Lecture 6: On the Substrate and Narrow

Where does energy come from?

Energy is required to form chemical bonds but is liberated by breaking them

Where do plant get their energy?

Plant uses solar energy to form H2O and CO2 into CHO

- Photosynthesis

Where do animals get energy from?

Cow eats the grass (along with CHO) and uses the energy to synthesize muscle

Where do we get our energy from?

Athlete eats meat and uses muscle protein/fat to synthesize ATP and power muscle action

What is a carbohydrate?

Carbohydrate= Carbo (carbon) + hydrate (H2O) 1 carbon : 2 hydrogens : 1 oxygen

What is food energy quantified using calories?

• "Calorie" is common term for kcal (1000 calories)

• 1 kcal (or 1 Calorie) is the amount of energy required to raise temperature of 1kg of water 1°C.

• 1kcal = 4.184 kilojoule

What is the dietary calories come from four macronutrients?

• Carbohydrates

• ~4kcal per g

• Proteins

• ~4kcal per g

• Fats

• ~9kcal per g

• Alcohol

• ~7kcal per g

What is the utilization of dietary CHO?

2/3 of glycogen stored in muscle, ~1/3 stored in liver

What can carbohydrates

• Glycolysis

• Oxidative phosphorylation

• Replenishing PCr stores

What are proteins composed of?

a chain of amino acids

What is protein utilization?

Deamination to gluconeogenesis

What are the ways that protein (coverted to CHO) can be used for?

• Glycolysis

• Oxidative phosphorylation

• Replenishing PCr stores

What happens when proteins is metabolized for energy?

are no longer available for other protein functions (like tissue repair)

What are the components of fat?

Triglycerides (glycerol+fatty acids)

What is the breakdown of triglycerides process involve?

Lipolysis and Beta-Oxidation

What is Lipolysis?

breakdown (hydrolysis) of triglyceride into its components

• Occurs in the cytosol • Before fatty acids can be oxidized they must be released from triglycerides and converted to fatty acyl CoA

What are the two steps of Lipolysis?

• Step 1: • Hydrolysis of triglycerides: reaction catalyzed by hormone sensitive lipase (HSL)

• Degradation of fatty acids: reaction catalyzed by acyl-CoA synthetase ACS

What is Beta- Oxidation?

oxidation of fatty acids and glycerol

What is Fat like in the mitochondria?

• Mitochondrial membranes impermeable to Fatty Acyl CoA

• Needs to be transported into the inner matrix

• Transport occurs using proteins and small molecule carnitine

• Fatty Acyl CoA attached to carnitine can pass through carnitine acylcarnitine translocase

What is breakdown of acyl CoA into Acetyl CoA?

• Each cycle (four steps) removes:

• 1 acetyl CoA unit

• 1 NADH

• 1 FADH2

• Fatty Acyl CoA (minus 2 carbons) re-enters cycle

• Process is repeated until fatty acid is completely broken down into acetyl CoAs

• Ex. 18-carbon fatty acid (oleoic acid) will go through 8 cycles of β-ox and yield 9 acetyl-CoA (18/2 = 9)

What do triglyceride hydrolyzed into?

glycerol and three fatty acid chains (lipolysis)

What is the overview?

• Glycerol undergoes glycolysis, etc.

• Each fatty acid chain enters mitochondria and undergoes beta-oxidation to convert to multiple acetyl CoAs

• Acetyl CoA enters Krebs, etc.

Each CHO molecule yields how many ATP?

32 ATP

Each triglyceride molecule yields how many ATP?

377 ATP

Aerobic energy stores (fat+ CHO) are??

Practically infinite

What is the rate of energy production for each system?

• PCr yields highest rate

• Glycolysis next fastest

• CHO oxidation is slower

• Fat oxidation is slowest