18.2 Linking glycolysis and the Krebs cycle

In eukaryotic cells, where do the remaining aerobic (oxygen-requiring) reactions of cellular respiration take place?

inside the mitochondria

Mitochondria: 1?

outer mitochondrial membrane

Mitochondria: 2?

inner mitochondrial membrane

Mitochondria: 3?

cristae

Mitochondria: 4?

intermembrane space

Mitochondria: 5?

matrix

Mitochondria: function of the outer mitochondrial membrane?

separates the contents of the mitochondrion from the rest of the cell, creating a cellular compartment with ideal conditions for aerobic respiration

Mitochondria: function of inner mitochondrial membrane?

contains electron transport chains and ATP synthase

Mitochondria: what are cristae?

projections of the inner membrane

Mitochondria: function of the cristae?

increase the surface area available for oxidative phosphorylation

Mitochondria: function of intermembrane space?

proteins pumped into this space by the electron transport chain - the space is small so the concentration builds up quickly

Mitochondria: function of the matrix?

contains enzymes for the Krebs cycle and the link reaction also contain mitochondrial DNA

The first step in aerobic respiration?

oxidative decarboxylation (the link reaction)

Why is oxidative decarboxylation referred to as the link reaction?

it’s the step that links anaerobic glycolysis, occurring in the cytoplasm, to the aerobic steps of respiration, occurring in the mitochondria

Oxidative decarboxylation: in eukaryotic cells, what does pyruvate enter?

the mitochondrial matrix

Oxidative decarboxylation: how does pyruvate enter the mitochondrial matrix?

by active transport via specific carrier proteins

Oxidative decarboxylation: what does pyruvate then undergo?

oxidative decarboxylation

Oxidative decarboxylation: what is removed from the pyruvate when it undergoes oxidative decarboxylation (2)?

carbon dioxide is removed (decarboxylation) along with hydrogen (oxidation)

Oxidative decarboxylation: what is pyruvate converted to through Oxidative decarboxylation?

(two-carbon) acetyl group

Oxidative decarboxylation: what are the hydrogen atoms removed accepted by?

NAD

Oxidative decarboxylation: what is NAD reduced (bonding with removed hydrogen ions) to form?

NADH (also known as reduced NAD)

Oxidative decarboxylation: what is the acetyl group bound by?

coenzyme A

Oxidative decarboxylation: what does the acetyl group form when bound by coenzyme A?

acetylcoenzyme A (acetyl CoA)

IUPAC name for the acetyl group?

the ethanoyl group

Oxidative decarboxylation diagram?

…

Where does Acetyl CoA deliver the acetyl group to?

the next stage of aerobic respiration - known as the Krebs cycle

Where is the NADH used?

in oxidative phosphorylation to synthesise ATP

Oxidative decarboxylation: what is all that’s left of the original glucose molecules?

acetyl groups

Where does the produced CO2 go (2)?

will either diffuse away and be removed from the organism as metabolic waste or, in autotrophic organisms, it may be used as raw material in photosynthesis

During the link reaction what does each pyruvate form (3)?

1 molecule of acetyl coenzyme A, one molecule of carbon dioxide and one molecule of NADH

How many times does the link reaction occur per molecule of glucose entering respiration?

twice