5 Cell Respiration

1) List out 2 differences between passive transport and active transport.

2) What is the main difference between reverse pinocytosis and secretion of exocytosis?

3) When do the following transportation process stop?

1) passive transport

2) active transport

4) What is the definition of water potential?

5) List out 2 factors that affect the rate of diffusion process across a membrane.

6) List out 3 characteristics of enzyme.

7) What is the difference between exergonic and

endogonic reaction?

8) Which type of inhibitor involved in allosteric

effect?

9) List out 2 factors that affect enzyme activities

and briefly explain.

10)a) List out 3 types of cofactor.

b) Which cofactor bound loosely to

enzyme?

Cellular Respiration a cellular process: - breaks down CHO and

other metabolites

- buildup of ATP consumes O2 and produces CO2 aerobic process usually involves breakdown of glucose to

CO2 and water Substrates for respiration: - glucose - fats - proteins

Cellular Respiration usually involves breakdown of glucose

to CO2 and water

energy extracted from glucose molecule:

released step-wise

allows ATP to be produced efficiently

oxidation-reduction enzymes include NAD+ and FAD as coenzymes

Glucose Breakdown: Summary Reaction

oxidation-reduction reaction

electrons are removed from substrates and received by O2, which combines with H+ to become H2O.

glucose is oxidized and O2 is reduced

+ + energy

Reduction

Oxidation

glucose

C6H12O6 6O2 6CO2 6H2O+

Phosphorylation

2 types: - substrate-level

- oxidative substrate-level:-

formation bond between ADP and P (from high-energy molecule which has an unstable P group)

catalysed by transferase (phosphorylase) does not required O2 occur in cytoplasm, nucleus or

mitochondria

Substrate-level phosphorylation

P

P

P ATP

enzyme

ADP

BPG

3PG

9

Phosphorylation

oxidative:- formation of ATP from ADP and

inorganic phosphates O2 is required inside mitochondria (cristae) involve electron transport system e- is transferred energy to form ATP

NAD+ and FADNAD+ (nicotinamide adenine dinucleotide)

a coenzyme of oxidation-reductionoxidize a metabolite by accepting e-

reduce a metabolite by giving up e-

used repeatedly FAD (flavin adenine dinucleotide)

a coenzyme of oxidation-reduction sometimes used instead of NAD+

accepts 2 e- and 2 H+ to become FADH2

11

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Cellular Respiration

ADP + PATP

intermembranespacecristae

CO2

H2O

glucose from

O2 from air

O2 and glucose enter cells,which release H2O and CO2.

Mitochondria useenergy fromglucose to form ATPfrom ADP + P .

Phases of Cellular RespirationCellular respiration includes 4 phases:

Glycolysisbreakdown of glucose into 2 molecules of pyruvate

occurs in cytoplasmATP is formeddoes not utilize O2

Transition (preparatory) reaction both pyruvates are oxidized in mitochondria e- energy is stored in NADH2 C are released as CO2 (1 from each pyruvate)

Citric acid cycleoccurs in the mitochondrion matrix and produces NADH and FADH2

releases 4 carbons as CO2

turns 2X (once for each pyruvate)produces 2 immediate ATP molecules per glucose molecule

Electron transport chainextracts energy from NADH & FADH2

passes electrons from higher to lower energy states

produces 32 or 34 molecules of ATP

Phases of Cellular Respiration

Electron transportchain andchemiosmosis

Mitochondrion

4 ADP

2

4 ATP total

net gain

2 ATP

Glycolysis

NADH

glucose pyruvate

Cytoplasm

ATP

e–

e–e–e–

e–

2 ATP

Preparatory reaction

NADH

NADH andFADH2


Mitochondrion

2

4 ATP total

net gain

2 ATP

Glycolysis

NADH

glucose pyruvate

Cytoplasm

ATP

e–

e–

e–

2 ATP

e–

e–

e–

4 ADP

Mitochondrion

Citric acid cycle


2 ADP 2

NADH

Glycolysis

NADH

glucose pyruvate

Cytoplasm

ATP2

4 ATP total

net gain

2 ATP

ATP

2 ATP

4 ADP


NADH andFADH2

e–

e–

e–

e–

e–

e–

e–

Mitochondrion


2 32 ADPor 34

32or 34

NADH

Glycolysis

NADH

glucose pyruvate

Cytoplasm

ATP

e–

e–

e–

e–

e–

e–

e–

Citric acid cycle


NADH andFADH2

2

4 ATP total

net gain

2 ATP

ATP

2 ATP

4 ADP

ATP2 ADP

Glucose Breakdown: Glycolysis

in cytoplasm Energy Investment Steps:

2 ATP are used to activate glucose Glucose splits into 2 G3P molecules

Energy Harvesting Steps: oxidation of G3P occurs by removal of e- and H+

2 e- and 1 H+ are accepted by NAD+ resulting 2 NADH

4 ATP produced by substrate-level phosphorylation

net gain:- 2 ATP both G3Ps converted to pyruvates

glucose

Glycolysis

3PG

BPG

G3P glyceraldehyde-3-phosphate

1,3-bisphosphoglycerate

3-phosphoglycerate

ATP

ADP

ATP

ADP

PPTwo ATP are used to get started.

Energy-investment Step

glucose

ATP

Glycolysis

3PG

BPG



3-phosphoglycerate

ATP

ADP

ATP

ADP

PP

P P

Two ATP are used to get started.

Splitting produces two3-carbon molecules.


glucose

G3P G3P

ATP

Glycolysis

3PG

BPG



3-phosphoglycerate

NAD+

NADHNADH

ATP

ADP

ATP

ADP

PP

P

P PP

P

PP

P

NAD+



Oxidation occurs as NAD+

receives high-energy electrons.


Energy-harvesting Steps

glucose

G3P

BPG

G3P

BPG

ATP

Glycolysis

3PG

BPG



3-phosphoglycerate

NAD+

NADHNADH

ATP

ADP

ATP

ADP

ATP

ADP

ATP

ADP

PP

P

P PP

P

PP

P P

P

NAD+





Substrate-level ATP synthesis.



glucose

G3P

BPG

G3P

BPG

3PG 3PG

ATP

ATP

Glycolysis

3PG

BPG


2

2


3-phosphoglycerate

NAD+

NADHNADH

ATP

ADP

ATP

ADP

ATP

ADP

ATP

ADP

PP

P

P PP

P

PP

P P

P

PP

NAD+






Oxidation occurs by removalOf water



glucose

G3P

BPG

G3P

BPG

PEP PEP

3PG 3PG

ATP

ATP

H2OH2O

Glycolysis

3PG

BPG


2

2


3-phosphoglycerate

NAD+

NADHNADH

ATP

ADP

ATP

ADP

ATP

ADP

ATP

ADP

ATP

ADP

ATP

ADP

PP

P

P PP

P

PP

P P

P

PP

NAD+






Oxidation occurs by removalof water.

Two molecules of pyruvate arethe end products of glycolysis.



pyruvate

glucose

BPG

G3P

BPG

PEP PEP

3PG 3PG

pyruvate

ATP

(net gain)

2

H2OH2O

Glycolysis

3PG

BPG

G3P

2

2


glyceraldehyde-3-phosphate


3-phosphoglycerate

ATP

ATP

ATP2

G3P

Glycolysis: Inputs and Outputs

Glycolysis

inputs outputs

2 pyruvate

NADH

net gain

glucose

2 NAD+

2

2

4 ADP + 4

ATP

ATP

P

2

2 ADP

4 ATP + TOTAL

2

Net product: 2 ATP 2 NADPH2 : enter electron

transport chain

2 pyruvate : enter Krebs cycle

Glucose Breakdown: Glycolysis

29


Pyruvate pivotal metabolite end product of glycolysis

if O2 is not available to the cell, fermentation, an anaerobic process, occurs in the cytoplasm. during fermentation, glucose is incompletely

metabolized to lactate, or to CO2 and alcohol (depending on the organism).

If O2 is available to the cell, pyruvate enters mitochondria by aerobic process.

The Preparatory (Prep) Reaction occurs before citric acid cycle

connects glycolysis to the citric acid cycle end product of glycolysis (pyruvate) enters

the mitochondrial matrix pyruvate converted to 2-carbon acetyl group

attached to Coenzyme A to form acetyl-CoA e- picked up (as hydrogen atom) by NAD+

CO2 released, and transported out of mitochondria into the cytoplasm

Preparatory Reaction

2 NAD+ 2 NADH

2 2 + 2 CoA + 2 CO2

2 pyruvate

O OHC

CH3

+ 2 CoA

CoA

CH3

pyruvatecarbondioxideacetyl CoA

C OC O

2 acetyl CoA + 2 carbondioxide

Citric acid cycle/Krebs cycle occurs in mitochondria matrix

O2 needed breakdown pyruvate and form H atom

for electron transport chain H carried by NAD and FAD ATP formed by substrate-level

phosphorylation turns twice for one glucose molecule. produces 4 CO2, 2 ATP, 6 NADH and 2

FADH2 (per glucose molecule)

The Citric Acid Cycle

35


inputs outputs

4 CO2

NADH

FADH22

2 acetyl groups

6 NAD+

2FAD

2

Citric acid cycle

P2ADP +

6

ATP

Citric Acid Cycle: Inputs and Outputs

37

Electron Transport Chain

also known cytochrome or respiratory chain

eukaryotes: mitochondria cristae aerobic prokaryotes: plasma

membrane series of carrier molecules: coenzyme and cytochromes receives electrons from NADH & FADH2

pass H to other carriers down energy gradient


H atom split into proton and electron only electrons are transferred energy rich electrons passed

successively from one to another produce ATP by oxidative

phosphorylation O2 serves as a final electron

acceptor O2-combines with H+ to form H2O


1 NADH + H+ form 3 ATP 1 FADH2 forms 2 ATPs Recycling of coenzymes increases

efficiency once NADH delivers hydrogens, it returns

(as NAD+) to pick up more hydrogens hydrogens must be combined with O2 to

make H2O O2 not present, NADH cannot release H no longer recycled back to NAD+


41


42



Glucose Catabolism: Overall Energy Yield

Net yield per glucose: From glycolysis – 2 ATP

From citric acid cycle – 2 ATP

From electron transport chain – 32 ATP

Energy content: Reactant (glucose) 686 kcal

Energy yield (36 ATP) 263 kcal

Efficiency 39%; balance is waste heat

Cyt

op

lasm

Mit

och

on

dri

on

Ele

ctro

n t

ran

spo

rt c

hai

n

2net

2

glucose

2 pyruvate

2 acetyl CoA

Citric acidcycle

subtotal subtotal

glycolysis

2 CO2

4 CO2

NADH

NADH

NADH

FADH2

2

2

6

2

4 or 6

6

18

4

324

36 or 38total

6 O2 6 H2O

ATP

ATP

ATP

ATP

ATP

ATP

ATP

ATP

ATPor 34

Process Location Input Output (per glucose)

Glycolysis Cytoplasm Glucose 2 Pyruvic acid, 2 NADH. 2 ATP

Krebs cycle Mitochondria— inner space, (matrix)

2 Pyruvic acid converted to 2 acetyl CoA

2 NADH+ (pyruvic acid conversion step), 6 NADH+, 2 FADH2, 2 ATP

Electron transport chain and oxidative phosphorylation

Mitochondria— inner membrane (cristae)

10 NADH, 2 FADH2

32 ATP (12 H2O)

Total: 36 ATP/glucose

Fermentation

an anaerobic process

produces limited amount of ATP

reduces pyruvate to either lactate or

alcohol and CO2

NADH passes its electrons to pyruvate

generate NAD+

2 NAD+

2

ATP

2

4 ADP

2 ADP

P

2 P

2 P

2

2

P

glucose

G3P

BPG

pyruvate

or 2 lactate 2 alcohol

2CO2(net gain)

ATP

+4 4

2

or

ATP

NADH

ATP

2

ATP

Fermentation Advantages

provides a quick burst of ATP energy for muscular activity.

Disadvantages lactate is toxic to cells. lactate changes pH and causes muscles to

fatigue. O2 debt and cramping

Efficiency of Fermentation 2 ATP produced per glucose of molecule during

fermentation is equivalent to 14.6 kcal.

Efficiency of Fermentation

Fermentation

P ATP2 ADP + 2 2 net gain

input

glucose

outputs

2 lactate or

2 alcohol and 2 CO2

Metabolic Pool: Catabolism Foods:

sources of energy rich molecules CHO, fats, and proteins

Catabolism: degradative reactions break down molecules tend to be exergonic

Anabolism: synthetic reactions build molecules tend to be endergonic

Electrontransportchain

proteins carbohydrates fats

aminoacids

glucose fattyacids

glycerol

acetyl CoA

Glycolysis

pyruvate

ATP

ATP

ATP

Citric acidcycle

ETC

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5 Cell Respiration