Bio chap 9

Exergonic

Releasing energy

Endergonic

Taking in energy

First law of thermodynamics

Energy can’t be created or destroyed

Catabolic pathway

The breakdown of organic molecules

Fermentation

Partial degradation of sugars that occur without oxygen

Aerobic respiration

Consumes organic molecules and oxygen an yields ATP

Anaerobic respiration

Consumes compounds other than oxygen

Cellular respiration

Includes aerobic and anaerobic respiration, but is often used to refer to aerobic respiration

Cellular respiration equation

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy (ATP + heat)

Oxidative phosphorylation

Electron transport and chemiosmosis

Where do we get the most ATP?

Oxidative phosphorylation

Redox reaction

The transfer of electrons during chemical reactions releases energy stored in organic molecules

What is used to synthesize ATP?

Redox reaction

OIL RIG

Oxygen

Is

Lost

Reduction

Is

Gain

An electron loses potential energy when

It shifts from a less electronegative atom toward a more electronegative one

Redox reaction

Transfer of electrons between reactions

Oxidation

The loss of electrons

Reduction

The addition of electrons to a substance

Reducing agent

The electron donor that reduces the electron acceptor

Oxidizing agent

The electron acceptor that oxidizes the electron donor

Oxygen atoms are very electronegative

True

The partial gain of electrons by O atoms and partial loss of electrons by bonding partners constitute

a redox reaction

NAD+ is a coenzyme that

function as an electrons carrier

What process(es) is NAD+ important to?

Producing energy, specifically in fermentation

Each NADH represents

Stored energy that is tapped to synthesize ATP

Dehydrogenase

removes hydrogen from the substrate

Kinase

Transfers phosphate

Isomerase

Rearranges molecules

For NAD+ to change to NADH,

A dehydrogenase must occur

Electron transport chain

Consists of a series of molecules built into the inner membrane of mitochondria

Used by cellular respiration to break the fall of electrons to O2 into several energy-releasing steps

ETC

If NADH transferred electrons directly to oxygen,

energy would be released in one explosive reacction

Three stages of cellular respiration

1. Glycolysis

2. Citric acid cycle

3. Oxidative phosphorylation

Glycolysis

Breaks down glucose into two molecules of pyruvate

Citric acid cycle

Completes the breakdown of glucose to CO2 with pyruvate

Oxidative phosphorylation

During this stage, the electron transport chain and chemiosmosis facilitate the synthesis of most of the cell’s ATP

The process that generates almost 90% of ATP

Oxidative phosphorylation

Substrate-level phosphorylation

Some ATP is also formed in glycolysis and the citric acid cycle by this process

When does substrate level phosphorylation occur?

When an enzyme transfers a phosphate groups directly from a substance to ADP

Glycolysis phase name

Energy investment phase

Glycolysis reactants

Glucose and 2 ATP

Glycolysis products

2 NADH, 2 pyruvate, and 2 net ATP (energy payoff phase)

The three rate limiting steps in glycolysis

Pyruvate, phosphofructokinase, and hexokinase

Glycolysis step 1

(hexokinase) costs 1 ATP to convert glucose into glucose 6-phosphate

Glycolysis step 2

Isomerization

Glycolysis step 3

(phosphofructokinase) Costs 1 ATP to convert fructose 6-phosphate into fructose

Glycolysis step 4

Split

Glycolysis step 5

Conversion

Glycolysis step 6

(dehydrogenase) makes 2 NADH

Glycolysis step 7

(phosphoglycerate kinase) Debt settled, 2 ATP made

Glycolysis step 8

Shuffle

Glycolysis step 9

2 water made

Glycolysis step 10

(pyruvate kinase) 2 ATP made

What happens to pyruvate before entering citric acid cycle?

It is converted to acetyl-CoA

Step 1 of oxidation of pyruvate

Oxidation of pyruvate’s carboxyl group, releasing the first CO2 of cellular respiration

Step 2 of oxidation of pyruvate

Reduction of NAD+ to NADH

Step 3 of oxidation of pyruvate

A combination of the remaining two-carbon fragment with coenzyme A to form acetyl-CoA

What starts citric acid cycle?

Acetyl-CoA

How many times does citric acid cycle occur?

Twice

What is citric acid cycle also known as?

Krebs cycle

Reactions of oxidation of pyruvate

1 pyruvate, 1 NAD+, 1 coenzyme A

Products of oxidation of pyruvare

1 acetyl-CoA, 1 CO2, 1 NADH, and 1 H+

Reactants of citric acid cycle

2 acetyl-CoA

Products of citric acid cycle

6 NADH, 2 FADH2, 2 ATP, 4 CO2 by product, and 2 water

Step 1 of citric acid cycle

Acetyl-CoA joins with oxaloacetate, releasing the CoA groups and forming a six carbon molecule called citrate

Step 2 of citric acid cycle

Citrate is converted into isocitrate by removing then adding a water molecule

Step 3 of citric acid cycle

Isocitrate is oxidized and releases a molecule of CO, leaving behind a ketoglutarate

Step 4 of citric acid cycle

a-ketoglutarate is oxidized reducing NAD+ to NADH and releasing CO2

Step 5 of citric acid cycle

Succinate made and CO2 is released, NADH is made, ATP

Step 6 of citric acid cycle

Succinate is oxidized, forming fumarate, and two hydrogen atoms are transferred to FAD, making FADH2,

Step 7 of citric acid cycle

Water is added to fumarate, converting it into malate

Step 8 of citric acid cycle

Oxaloacetate is regenerated by oxidation of malate and NAD+ is reduced to NADH

Per glucose, what was made in citric cycle?

6 NADH, 2 FADH2, 2 ATP, 4 CO2

What does chemiosmosis couple up with in ATP synthesis

ETC

What does NADH and FADH2 donating electrons to the ETC do?

Powers ATP synthesis via oxidative phosphorylation

Where is the ETC in prokaryotes?

Embedded in plasma membrane

Chemiosmosis

The diffusion of ions through a semipermeable membrane, like osmosis, from greater ion concentration into less ion concentration until the internal and external concentrations are equal

Is ATP produced in oxidative phosphorylation

Yes

Step 1 of oxidative phosphorylation

Delivery of electrons by NADH and FADH2

Step 2 of oxidative phosphorylation

Electron transfer and proton pumping

Step 3 of oxidative phosphorylation

Splitting of oxygen to form water

Step 4 of oxidative phosphorylation

Gradient-driven synthesis of ATP

Energy coupling mechanisms of chemiosmosis

The use of energy in H+ gradient to drive cellular work

What is the energy released as electrons that are passed down the electron transport chain used for?

To pump H+ from the mitochondrial matrix into the intermembrane space

In chemiosmosis, how does H+ move after being pumped into the intermembrane space?

Moves down its concentration gradient back across the membrane, passing through the protein complex ATP synthase

Step 1 of ETC

NADH donates

Step 2 of ETC

FADH2 donates

Step 3-5 of ETC

Pump H+

Step 6 of ETC

Oxygen accepts

Step 7 of ETC

Water made

Step 8 of ETC

H+ flows back

Step 9 of ETC

ATP synthase spins

Step 10 of ETC

ATP payday

The three reasons why the exact number of ATP produced is not know

1. Photophosphorylation and the redox reactions are not directly coupled; the ratio of NADH to ATP molecules is not a whole number

2. ATP yield varies depending on whether electrons are

passed to NAD+ or FAD

3. The proton-motive force is also used to drive other

kinds of work

What does the ETC need to operate?

Oxygen

Oxidizing agent in glycolysis

NAD+

Fementation

Extension of glycolysis that oxidizes NADH by transforming electrons to pyruvate or its derivatices

Two common types of fermentation

Alcohol and lactic acid fermentation

Pyruvate in alcohol fermentation

Pyruvate is converted to ethanol by

• The release of CO2 from pyruvate

• Production of NAD+ and ethanol

Pyruvate in lactic acid fermentation

Pyruvate is reduced directly by NADH to form lactate and NAD+