revision cell respiration option c

7/29/2019 Revision Cell Respiration Option C

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Biology SL Revision Notes Ioana Holt

Cell Respiration

Contents

State that oxidation is loss of electrons from an element .................................................. 2

State that reduction is gain of electrons ................................................................................... 2

State that oxidation frequently involves gaining oxygen or losing hydrogen ............ 2

State that reduction frequently involves losing oxygen or gaining hydrogen ............ 2

Draw and label a diagram showing the structure of a mitochondrion as seen in

electron micrographs ...................................................................................................................... 2

Outline the process of glycolysis ................................................................................................. 2

Explain the link reaction ................................................................................................................ 3

Explain the Krebs cycle ................................................................................................................... 4

Explain oxidative phosphorylation in terms of chemiosmosis ........................................ 5

Explain the relationship between the structure of the mitochondrion and its

function ................................................................................................................................................ 6


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State that oxidation is loss of electrons from an element

State that reduction is gain of electrons

State that oxidation frequently involves gaining oxygen or losing hydrogen

State that reduction frequently involves losing oxygen or gaining hydrogen

Draw and label a diagram showing the structure of a mitochondrion as seen

in electron micrographs

Outline the process of glycolysis

Glycolysis takes place in the cytoplasm: it produces 2 pyruvate molecules, 2 ATP, 2

NADH, and 1 H+ from every glucose molecule.

Glycolysis has 4 main stages

1. Phosphorylation (means phosphates are added)

Two phosphate groups are added to 1 glucose molecule to create 1 hexose biphosphate

molecule. The phosphate groups are provided by 2 ATP molecules.

2. Lysis (means molecules are split)

The hexose biphosphate molecule is broken into 2 molecules of triose phosphate.

3. Oxidation (means hydrogens are lost)


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Two atoms of hydrogen are removed from each triose phosphate molecule and added to

2 molecules of NAD+.

4. ATP formation (means ADP is phosphorylated)

Pyruvate is formed by transferring 2 phosphate groups from each triose-phosphatemolecule to 4 molecules of ADP.

Explain the link reaction

http://www.youtube.com/watch?v=3wCGkmfEV9I

Glycolysis in the cytoplasm produces 2 pyruvate molecules.

Most of the energy that was stored in the glucose molecule is still present in pyruvicacid.

When oxygen is present, pyruvate is transported to the mitochondrial matrix and more

reactions take place, freeing more energy.

The reactions begin with a step known as the link reaction, so-called because it forms a

link between glycolysis and the Krebs cycle.

The link reaction involves oxidative decarboxylation of pyruvate: oxidative because an

H+ is removed; decarboxylation because a CO2 is removed.

And the link reaction involves the reduction of NAD+ to NADH, and it produces acetyl

coenzyme A (acetyl CoA) and CO2.


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Explain the Krebs cycle

http://www.youtube.com/watch?v=aCypoN3X7KQ

The Krebs cycle is a series of steps (chemical reactions) that occurs in a mitochondrion.

The Krebs cycle begins with the entry of a 2-carbon molecule that gets delivered by

acetyl CoA. The 2-carbon molecule bonds with a 4-carbon molecule forming citrate, a 6-

carbon molecule. Citrate is converted (by a series of reactions) back to the 4-carbon

molecule (thus its a cycle).

CO2 is removed in two of the reactions (decarboxylations).

ATP is produced directly in one of the reactions (substrate-level phosphorylation)

Hydrogen is removed in four of the reactions (oxidations).

For each glucose molecule (at the start of glycolysis) there will be two turns of the Krebs

cycle.

The two turns of the cycle produce 4 CO2, 6 NADH + H+, 2 FADH2 and 2 ATP.


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Explain oxidative phosphorylation in terms of chemiosmosis

http://www.youtube.com/watch?v=E82IFHFOQJ8&feature=related

The last step of aerobic respiration is called oxidative phosphorylation because ATP is

produced using energy from oxidation reactions. In this step electrons and hydrogens

from NADH and FADH2 are passed along an electron transport chain from one carrier

molecule to another.

The electron carriers are strategically located in the inner membrane of the

mitochondria. They are mainly proteins that shift between reduced and oxidized states

as they accept and donate electrons. The final electron carrier is O2 which bonds with

H+ to form water.

If no O2 is present then the electron transport chain can not function. As a result, NAD+

and FAD molecules are not produced, and the Krebs cycle can not operate.

As the electrons are passed down the electron transport chain, protons are pumped

across the membrane into the inter-membrane space. This creates a proton gradient,

which is a store of potential energy, and in turn powers the synthesis of ATP.

The inner membrane of a mitochondrion is impermeable to protons but they flow back

into the matrix through ATP synthase molecules that are embedded in the membrane.

As the ions flow down the gradient, energy is released and used to phosphorylate ADP.

When ATP synthesis is coupled to a concentration gradient of H+ it is called

chemiosmosis.


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Explain the relationship between the structure of the mitochondrion and its

function

Matrix

The matrix is the mitochondrions cytoplasm. It is the fluid contained inside the inner

membrane. The matrix contains enzymes for the Krebs cycle.

Inter-membrane space

The intermembrane space is in-between the inner and outer membrane of a

mitochondrion. It functions to store protons, which are then used to make ATP as they

flow down a concentration gradient.

Cristae

Cristae are infoldings of the inner membrane, which is the location of the electron

transport chain of cell respiration. The cristae increase surface area of the inner

membrane; thus increasing the rate of ATP formation.

revision cell respiration option c

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