[WEEK12] The Chemistry of Exercise

-ATP is the energy currency of the cell

-Dephosphorylation of ATP (removal of P) releases energy

-ATP is produced by cells by breaking down the food we eat in a process known as cellular respiration

 

-Muscles utilise ATP to power contraction through Actin-Myosin cross bridge recycling

 

-> FOR MUSCLE CONTRACTION , ATP is used as an ENERGY SOURCE

-> ATP is produced by CELLULAR RESPIRATION

< FUELS of MUSCLE >

-Glucose

-Fatty acids

-Ketone bodies

 

< WAYS of MUSCLE FIBER can form ATP during contractile activity >

1) Phosphorylation of ADP by creatine phosphate

-ATP-CP system

-Utilised at the beginning of excerise

 

2) Phosphorylation of ADP via glycolysis in the cytosol

-Anaerobic glycolysis

-Utilised during high intensity excerise

 

3) Oxidative phosphorylation of ADP in the mitochondria

-Aerobic Glycolysis

-Utilised during low intensity

 

 

 

 

 

 

Carbohydrate

 

 

 

 

Aminoacid

STOMACH PANCREAS SMALL INTESTINE LIVER !!!!!!!

The excess of amino acid from the pool becomes free ammonia and secreted by the kidney in the form of urea

 

Dairy Meat Animal product has COMPLETE amino-acid 

But if we consume plant based products to source amino-acid, we have to combine them to ensure we get all COMPLETE amino acid

 

'EATING A RANGE OF FOODS TO ENSURE THAT ALL ESSENTIAL AMINOACIDS ARE CONSUMED'

 

 

MEAT, EGGS, CHICKPEAS, NUTS, LENTILS, DAIRY

 

*Protein quality => variety / content of amino acids (amount of essential amino acids in the protein source)

*The quality of protein is measured by its digestibility and its amino acid content

 

<Digestibility>

-Depends on protein's food source

=>animal proteins 90-99% absorbed

=>plant proteins 70-90% absorbed

=>soy and legumes 90% abosorbed

 

 

LIPIDS

FATTY ACIDS, TRIGLYCERIDES, PHOSPHOLIPIDS, CHOLESTEROL

1) FATTY ACIDS

-> one side carboxylic acid

-> one side methyl

 

CAN BE 

->saturated

->monounsaturated (MUFA)

->polyunsaturated (PUFA)

 

THEY CAN VARY by the location of the double bonds

The omega number refers to the position of the first double bond

(count from the methyl end!!!)

 

 

2) TRIGLYCERIDES

 

3) PHOSPHOLIPIDS

 

4) CHOLESTEROL

(streoids -> cholesterol (sterol), estradiol, testosterone)

-> FOUR RING ARRANGED

=> cell membrane fluidity , cellular process

=> precursor of bile, steroid hormones, vitamin D

=> Can be synthesised mainly in the liver (acetyl coA -> cholesterol)

,endogenous cholesterol

=> 

 

-Sterols are a sub-group of steroids

-Cholesterol is the most common sterol

-They have multiple ring structure

-The most well known sterol is cholesterol

-Other sterol include bile, vitamin D, and some hormones

-Exogenous sterols are found in both plants and anima foods

-Exogenous cholesterol is only found in animal foods (meat, eggs, fish, poyltry and dairy products)

<Fat transport>

-Lipoprotein transport lipids through the bloodstream

-They are made up of CHOLESTEROL, TRIGLYCERIDES, PHOSPHOLIPIDS, and PROTEINS

basic structure of lipoprotein

Protein tags determine destination of the protein , function of each lipoprotein

(LDL carries cholesterol from the liver to the other tissues)

(HDL carries cholesterol returns excess cholesterol to the liver)

 

https://www.youtube.com/watch?v=9dghtf7Z7fw 

1. Dietary cholesterol packed into chylomicron travels bloodstream and transported to the liver

2. Liver pacakages dietary + endogenous cholesterol + triglycerides packed into VLDL

3. VLDL travels blood stream to other organs

4. Liver and other adipose tissue extracts triglycerides from the VLDL and changes it into LDL

5. Peripheral cells take up LDL by the endocytosis, and using LDL receptor

6. Cholesterol is used in cell function and cell membrane

7. Excess cholesterol is excreted from the cell and transported into the blood stream as HDL, return to liver

8. Liver consume cholesterol to produce bile

9. Bile secreted to small intesine to help fat breakdown

10. Part of the bile is excreted in feces

11. Rest is recycled back to the liver

 

LDL = major carrier of cholesterol (highest content of cholesterol)

HDL = removes cell's excess cholestrol to the liver

 

(Drugs used to lower cholesterol)

-inhibitors of endogenous production (statins)

-inhibitors of absorption (ezetimibe, lomitapide, plant sterols)

-Inhibitors of bile reuptake (cholestyramine)

(Lipoprotein types)

1) Chylomicrons : largest, but least dense

Reduce in size as triglycerides are removed

2) VLDLs : very low density lipoproteins

3) LDL : low density (Bad) lipoproteins

4) HDL : high density (Good) lipoproteins

 

 

Chemistry of Exercise

 

--> Ketone bodies can be produced during long starvation or in the period of time when we use large amount of fat for energy

 

--> ATP- CP system

( begining or excersie , buffer for ATP  before generating large amount of energy )

 

--> Glycolysis 

( anaerobic glycolysis, high intensity exercise or early stage of excersie, lactate )

(-muscle glycogen 

-liver glycogen (release to the blood stream, free glucose)

-circulating glucose)

( inthe cytosol , net gain 2ATP ) 

 

*Glucose break downs into lactate by glycolysis, producing 2 ATP, producing NADH

->To allow glycolysis to continue, we need NAD+ again

->By converting pyruvate into lactate, we need to convert NADH to NAD+

Then we can continue glycolysis 

 

*Lactate to pyruvate / pyruvate to glucose = gluconeogenesis

Once we produce glucose, we store that to the liver in glycogen form = glycogenesis (formation of glycogen)

 

*During high intensity excersie, we produce high amount of lactate

We take time to cool down  = give time for lactate to move to the cell and make glycogen OR even use it back to glucose

 

 

--> Mitochondria 

( aerobic, 

 

ATP is the energy currency of the cell. Dephosphorylation of ATP (removal of a phosphate) releases energy. ATP is produced by cells by breaking down the food we eat in a process known as cellular respiration.

 

 

(Skeletal muscle metabolism) 

Muscle can utilise a variety of fuels:

• Glucose
• Fatty Acids 
• Ketone Bodies

Energy demands and fuel consumption is dependent upon substrate availability and muscle activity. There are three ways a muscle fibre can form ATP during contractile activity. 

1. Phosphorylation of ADP by creatine phosphate
   • ATP–CP system
   • Utilised at the beginning of exercise
2. Phosphorylation of ADP via glycolysis in the cytosol
   • Anaerobic Glycolysis
   • Utilised during high intensity exercise
3. Oxidative phosphorylation of ADP in the mitochondria 
   • Aerobic Glycolysis
   • Utilised during low intensity

 

(High intensity - anaerobic glycolysis)

During high intensity exercise, glycolysis is used to break down glucose to form ATP. 

Glycolysis can operate when oxygen is reduced. The glucose for glycolysis can be obtained from 2 sources:

• Muscle glycogen
• Blood glucose – supplied by liver from the breakdown of glycogen stores or from food.

This results in the production of lactate which can be released into the blood and recycled in the tissues

 

(Lactate)

 

Lactate is NOT a waste product. It is thought that of the lactate produced by our bodies, the following occurs:

• 65% is oxidised (energy)
• 20% is converted to glycogen (via gluconeogenesis and glycogenesis). 
• 10% is converted to protein (keto acid for transamination reactions)
•  5% is converted to Glucose (gluconeogenesis) 

Removal of lactate takes about 1 hour if cooling down with gentle exercise. Take note that it can take 2 hours or more if you don’t warm down with gentle exercise.

Lactate does NOT contribute directly to acidosis, the burn in muscles during intense exercise, or the soreness experienced in the 48 hours following intense exercise.

 

 

 

 

 

 

 

(low intensity - aerobic glycolysis)

• Low intensity = aerobic glycolysis
• Fuels for Aerobic Glycolysis
  • First 5-10 minutes of exercise: muscle glycogen 
  • Next 30 minutes: blood borne fuels (glucose and fatty acids) 
  • Beyond 30min: fatty acids more important, glucose utilisation decreases.

 

 

 

 

 

 

 

 

 

 

 

The intensity of the exercise will determine the effect on muscle glycogen stores:

• High intensity exercise: predominately anaerobic, deplete glycogen stores
• Medium Intensity: mix of anaerobic and aerobic, use less muscle glycogen 
• Low Intensity: predominately aerobic, little effect on muscle glycogen

So what happens to blood glucose levels during exercise?

Blood glucose levels change very little in short term for mild to moderate exercise and may increase slightly with strenuous short term exercise. 

During prolonged exercise of more than 90 minutes, plasma glucose concentration decreases sometimes by as much as 25%.

Output by the liver increases proportionally to utilisation until the later stages of exercise when begins to lag.

Sources of Fuel that are used to increase plasma glucose and balance the effect caused by increased glucose utilisation.

• Lipolysis (fat breakdown), 
• glycogenolysis (glycogen breakdown) 
• gluconeogenesis (New Glucose) *Limited

How does anaerobic glycolysis differ from aerobic glycolysis?

Anaerobic – absence of oxygen. Glycolysis proceeds but pyruvate is converted to lactate. Net gain of 2 ATP per glucose. 

Aerobic – presence of oxygen. Glycolysis proceeds, pyruvate is converted to acetyl CoA. Citric acid cycle and oxidative phosphorylation. Net gain of 38 ATP per glucose.

 

What is the role of lactate in anaerobic glycolysis?

 

Under anaerobic conditions, pyruvate is reduced to lactate; this allows for regeneration of NAD+ so that glycolysis can continue and produce ATP.

 

How is most ATP formed during aerobic glycolysis?

 

Under anaerobic conditions, most ATP is formed through oxidative phosphorylation. Reduced electron carriers (NADH and FADH2) pass electrons through the electron transport chain. Hydrogen ions (H+) are pumped out into the mitochondrial inner membrane space. As the H+ ions flow back into the mitochondrial matrix, this provides the energy for phosphorylation of ADP to ATP. The electron carriers are oxidised to NAD+ and FAD, and O2 is reduced to H2O.

 

How does the supply of fuel for aerobic glycolysis change during prolonged exercise?

 

As the duration of exercise extends, fatty acids supply a higher percentage of fuel.

 

How is excess glucose stored in the body? 

 

After a meal, glucose (a monosaccharide) is converted to glycogen (a polysaccharide). There is a finite amount of glycogen we can store; excess glucose is broken down to acetyl CoA, then converted to fatty acids and triglycerides.

 

Describe how the intensity of exercise affects muscle glycogen stores.

 

There more intense the exercise is, the more rapidly the glycogen stores will be depleted.

 

If glucose is used to fuel exercise, why does the level of blood glucose change very little in short term for mild to moderate exercise?

 

Glycogen is hydrolysed to release glucose in order to maintain glucose homeostasis.