IMMS: 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?
Life-sustaining chemical reactions taking place within each cell.
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 the difference between daily energy expenditure (DEE) and basal metabolic rate?
DEE = total number of calories burned in 24h period, including for physical activity.
Basal metabolic rate = number of calories per hour needed to stay alive at complete rest, not including digestion or physical activity.
How much protein is needed in the diet per day?
0.8g/kg/day.
What is the most energy dense: protein, lipids, or carbohydrates?
Lipids (9kcal/g)
Protein & carbohydrates are only 4kcal/g
How much does 10ml of alcohol weigh?
How many units of alcohol is this?
8mg (less dense than water).
One unit of alcohol.
What is the average basal metabolic rate?
1kcal/kg/hour average (but depends on a variety of factors).
Name 7 factors that affect basal metabolic rate (BMR).
F A B M I S T
Food intake
Age
BMI
Muscle mass
Infection/disease
Sex
Thyroid function
How many kcal/g is alcohol?
7kcal/g
What are the 9 essential amino acids?
Happy Iguana Left Lisbon, Making a Pilgrimage To TransylVania.
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
What is another name for Vitamin A?
Retinol.
Name the 8 B vitamins.
The Right Number Potentially Passes By Four Cunts
B1: Thiamin
B2: Riboflavin
B3: Niacin
B5: Pantothenic acid
B6: Pyridoxine
B7: Biotin
B9: Folate
B12: Cobalamin
Can B vitamins be stored in the body?
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.
What is the main function of calciferol (Vitamin D)?
Regulating the amount of calcium and phosphate in the body.
Which vitamin is tocopherol?
Vitamin E.
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?
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 Krebs Cycle?
Citrate Is Krebs Starting Substrate For Making Oxaloacetate
Acetyl CoA -> Citrate -> Isocitrate -> alpha Ketoglutarate -> Succinyl-coA -> Succinate -> Fumarate -> Malate -> Oxaloacetate
Where does the Krebs Cycle occur and in what conditions?
Mitochondrial matrix under aerobic conditions.
What provides the final common pathway for oxidation of carbohydrates, fats, and proteins?
The Krebs Cycle.
Where does oxidative phosphorylation occur and in what conditions?
Inner mitochondrial membrane under aerobic conditions.
Which generates more energy, Krebs Cycle or oxidative phosphorylation?
Oxidative phosphorylation, around 30 ish ATP per glucose molecule.
What are the two key components 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 are the five components of Adenosine 5’ Triphosphate (ATP)?
Adenine base + ribose + three phosphate groups which are linked with high energy bonds.
How does hydrolysis of ATP into ADP release energy?
Breaking bond between phosphate groups releases energy.
What is glycolysis?
Metabolic pathway which converts glucose into 2x pyruvate, with a net gain of 2x ATP.
Where does glycolysis occur and in what conditions?
In cytoplasm, can occur in anaerobic or aerobic conditions.
What is the primary method of ATP generation for erythrocytes and why?
Glycolysis, because erythrocytes lack mitochondria (Krebs and oxidative phosphorylation occur in mitochondria).
What are the two stages of glycolysis?
- Preparative phase (uses 2x ATP).
- ATP generating phase.
Why is the preparative phase in glycolysis important?
The preparative phase involves the phosphorylation of glucose; making it more polar therefore unable to pass back through the cell membrane. This commits it to the glycolytic pathway.
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).
Describe the structure of fatty acids.
Carboxylic group head, with aliphatic hydrocarbon chain tail. The hydrocarbon chain can be saturated or unsaturated.
Fatty acids are a type of lipid. Give three examples of other types of lipids.
Glycerides (made of glycerol & fatty acids), sterols (e.g. cholesterol, does not contain fatty acids), and complex lipids (e.g. lipoproteins, phospholipids).
Describe the structure of a triglyceride.
Three fatty acids esterified to a glycerol molecule.
What is esterification?
Esterification is a chemical reaction that combines an alcohol and an organic acid to produce an ester and water. For example, glycerol + 3x fatty acids = triglyceride + water.
What is the structure of a phospholipid, also known as glycerophospholipid?
Phosphate head, glycerol, and 2x fatty acid tails.
How are triglycerides transported in the blood?
Packaged into chylomicrons, a type of lipoprotein.
How do long-chain fatty acids enter the mitochondria for beta-oxidation?
Via the carnitine shuttle.
How do fatty acids produce acetyl-CoA?
Through beta-oxidation cycle. One acetyl-CoA produced each round of cycle.
What molecules are produced by the liver from acetyl-CoA to be used as an alternative fuel source?
Ketones.
What are acetone, acetoacetate, and beta-hydoxybutyrate all examples of?
Ketones.
When does beta-oxidation occur?
When the demand for energy outweighs the amount of glucose available in cells for glycolysis. For example, during exercise, fasting, febrile illness, hypothermia.
During high rates of fatty acid beta-oxidation, large amounts of acetyl-CoA are generated. Why does this result in raised ketones?
The large amount of acetly-CoA produced exceeds the capacity of Krebs cycle. Excess acetyl-CoA is then used in ketogenesis.
What affects do glucagon and insulin have on ketogenesis?
Glucagon activates ketogenesis. Insulin inhibits ketogenesis.
What is homeostasis?
The maintenance of a constant internal environment.
Explain the difference between autocrine and paracrine communication.
Autocrine: cells communicating within themselves.
Paracrine: cells communicating with neighbouring cells via signal diffusing across gap between cells.
What is endocrine communication?
Endocrine: cells communicating with other cells elsewhere in the body via hormones in the bloodstream.
What is a hormone?
A molecule which acts as a chemical messenger.
What are the different types of hormones?
Amine, peptide, and steroid hormones.
What is the smallest type of hormone. Describe their structure.
Amine/amino acid-derived hormones e.g. adrenaline. They are derived from single amino acids.
What amino acids are amine hormones derived from?
Tyrosine and tryptophan.
What do peptide and amine hormones have in common?
Both are synthesised in advance and stored in vesicles for a rapid response. Both are hydrophilic therefore dissolve in the blood.
Describe the structure of peptide hormones.
Made of amino acids, varying in size from a few amino acids to small proteins. Some have carbohydrate side chains (glycoproteins).
What type of hormone is made from cholesterol, and is therefore a lipid?
Steroid hormone.
How are steroid hormones transported to target cells?
Created in the cell then diffuses through cell membrane, enters blood.
Bound to transport protein in blood e.g. albumin to travel to the target cell.
Diffuses through target cell membrane to receptor inside the cell.
What type of hormone is most commonly involved in positive feedback loops?
Peptide hormones. E.g. oxytocin in labour.
What sort of feedback loop does homeostasis use?
Negative feedback loops.
What are the 3 main roles of microtubules?
- Give structure to the cell.
- Allow cell to change shape e.g. to engulf something.
- Move chromosomes during cell division.
Where are proteins synthesised?
Ribosomes studded on surface of rough endoplasmic reticulum.
Where are lipids synthesised?
Smooth endoplasmic reticulum.
What is the function of the golgi body?
Further modifies, processes, and packages proteins and lipids into vesicles for transport.
Describe in two words the structure of a cell membrane.
Phospholipid bilayer.
Why is the specific phosphate group, and whether it is cytoplasmic or exoplasmic, in the cell membrane phospholipid bilayer important? Give an example.
Specific phosphate groups are used as signals.
For example, serine (PS) is usually cystoplasmic, flips to exoplasmic to signal apoptosis is to occur.
What is a term for a molecule with both hydrophobic and hydrophilic parts?
Amphipathic molecule.
Name 3 factors that affect phospholipid bilayer fluidity.
Degree of saturation of fatty acids.
Presence and amount of cholesterol.
Temperature.
In normal conditions, what is the differences between intracellular levels of K+, Na+, and Cl- to extracellular levels?
Intracellular has higher K+ levels and lower Cl- and Na+ levels than extracellular.
Uniport membrane transporters transport a single substance across the cell membrane.
What is the function of antiport and symport membrane transporters?
Antiport = two substances in opposite directions
Symport = two or more substances in same direction
How does water move across cell membranes?
Simple diffusion via aquaporins - protein channels across the membrane. (Not facilitated diffusion because water doesn’t bind to a protein!)
How is glucose transported across cell membranes?
Facilitated diffusion using carrier proteins.
Primary active transport requires energy e.g. from ATP to move molecules across a membrane against their concentration gradient.
What is secondary active transport?
Secondary active transport uses an electrochemical gradient of one type of molecule, generated by primary active transport, to move a different type of molecule against its concentration gradient in a co-transporter
More than half of all drugs mimic or inhibit various G-Protein Coupled Receptors (GPCRs). What are GPCRs?
GPCRs are the largest family of cell membrane receptors in the human genome, used in cell signalling and regulate nearly every aspect of human physiology and disease.
What is a desmosome?
Type of junctional complex, connects the cytoskeletons of neighbouring cells to anchor them together.
Substances can be absorbed through epithelium via the transcellular route, passing through the cell membrane and cytoplasm.
What is an alternative route of substances, avoiding passing across cell membranes? What controls this route?
The paracellular route; substances cross epithelium by diffusion across intracellular space.
Controlled by tight junctions (protein complexes).
Give an example of fenestrated epithelium.
Epithelium of glomerulus.
Which has an overall negative charge, intracellular cytoplasm or extracellular fluid?
Intracellular cytoplasm.
What is the name of the equation used to calculate diffusion potential?
Nernst Equation.
How would you calculate how many litres of water should be in a healthy person weighing 70kg?
60% of body weight.
70 x 0.6 = 42L
Where is most of the water in the body stored? What percentage of body weight is this?
Intracellularly.
40% of body weight.
Water in extracellular fluid makes up 20% of all body weight. How is this 20% divided between interstitial and intravascular?
Interstitial = 16% of total body weight
Intravascular = 4% of total body weight
Is plasma hypertonic, isotonic, or hypotonic? Why?
Isotonic. Means that there is no net flow of water (erythrocytes do not swell or shrink!).
What is the predominant cation in intracellular fluid?
Potassium.
In normal conditions, what is the difference between intracellular and extracellular osmolality?
Zero! Should be equal, osmosis of water across cell membrane should keep osmolality balanced.
In capillaries, what causes reabsorption of water from interstitial fluid in the plasma?
Oncotic pressure, caused by a difference in protein concentration between plasma and interstitial fluid.
What happens to excess water in interstitial fluid which is not reabsorbed into plasma or diffused into cells?
Enters lymphatic system.
What is oedema?
Excess accumulation of fluid in interstitial space.
Name 3 causes of oedema.
- Hypoalbuminaemia.
- Obstruction causing issue of venous/lymphatic return.
- Inflammation causing increase in capillary permeability.
What causes transudate?
Fluid being pushed through capillary by high pressure into interstitial space.
What causes exudate?
Exudate is caused by capillaries becoming more permeable (e.g. due to infection), allowing fluid including proteins to leak out.
Which enzyme catalyses the rate-limiting step of the Krebs cycle?
Isocitrate dehydrogenase.
What enzyme catalyses the rate-limiting step in aerobic glycolysis?
PFK1 (phosphofructokinase)
