Respiration

1
Respiration

• Organic molecules are broken down in a series of
  stages to release chemical potential energy.
  This is used to synthesise ATP.
• Many cells only break down glucose but some break
  down fatty acids, glycerol and amino acids.

2
Aerobic respiration

• Glycolysis
• Link reaction
• Krebs cycle
• Oxidative phosphorylation

3
Glycolysis

• The splitting or lysis of glucose
• Glucose (6C) is gradually split into 2 molecules
  of pyruvate (3C) in a series of steps.
• ATP is required in the first few steps
• Energy is released in the later steps and used to
  make ATP.
• Overall there is a net gain of 2ATP

4
Glycolysis

• Takes place in the cytoplasm
• First stage phosphorylation of glucose
• This is where ATP is required to add P to glucose
• 2 ATP molecules are used for each glucose
• First ATP added hexose phosphate (6C)
• Second ATP added hexose bisphosphate (6C)
• This then breaks down to give 2 molecules of
  triose phosphate (3C)
• Phosphorylation needs to happen to make the
  glucose react easier. Glucose does not usually
  react easily.

5
Glycolysis

• Hydrogen is then removed from the triose
  phosphate
• It is a hydrogen carrier called NAD which mops up
  the H ions
• NAD Nicotinamide adenine dinucleotide
• When NAD collects H we say it is reduced or NADH
• H can then easily be transferred to other
  molecules
• 2NADH molecules are produced per glucose

6
Glycolysis

• http//science.nhmccd.edu/biol/glylysis/glylysis.h
  tml

7
Glycolysis

• The end product is pyruvate
• This is energy rich.
• Energy is released using the Krebs cycle

8
The Link reaction

• This reaction prepares the pyruvate for the Krebs
  cycle

9
The Link Reaction

• The pyruvate needs to travel from the site of
  glycolysis (cytoplasm0
• It moves by active transport to the outer and
  inner membranes of the mitochondria and into the
  matrix
• See p10

10
The Link Reaction

• Pyruvate is decarboxylated (CO2 taken)
• Then dehydrogenated (H taken)
• It then combines with coenzyme A
• This forms acetyl coenzyme A
• This enters the Krebs cycle

11
The link reaction

• Pyruvate reacts with CoA
• H is transferred to NAD in this process
• Acetyl CoA CO2 NADH

12
Note

• Fatty acids can also be used to produce coenzyme A

13
The Krebs Cycle p8

• A sequence of enzyme controlled reactions.
• Acetyl CoA from link reaction combines with
  oxaloacetate (4c) to form citrate (6C)
• Steps involving dehydrogenating and
  decarboxylating
• H carriers NAD and FAD involved
• Oxaloacetate is regenerated

14
Krebs cycle

• The release of H is important because they are
  required in the next stage oxidative
  phosporylation

15
Oxidative Phoshorylation

• In the final stage energy needs to be generated
  to turn ADP back to ATP
• This comes from the electron transport chain.
• It occurs in the mitochondrial membranes

16
Oxidative phosphorylation

• NADH and FADH are passed on to the e transport
  chain
• H are removed
• H are then split into ion and e
• E passed on to the first e carriers
• H ion stays in solution in the matrix
• The e is passed on to O2 which is in the matrix

17
Oxidative Phosphorylation

• Oxygen then combines with h ion to form water
• The movement of the e down the chain of carriers
  released energy
• The e moves from higher energy carriers to lower
  energy carriers
• This energy changes ADP to ATP

18

• 3 ATP produced per NADH
• 2 ATP produced per FADH
• This usually doesnt happen because energy is
  needed to transfer ADP to the mitochondrion and
  ATP back to the cytoplasm