1. Exercise biochemistry

2. Skeletal muscle Muscle 3 forms Only skeletal is voluntary Function
One of 4 principle tissue of the body
Muscle, nerve, connective, epithelial
3 forms
Skeletal, smooth, cardiac
Only skeletal is voluntary
Function
Exerts force (for locomotion)
Energy is chemical
Other functions
Heat production
Posture
Protection
Shape

3. Muscle structure Muscle layers Each muscle fiber Epimysium
Surrounds whole muscle
Perimysium (fascia)
Surrounds (bundles of fibers)
Endomysium
Surrounds individual muscle fibers
Each muscle fiber
One nerve ending
Motor endplate
Connection between muscle fiber and nerve
Neurotransmitter
Acetylcholine (Ach)

4. Muscle structure Muscle blood flow
Capillaries surround the muscle fibers
Travel in 3 dimensions
Capillaries are very “tortuous”
Capillaries are fed by an arteriole
Great ability to adapt to changes in work
Skeletal muscle blood flow
Can increase markedly from rest to maximal exercise
This is dependent upon the muscle type
Slow twitch
Large capacity to increase flow
Fast twitch
Oxidative; moderate ability to increase flow
Glycolytic; poor ability to increase flow

6. Muscle fiber structure
Myocytes
Multinucleated
Thin µm
Length varies
3 mm to 30 cm
Interior
Sarcoplasm
Mitochondria, myoglobin (gives muscle it’s “red” appearance) and myofibrils
Sarcoplasmic reticulum
Surrounds myofibrils
Growth, repair, maintenance
T-tubules
Involved in nerve transmission and calcium release

7. Muscle fiber structure
Skeletal muscle has a unique “banded” appearance
Due to “Dark” A bands and “Light” I bands
A bands: Myosin and actin
Anisotropic: different properties in different directions
I bands: just actin
Isotropic: Same properties in all directions
H zone
Light zone (“helle”) that contains M line (middle)
No overlap between actin and myosin
Z disc
Separate sarcomeres
When actin connects
Also connects adjacent myofibrils

8. Molecular composition of the myofilaments
Myosin filament
Rod-like tail with two heads
ATPase located here
Interacts with actin
Globular (G actin) and fibrous (F actin)
Tropomyosin
Stiffens the actin filament
Troponin
Troponin I: Binds to actin
Troponin T: Binds to tropomyosin
Troponin C: binds calcium

9. Force development Force development Sarcomeres shorten
Actin and myosin slide over one another
Calcium allows tropomyosin to move “Unblocking” actin
Ca2+ binds to troponin C
Myosin interacts with actin (1)
Myosin head moves actin
ADP + Pi are released (2)
ATP binds to myosin head
Allows myosin to disengage from actin (3)
ATP is broken down
This allows for myosin head movement (4)
Cycle starts again

10. Control of force development2
Neurotransmitter release
Acetylcholine
Action potential propagation
Sarcolemma to T-tubules
Calcium release
Terminal cisternae of SR
Calcium concentration rises in sarcoplasm
Binds to troponin C
Causes tropomyosin shift
5) Contraction occurs
Calcium resequestered
When neural stimuli ceases
Tropomyosin blockage restored 1 6 3 4 5

11. Motor units A motor neuron and the fibers it innervates All or none
Number of fibers varies
Muscle that perform very fine movements (eye, hands)
Small motor units
Muscle involved in larger movements
Large motor units
All or none
A stimulus will either activate the entire motor unit, or none of it

12. Muscle fiber types Type 1 Type 2
Slow twitch, very high fatigue resistance, used for prolonged activity, red
Type 2
Two types
Type 2a, fast-twitch oxidative, intermediate fatigue resistance, used for longer high intensity exercise
Type 2b, fast-twitch glycolytic, fast to fatigue, used for very brief high intensity contractions

13. Muscle fiber types Size principle
Larger fiber types recruited as intensity increases
Type 1, type 2a, type 2b
Human muscle contains a mixture of fiber types
Postural muscle
High proportion of type 1
Rapid movement muscle
Hand and eye
High proportion of type 2
Many are mixed fiber muscle
Quadriceps
This seems to be determined primarily at birth
Distance runners have a high percentage of type 1 fibers
Sprinters, type 2

14. Types of muscle action Concentric contraction Eccentric “contraction”
Muscle shortens while developing force
Eccentric “contraction”
Muscle lengthens while generating force
Isometric contraction
Muscle generates force with no change in length

15. Plasticity of muscle Plasticity Ability to adapt Alterations in Size
Fiber composition (small)
Metabolic capacity
Capillary density

16. Sources of energy for muscular contraction
Adenosine triphosphate
Provides the energy for muscular contraction
1) ATP↔ADP +Pi + energy
ATPase
2) PCr + ADP ↔ ATP + Cr
Reactions 1 and 2 work together
3) Anaerobic metabolism of glucose
Yields lactate and small amt of ATP
4) Aerobic metabolism of CHO, fast and proteins
Aerobic metabolism yields lots of ATP, but it is slow

17. Phosphagen system

18. Energy systems Immediate energy system Resynthesizes ATP very fast
Phosphagen system
Relies on Phosphocreatine (PCr) to quickly resynthesize ATP
PCr + ADP ↔ ATP + Cr
Creatine kinase
Resynthesizes ATP very fast
Very small amounts of ATP and PCr stored in the muscle
Enough for about 10s of activity

19. Glycolytic system
Since most activity lasts longer than 10s or so, need another system
Glycolytic system
Uses glucose or glycogen
Glycolysis
Breaks down glucose to 2 pyruvate molecules
Anaerobic glycolysis
Pyruvate is converted to lactate
Small amount of ATP
Allows work to continue for about 2-5 minutes
Dependent upon pain tolerance

20. Aerobic metabolism Requires Mitochondria, oxygen Can use Huge capacity
Carbohydrates, fats or proteins
Huge capacity
Virtually unlimited
Slow ATP delivery
Sustains long-term, low-intensity work

21. Tricarboxylic acid cycle
AKA
Kreb’s cycle and Citric acid cycle
Function
Break down Acetyl-CoA to CO2 and H+
Also forms small amount of ATP
H+ carried by
NADH and FADH2
To ETC
Net production
1 ATP (GTP transfers terminal P to ADP; nucleotide diphosphokinase)
3 NADH
1 FADH2

22. Tricarboxylic acid cycle
1st step
Formation of citrate
Citrate synthase
2cd step
Formation of isocitrate
Isomer of citrate
3rd step
Formation of alpha-ketoglutarate
Isocitrate dehydrogenase
1 NADH
4th step
Formation of Succinyl CoA
Alpha-ketoglutarate dehydrogenase

23. Tricarboxylic acid cycle
5th step
Formation of succinate
Succinyl-CoA synthetase
1 ATP
6th step
Formation of fumarate
Succinate dehydrogenase
1 FADH2
7th step
Formation of malate
8th step
Formation of oxaloacetate
Malate dehydrogenase
1 NADH

24. Tricarboxylic acid cycle
Summary
Acetyl-CoA + ADP + 3NAD+ + FAD ↔ 2CO2 + ATP + 3NADH + 3H+ + FADH2 + CoA
Citrate synthase
Key regulatory enzyme
Inhibited by
ATP, NADH, Succinyl-CoA
Thus, when cellular energy state is HIGH, TCA cycle is inhibited
Stimulated by
ADP, NAD+, Acetyl-CoA
Basically
Stimulated by substrate, inhibited by products

25. Electron transport chain
Linked proteins which remove the electrons from H+
This separates the charge and creates, in essence, a molecular battery
This charge difference powers the formation of ATP
The electrons (and H+) then combine with molecular O2 to form H2O

26. Electron transport chain
NAD and FAD
Electron (and H+) carriers
So much of metabolism is providing an electro-chemical charge difference across the inner membrane of the mitochondria to drive ATP formation

27. Electron Transport Chain
Step 1
NADH dehydrogenase complex
2 e- transferred to FMN to form FMNH2
1 ATP formed
Step 2
Coenzyme Q
Accepts e- from FADH2
Step 1 and 2
Dropping off H+ and e-

28. Electron transport chain
Step 3
Cytochrome chain
Electrons are transferred from CoQ to each cytochrome
Cytochrome b
Cytochrome c
1 ATP
Cytochrome oxidase
Step 3 summary
Electron transport and ATP formation (oxidative phosphorylation)

29. Energy storage Marathon Glycogen: Lipids
Storage form of glucose
Muscle (~350g) , liver (~80g) and blood (~5g of glucose)
Total (70 kg man; 15% bodyfat)
~435g
Lipids
Stored primarily in adipocytes
Also in muscle and around organs as well circulating in blood (Fatty acids)
~10,500g
Marathon
Requires ~ kcal of energy
Requires about 750g of CHO
Only requires ~ 330g of fat

30. Energy storage