IMMS 2: Cells & metabolic processes Flashcards
Metabolic fuels & diet; Glycolysis, Krebs & oxidative phosphorylation; Fatty acid oxidation & ketones; Living control mechanisms; Membrane ultrastructure & transport; Water & sodium
What is metabolism?
Sum of chemical reactions taking place within each cell.
Name the four main pathways dietary components are metabolised by.
- Biosynthetic (creating molecules).
- Fuel storage.
- Oxidative processes (breaking down molecules to make energy).
- Waste disposal.
What is a xenobiotic?
A substance that has never come from a living thing e.g. chemicals that have been completely synthesised. Needs to be broken down in the body and excreted.
What is an anabolic process?
A process where larger molecules are synthesised from smaller components. Used in constructive metabolism e.g. storage of fats.
What is a catabolic process?
A process where larger molecules are broken down into smaller components. Used in oxidative and waste disposal processes.
What is daily energy expenditure (DEE)?
Total number of calories burned in 24h period, including for physical activity.
How much protein is needed in the diet per day and why?
0.8g/kg/day to gain essential amino acids.
What is the most energy dense: protein, lipids, or carbohydrates?
Lipids; 9kcal/g
Protein & carbohydrates are only 4kcal/g
How is excess fuel stored for lipids, carbohydrates, and protein?
Lipids: adipose tissue (15% water).
Carbohydrates: glycogen in liver and muscle.
Protein: muscle (80% water).
How much does 10ml of alcohol weigh and how many units of alcohol is this?
8mg (less dense than water). One unit of alcohol.
What is the basal metabolic rate?
Energy needed to stay alive at complete rest (not including digestion).
1kcal/kg/hour average but depends on a variety of factors.
What lowers basal metabolic rate?
Lowers with age
Female (higher BMR in males)
Starvation
Hypothyroidism
Decreased muscle mass
Lower BMI
(infection/chronic disease and low ambient temp raise BMR)
How many kcal/g is alcohol?
7kcal/g
What happens during an overnight fast?
Insulin secretion reduces, glycogen stored in the liver is broken down using glycogenolysis. Glycogen stores depleted down to 80g remaining.
What happens during a fast lasting longer than four days?
Change in metabolism, reduction in BMR. Liver creates ketones from fatty acids. Brain adapts to using ketones.
When does gluconeogenesis occur?
When glycogen stores have been depleted. Instead need to create glucose from breaking down fat (lipolysis) or protein (proteolysis).
Define malnutrition.
Deficiency, excess, or imbalance of energy, protein, or other nutrients, causing adverse effects.
What are the 9 essential amino acids?
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
What is the main function of retinol and can it be stored?
Retinol = Vitamin A
Immune system, vision in dim light, skin and other epithelium.
Excess retinol can be stored in the liver.
Name some important B vitamins and can they be stored in the body?
Thiamin (B1)
Riboflavin (B2)
Niacin (B3)
Pantothenic acid (B5)
Pyridoxine (B6)
Biotin (B7)
Folate (folacin/B9) and folic acid (manmade folate)
Cobalamin (B12)
Most B vitamins cannot be stored. Folate and B12 can be stored in the liver.
What happens if you take too much pyridoxine?
Too much pyridoxine (B6) can cause peripheral neuropathy.
What do cobalamin, folate, and iron have in common?
They are needed for making red blood cells. Deficiencies can cause B12/folate/iron deficiency anaemias.
Which vitamin is needed to prevent scurvy?
Ascorbic acid/vitamin C.
Needed for healthy skin/bones/cartilage, wound healing.
What is the main function of calciferol?
Vitamin D. Regulating the amount of calcium and phosphate in the body.
Why is vitamin E (tocopherol) important?
Maintaining healthy skin and eyes, strengthening the immune system.
Which vitamin, stored in the liver, is vital for clotting and wound healing?
Vitamin K
What mineral is needed in diet for making thyroid hormones?
Iodine
Which vitamins are fat soluble?
A, D, E, K
Which vitamins are water soluble?
Vitamin C and most of the B vitamins.
What percentage of daily energy should come from free sugars?
No more than 5%
What is the maximum amount of saturated fat for women and men?
20g for women. 30g for men.
What is the recommended maximum amount of salt per day?
2.4g/day of sodium = 6g of salt
What are the guidelines around alcohol intake?
No more than 14 units of alcohol per week, spread over at least 3 days, with some alcohol free days.
What are the substrates and intermediates of the Kreb’s Cycle?
“Citrate Is Kreb’s Starting Substrate For Making Oxaloacetate”
Starting substrate = acetyl CoA -> Citrate -> Isocitrate -> alpha Ketoglutarate -> Succinyl-coA -> Succinate -> Fumarate -> Malate -> Oxaloacetate
How many enzymatic reactions are in the Kreb’s Cycle?
8
Where does the Kreb’s Cycle occur and in what conditions?
Mitochondrial matrix under aerobic conditions.
What are the main purposes of the Kreb’s Cycle?
- Generates energy for the cell.
- Provides final common pathway for oxidation of carbohydrates, fats, protein.
- Produces intermediates for synthesis of amino acid, glucose, heme etc.
What is the energy gain from the Kreb’s Cycle?
6xNADH + 2xFADH2 + 2xGTP
Where does oxidative phosphorylation occur and in what conditions?
Inner mitochondrial membranes under aerobic conditions.
Which generates more energy, Kreb’s Cycle or oxidative phosphorylation?
Oxidative phosphorylation, around 30 ish ATP per glucose molecule.
What are the two key parts of oxidative phosphorylation?
The Electron Transport Chain (ETC) and chemiosmosis.
How is H2O produced in respiration?
The final electron acceptor in ETC is oxygen, which picks up the final electrons and hydrogen = H2O.
What is ATP?
Adenosine 5’ triphosphate.
Adenine base + ribose + three phosphate groups which are linked with high energy bonds.
What does hydrolysis of ATP result in?
Release of energy from breaking bonds between phosphate groups. ATP = ADP + energy.
What is glycolysis?
Metabolic pathway which converts glucose by splitting it into two three-carbon molecules called pyruvates. A small amount of ATP is generated.
Where does glycolysis occur and in what conditions?
In cytosol (liquid part of cytoplasm), can occur in anaerobic or aerobic conditions.
Why do RBCs use glycolysis?
RBCs don’t have mitochondria, which is where Kreb’s and oxidative phosphorylation occurs, so have to use glycolysis.
What are the two stages of glycolysis?
- Preparative phase (uses 2x ATP).
- ATP generating phase (produces 4x ATP, 2x NADH, 2x pyruvate).
Why is the preparative phase in glycolysis important?
The preparative phase involves the phosphorylation of glucose, which makes it more polar, “trapping” it in the cell (can’t pass back through membrane), which commits it to the glycolytic pathway.
Why does vigorous exercise lead to lactic acid build up?
In aerobic conditions, pyruvate (product of glycolysis) enters mitochondria and is used in Kreb’s cycle.
In anaerobic conditions, pyruvate (catalysed by lactate dehydrogenase) => 2NAD+ and lactic acid as byproduct.
In vigorous exercise, not time to break down lactate in liver, so builds up in tissue.
What is allosteric regulation?
An inhibitor or activator binds to a protein (e.g. enzyme) and alters its activity by changing its shape (e.g. activator binds, active site of enzyme becomes compatible with substrate).
What are the key hormones involved in glycolysis?
Insulin, glucagon, and catecholamines.
What is the structure of fatty acids?
Carboxylic head group with aliphatic tail. This tail is a hydrocarbon chain which can be saturated or unsaturated.
Are fatty acids and lipids the same thing?
No, fatty acids are a class of lipids. Examples of other classes of lipids are glycerides (glycerol-containing lipids), non-glycerides (e.g. steroids), and complex lipids (e.g. lipoproteins).