Energy Systems

Question 1

where does the energy we use for muscle contractions come from

Answer 1

adenosine triphosphate (ATP). the energy that is stored in ATP is released by breaking down the bonds that hold this compound together. enzymes are uysed to break down the bonds.

Question 2

what enzyme breaks down ATP into ADP + Pi

Answer 2

ATPase

Question 3

The conversion of fuel into energy takes place in one of three pathways which are

Answer 3

• aerobic system
• the ATP-PC system
• the anaerobic glycolytic system

Question 4

When is the aerobic system the preferred pathway

Answer 4

When the exercise intensity is low and oxygen availability is high

Question 5

What are the by-products of the aerobic system

Answer 5

• Carbon Dioxide
• water

Question 6

The complete oxidation of glucose can produce how many ATPs (aerobic systems)

Answer 6

38 ATPs

Question 7

The aerobic system has 3 stages which are

Answer 7

• Glycolysis
• Kreb’s Cycle
• Electron Transport Chain

Question 8

What is glycolysis

Answer 8

• the breakdown of glucose into pyruvate
• takes place in the sarcoplasm
• for every molecule of glucose undergoing glycolysis, a net of two molecules of ATP is formed.

Question 9

What happens to the pyruvate so it can move to the next stage of the system

Answer 9

The pyruvic acid is oxidised into two acetyl groups and is then carried into Kreb’s cycle by coenzyme A

Question 10

Where does the coenzyme a come from (aerobic system)

Answer 10

The products of the metabolism of fats and proteins are reduced to the molecule acetyl coenzyme a.

Question 11

what is the kreb’s cycle

Answer 11

the two acetyl groups (formerly pyruvic acid) diffuse into the matrix of the mitochondria. and they undergo a complex cycle of reactions

Question 12

describe what happens in the kreb’s cycle

Answer 12

• the two acetyl groups combine with oxaloacetic acid to from citric acid.
• hydrogen is removed from the citric acid and the now rearranged form of citric acid undergoes oxidative carboxylation (simply meaning carbon and hydrogen are given off)
• the carbon forms carbon dioxide which is transported to the lungs and breathed out
• the hydrogen is transported to the electron transport chain
• the result of these reactions result in the production of 2 ATP molecules

Question 13

what is the electron transport chain

Answer 13

• the hydrogen from the krebs cycle is carried to the electron transport chain by hydrogen carriers
• occurs in the cristae of the mitochondria
• the hydrogen splits into hydrogen and electrons and they are charged with potential energy
• the hydrogen ions are oxidised to from water while the hydrogen electrons provide the energy to re-synthesise ATP
• throughout this process 34 ATP are formed

Question 14

other than glucose what other fuels can the aerobic system use

Answer 14

• fats in the form of fatty acids and proteins in the from of amino acids

Question 15

what is beta oxidation

Answer 15

• when stored fat is broken down into glycerol and free fatty acids
• the fatty acids then undergo a process called beta oxidation where it is converted to coenzyme a (the entry molecule for the krebs cycle)

Question 16

what can produce more ATP from one molecule: fatty acids or glucose

Answer 16

• fatty acids

Question 17

what is the predominant energy source for the aerobic system

Answer 17

in long duration, low intensity exercise, fatty acids are the predominant energy source however does depend on the performer

Question 18

what are the advantages of the aerobic system

Answer 18

• more ATP can be produced (36 molecules)
• there are no fatiguing by-products
• lots of glycogen and triglyceride stores so exercise can last for a long time

Question 19

what are the disadvantages of the aerobic system

Answer 19

• complicated system so cannot be used straight away. it takes a while for enough oxygen to become available to meet the demands of the activity and ensure glycogen and fatty acids are completely broken down
• fatty acids transportation to muscles is low and also require 15% more oxygen to be broken down than glycogen

Question 20

what does it mean if something is reduced

Answer 20

• it means the molecules has gained hydrogen or lost oxygen

Question 21

what does it mean if something is oxidised

Answer 21

• it means the molecule has gained oxygen or lost hydrogen

Question 22

what is the fuel of the atp-pc system

Answer 22

phosphocreatine (PC)

Question 23

what is phosphocreatine

Answer 23

an energy rich phosphate compound found in the sarcoplasm adn can be broken down quickly and easily to release energy and re-synthesise ATP

Question 24

what activities may the ATP-PC system be useful for

Answer 24

single maximum movements such as long lump take-off or shot putt

Question 25

what is the atp-pc system

Answer 25

• anaerobic process
• re-sythesises ATP when the enzyme creatine kinase detects high levels of ADP

Question 26

what is the equation for how PC releases energy

Answer 26

PC –> Pi + C + energy

this energy is then used to convert ADP to ATP in a coupled reaction

Energy –> + Pi + ADP –> ATP

Question 27

For every PC how much ATP do you get

Answer 27

1 molecule of ATP

Question 28

what are the advantages of the ATP-PC system

Answer 28

• ATP can be re-synthesised rapidly
• phosphocreatine stores can be-synthesised quickly
• no fatiguing by products
• possible to extend the time the atp-pc system can be utilised through use of creatine supplementation

Question 29

what are the disadvantages of the atp-pc system

Answer 29

• there is only a limited supply of phosphocreatine in the muscle cell, only can last for 10 seconds
• one mole of ATP can be re-synthesised for every mole of PC
• PC re-synthesis can only take place in the presence of oxygen

Question 30

what is the anaerobic glycolytic system

Answer 30

an energy system that provides energy for high-intensity exercise and for longer than the atp-pc system

Question 31

what is said to be the duration of the anaerobic glycolytic system

Answer 31

• depends on the individuals fitness and how high the intensity of the exercise is
• e.g. a 400m athlete who has jus run the 400m wont be albe to do it again at the same pace because working flat out to exhaustion means the system will last much shorter time
• usually lasts up to 2-3 minutes

Question 32

how does the anaerobic glycolytic system work

Answer 32

• starts with anaerobic glycolysis (where PC stroes are low and the enzyme glycogen phosphorylase breaks down the glycogen into glucose and then further broken down into pyruvic acid by phosphofructokinase where the product of this reaction is 2 ATP)
• the pyruvic acid is then further broken down into lactic acid by the enzyme lactate dehydrogenase

Question 33

where does the anaerobic glycolytic system take place

Answer 33

sarcoplasm

Question 34

what is the net result of atp produced from this system

Answer 34

2 molecules of ATP for 1 molecule glucose

Question 35

what are the advantages of the anaerobic glycolytic system

Answer 35

• ATP can be re-synthesised quickly due to very few chemical reactions
• lasts longer than the ATP-PC system
• in the presence of oxygen, lactic acid can be converted back into the liver glycogen or used as a fuel through oxidation into carbon dioxide and water
• it can be used to produce an extra burst of energy

Question 36

what are the disadvantages of the anaerobic glycolytic system

Answer 36

• lactic acid as the by-product means enzymes become denatured and prevents them from increasing the rate of reaction
• only a small amount of energy can be released from glycogen under anaerobic conditions