Transcript Powerpoint lecture slides

Laws of thermodynamics

Energy is never created or destroyed, only transformed

Entropy (disorder) increases
Transforming energy

Convert energy source to ATP: usable cellular energy
light
food
ATP
ATP: Energy Currency for the cell

Phosphate bonds are highly unstable.
DG = -7.3 kcal/mol
H2 O
Pi
ATP powers many reactions in cells
ATP powers many reactions in cells
Active transport

Specific transport protein required

Energy required!

Any kind of molecules

Either direction


Can move against gradient
Can transport all molecules

No equilibrium
Simple active transport

Energy from ATP
Simple active transport

Energy from ATP

Directional transport

One kind of molecule
Simple active transport

PMCA transporter removes Ca2+ from cytoplasm

Very low [Ca2+] required for signaling
Ca2+
ATP
ADP
How do we get ATP from Glucose?

Transfer energy stored in glucose to a storage molecule
 ATP
 NADH

Glycolysis- Oxidizing glucose to pyruvate

Citric Acid Cycle – Oxidizing pyruvate to CO2

Election Transport – Collecting electrons from NADH and
transferring this energy towards making ATP.
Carbohydrates

H-C-OH units

Often used for energy by cells

Glucose is a simple 6C sugar
Carbohydrates

Polymer: polysaccharides (complex carbohydrates)
 starch
 cellulose
 glycogen
 chitin
 peptidoglycan
Oxidation
Gain of electrons

Increased number of bonds to O
 O pulls e– from C
–
–
–
H–C–H
H–C–H
H–C–H
–
O
–
OH
–
H
H
H
most
reduced
O
–
–

H – C – OH
O=C=O
most
oxidized
Oxidation reactions

When one molecule is oxidized, another is reduced

Electron carriers (“coenzymes”): NAD+, FAD
–
oxidation
H–C–H
–
H–C–H
–
–
O
OH
H
2 e–
NAD+
reduction
oxidation
NADH
“Burning” sugars

Glucose → CO2 is highly exergonic

Same reaction as burning paper or wood

Oxidation
glucose
free
energy
(G)
CO2
reaction progress →
“Burning” sugars

Glucose → CO2 is highly exergonic

Same reaction as burning paper or wood

Oxidation
O=C=O
“Burning” sugars

Glucose → CO2 is highly exergonic

Same reaction as burning paper or wood

Oxidation
glucose
free
energy
(G)
CO2
reaction progress →
“Burning” sugars

Glucose → CO2 is highly exergonic

Same reaction as burning paper or wood

Oxidation
glucose
free
energy
(G)
CO2
reaction progress →
“Burning” sugars

Biochemical pathway

Enzymes catalyze steps

Energy captured in ATP
glucose
free
energy
(G)
CO2
reaction progress →
“Burning” sugars

Oxidized molecules have less chemical energy

Energetic electrons transferred to carriers
–
H–C–H
oxidation
–
–
O
OH
H–C–H
lower
energy
–
higher
energy
H
2 e–
glucose
NAD+
free
energy
(G)
CO2
reaction progress →
reduction
NADH
Aerobic cell respiration

Complete oxidation of glucose
glucose
4 stages:

Glycolysis

Citric acid cycle

Electron transport

Chemiosmosis
oxidation
6 CO2
1. Glycolysis

Partial oxidation of glucose in cytosol
glucose
Yum!
oxidation
2 pyruvate
2 ATP, 2 NADH
gluT
1. Glycolysis

First step: phosphorylation catalyzed by hexokinase
 Energy invested
 Allows facilitated transport
glucose
hexokinase
ATP
ADP
P
glucose 6-phosphate
1. Glycolysis

Another phosphorylation step

6C molecule split into two 3C molecules
glucose
6-phosphate
glucose
hexokinase
ATP
ADP
P
P
PFK
ATP
P
ADP
P
P
1. Glycolysis

Oxidation

Energy stored as high-energy e– on NADH
NAD+
glucose
6-phosphate
glucose
hexokinase
ATP
ADP
P
PFK
ATP
NADH
P
P
P
P
P
P
P
ADP
P
NAD+
NADH
1. Glycolysis

2 ATP synthesis steps

Net gain of 2 ATP per glucose

6C glucose → 2 3C pyruvates
NAD+
glucose
6-phosphate
glucose
hexokinase
ATP
ADP
P
P
PFK
ATP
NADH
P
ADP
ATP
P
ADP
P
P
ADP
ATP
pyruvate
P
P
NAD+
P
NADH
P
P
ADP
ATP
ADP
ATP
2. Citric Acid Cycle (CAC)

AKA tricarboxylic acid cycle (TCA), AKA Krebs cycle

Occurs in matrix of mitochondria (or cytosol in prokaryotes)
2. Citric Acid Cycle (CAC)

“Transition step”
 Transport into matrix
 Connects glycolysis to CAC
pyruvate
o.m.
i.m.
Coenzyme A
NADH
NAD+
cytosol
matrix
CO2
acetyl
CoA
2. Citric Acid Cycle (CAC)

“Transition step”
 Large protein complex spans o.m. and i.m.
 Transporter and enzyme
 Oxidation of one carbon to CO2
pyruvate
 Attachment of coenzyme A
o.m.
i.m.
Coenzyme A
NADH
NAD+
cytosol
matrix
CO2
acetyl
CoA
2. Citric Acid Cycle (CAC)

2C acetyl CoA + 4C = 6C citric acid
acetyl
CoA
CoA
citric acid
2. Citric Acid Cycle (CAC)

2 oxidation reactions complete the oxidation of glucose
acetyl
CoA
CoA
citric acid
NADH
CO2
NAD+
NADH
CO2
NAD+
2. Citric Acid Cycle (CAC)

One GTP synthesized and converted to ATP
acetyl
CoA
CoA
citric acid
NADH
CO2
NAD+
NADH
CO2
NAD+
GDP
GTP
ADP
ATP
2. Citric Acid Cycle (CAC)

Two more oxidation steps regenerate original 4C molecule
acetyl
CoA
CoA
citric acid
NADH
CO2
FADH2
NAD+
FAD
NADH
CO2
NAD+
GDP
NADH
NAD+
GTP
ADP
ATP
2. Citric Acid Cycle (CAC)

Where’s the carbon from glucose?
2. Citric Acid Cycle (CAC)

Where’s the carbon from glucose? 6 CO2

Where’s the energy from glucose?
2. Citric Acid Cycle (CAC)

Where’s the carbon from glucose? 6 CO2

Where’s the energy from glucose?
 4 net ATP (2 from glycolysis, 2 for each pyruvate in CAC)
2. Citric Acid Cycle (CAC)

Where’s the carbon from glucose? 6 CO2

Where’s the energy from glucose?
 4 net ATP (2 from glycolysis, 2 for each pyruvate in CAC)
 10 NADH (2 glycolysis, 2 transition, 6 CAC)
2. Citric Acid Cycle (CAC)

Where’s the carbon from glucose? 6 CO2

Where’s the energy from glucose?
 4 net ATP (2 from glycolysis, 2 for each pyruvate in CAC)
 10 NADH (2 glycolysis, 2 transition, 6 CAC)
 2 FADH2 (CAC)