Cellular Respiration

1

Cellular respiration
2
Overview

• Cellular respiration is the process that
  releases energy by breaking down food molecules
  in the presence of oxygen.

6O2 C6H12O6 6H2O CO2
energy
3
Fermentation

• The process of releasing energy in the absence
  of oxygen

4
How much energy is in food?

• One calorie is the amount of energy needed to
  raise one gram of water by 1 degree Celsius.
• One Calorie one kilocalorie (food labels)
• One gram of sugar yields 3811 calories of heat
  energy

5
Both processes begin with glycolysis (anaerobic)

• The process in which one molecule of glucose is
  broken in half, producing 2 molecules of pyruvic
  acid. (3-C compound)
• 2 ATPs are needed to start reaction, and 4 are
  produced, so there is a net gain of 2 ATP.
• Electrons are passed to NAD molecules
• Takes place in the cytoplasm

6
GlycolysisC6H12O6 NAD 2 pyruvic acids
NADH
7
Fermentation

• When oxygen is not present, fermentation releases
  energy from food molecules.
• NADH is converted back to NAD by passing high
  energy electrons to pyruvic acid, allowing
  glycolysis to continue.

8
2 paths of fermentation

• Alchoholic fermentation
• Yeasts and other microorganisms use pyruvic acid
  to form ethyl alchohol and CO2 and NAD

• Lactic Acid Fermentation
• In some cells, such as muscle cells, pyruvic acid
  is converted to lactic acid and NAD

9
Krebs Cycle (citric acid cycle)

• Pyruvic Acid is broken down to carbon dioxide in
  a series (5 steps) of energy-extracting reactions
• Takes place in the mitochondrial matrix
• CO2 is the by-product
• One glucose (2 turns of cycle) ?
• 6 NADH 2 FADH2 2 ATP 4 CO2

10
ELECTRON TRANSPORT CHAIN

• Takes place in cristae (inner mitochondrial
  membrane)
• 32 ATP produced in most eukaryotes prokaryotes
  34
• High-energy electrons (from NADH and FADH2 ) are
  passed along a series of carrier proteins (ETC)
  until the end where there is an enzyme that bonds
  the e-s to hydrogen ions and oxygen ? water.
• The energy passed along the ETC is used to move
  H ions into the intermembrane space.
• ATP synthase provides channels for H ions to
  pass through.
• Each time it rotates an ADP and a P are
  attached.
• Aerobic respiration is about 40 efficient. The
  rest of the energy is lost as heat.

11
Energy and exercise

• Muscle cells normally contain small amounts of
  ATP, enough for a few seconds of intense activity
• Muscles use lactic acid fermentation (about 90
  sec) Extra oxygen is needed to break it down.
• Glycogen is used for about 20 minutes. Then,
  stored molecules must be broken down