Does it matter what you eat for cellular

respiration?

• Examine the different substrates used for respiration

• Investigate the affect on a model organism of using different respiratory substrates

• Examine the effect of exercise or starvation on respiratory substrates.

• How is the substrate route controlled?• Creatine phosphate system as a booster for

maximum muscular

Carbohydrates

• Both starch/glycagon are chains of glucose molecules.

• Broken down into glucose• Disaccharides like sucrose or maltose also

broken down into glucose or used as intermediates in glycolytic pathway.

Glucose

Pyruvate

Fructose

StarchGlycogen

MaltoseSucrose

Fats

• Broken down into glycerol and fatty acids

• Glycerol converted glycolytic intermediate

• Fatty acids are metabolised and enter as acetyl coenzyme A for use in citric acid cycle.

Glucose

Pyruvate

Intermediate

Acetyl coenzyme A (2C)

Acetyl Coenzyme A

FAT

Proteins

• Broken down into amino acids

• Then used for protein synthesis

• Excess undergo deamination, making urea and intermediates, and regenerating ATP.

Glucose

Acetyl Coenzyme A

Pyruvate

Citric Acid Cycle

Amino acid (eg alanine)

intermediate

Amino acid (eg leucine)

P R OT

E I N

Amino acid (eg aspartic

acid)

urea

urea

urea

Investigation / LO3

• Follow instructions will be examined• p108-110• Answer ALL questions (especially point 6

and 7!)

So what happens during exercise?

Burn baby burn .....

• Several minutes at the start of aerobic exercise body burns carbohydrates.

• After 20-30 minutes of continued exercise respiratory substrate shifts to 50% carbohydrates/50% fat

• First hour of exercise less than 2% of respiratory substrates are protein

• Prolonged exercise protein usage can reach 5-15% if prolonged exercise last 5 hours (marathon running)

• Marathon running thus needs refreshments throughout!

So what about this .....

Creatine Phosphate System

• ATP is immediate source, but the ATP stored is only able to do a few contractions.

• For repetitive muscular contractions, creatine phosphate donates it’s phosphate for ATP synthesis.

During strenuous activity ......

ener

gy

creatine

creatine phosphate

ATP

ADP

Phosphorylation of ADP

• ATP formed is used to sustain maximal muscular contraction for a few more seconds.

• Helps for 100m sprint/golf swing and lifting/ lowering heavy weight.

Creatine Phosphate System

• During rest period ATP generates creatine phosphate by phosphorylation.

• Creatine phosphate acts as a high-energy reserve which is available for muscles during the next period of strenuous activity.

During rest period ......

ener

gy

creatine

creatine phosphate

ATP

ADP

Phosphorylation of creatine

Summary

Copy and complete the diagram below:

ATPCreatine

Creatine phosphate

• Phosphate and energy are being transferred between molecules.

• This is a very fast way of producing ATP for a short period of time.

So what happens during starvation?

Starving Marvin!• Definition “body continously expends more energy

than it takes in as food”• Early stages – uses up glycogen, mobiles fat

reserves• Prolonged – liver cells continue to use fatty acids

for forming acetyl coenzyme A, forming ATP as usual, some forms ketones which are transported to the brain via the blood

• Tissue protein is used as source only during prolongued stages when glycogen/fats exhausted

• Skeletal muscle and then other tissues are used up, person emancipated and death soon follows.

So which path ......

• Controlled by regulation we examined earlier, as carried out by enzymes

• Controls were?

• Suitable temperature• Appropriate pH• Correct substrate• Adequate supply of substrate• Presence of an inhibitor (more next time)

In this case the third step is by phosphofructokinase, an irreversible step thus a key regulatory point. High concentrations of ATP inhibit phosphofructokinase

• Prevents build up of intermediate is prevented

• ATP only produced from respiratory pathway as required

• Resources con served

Other metabolic pathways (eg. stored as glycogen)

Glucose (6C)

Intermediate 1

Intermediate 2

Intermediate 3

ATP

ADP+ Pi

ATP

ADP+ Pi

Phosphorylation at step 1

Phosphorylation at step 3 catalysed by phosphofructokinase

Irreversible step

Citric Acid Cycle & Electron Transport Chain

ATP & citric acid inhibit phosphofructikinase! So go back to intermediate 2

Question Tennis

Get in two rows, facing each other. The first student asks the student opposite a question about the lesson. If they get it right the person sat next to them gets to ask a question of the student opposite. If they get it wrong, the first team continue asking the questions.

Extension / Homework

Creatine supplements

Many athletes take creatine supplements.

Why do you think they do this?

What sort of sports would this be an advantage in?

Answer…

When athletes take creatine in supplements it is converted into creatine phosphate in the muscles. Taking supplements maximises the levels of creatine phosphate stored in the muscles, therefore the amount of energy stored is also maximised.

Creatine is not banned by major sporting bodies. It may be of most use in activities where short bursts of energy are required. Can you think of any?

Assessment

Your task is to write an article on creatine supplements for a sporting magazine.Your article should include:•a description of what creatine phosphate is used for by the body•a description of the role of creatine supplements•the type of activities that may benefit from creatine supplements•any other information you think is relevant.

Remember…

Most importantly your article should be easy to follow and make sense.

Do not copy and paste text – put any research you do into your own words.

The people reading a sporting magazine may not be scientists. They have to be able to understand the article.

SQA Arrangements p25

• Starch and glycogen are broken down to glucose for use as a respiratory substrate. Other sugar molecules can be converted to glucose or glycolysis intermediates for use as respiratory substrates. Proteins can be broken down to amino acids and converted to intermediates of glycolysis and the citric acid cycle for use as respiratory substrates. Fats can also be broken down to intermediates of glycolysis and the citric acid cycle.

p25

• 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.

SQA p26• 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.

• When demand for energy in muscles is low ATP produced by cellular respiration acts as a source of phosphate for the phosphorylation of creatine into creatine phosphate, which acts as a store of energy for the muscle tissue.