinked tails, pack
loosely
Cholesterol and membrane fluidity

Remember lipid structure
 Saturated
fats = no double bonds, straight tails, pack
tightly
 Unsaturated fats = double bonds, kinked tails, pack
loosely
Membrane Fluidity


Membranes must be
fluid to function
Different organisms
have different
compositions in their
membranes
 Types
of proteins
 Types of
phospholipids
 Amount of cholesterol
Fluid Mosaic Model
human
cell
mouse
cell
+

Membrane components move
laterally around in the
membrane
Phospholipids can travel the length of a bacteria cell in 1 second!
Animation: Starr Ch
6 – Fluid Mosaic
Cell Membrane Structure
Proteins
 Each type of protein in a
membrane has a specific
function





Adhesion proteins
Recognition proteins
Receptor proteins
Enzymes
Transport proteins
(active and passive)
Cell Membrane Structure
Adhesion
Protein
Enzyme
Receptor Protein
Recognition
Protein
Passive
Transporter
Active
Transporter
Cell Membrane Structure



Froze membrane,
then split apart
Some proteins go all
the way through
(INTEGRAL
PROTEINS)
Some proteins are on
one side or the other
(PERIPHERAL
PROTEINS)
Complete Membrane Structure
14
How does it all get into the membrane?

Proteins synthesized in?

Secreted proteins
 Transmembrane proteins




Lipids synthesized in?
Carbohydrate
modifications (glycolipid
or glycoprotein) added
in?
Shipped via vesicles to
membrane
Fate of proteins
Cell Membrane: Gate and
Gatekeeper
Structure allows cell to control what can
pass through the membrane
 Selectively permeable barrier

Allows some
things through but
not others
16
What needs to go across the
membrane?

INTO the cell:

Sugars
 Amino Acids
 O2
 Other nutrients

OUT OF the cell:

Metabolic waste
 CO2

Regulation of
concentrations of ions :
Na+, K+, Ca2+, Cl-
Muscle Cells
Selectively Permeable

What goes through the
membrane?
 Small,
uncharged
molecules (oxygen,
carbon dioxide)

What doesn’t go
through the
membrane?
 Charged
molecules
 Larger polar or
nonpolar molecules
(sugars, amino acids)
Textbook Figure
Aquaporins – “water channels”
Allows 3 x 109 water molecules to pass through
membrane per second
Concentration Gradients
Concentration
 The amount of something
in a certain space
Concentration Gradient
Movement of substances into and
out of cells
GENERAL RULE #1:
 Movement from HIGH concentration to
LOW concentration does not require
energy
22
Passive Transport
Passive Transport
What can be Passively
Transported?
Membrane is selectively permeable to
small molecules (oxygen, carbon dioxide)
 Larger molecules and ions enter through
protein carriers

Small Molecules
Ion channels
Carrier proteins
25
What can be Passively
Transported?

Membrane is selectively permeable to
small molecules (oxygen, carbon dioxide)
– movement from high
concentration to low concentration (passive)
 DIFFUSION
© 2006 W.W.
26
What can be Passively
Transported?

Larger molecules and ions (water, salt,
sugars, amino acids) enter through protein
carriers
Osmosis

Water moving passively across the
membrane
2% sucrose
2% sucrose
10% sucrose
water
28
Osmosis

Red blood cells in various salt
concentrations
29
Tonicity
Ability of a solution to cause a change in
water content via osmosis
 TONIC refers to the SOLUTE

Same concentration of solute
inside and outside the cell
Salt concentration
outside HIGHER than
inside the cell
Salt concentration
outside LOWER than
inside the cell
Example of Passive Transport:
Osmosis

Water moving passively across the
membrane
Isotonic
Plant
Cells
Solution
Hypertonic Hypotonic compared to
cell: “the
solution is
hypertonic to
the cell”
Animal
Cells
31
Osmosis – Turgor pressure
Factors that affect passive
transport
Size
 Temperature
 Steepness of the concentration gradient
 Charge
 Pressure

Movement of substances into and
out of cells
GENERAL RULE #2:
 Movement from LOW concentration to
HIGH concentration requires added
energy
34
Active Transport
What must be Actively
Transported?



Anything moving against the concentration
gradient (low to high)
Active carriers use energy from ATP
Energy changes the shape of the carrier
Energy
36
Example of Active Transport:
Endocytosis and Exocytosis




37
EXOCYTOSIS:
Outward budding of
the membrane
Forms a vesicle
Remove waste,
release molecules the
cell has made
Exocytosis Animation
Example of Active Transport:
Endocytosis and Exocytosis



38
ENDOCYTOSIS:
Inward budding of the
membrane
Forms a vesicle
Take in food, remove
cholesterol from
blood, immune cells
“eat” invaders
ANIMATION: Endocytosis
Cain Ch6 2b
Endocytosis
Exocytosis
coated pit
lysosome
Golgi
Transport into and out of cells
Example in Real Life

Paramecium are a
single-celled organism
that is found in freshwater ponds. Which
direction would osmosis
(passive transport)
cause water to move
with respect to the
Paramecium?
Example in Real Life

What would happen
to the Paramecium if
this continued?
Example in Real Life

The contractile
vacuole of a
Paramecium
constantly pumps
water out of the cell.
Is this active or
passive transport?
Example in Real Life

You have probably
heard that eating a lot
of salt will make your
body retain water so
you gain weight. When
you eat a lot of salt, it is
transported inside your
cells. Why would eating
a lot of salt make your
body retain water?
Example in Real Life

A shipwrecked sailor is
stranded on a small desert
island with no fresh water to
drink. She knows she could
last without food for up to a
month, but if she didn't have
water to drink she would be
dead within a week. Hoping to
postpone the inevitable, her
thirst drove her to drink the
salty seawater. She was dead
in two days. Why did drinking
seawater kill the sailor faster
than not drinking any water at
all?
Example in Real Life

Describe why oxygen
would diffuse into
cells inside your
lungs.
Example in Real Life

Why does putting salt
on a slug kill it?
Scientific Method Practice
OBSERVATION: Cells gain or lose water via
osmosis when placed in different
concentrations of salt.
 Design an experiment to determine the
concentration of salt inside a human red
blood cell.
 Hypothesis, Prediction, Independent
variable, dependent variable, control,
constants
Scientific Method Practice






Hypothesis: RBCs contain 5% salt.
Prediction: HYP TRUE - RBCs in <5% salt will
swell, RBCs in >5% salt will shrink. HYP FALSE –
other observation about cell size
Independent variable: % salt in water
Dependent variable: size of cell (shrink, grow)
Control: RBC in blood serum (shouldn’t change)
Constants: source of RBCs, amount of liquid
added, time after addition, # of RBCs observed
Real-life Results
Hypotonic
Isotonic
Hypertonic
100 mOs
500 mOs
300 mOs
Cell Communication in Multicellular
Organisms
Cells are specialized for different jobs, but
cooperate so organism functions
 Cells need to coordinate their activities

 Neighboring
cells communicate via direct
connections
 Distant cells communicate via chemicals:
hormones
51
Direct Communication
Indirect Communication

Cells release small proteins or molecules
 Hormones,
Pheromones, Steroids,
Neurotransmitters
Other cells have protein receptors
 Signaling molecules produce changes in
the receiving cell ANIMATION: Campbell

Ch 11 – Signaling
Overview
53
Lab 6 Debriefing
0.9%
NaCl
Isotonic
Plant
Cells
0%
4%
NaCl
NaCl
Hypertonic Hypotonic Solution
compared to
cell: “the
solution is
hypertonic to
the cell”
Animal
Cells
54
Osmosis – Turgor pressure
0.9%
NaCl
4%
NaCl
Dialysis Tube Experiment
Iodine
Iodine
Glucose
Diffusion
56
Photosynthesis
(briefly) and
Cellular Respiration
57
Capturing Energy
Sun is primary source of energy
 Energy flows through life systems


Producers
Sugars out
O2 out
Photosynthesis

Primary consumers

Secondary
consumers
Respiration
CO2 and H2O out
58
What this means…
All energy needs are met by the plant
kingdom
 All this energy originally comes from the
sun
 Photosynthesis converts the energy in
sunlight into chemical energy that can be
stored in the plant

59
Energy in the Cell
CELLULAR RESPIRATION
PHOTOSYNTHESIS
Photosynthesis and Cellular
Respiration

An exchange of molecules and energy
© 2006 W.W.
61
Sunlight energy
ECOSYSTEM
Photosynthesis transforms
kinetic energy (light) into
potential energy (chemical
bonds in glucose)
 Cellular respiration moves
energy stored in glucose
into ATP, which can be
used for cellular work

Photosynthesis
in chloroplasts
CO2
Glucose
H2O
O2
Cellular respiration
in mitochondria
ATP
(for cellular work)
Heat energy
ANIMATION: Starr Ch 6 –
Energy Changes
62
H2O
Cellular Respiration
O2

CO2
Think of what
happens when you
breathe – closely
related to CR
63
Cellular Respiration and Gasses
Breathing brings O2 into the body from the
environment
 O2 is distributed to cells in the bloodstream
 In cellular respiration, mitochondria use O2
to harvest energy and generate ATP
 Breathing disposes of the CO2 produced
as a waste product of cellular respiration

64
Summary Equation

Remember laws of thermodynamics!
 First
law?
 Second law?
HEAT
Glucose
Oxygen gas
Carbon
dioxide
Water
Energy
65
ATP – An Energy Carrier
Molecules
Temporarily stores and transfers energy
 ATP stores energy in phosphate bonds

 Transfers
this energy with phosphate
 Phosphorylation
66
Other Energy Carriers
NADP+ and NAD+

Pick up electrons


NADPH and NADH
Donate these
electrons and energy
67
Energy in Bonds


Energy is contained in
the arrangement of
electrons in a
molecule
An electron on
Carbon has more
energy than an
electron on Oxygen
68
Burning sugar


Electrons “fall” from
carbon in glucose to
oxygen in water
Energy released
rapidly as light and
heat
69
Cellular Respiration


Electron “fall” is
carefully controlled
Energy released in
small amounts and
stored in ATP
What does the cell use
to carefully control the
energy release?
70
Where are these electrons that are
moving?
 What is moving from a carbon to an
oxygen?

71
Oxidation – Reduction
Reactions
Oxidation: loss of electrons from an atom
(loss of a H atom)
 Reduction: addition of electrons to an
atom (gain of a H atom)

 Think:

reduction in CHARGE due to more e-
Always paired (one loses an e-, one gains)
72
What molecule gets OXIDIZED (loses e-)?
 What molecule gets REDUCED (gains e)?

73
More Redox Reactions


What molecule gets OXIDIZED (loses e-)?
What molecule gets REDUCED (gains e-)?
74
Redox Reactions in Cellular
Respiration

Glucose loses electrons (in H atoms) and
becomes oxidized
75
Redox Reactions in Cellular
Respiration
Glucose loses electrons (in H atoms) and
becomes oxidized
 O2 gains electrons (in H atoms) and
becomes reduced
 Along the way, the electrons lose potential
energy, and energy is released

76
Redox Reactions in Cellular
Respiration
Glucose loses electrons (in H atoms) and
becomes oxidized
 O2 gains electrons (in H atoms) and
becomes reduced
 Electrons lose potential energy, and
energy is released

77
Important Players

Dehydrogenase removes electrons from
glucose
 What
type of molecule is dehydrogenase?
 How are the electrons removed?
78
Important Players

Electrons are transferred to the coenzyme
NAD+, which is converted to NADH
 Is

this oxidation or reduction?
NAD+ shuttles electrons in CR redox
reactions
79
These reactions
NAD+ Function
Animation (Online)
Oxidation
Dehydrogenase
Reduction
NAD
NADH
2H
2H


2
e
H
(carries
2 electrons)
80
Bigger picture

Electron transfer to
NAD+ is the first step
in an ELECTRON
TRANSPORT CHAIN
NADH
NAD
H
ATP
2e
Controlled
release of
energy for
synthesis
 Series
of redox
reactions
 Pass from different
carrier molecules
eventually to O2
of ATP
2 H
2e
1
2
O2
H2O
81
Cellular Respiration

STEP 0: Eat to get glucose
 Glucose
is absorbed by cells in small intestine
 Glucose enters the bloodstream and is
transported to all the cells in your body
 How is this different in a plant?
82
Inside a cell



STEP 1: Glycolysis
STEP 2: Citric Acid
Cycle
STEP 3: Oxidative
Phosphorylation
83
Cellular Respiration
GLUCOSE
84
STEP 1: Glycolysis

Occurs in CYTOPLASM

Glucose is split into 2 molecules of pyruvate

2 ATP and 2 NADH are made for each pyruvate
85
STEP 1: Glycolysis
Animation: Campbell
Ch 6 – Glycolysis
GLYCOLYSIS
ANIMATION
(online)
86
STEP 1: Glycolysis Summary

Preparatory phase:
 Glucose
is energized using 2 ATPs
 Splits into 2 three-carbon intermediates
87
STEP 1: Glycolysis Summary

Energy Payoff phase:
 Redox
reaction generates NADH
 2 ATP and pyruvate produced per intermediate
88
STEP 1: Glycolysis Summary
2
ATP
2
NAD
2
NADH
2 H
Glucose
2 Pyruvate
4ADP
4 P
4
ATP
1. One glucose (6C) converted into 2 pyruvates (3C)
2. 2 ATP in  4 ATP out
3. Two NAD+ are converted into 2 NADH & 2H+
(These go to Electron Transport.)
89
Cellular Respiration Organizer
glucose
2 ATP
ATP
6 carbon sugar
Glycolysis
2 NADH 2 pyruvate
4 ATP
(2 net)
ATP
CYTOPLASM
3 carbon sugar
90
So far…
91
Glycolysis Citric Acid (Krebs)
Cycle
92
Mitochondria Structure
Two membranes
Mitochondrion
 Outer
membrane
 Intermembrane
space
 Inner membrane
Folded into cristae
 Contains fluid
mitochondrial
matrix

Outer
membrane
Intermembrane
space
Inner
membrane
Cristae
Matrix
TEM 44,880

93
STEP 2: The Citric Acid Cycle




Occurs inside matrix of
MITOCHONDRIA
Completes breakdown
of glucose to CO2
Makes 1 ATP per
pyruvate
Passes electrons to
ETC
94
STEP 2: Citric Acid Cycle
Animation:
Campbell Ch 6 –
TCA

Also called TCA (The
Citric Acid cycle)

Also called the Krebs
Cycle
ONLINE: TCA
ANIMATION

REMEMBER:
There’s TWO
pyruvates!!
95
STEP 2: TCA Summary

Pyruvate (x2) is groomed for TCA cycle:
 Carbon
atom released as CO2
 2C compound oxidized; NAD+ reduced to
NADH
 Coenzyme A joins 2C
96
STEP 2: TCA Summary

Completes oxidation of glucose:
 Releases
2 CO2 molecules
 Net energy yield per pyruvate (there’s 2!) = 1
ATP, 4 NADH (1 from prep, 3 from TCA), 1
FADH2
97
Cellular Respiration Organizer
glucose
2 ATP
ATP
Glycolysis
4 ATP
(2 net)
ATP
2 NADH 2 pyruvate
2 Coenzyme
A
Krebs
Cycle
MITOCHONDRIAL
MATRIX
6 CO2
2 ATP
ATP
8 NADH, 2 FADH2
98
So far…
99
TCA  Electron Transport Chain
and Chemiosmosis
100
Step 3: Electron
Transport Chain

Occurs ON inner
mitochondrial membrane
101
Step 3: Electron
Transport Chain



Electrons passed down
from NADH to ETC
H+ ions pumped inside
inner mitochondrial
membrane
Electrons passed down
ETC to O2 which
accepts electrons and
becomes 2 H2O
102
STEP 3: Electron Transport
Chain
Animation: Campbell
Ch 6 – ETC
103
STEP 3: ETC Summary

Electons passed from NADH and FADH to
proteins in ETC to O2
H
H
H
Protein
complex
Intermembrane
space
H
H
Electron
carrier
H
H
H
H
ATP
synthase
Inner
mitochondrial
membrane
Electron
flow
Mitochondrial
matrix
FADH2
FAD
NAD
NADH
H
1
2
O2
 2 H
H
H
H2O
Electron Transport Chain
OXIDATIVE PHOSPHORYLATION
ADP
 P
ATP
H
Chemiosmosis
104
STEP 3: ETC Summary

Transports H+ into inner membrane space
in mitochondria creating a gradient
H
H
H
Protein
complex
Intermembrane
space
H
H
Electron
carrier
H
H
H
H
ATP
synthase
Inner
mitochondrial
membrane
Electron
flow
Mitochondrial
matrix
FADH2
FAD
NAD
NADH
H
1
2
O2
 2 H
H
H
H2O
Electron Transport Chain
OXIDATIVE PHOSPHORYLATION
ADP
 P
ATP
H
Chemiosmosis
105
STEP 3: ETC Summary

H+ gradient is POTENTIAL energy
H
H
H
Protein
complex
Intermembrane
space
H
H
Electron
carrier
H
H
H
H
ATP
synthase
Inner
mitochondrial
membrane
Electron
flow
Mitochondrial
matrix
FADH2
FAD
NAD
NADH
H
1
2
O2
 2 H
H
H
H2O
Electron Transport Chain
OXIDATIVE PHOSPHORYLATION
ADP
 P
ATP
H
Chemiosmosis
106
STEP 3: ETC Summary

CHEMIOSMOSIS: H+ flowing (downhill)
from high to low concentration releases
KINETIC energy
H
H
H
Protein
complex
Intermembrane
space
H
H
Electron
carrier
H
H
H
H
ATP
synthase
Inner
mitochondrial
membrane
Electron
flow
Mitochondrial
matrix
FADH2
FAD
NAD
NADH
H
1
2
O2
 2 H
H
H
H2O
Electron Transport Chain
OXIDATIVE PHOSPHORYLATION
ADP
 P
ATP
H
Chemiosmosis
107
STEP 3: ETC Summary

Energy from H+ flowing downhill is stored
in bond of ATP
H
H
H
Protein
complex
Intermembrane
space
H
H
Electron
carrier
H
H
H
H
ATP
synthase
Inner
mitochondrial
membrane
Electron
flow
Mitochondrial
matrix
FADH2
FAD
NAD
NADH
H
1
2
O2
 2 H
H
H
H2O
Electron Transport Chain
OXIDATIVE PHOSPHORYLATION
ADP
 P
ATP
H
Chemiosmosis
108
STEP 3: CHEMIOSMOSIS

Generates majority of ATP (34)
109
Cellular Respiration Organizer
glucose
2 ATP
ATP
Glycolysis
4 ATP
(2 net)
ATP
CYTOPLAS
M
2 NADH 2 pyruvate
Krebs
Cycle
MITOCHONDRIAL
MATRIX
6 CO2
2 ATP
ATP
8 NADH, 2 FADH2
ATP
oxygen
Electron Transfer Chain
Chemiosmosis
32 ATP
INNER
MITOCHONDRIAL
MEMBRANE
110
So far…
111
Cellular Respiration Overview
Animation

NML_Cain3_CD3/Student_Animations/Full
/Macintosh/cain_ch08a02.app
112
Cellular Respiration

Aerobic metabolism: three steps
 Glycolysis,
Citric Acid Cycle, & Oxidative
Phosphorylation
 Releases LOTS of energy – typically 36 ATP
per molecule of glucose
113
“Aerobic” Respiration?

Requires OXYGEN – WHY and WHERE?
 Last
e- acceptor in ETC
114
Some poisons interrupt CR
Rotenone
H+
H+
H+
NA
D
H+
H+
H+ H+ H+
H+
ATP
synthase
FAD
FADH2
NADH
H+
1
2
+
O2 + 2 H+
H+
H+
Electron Transport Chain
H2O
ADP + P
ATP
Chemiosmosis
Rotenone: binds with ETC proteins and prevents e- from
passing on
115
Some poisons interrupt CR
Rotenone
Cyanide,
carbon monoxide
H+
H+
H+
NAD
H+
H+ H+ H+
1
2
+
ATP
synthase
O2 + 2 H+
H+
H+
H+
FAD
FADH2
NADH
H+
H+
Electron Transport Chain
H2O
ATP
ADP + P
Chemiosmosis
Cyanide, CO: block passage of electrons to O2
116
Some poisons interrupt CR
Rotenone
Cyanide,
carbon monoxide
H+
H+
H+
NAD
H+
H+
H+ H+ H+
1
2
+
ATP
synthase
O2 + 2 H+
H+
H+
H+
FAD
FADH2
NADH
Oligomycin
H+
Electron Transport Chain
H2O
ADP + P
ATP
Chemiosmosis
Oligomycin: Blocks passage in ATP Synthase so H+
gradient can’t be used
117
Some poisons interrupt CR
Rotenone
Cyanide,
carbon monoxide
H+
H+
H+
Oligomycin
H+
H+
H+ H+ H+
H+
ATP
synthase
DNP
FAD
FADH2
NAD
NADH
1
2
+
O2 + 2 H+
H+
H+
H+
Electron Transport Chain
H2O
ATP
ADP + P
Chemiosmosis
DNP (uncouplers): make mitochondrial membrane
“leaky” to H+ so gradient can’t be formed
118
Atkins Diet



Use fats for glycolysis in
the absence of sugars
Fats are broken down
and enter as ActylCoA
Produce ketones when
metabolized and change
pH of blood
119
Respiration Practice

Complete Respiration Practice Worksheet
120
Cellular Respiration Review
Occurs in all eukaryotes
 Generates ATP
 Involves oxidation – reduction reactions

 Oxidation
= loss of electron / H atom; gain of
charge
 Reduction = gain of electron / H atom; loss of
charge
Glycolosis




Takes place in
cytoplasm
Starts with glucose
Uses 2 ATP to prepare
glucose
Generates 2 NADH



Is this oxidation or
reduction?
Generates 4 ATP
NET YIELD: 2 NADH
(goes to ETC) and 2
ATP
The Citric Acid (Krebs) Cycle




Takes place in
mitochondrial matrix
Uses Coenzyme A to
prepare pyruvate
Completes breakdown of
glucose to CO2
Each molecule of
pyruvate processed
generates



4 NADH
1 FADH2
1 ATP
So far…
124
ETC and Chemiosmosis




ETC: Takes place on
inner mitochondrial
membrane
Electrons from NADH
and FADH2 pass
electrons down ETC
O2 is the final oxygen
acceptor
Generates a H+
gradient
Chemiosmosis

Chemiosmosis: H+
gradient powers ATP
Synthase enzyme to
phosphorylate ADP to
make ATP
ADP + P  ATP

Yield = 32-34 ATP
molecules
So far…
127
What if there’s no Oxygen?
O2 can’t act as final electron acceptor
 ETC can’t happen
 Can still get 2 ATP from glycolysis (doesn’t
require O2)

What if there’s no Oxygen?
Can generate 2 ATP
 Makes 2 NADH

What if there’s no Oxygen?
PRESENCE OF O2
 NADH goes to
ETC
ABSENCE OF O2
•ETC can’t function
•NADH must be
oxidized back to
NAD+
Anaerobic Respiration
Cellular respiration in the absence of
oxygen
 Oxidizes NADH to replenish NAD+

Lactic Acid Fermentation
 Ethanol Fermentation

Anaerobic Respiration
LACTIC ACID
FERMENTATION
 Occurs in muscle cells
 Oxidizes NADH to NAD+ by reducing pyruvate to
lactate (lactic acid)
Anaerobic Respiration
AlCOHOL
FERMENTATION
 Occurs in yeast
 Oxidizes NADH to NAD+ by reducing pyruvate to
ethanol (ethyl alcohol)
Why we like fermentation
Often used by
bacteria to make
tasty foodies


Used for thousands of
years
Method of preserving
food
Other Organic Molecules as Fuel
Carbohydrates: Enter at
beginning of glycolysis
•Examples: Starch, Glycogen
Other Organic Molecules as Fuel
Fats: Hydrolyze fatty
acids off of glycerol
Glycerol glycolysis
Fatty Acids  broken
into 2-C pieces and sent
to TCA
1 g fat yields
2x ATP as 1g
starch
Other Organic Molecules as Fuel
Proteins: Hydrolyze to amino
acids, build more proteins
Can be used in glycolysis or
TCA
Other Organic Molecules as Fuel
From what organic molecule
can we get the most ATP per
gram?
Why does fat contain so much
energy?

Energy is stored in
the C – C bonds
within a molecule