1. Higher Human Biology Unit 1 – Human Cells
Section 8 – Energy Systems in Muscle Cells

2. What can you remember? What are the three types of muscle tissue?
Skeletal, cardiac and smooth
What are the three types of muscle tissue?
What are the products of anaerobic respiration in animal cells.
Where does glycolysis take place
What molecule donates its phosphate so that phosphorylation can take place?
What gas is produced when 3 carbon pyruvate is converted into 2 carbon Acetyl CoA
Lactate
Cytoplasm
ATP
Carbon dioxide

3. Energy for Exercise
Food is the source of energy for the human body and it also provides nutrients for growth and repair. When food is eaten, this is what happens….
The food is broken into soluble chemicals (e.g. glucose) by digestion in the gut.
The soluble chemicals pass through the gut wall into the blood.
The blood carries the soluble food chemicals to all of the body’s cells, where they will be used for

4. Substrates for Respiration
Carbohydrates
Starch and glycogen are made up of chains of glucose. This means that they can act as respiratory substrates since they can be broken down into glucose.
Sucrose and maltose – these can be converted to glucose or intermediates
Fats - These are broken down into glycerol and fatty acids
Glycerol – converted to a glycolytic intermediate
Fatty Acids – these are metabolised into metabolic fragments that enter the pathways as acetyl coenzyme A.
Proteins
These are broken down into amino acids by enzymes. These undergo deamination forming urea and respiratory intermediates.

5. Carbohydrates
Starch (plants) and glycogen (animals) are made up of chains of glucose molecules.
They can be broken down into glucose and used as a respiratory substrate

7. Fats
When required, fat can be broken down into fatty acids and glycerol and be used as a respiratory substrate

9. Proteins
Protein are composed of amino acids and are broken down in our diet
Excess amino acids can be lost as urea or used as a respiratory substrate

11. a – Lactate Metabolism We will be learning to…
Describe the process of lactate metabolism when muscle cells do not get enough oxygen to support the electron transport chain during strenuous exercise.
State that pyruvate is converted to lactate
Describe how this conversion involves the transfer of hydrogen from the NADH produced during glycolysis to pyruvate in order to produce lactate.
State that this regenerates the NAD needed to maintain ATP production through glycolysis.
State that lactate builds up and muscle fatigue occurs
Describe how the oxygen debt is repaid when exercise is complete
State that this allows respiration to provide the energy to convert lactate back to pyruvate and glucose in the liver.

12. Lactate Metabolism
During vigorous exercise, the muscle cells do not get enough oxygen and the ATP only lasts a few seconds. Oxygen is needed for the citric cycle and the electron transport chain. Without the oxygen these stages do not occur
Under these conditions pyruvate is converted to lactate. Only glycolysis is able to provide more ATP. It generates 2 ATP and 2 NADH from each molecule of glucose.

13. Glucose 2 NAD+ 2ADP +Pi Glycolysis 2ATP 2 NADH (net) 2 Pyruvate 2 NADH
This conversion involves the transfer of hydrogen from the NADH produced during glycolysis to pyruvate in order to produce lactate.
This regenerates the NAD needed to maintain ATP production through glycolysis.
Glucose
2 NAD+
2ADP
+Pi
Glycolysis
2ATP
(net)
2 NADH
2 Pyruvate
2 NADH
NAD+ Regeneration
2 NAD+
2 Lactate

14. Oxygen Debt
Lactate accumulates and muscle fatigue occurs. The oxygen debt is repaid when exercise is complete. This allows respiration to provide the energy to convert lactate back to pyruvate and glucose in the liver.

15. Lactate Metabolism Only glycolysis produces ATP (2 instead of 38)
The pyruvate is converted into lactate
Lactate can build up and cause fatigue and an oxygen debt builds up
This process is reversible when at rest and more oxygen becomes available.
The lactate is transported to the liver to be converted back to pyruvate.
They are often used interchangeably to indicate the reduced form of NAD +  NAD+ . The overall reaction when oxidizing some molecule RH  2  RH2 is: RH  2 +NAD + ⟶NADH+H + +R RH2+NAD+⟶NADH+H++R . The proper reduced NAD +  NAD+ is NADH NADH (it accepts two electrons and one proton), but sometimes NADH  2  NADH2 is used to account for that second hydrogen that gets removed from the substrate being oxidized. The notation NADH  2  NADH2 doesn't really take into account the fact that the second hydrogen is charged, and not bound to the NAD NAD in the same way that the first hydrogen is, so it is confusing. The notation: "NADH+H +  NADH+H+ " is more correct and is also sometimes used.

16. b – Types of Skeletal Muscle
We will be learning to…
State that there are two types of skeletal muscle fibres.
Describe the properties of slow-twitch muscle fibres
State that they are useful for endurance activities
Describe the properties of fast-twitch muscles
State that they are useful for short periods of activity
Explain that most human muscle tissue contains a mixture of both types of skeletal muscle
Describe how athletes patterns of muscle fibres match their sport

17. Control of Muscle Fibres
Muscle tissues work by exerting a force when they contract. This can be controlled by involuntary movements e.g. smooth muscle contractions of the heart chambers or voluntary contractions when parts of the skeleton is moved.

18. Types of Skeletal Muscle
There are two types of skeletal muscle fibres.
Fast Twitch
Slow Twitch

19. Slow-twitch Muscle Fibres
Slow twitch muscle fibres contract relatively slowly, but can sustain contractions for longer. They are useful for endurance activities such as rowing, long distance running, cycling or cross-country skiing
Slow twitch muscle fibres rely on aerobic respiration to generate ATP and have many mitochondria, a large blood supply and a high concentration of the oxygen storing protein myoglobin. The major storage fuel of slow twitch muscle fibres is fats.

20. Myoglobin
Myoglobin is an oxygen-storing protein present in muscle cells. It has a stronger affinity for oxygen than haemoglobin. This means that the oxygen has a higher chance of binding with myoglobin than haemoglobin. Due to this high affinity myoglobin is able to extract oxygen from blood for use by muscle cells, especially those in slow-twitch muscle fibres

21. Fast-twitch Muscle Fibres
Fast twitch muscle fibres contract relatively quickly, over short periods. They are useful for activities such as sprinting or weightlifting
Fast twitch muscle fibres can generate ATP through glycolysis only and have fewer mitochondria and a lower blood supply compared to slow twitch muscle fibres. The major storage fuel of fast twitch muscle fibres is glycogen.

22. Most human muscle tissue contains a mixture of both slow and fast twitch muscle fibres. This is genetically determined. Athletes show distinct patterns of muscle fibres that reflect their sporting activities.

23. Skeletal Muscle Fibres
Physical activity requires parts of the body to move and is brought about by skeletal muscle fibres (either slow-twitch or fast-twitch).
Skeletal muscles contain a genetically determined mixture of slow-twitch and fast-twitch fibres. In most muscles the ratio is balanced.
However in other muscles one will dominate
For example the back contains mainly slow-twitch muscles and the eyes mainly fast-twitch muscles

24. Feature Type 1 Slow-Twitch Type 2 Fast-Twitch
Muscle contraction speed
Slow
Fast
Length of time for which contraction lasts
Long
Short
Speed at which fibre becomes fatigued
Respiratory Pathways to make ATP
Aerobic Respiration
Glycolysis
Number of mitochondria
Many
Few
Blood supply
Large
Small
Concentration of myoglobin in cells
High concentration
Low concentration
Storage fuels used
Fats
Glycogen/Creatine phosphate
Activities
Long distance running, skiing
Sprints, Weightlifting

25. Now I can…..
a – Lactate Metabolism
Describe the process of lactate metabolism when muscle cells do not get enough oxygen to support the electron transport chain during strenuous exercise.
State that pyruvate is converted to lactate
Describe how this conversion involves the transfer of hydrogen from the NADH produced during glycolysis to pyruvate in order to produce lactate.
State that this regenerates the NAD needed to maintain ATP production through glycolysis.
State that lactate builds up and muscle fatigue occurs
Describe how the oxygen debt is repaid when exercise is complete
State that this allows respiration to provide the energy to convert lactate back to pyruvate and glucose in the liver.

26. Now I can….. State that there are two types of skeletal muscle fibres.
b – Types of Skeletal Muscle
State that there are two types of skeletal muscle fibres.
Describe the properties of slow-twitch muscle fibres
State that they are useful for endurance activities
Describe the properties of fast-twitch muscles
State that they are useful for short periods of activity
Explain that most human muscle tissue contains a mixture of both types of skeletal muscle
Describe how athletes patterns of muscle fibres match their sport

27. CfE HH Biology 2017 A Q7 C

28. CfE HH Biology 2016 A Q9 B

29. CfE HH Biology 2015 A Q8 D

30. Word
Definition
Fast-twitch fibre
type of muscle fibre used in short bursts of activity
Lactate
produced by the fermentation of pyruvate in mammalian muscle cells
Muscle Fatigue
painful condition caused by the accumulation of lactic acid in the muscles
Myoglobin
protein in muscle tissue that can bind with oxygen
Oxygen Debt
builds up during fermentation in the muscle cells
Skeletal Muscle
muscle attached to the skeleton that brings about locomotion
Slow-twitch fibre
type of muscle fibre used in endurance activities