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A2 Biology - F214 > F214 - Respiration > Flashcards

F214 - Respiration Flashcards

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1
Q

Energy

Definition

A

The ability to do work

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2
Q

What do organisms require energy for?

A
  • active transport
  • endocytosis / exocytosis
  • anabolic reactions
  • movement of cilia, flagella etc.
  • spindle formation
  • activation, lowering the energy required for a reaction to take place
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3
Q

Structure of ATP

A

Ribose sugar, adenosine bonded to adenine and a chain of three phosphates

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4
Q

ATP - Universal Energy Currency

A
  • used in all cells
  • energy rich compound that can easily be hydrolysed to release energy
  • can be broken down gradually to release small packets of energy
  • an immediate energy source for biological processes
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5
Q

Oxidation

Definition

A

Reactions involving the loss of electrons

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6
Q

Reduction

Definition

A

Reactions involving the gain of electrons

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7
Q

Coenzymes - NAD

A
  • organic non protein molecule
  • helps dehydrogenase enzymes to carry out oxidation reactions
  • when one molecule of NAD has accepted two hydrogen atoms it is reduced
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8
Q

Coenzymes - Coenzyme A

A
  • carries acetate/ethanoate groups
  • made from pantothenic acid, adenosine, 3 phosphates and cysteine
  • carries acetate groups formed from pyruvate, fatty acids and some amino acids from the link reaction to the kerbs cycle
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9
Q

Where does glycolysis take place?

A

Cytoplasm

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10
Q

Glycolysis

Description

A
  • glucose converted to glucose 6-phosphate, requires 1 ATP
  • glucose 6-phosphate rearranged to form isomer fructose 1-phosphate
  • fructose 1-phosphate converted to hexose 1, 6-bisphosphate, requires 1 ATP
  • hexose bis phosphate splits to form two molecules of triose phosphate
  • each triose phosphate molecule converted to one molecule of pyruvate, one NAD reduced and one ATP produced per pyruvate
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11
Q

Glycolysis

Net Production

A

2 pyruvate
2 ATP
2 reduced NAD

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12
Q

What happens to pyruvate at the end of glycolysis?

A

Actively transported into mitochondria

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13
Q

Mitochondria

Inner Membrane

A

Different lipid composition to outer membrane
Impermeable to most small ions including protons
Folded to form cristae to increase surface area
Many electron carrier proteins and ATP synthase enzymes

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14
Q

Mitochondria

Outer Membrane

A

Similar lipid composition to other organelle membranes
Contains enzymes
Channels / carriers for pyruvate

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15
Q

Mitochondria

Matrix

A

Mitochondrial DNA coding for enzymes and other proteins
Mitochondrial ribosomes
Enzymes to catalyse link reaction and Kreb’s cycle
Molecules of coenzyme NAD

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16
Q

Where does the Link Reaction take place?

A

Mitochondrial matrix

17
Q

The Link Reaction

Description

A
  • pyruvate is dehydrogenated (reducing NAD) and decarboxylated (releasing 1CO2) to form 1 molecule of acetate
  • acetate group combined with coenzyme A to form acetyl coenzyme A
  • coenzyme A carries acetate group to the Kreb’s cycle
18
Q 
The Link Reaction 
Net Production (per pyruvate)
A

1 acetyl coenzyme A
1 carbon dioxide
1 reduced NAD

19
Q

Where does the Kreb’s Cycle take place?

A

Mitochondrial matrix

20
Q

The Kreb’s Cycle

Description

A
  • acetyl coenzyme A combined with oxaloacetate to form citrate, coenzyme A released
  • citrate decarboxylated and dehydrogenated to form alpha-ketoglutarate, releasing 1 CO2 and reducing 1 NAD
  • alpha-ketoglutarate is decarboxylated and dehydrogenated to form oxaloacetate, releasing 1 CO2, reducing 2 NAD and 1 RAD, and substrate level phosphorylation produces 1 ATP
21
Q 
The Kreb's Cycle 
Net Production (per cycle)
A

2 carbon dioxide
3 reduced NAD
1 reduced FAD
1 ATP

22
Q

Where does oxidative phosphorylation take place?

A

Inner mitochondrial membrane

23
Q

Oxidative Phosphorylation and Chemiosmosis

Description

A
  • reduced NAD is oxidised forming NAD and hydrogen
  • the hydrogen is split into electrons and protons
  • the protons go into solution in the matrix and the electrons are passed along a four protein transport chain through a series of redox reactions that release energy
  • FAD is also oxidised but electrons only enter the transport chain at electron carrier two
  • the energy released is used to pump protons into the inter membrane space establishing proton concentration, electrochemical and pH gradients
  • the protons diffuse back through the membrane down the gradient through ATP synthase which drives the rotation of part of the enzyme, ADP is joined to an inorganic phosphate forming ATP
  • electrons are passed to the final electron acceptor, molecular oxygen, where they combine with protons from the matrix to form water
24
Q

Oxidative Phosphorylation

Definition

A

The formation of ATP, in the presence of oxygen, by chemiosmosis

25
Q

Chemiosmosis

Definition

A

The flow of hydrogen ions through ATP synthase enzymes

The force of this flow allows ATP to be produced

26
Q

Inefficiencies in Respiration

A
  • some protons leak across the mitochondrial membrane reducing the proton motive force
  • some ATP is used to actively transport pyruvate into the mitochondria
  • some ATP is used as a shuttle to bring hydrogen from reduced NAD made during glycolysis in the cytoplasm into the mitochondria
27
Q

Anaerobic Respiration in Mammals

A
  1. Glycolysis
  2. Conversion of pyruvate to lactate catalysed by lactate dehydrogenase, this process oxidises one molecule of reduced NAD to NAD
28
Q

Anaerobic Respiration in Plants and Yeast

A
  1. Glycolysis
  2. Decarboxylation of pyruvate to form ethanal, catalysed by pyruvate decarboxylase, releases one molecule of carbon dioxide
  3. Ethanal converted to ethanol, catalysed by ethanol dehydrogenase, oxidised one molecule of reduced NAD to NAD
29
Q

Why does anaerobic respiration produce a much lower yield than aerobic respiration?

A

If oxygen is absent then the electron transport chain cannot function as molecular oxygen is the final electron acceptor in oxidative phosphorylation
The link reaction and Kreb’s cycle stop
Glycolysis is the only source of ATP in anaerobic respiration
Anaerobic respiration recycles reduced NAD so that glycolysis can continue and small amounts of ATP can be produced

30
Q

Respiratory Substrate

Definition

A

An organic molecule that can be broken down to release energy in respiration

31
Q

Respiratory Substrates

Carbohydrates

A
  • primary respiratory substrate is glucose
  • some mammalian cells (e.g. brain, red blood) can only respire glucose
  • glucose can be stored as glycogen in animals and starch in plants
  • starch and glycogen hydrolysed to form glucose
  • 15.8 kJ/g
32
Q

Respiratory Substrates

Lipids

A
  • if carbohydrates run out, lipids respired instead
  • triglycerides hydrolysed by lipase to fatty acids and glycerol
  • glycerol converted to glucose and respired
  • fatty acids are combined with coenzyme A and transported to the matrix where they are split into two acetate groups which take part in the Kreb’s cycle
  • 39.4 kJ/g
33
Q

Respiratory Substrates

Proteins

A
  • excess amino acids from protein digestion can be deaminated, the rest of the molecule is converted to glycogen or fat
  • when an organism undergoes fasting, starvation or prolonged exercise protein from muscles can be hydrolysed to amino acids for respiration but this is a destructive process
  • 17.0 kJ/g
34
Q

Evidence for Chemiosmosis

A
  • lower pH in intermembrane space than in mitochondrial matrix
  • more negative potential on the matrix side of the inner mitochondrial membrane
  • no ATP made in mitoblasts (mitochondria without outer membrane)
  • no ATP made if headpieces are removed form stalked particles (ATP synthase)
35
Q

Respiration

Definition

A

The breakdown of complex organic molecules in the presence of oxygen to release energy

A2 Biology - F214 (6 decks)

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