HAP Lecture 5 nutritional energy and role of ATP

What are the four things for which we need support of physiological output?

1) To 'maintain' the body
2) Development/growth/production
3) specific achievements (sports, illness)
4) Quality of life (health, life expectancy)

What is the difference between immaterial and material output in nutrient flow?

Immaterial output is for the maintenance of the body and to generate heat and energy. The input goes to waste (CO2, urea).
While material output is for growing, producing, or storage. The input goes to the product, like muscle or fat.

What is the main energy source of the brain?

Glucose (sometimes bit of ketone bodies). The brain does NOT use lactate

What is the main energy source of skeletal muscle (resting conditions)

Fatty acids (sometimes bit of glucose or ketone bodies). In rest, they do NOT use lactate

What is the main energy sources of the liver?

Fatty acids, sometimes a bit of glucose or lactate. The liver does NOT use ketone bodies.

What is the main energy sources of the heart?

Primarily fatty acids, but glucose, ketones and lactate can be used as well

What is the ATP:ADP ratio in a cell?

~500:1

What is special about ATP and lipid metabolism?

Can go from ATP > AMP = 2 ATP energy equivalents are released

What escape route do cells use when they are running out of energy?

They use 2 ADP to make ATP + AMP. Cells immediately get triggered when the AMP is there, because it signals they are running out of energy

What is the gross energy (GE),energy lost?

The total amount of energy present in the food, some is lost via faeces

What is digestible energy (DE), and how is some of the digestible energy lost?

This is energy that can be digested in the body, and some of it is lost via faeces. It is the amount of energy that is absorbed.

What is metabolisable energy (ME), and how is some of it lost?

This is energy that is actually deposited in tissues like protein and fat, some of it is lost in urine and gas

What is net energy, and how is some of it lost?

It is energy for maintenance, production and physical activity. Some of it is lost via heat.

How much energy does a mole of glucose release when it is oxidized?

2816 kJ

Why are there no losses in the body when you give pure glucose?

Because all glucose is absorbed

Give the macronutrient digestibility (from highest to lowest)

Carbohydrates, lipids, proteins.
It thus depends on the nutrient how much you have to subtract from the gross energy to get the digestible energy.

What is the mean carbohydrate absorption from food?

98% in humans, a lot absorbed in the duodenum

What is the mean triglyceride absorption from food?

95% in humans. Mainly absorbed in the jejunum.

What is the mean absorption of protein from food?

93%. Protein digestion is slow in onset and incomplete. Mainly absorbed in the jejunum and ileum

How much of the digestible energy from protein is lost in protein? (leaving you with metabolisable energy)

5.2 kJ per gram of protein

What type of energy do we use to calculate the energetic content of food?

Metabolisable energy

For what three things is ATP used?

1. Mechanical work

2. Electrical work

3. Chemical work
   (think of muscle action, nerve transmission, glandular secretion, digestion, circulation, tissue synthesis)

Why is metabolisable energy not the same in all species?

Humans cannot digest cellulose, but other animals like horses, cows and sheep can

Maltose has two glucose molecules, but is not exactly 180*2 = 360 in MW. Why not?

Because 18 MW is lost as water when a bond is formed between two glucose molecules.

What is the difference between an exothermic and an endothermic reaction?

An exothermic reaction releases heat or light to the surroundings.
An endothermic reaction is a reaction where heat is absorbed from the environment.

What three types of triphosphates exist?

Adeninetriphosphate, guaninetriphosphate, uraciltriphosphate

How can an exothermic reaction be started?

The activation energy needs to be high enough. It is the energy needed to break a chemical bond. Eventually, more energy than the activation energy is released when the new bond is formed, and the reaction proceeds with an output of energy.

How is the synthesis of ATP fueled?

By the oxidation of nutrients

What is 'substrate-level phosphorylation'?

Taking a phosphate from a food molecule, and directly attaching it to ADP to make ATP.

What is glycolysis?

The process of breaking down one glucose molecule into two pyruvate molecules. It happens in the cytoplasm of the cells and does not need oxygen.

What are reduced coenzymes?

Carrier molecules loaded with electrons from food (like NADH, FADH2)

What are oxidized coenzymes?

The carrier molecules after they have dropped off their electrons.

What is the similarity between glycolysis and oxidative phosphorylation?

They both make ATP

What are the differences between glycolysis and oxidative phosphorylation (the two main methods for making ATP)?

1. Glycolysis happens in cytoplasm, Oxidative Phosphorylation in mitochondria.

2. Glycolysis generates 2 ATP per glucose molecule, Oxidative Phosphorylation +30 ATP per molecule.

3. Glycolysis is fast, but Oxidative Phosphorylation is slow and efficient.

What are 5 things for which intracellular ATP is used?

1) Endothermic (metabolic) reactions
2) Keep H+ gradient and cellular transporters
3) ABC transporters
4) metabolic trapping
5) protein regulation

What is the role of ATP in endothermic reactions?

Endothermic reactions proceed with overall hydrolysis of ATP > ADP + phosphate

What three things are needed to make ATP?

ADP, phosphate, energy

How are glycolysis and oxidative phosphorylation connected?

Oxidative phosphorylation uses the products of glycolysis to produce ATP more efficiently

What is the linkage between ATP utilization and the oxidation of metabolic fuels? (oxidative phosphorylation)

Metabolic fuels provide electrons to produce reduced coenzymes, these go to the mitochondrial ETC where they are transferred to complex V, which uses them to generate ATP from ADP, which is used from physical and chemical work. ADP is the result after the work and this is again used by complex V

How does ATP play a role in transport of materials across cell membranes?

It creates a proton gradient: ATP-powered pump used energy from ATP hydrolysis to actively more protons (H+) across membranes

How is ATP used to keep sodium homeostasis?

The sodium pump uses ATP to pump sodium out of the cell> primary active transport

What is needed to hydrolize ATP, and where does this come from?

ATP needs H+ and OH-, aka water, to hydrolise to ADP and Pi.
H+ gets it from inside cell, OH- from outside cell.
Sodium can be used to counterbalance this. This happens in the membrane for the sodium pump.

How does ATP help in amino acid uptake?

Absorption of amino acids happens with sodium, to normalise this there is a sodium-potassium gradient to balance out the protons.

What are ABC transporters, and how does ATP play a role in them?

ATP-binding cassette proteins. Hydrolysis of ATP to phorphorylate the protein allows substrate to enter the ABC transporter.

What is the role of ATP transport in metabolic trapping?

Glucose enters (liver) cells, where it needs to be stored as glycogen: in liver cells, phosphorlyated to glycose-6-phosphate, catalyzed by enzymes hexokinase or glucokinase which use ATP as a phosphate donor. Glucose-6-phosphate cannot cross cell membranes anymore.

How does ATP play a role in activation or inactivation of enzymes?

ATP is sometimes used to phosphorylate proteins, this regulation can happen in milliseconds

What is the role of creatine phosphate in muscles?

Cells store massive amounts of ATP. ATP is used to phosphorylate creatine into creatine phosphate, the creatine phosphate now contains the energy. When you need the energy it goes back to creatine, and you have extra ATP for muscle contraction. Creates and extra 'storage'.

Why is storage of glucose as glycogen more efficient than storage of fat?

Because storage of glucose generates less heat than storage of fat: about 95% vs 82% efficiency.

How efficient is the oxidation of glucose to ATP? (glucose contains 2816 kJ/mol)

35%> about 990 kJ is trapped in ATP, and 1826 kJ is released as heat