Chapter 4: ATP and energy release

1
Chapter 4 ATP and energy release

• Higher Human Biology

Unit 1 Cell Function and Inheritance
2
Lesson Aims

• To compare aerobic and anaerobic respiration
• To learn about structure and function of ATP
• To learn about the three stages of respiration

3
Previous Knowledge

• What is the definition of Respiration?
• Difference between aerobic respiration and
  anaerobic respiration?
• How can you show that a living thing gives off
  energy when it is respiring?
• How can you prove that an organism releases CO2
  during respiration?

4
Previous Knowledge
Glucose O2 CO2 Water energy
Glucose Lactic acid energy
Glucose Ethanol CO2 energy
aerobic respiration
anaerobic respiration (animals)
anaerobic respiration (plants)

• aerobic respiration anaerobic
  respiration (plants) anaerobic
  respiration (animals)

Remember that respiration occurs in EVERY LIVING
THING
5
Metabolism

• Metabolism - all chemical reactions that occur in
  cells
• Catabolism produces energy when bonds between
  atoms in our food are broken
• Anabolism requires energy to make new bonds
  building up molecules

6
Aerobic Respiration

• Organisms break down organic materials through
  the process of aerobic cellular respiration. 
• The goal of this process is to break down organic
  material and harness the released energy in the
  form of ATP, the universal currency of biological
  energy. 

7
Anaerobic Respiration

• A few organisms can live without oxygen
  (anaerobically).  These organisms are capable of
  metabolizing organic material, but their ATP
  yield is much lower than that found in aerobic
  respiration.

8
ATP

• ATP Adenosine triphosphate
• ATP is a molecule that transports energy made
  during respiration and releases it for cellular
  processes (e.g. unzipping DNA, making enzymes)

9
GEEKY SCIENCE JOKE

• Man goes into a bar,
• Barman says What can I get you?
• Man says Ill have a pint of Adenosine
  triphosphate
• Barman says Ahhhh that will be ATP
• (80p.... Get it!!!! boom-chh)

10
Experiment the contraction of muscle fibre by ATP
In this experiment, the substance under
investigation is adenosine triphosphate (ATP).
This substance occurs in all living cells. The
tissue used in this experiment is muscle. The
contraction of the muscle is evidence that energy
is being used. Ringer's solution is a solution of
salts in water at about the same osmotic
concentration as tissue fluid.
11
Analysing the results.

• When each of the slides has been exposed to its
  appropriate solution for at least five minutes,
  measure the lengths of the muscle filaments
  again, record this in your table and work out the
  amount of contraction and percentage contraction.
  

A (ATP) B (Water) C (Glucose)
1st length
2nd length
Decrease
contraction
12
Experiment Discussion

1. Which of the three solutions caused the greatest
   percentage contraction?
2. Glucose is generally considered to be the main
   source of energy for reactions such as muscle
   contraction (e.g. athletes may eat glucose
   tablets before strenuous effort). Discuss whether
   your results support this view.
3. The animal from which the muscle was obtained has
   probably been dead for many days. Does the fact
   that muscle fibres will still contract mean that
   the muscle is still alive?
4. Discuss whether the results of the experiment
   entitle you to say that ATP causes muscle
   contraction in living organisms.

13
ATP releases energy by breaking the 3rd chemical
bond
Energy stored in this bond
Pi
Pi
Pi
adenosine
14
This leaves us with an energy-less molecule
called ADP (adenosine diphosphate) and a spare
phosphate

• These molecules are recycled as the chemical
  energy released during respiration remakes the
  third bond to make ATP

15
The ATP EQUATION

• The process is therefore a reversible reaction
• ATP ADP Pi

Energy released
Energy required
When ATP is synthesised (made) we refer to it as
phosphorylation (adding a phosphate).
16
Energy Transfer
ADP Pi
Cellular reactions
Chemical energy from Respiration
e.g. Protein synthesis Muscle contraction Active
transport Nerve impulses
ATP
17
Respiration

• 3 stages
• Glycolysis
• Krebs cycle
• Cytochrome system

18
OILRIG

• In a biochemical pathway, OXIDATION occurs when
  hydrogen is removed from a substrate. This
  releases energy.
• REDUCTION adds hydrogen and costs energy.
• Respiration is an oxidation reaction
• Like all biochemical pathways, respiration is
  controlled by enzymes

19
ATP TOTAL GLYCOLYSIS 2 CYTOCHROME SYSTEM
36 TOTAL 38
GLUCOSE C6H12O6
PYRUVIC ACID
CYTOPLASM GLYCOLYSIS OCCURS HERE
MITOCHONDRION AEROBIC RESPIRATION OCCURS HERE
ACETYL- CoA
H2O
KREBS CYCLE
CYTOCHROME SYSTEM
20
Glycolysis -1st stage

• Glycolysis is a part of both aerobic respiration
  and anaerobic respiration this stage doesnt
  require oxygen.
• Takes place in the cell cytoplasm
• Here, a molecule of glucose (6C) is split into
  two molecules of pyruvic acid (3C).
• Net gain of 2 ATP
• Hydrogen released is transferred to Cytochrome
  system by NAD
• If no oxygen present, pyruvic acid converted to
  lactic acid

21
Glycolysis
22
Mitochondria Structure
23
Mitochondria

• Mitochondria are found in the cytoplasm of cells
• The fluid-filled interior of the mitochondrion is
  called the matrix
• The cristae of the mitochondria is located on the
  inner membrane
• The folded inner membrane of the mitochondria
  provides a large surface area
• More active cells (e.g. muscle, sperm nerve
  cells) have many cristae in their many
  mitochondria as they require more ATP (energy)

Complete Torrance TYK questions 1-3
24
Krebs Cycle Stage 2.

• Aerobic _ Only proceeds when oxygen is present.
• Takes place in matrix of mitchondria
• Also called TCA (Tricarboxylic Acid Cycle ) or
  Citric acid cycle
• Pyruvic acid (3C) diffuses into matrix and is
  broken down into Acetyl CoA (2C)
• Acetyl CoA binds with 4C molecule to give citric
  acid
• Citric acid broken down into 4C molecule by
  series of enzyme-controlled reactions
• Produces CO2
• Hydrogen released is transferred to Cytochrome
  system by NAD

25
Krebs Cycle
26

• Throughout Glycolysis and the Krebs Cycle, the
  substrate is continually altered by the removal
  of carbon (in the form of CO2) and the removal of
  Hydrogen.
• What happens to the CO2?
• What happens to the Hydrogen?

27
Cytochrome System -3rd stage

• Ever wondered what the heck happened to all that
  NAD ? NADH2?
• Also called electron transfer chain
• Hydrogen passed along chain
• The NAD carries the H to the Cristae of the
  Mitochondria.
• The energy from the H electrons is the energy
  needed to synthesise ATP from ADP and Pi
  (remember? The 3rd bond etc.?)

28
Cytochrome System Cont

• 36 ATP molecules are made from each molecule of
  glucose in the cytochrome system
• Once the Hydrogen has been passed through the
  system and lost the electrons, it joins with
  OXYGEN as its finale.
• The oxygen is therefore said to be the final
  hydrogen acceptor. This makes WATER!

29
Cytochrome System hydrogen chain.
30
The Big Picture..
31
Summary

• One molecule of glucose gives a total yield of 38
  ATP
• 2 from glycolysis
• 36 from cytochrome system
• The Citric acid cycle turns twice for each
  molecule of glucose as there are 2 x PA (see page
  7 of workbook)
• Glucose O2 ? CO2 H2O 38 ATP
• Respiration is carefully controlled by various
  ENZYMES!

32
Anaerobic Respiration

• If Oxygen is not present, then the biochemical
  process we have studied aerobic respiration
  cannot happen.
• Glucose (6C)
• Pyruvic Acid (3C) Lactic Acid (3C)

2 ATP
33
Anaerobic Respiration

• If Oxygen is not present, then the biochemical
  process we have studied cannot happen.
• Glucose (6C)
• Pyruvic Acid (3C) Lactic Acid (3C)

2 ATP
O2 available
CAC
34

• Oxygen debt and reversible
• Only the 2 ATP from Glycolysis is made
• Therefore the net gain of anaerobic respiration
  is 2 ATP

35
Anaerobic Respiration (Plants)

• In plants and yeast anaerobic respiration takes a
  different and irreversible pathway.
• Glucose (6C)
• Pyruvic Acid (3C) CO2 Ethanol

2 ATP
How many carbons? Justify answer.
36
TASK!!! Essay Question

• An essay question is usually 10 marks in the exam
  you would have about 15 minutes to complete each
  essay.
• Give an account of Respiration under the
  following headings
• Glycolysis (3)
• Krebs Cycle (4)
• Cytochrome system (3)

37
(i) Glycolysis Max 3

• 6C Glucose is broken down into 2 molecules of 3C
  Pyruvic Acid
• Hydrogen is released and picked up by NAD to
  become NADH2
• NADH2 goes to Cytochrome System (or cristae of
  mitochondria)
• Glycolysis makes 4 ATP but costs 2 ATP resulting
  in a net gain of 2 ATP
• Glycolysis takes place in the cytoplasm of the
  cell

38
(ii) Krebs Cycle Max 4

• 3C PA is converted in 2C Acetyl CoA
• Acetyl CoA enters the matrix of the mitochondria
• Acetyl CoA joins with 4C intermediate compound to
  form 6C Citric Acid
• Citric Acid is changed into a 5C compound which
  is then changed into a 4C compound
• Each time a Carbon is removed, it is released as
  CO2 and eventually breathed out
• Hydrogen is also released (oxidation) which
  combines with NAD to make NADH2 (reduction)
• NADH2 goes to Cytochrome System

39
(iii) Cytochrome System Max 3

• Cytochrome System is located on the cristae of
  the mitochondrion
• NADH2 is reduced/released Hydrogen
• As Hydrogen is passed along Cytochrome System, it
  loses electrons which released energy
• This energy is needed to regenerate ATP by
  phosphorylation/from ADP and Pi
• The Hydrogen then combines with Oxygen to form
  metabolic water
• The Cytochrome system makes 36 ATP