g) Cellular Respiration

Higher Human Biology

What can you remember

about respiration?

1. What is respiration?

2. What are the raw materials?

3. What are the products?

4. Where does it occur?

5. Why does this happen?

6. What molecule do we need for energy?

Lesson starter 2

• This morning to get you in the respiration mood

we are going to complete an exercise video!!

• Measure your pulse rate before and after

• You can also use the stethoscope to listen to

your breathing!

• Then answer the following:

• What happened to your breathing?

• What happened to your pulse rate?

• What happened to your blood circulation?

• Were you respiring?

Respiration

• Respiration is the process by which chemical energy is released from food (by oxidation).

• It occurs in every living cell and involves the regeneration of ATP by a series of chemical reactions.

Respiration

However if not enough oxygen can be taken in during exercise then ANAEROBIC REPSIRATION OCCURS

In normal conditions our body uses oxygen to fully break down glucose in AEROBIC REPSIRATION :

glucose + oxygen energy + water + carbon dioxide

glucose lactic acid + little energy

Video

Learning Intentions

• State the role of ATP in the transfer of energy and the phosphorylation of molecules by ATP.

ATP- Adenosine Tri-Phosphate

• High energy molecule

• Made up of adenosine and three inorganic phosphate molecules

video

ADENOSINE Pi Pi Pi

Energy Release

• The energy stored in ATP is released when the bond to the last phosphate is broken.

• Adenosine Diphosphate (ADP) and an inorganic phosphate (Pi) are produced

ADENOSINE Pi Pi Pi

Energy

•ATP breakdown to ADP + Pi releases energy

•Making ATP from ADP + Pi requires energy which comes from the breakdown of glucose during respiration •There is a constant supply of ATP in our cells because it is synthesised as fast as it is used

ATP ADP + Pi

Breakdown

releasing energy

Build up requiring

energy (High energy

state)

(Low energy

state)

Phosphorylation

• Phosphorylation is an enzyme controlled process by which a phosphate group is added to a molecule.

• Phosphorylation occurs, for example, when Pi is added to ADP to make ATP.

ADP + Pi ATP

Phosphorylation

• Phosphorylation also occurs when phosphate (Pi) and energy are transferred from ATP to the molecules of a reactant in a metabolic pathway making them more reactive.

Glucose Glucose -1 Phosohate

ATP ADP

Learning Intentions

• Describe the energy investment and energy payoff stages of glycolysis

Aerobic Respiration

• There are 3 stages of respiration: – Stage 1 = GLYCOLYSIS

– Stage 2 = KREBS CYCLE (or CITRIC ACID CYCLE)

– Stage 3 = ELECTRON TRANSFER SYSTEM

Glycolysis

• Takes place in the cytoplasm of the cell.

• Does not require oxygen.

• Glucose (6C) is broken down first into an intermediate compound, then into two molecules of Pyruvate (3C).

• Net gain of 2 ATP.

Fate of Hydrogen

• Dehydrogenase enzymes remove hydrogen ions from the substrate along with associated high-energy electrons.

• These hydrogen ions and high-energy electrons are passed to the coenzyme NAD, or FAD in the Krebs cycle forming NADH or FADH.

• NADH and FADH then travel to the electron transport chain

Energy Investment Stage

6C GLUCOSE 2 ATP

2 ADP+Pi

INTERMEDIATE COMPOUND

• The first phosphorylation leads to a product that can continue to a number of pathways e.g. fermentation in the absence of oxygen.

• 2ATP are used up per glucose molecule

Energy Payoff Stage

• The second phosphorylation is catalysed by the enzyme phosphofructokinase - this is an irreversible reaction leading only to the glycolytic pathway.

• 4 ATP are produced per glucose molecule

2x 3C PYRUVATE

4 ATP

4 ADP+Pi 2 NAD

2 NADH2

INTERMEDIATE COMPOUND

• Hydrogen ions are released by the action of a dehydrogenase enzyme

• The coenzyme NAD picks up the H+ ions to form NADH and is carried to the 3rd stage – the electron transport chain.

6C GLUCOSE

2x 3C PYRUVATE

2 ATP

2 ADP+Pi

4 ATP

4 ADP+Pi NAD

NADH2

Glycolysis

INTERMEDIATE COMPOUND

Energy investment

stage

Energy payoff stage

Phosphofrucktokinase

Occurs in the cytoplasm Does not require oxygen Net gain of 2ATP

Dehydrogenase

Glycolysis Summary

• Takes place in the cytoplasm of the cell and does not require oxygen. Glucose (6C) is broken down into pyruvate (3C) in 2 steps with a net gain of 2ATP. Pyruvate progresses to the Krebs cycle if oxygen is available.

• The first phosphorylation leads to an intermediate that can continue to a number of pathways. 2 ATP are used up per glucose molecule. This is the energy investment

Glycolysis Summary Cont’d • The second phosphorylation is catalysed by

phosphofructokinase. This is an irreversible reaction leading only to the glycolytic pathway. 4 ATP are produced per glucose molecule. This is the energy pay off stage.

• Dehydrogenase enzymes remove hydrogen ions with associated high-energy electrons. These hydrogen ions and high-energy electrons are passed to the coenzyme NADH2.

Learning Intentions

• Describe the events of the Kreb’s cycle

The mitochondria has an inner and outer membrane:

•The inner membrane has many folds called cristae

•The fluid filled interior is called the matrix

Mitochondria

– Stage 2 = the Krebs cycle in matrix

– Stage 3 = the cytochrome system in cristae

Mitochondria

Krebs Cycle

• Takes place in the matrix of the mitochondria.

• Requires oxygen.

• Pyruvate is converted to Acetyl which combines with Coenzyme A.

• Acetyl CoA then enters Krebs and combines with oxaloacetate a 4C compound to form 6C citric acid.

Lesson starter

1. What is the main difference between anaerobic and

aerobic?

2. What are the names of the 3 stages involved in aerobic

respiration?

3. a) What stage can occur anaerobically?

b) where does this stage occur?

c) what is broken down and into what?

d) name the two parts of this stage

e) is there energy made? How much?

4. Where does the a) 2nd stage b) 3rd stage occur?

5. What is the final product of stage 1 converted to at the

beginning of this stage?

Krebs Cycle

• Citric acid is converted back to oxaloacetate by a series of enzyme controlled reactions.

• During the cycle, carbon is released in the form of carbon dioxide.

• Dehydrogenase enzymes remove hydrogen and high energy electrons which are passed to the coenzymes NAD or FAD forming NADH2 or FADH2

• Some ATP is also made

Kreb’s Cycle CO2

NAD

NADH2

PYRUVATE (3C)

ACETYL COA (2C)

CITRIC ACID (6C)

5C COMPOUND

4C COMPOUND

4C OXALOACETATE

4C COMPOUND

NAD

NADH2

CO2

CO2

FAD

NAD

NAD FADH2

NADH2

NADH2

ACETYL (2C) COENZYME A

Occurs in the matrix of the mitochondria

Does require oxygen NADH2 and FADH2 taken to the

electron transfer chain

ADP + Pi

ATP

Kreb’s Cycle Summary

• Takes place in the matrix of the mitochondria and only occurs if oxygen is present.

• Pyruvate (3C) is converted to an acetyl group.

• The acetyl group combines with coenzyme A to form acetyl coenzyme A (2C).

• Acetyl coenzyme A combines with oxaloacetate (4C) to form citric acid (6C).

• Citric acid is converted back into oxaloacetate by a series of enzyme controlled reactions during which carbon dioxide is released, some ATP is produced and dehydrogenase enzymes remove hydrogen.

Learning Intentions

• Describe the events of the electron transfer chain

• Describe the process of ATP synthesis

• Takes place on the cristae of the mitochondria.

• The NADH2 and FADH2 are reduced to NAD and FAD

• The reduced NAD/FAD transfer the high energy electrons to a chain of carriers called the cytochrome system

Electron Transfer Chain

Electron Transfer System

FADH2/ NADH2

FAD/ NAD

OXYGEN (Final hydrogen acceptor)

WATER

ADP +Pi ADP +Pi ADP +Pi

ATP ATP ATP

SERIES OF HYDROGEN CARRIERS

Animation https://www.youtube.com/watch?v=00jbG_

cfGuQ

The energy from the electrons is used to pump H ions across the inner mitochondrial membrane.

Electron Transfer Chain

The return flow of H ions drives ATP synthase and produces the bulk of the ATP generated by cellular respiration.

Electron Transfer Chain

The final electron acceptor is oxygen which combines with hydrogen ions and low energy

electrons to form water .

Electron Transfer Chain

Lesson starter

1. What does glycolysis mean? 2. What are the names of the two parts involved in

glycolysis? 3. In part one, how many ATP molecules are made? 4. In part two, how many ATP molecules are made? 5. What enzyme helps with this (Q4)? 6. What is phosphorylation? 7. In the Kreb’s cycle 4C OXALOACETATE joins with 2C Acetyl

COA to make? 8. How many times in the Kreb’s cycle does NAD become

NADH2? 9. What type of enzymes help with this process (Q5)?

Lesson starter

Complete the 3 stages of aerobic respiration worksheet

• Energy from the electrons is used to pump H+ across the inner membrane of the mitochondria.

• The return flow of H ions drives ATP synthase and produces the bulk of the ATP generated by cellular respiration.

• The final electron acceptor is oxygen which combines with hydrogen ions and low energy electron to form water

Electron Transfer Chain

ATP Production

• 36ATP are made from the electron transport chain

• 2 ATP from glycolysis

• 38 ATP in total per glucose molecule

Electron Transport Chain Summary

• Hydrogen and electrons are passed to coenzymes NAD and FAD.

• NADH and FADH2 release electrons to the electron transport chain.

• Electrons are passed along the chain of carriers.

• Energy is released which pumps hydrogen ions across the (inner) mitochondrial membrane.

• The return flow of hydrogen ions synthesises ATP using the enzyme ATP synthase.

• Oxygen acts as the final hydrogen acceptor and water is formed.

Lesson starter (you can use your textbook)

1. What compound is represented by the letters ATP?

2. What is the structural difference between ATP and

ADP?

3. Explain each of the following statements:

a) In glycolysis, the net gain of ATP is 2 and not 4.

b) Living organisms only have a small amount of

oxaloacetate.

c) A human body can produce ATP at a rate of around

400g/l, yet at any given moment there are only about

50g present in the body.

Make a table with the heading glycolysis, Krebs cycle and electron transport chain. Put the following statements under

the correct headings.

1.It brings about the breakdown of glucose to pyruvate

2.It ends with the production of water

3.It begins with acetyl coA combining with oxaloactetate

4.It involves a cascade of electrons, which are finally accepted by oxygen

5.It has an energy investment and an energy payoff stage

6.It results in the production of NADH

7.It involves the production of CO2

8.It results in the production of ATP

First Stage gl

yco

lysi

s

4 ATP PYRUVATE

Second Stage K

reb

’s C

ycle

2C ACETYL COENZYME A

2C ACETYL COA

4C OXALOACETATE

6C CITRATE

CO2

NAD NADH

FADH

NADH/ FADH

Third Stage

NADH/ FADH

elec

tro

n t

ran

sfer

ch

ain

NAD/ FAD

ADP + Pi ATP

WATER

Regulation of the respiratory

pathway

Learning Intentions

• Give examples of substrates that can be used in respiration

Carbohydrates • Starch and glycogen are both complex carbohydrates. They are

composed of chains of glucose molecules.

• They act as respiratory substrates since they can be broken

down to release glucose as required.

• Other sugar molecules such as maltose and sucrose can also

be converted to glucose or intermediates in the glycolytic

pathway and used as respiratory substrates

Fats

• When required for use as a respiratory substrate, a

molecule of fat is broken down into fatty acids and

glycerol.

• Glycerol is converted to a glycolytic intermediate.

• Fatty acids are metabolised into molecular

fragments that enter the pathway as acetyl coA for

use in the Krebs cycle

Proteins

• Proteins in the diet are broken down to their component amino

acids by digestive enzymes.

• Amino acids in excess of the body’s needs undergo

deamination, forming urea and respiratory pathway

intermediates which enter both the glycolytic and Krebs cycle

pathways.

Substrates for Respiration

• Starch and glycogen are broken down to glucose

• Fats can be broken down into fatty acids and glycerol. Glycerol is converted to a glycolytic intermediate and fatty acids converted for use in the Kreb’s cycle

Substrates for Respiration

• If both carbohydrate and fat stores have been used up (eg during starvation) then protein can be broken down to amino acids and converted to intermediates of glycolysis and the Kreb’s cycle for use as respiratory substrates.

Substrates for Respiration

Show me boards

1. How many membranes does the mitochondria have?

2. Where does glycolysis take place?

3. What is glycolysis?

4. Where does the Krebs cycle occur?

5. Why is there only a small amount of oxaloacetate present in living organisms?

6. What is the final hydrogen acceptor?

7. What stage does this occur in?

8. Where does the ETC take place?

9. ATP ADP+Pi – releasing or requiring energy?

10.How many molecules of ATP are made at the end of aerobic respiration?

11.What is phosphorylation? Give an example

12.What is respiration?

13.What are the three substrates for respiration?

14.Give one example of how proteins contribute to aerobic respiration

The following chart shows stages in the complete breakdown of glucose in

aerobic respiration.

Glucose

Stage X

Pyruvic acid

Stage Y

Krebs cycle

Stage Z

At which stage or stages is hydrogen released to be picked up by hydrogen

acceptors?

Stages X, Y and Z

Stages X and Y only

Stages Y and Z only

Stage Z only

The diagram shows part of a liver cell with four

parts labelled. In which part is most ATP

produced?

a)

Which of the following is an insoluble

polysaccharide?

a) Glycogen

b) Glucose

c) Sucrose

d) Maltose

The diagram below shows a metabolic pathway that is controlled by end

product inhibition.

Substance 1

Enzyme 1

Substance 2

Enzyme 2

Substance 3

Enzyme 3

Substance 4

For Substance 4 to bring about end product inhibition, with which of the

following would it interact.

a)Enzyme 1

b) Enzyme 3

c) Substance 1

d) Substance 3

Substrates for Respiration Summary

• Starch and glycogen are broken down to glucose for use as a respiratory substrate.

• Proteins can be broken down to amino acids and converted to intermediates of glycolysis and the Krebs cycle for use as respiratory substrates.

• Fats can also be broken down to intermediates of glycolysis and the Krebs cycle.

Learning Intentions

• Explain the regulation of the pathways of cellular respiration

Regulation of Cellular Respiration

• The cell conserves its resources by only producing ATP when required

• Feedback inhibition regulates and synchronises the rates of the glycolytic and citric acid cycle pathways

• If more ATP than the cell needs is produced the ATP inhibits phosphofructokinase slowing glycolysis

• High concentrations of citrate also inhibit phosphofructokinase

• When citrate concentration drops the enzyme is no longer inhibited

Regulation of Respiration Summary

• Phosphofructokinase activity can be inhibited by ATP and citric acid.

• These feedback mechanisms help to synchronise the activity of glycolysis and the citric acid cycle to ensure the cell conserves its resources by only producing ATP from cellular respiration when it is required.

Task – page 110

• Write a few bullet points for each of the

following uses of respiratory substrates:

• Exercise

• Marathon Running

• Starvation

Aerobic respiration finished!!!!

Learning Intentions

• Explain the role of creatine phosphate in energy release

Energy Systems in Muscle Cells

• During strenuous muscle activity the cell breaks down its reserves of ATP and releases energy

• Muscle cells can only store enough ATP for a few muscle contractions

• Muscle cells have an additional source of energy

Creatine Phosphate

•Creatine phosphate acts as a high energy reserve available to muscle cells during strenuous exercise

•During strenuous exercise creatine phosphate breaks down releasing energy and phosphate which are used to convert ADP to ATP by phosphorylation

• This system can only support strenuous muscle activity for around 10 seconds before the supply of creatine phosphate runs out

• When ATP demand is low, ATP from cellular respiration restores the levels of creatine phosphate

Creatine Phosphate

Creatine Phosphate Summary

• During strenuous activity muscle cells break down ATP releasing ADP and phosphate, along with energy.

• Creatine phosphate in the muscle cells breaks down to provide energy and phosphate to convert ADP to ATP by phosphorylation.

• This system sustains maximal muscle contraction for a short period of time, eg about a 100 metre sprint.

Learning Intentions

• Describe the events that occur in anaerobic respiration

Lactic Acid Metabolism

• If strenuous exercise continues the cells respire anaerobically as they do not get enough oxygen

• Neither the Kreb’s cycle nor electron transport chain can generate the ATP required

• Only glycolysis is able to provide more ATP.

• This results in pyruvate being converted to lactic acid (lactate)

Lactic Acid Metabolism

• The conversion of pyruvate to lactic acid (lactate) involves the transfer of hydrogen from NADH produced during glycolysis to pyruvate in order to produce the lactic acid

• NAD is regenerated to maintain ATP production during glycolysis

• Only 2 molecules of ATP are produced from each molecule of glucose

Oxygen Debt

Glucose

(6C)

Pyruvate

(2 X 3C)

Lactic Acid

(2 X 3C)

Oxygen debt builds up

Oxygen debt repaid

•As lactic acid builds in the muscles it causes fatigue and an oxygen debt builds up

•When the oxygen debt is repaid, the lactic acid is converted back to pyruvate which then enters the aerobic pathway.

Video

Aerobic vs Anaerobic

Aerobic

Respiration

Anaerobic

Respiration

Number of ATP

molecules per

glucose

molecule

38 2

Products of

reaction (other

than ATP)

Carbon

dioxide and

water

Lactic acid

Location in cell Mitochondrion

Cytoplasm

Cytoplasm

Lactic Acid Metabolism Summary

• During vigorous exercise, the muscle cells do not get sufficient oxygen to support the electron transport chain. Under these conditions, pyruvate is converted to lactic acid.

• This conversion involves the transfer of hydrogen from the NADH (produced during glycolysis)

• This regenerates the NAD needed to maintain ATP production through glycolysis.

Lactic Acid Metabolism Cont’d

• Lactic acid accumulates in muscle causing fatigue and an oxygen debt.

• When exercise stops, the oxygen debt is repaid and this allows lactic acid to be converted back into pyruvate and glucose (in the liver).

Regulation of the respiratory

pathway

Homework for tomorrow

Find out:

1.What are Creatine supplements?

2.What are the used for?

3.What are the side effects?

Plan of action

• Today: a few slides left and then complete

WYSK

• Friday: Study period – Unit 1

• Monday: Study period – unit 1

• Tuesday – Study period – unit 1

• Wednesday double period – unit 1 NAB

Learning Intentions

• State the differences between slow twitch and fast twitch muscle fibres

Types of Skeletal Muscle Fibre

• Skeletal muscles bring about movement of the body

• The two different types of

skeletal muscle fibres are: slow twitch (type 1) muscle

fibres

fast twitch (type 2) muscle fibres.

Video

Slow Twitch (Type 1) • These contract slowly, but

sustain contractions for a long time

• Good for endurance activities such as marathon running

• They rely on aerobic respiration to generate ATP

• Have many mitochondria and a large blood supply and a high concentration of the oxygen storing protein myoglobin

• Major storage fuel is fats

Fast Twitch (Type 2) • These muscle fibres contract

quickly but cannot maintain contractions for a long time

• They are good for bursts of activity such as sprinting or weightlifting

• Generates ATP through glycolysis

only

• Have only a few mitochondria and a low blood supply

• Their major storage fuels are glycogen and creatine phosphate video

Slow Twitch Summary

• Slow twitch muscle fibres contract slowly, but maintain contractions for a long time.

• They rely on aerobic respiration to generate ATP

• They have many mitochondria, a large blood supply and a high concentration of the oxygen storing protein myoglobin.

• Their major storage fuel is fats.

• They are good for endurance activities like long distance running, cycling or cross-country skiing.

Fast Twitch Summary

• Fast twitch muscle fibres contract quickly, but cannot maintain contractions for as long time.

• They generate ATP through glycolysis only.

• They have few mitochondria and a lower blood supply than slow twitch muscle fibres.

• Their major storage fuels are glycogen and creatine phosphate.

• These muscle fibres are good for activities like sprinting or weightlifting.