Metabolism Flashcards
What is the difference between resting metabolic rate and basal metabolic rate?
Metabolic rate is the energy used per unit of time (I.e. kcal/day)
resting metabolic rate refers to the number of calories burnt at rest
basal metabolic rate refers to the number of calories needed at minimum for basic functions at rest
Which hormones regulate basal metabolic rate?
Thyroid hormones (T3 & T4)
What is the typical basal metabolic rate for females & males?
Females 1400 kcal/day
Males 1700 kcal/day
What metabolites are carbohydrates broken down into and how are these stored?
glucose
stored as glycogen or used directly for energy
What metabolites are lipids (fats) broken down into and how are these stored?
fatty acids
stored as triglycerides
What metabolites are proteins broken down into and how are these stored?
amino acids
stored as proteins
How does the energy yield from breaking down carbs/proteins compare with that of fats?
fats have twice the energy yield of carbs/proteins
True or false… anabolic reactions require energy?
true
Where does ‘first pass’ metabolism occur? Why is this?
in the liver as blood from the intestinal system flows directly there via the hepatic portal vein before moving into the main bloodstream
this is because the liver is closely linked with the pancreatic blood supply so hormones like insulin and glucagon can exert their effects here first
Is more glucose (glycogen) stored in the liver or in the skeletal muscle?
skeletal muscle
Where does energy exist within ATP?
between the phosphate bonds, hence when one is broken it creates energy
What gives cells specificity in metabolism?
they produce the enzymes needed for the process
i.e. the liver produces glycogen synthase hence it can synthesise glycogen
Describe the process of glycogenesis
blood glucose enters liver cell
hexokinase changes it to glucose-6-phosphate (ATP)
then to glucose-1-phosphate
then glycogen synthase changes it to glycogen
Describe the process of glycogenolysis
glycogen in liver cell
glycogen phosphorylase changes it to glucose-1-phosphate
then to glucose-6-phosphate
glucose-6-phosphatase converts to glucose
glucose moves to blood stream
What key metabolic functions does the liver have?
gluconeogenesis (synthesis of new glucose from lactate & amino acids)
ketogenesis (synthesis of ketones from fatty acids & amino acids for alternative energy)
lipogenesis (synthesis of lipids from glucose & amino acids)
Does skeletal muscle only get energy from glucose?
usually yes- in a fasted state it can use lipids as an energy source
Can glycogen stored in skeletal muscle be used elsewhere in the body for energy?
no- skeletal muscle that stores it, uses it
What function does adipose tissue have other than storing lipids?
it is also an endocrine organ releasing hormones (aka adipokines) i.e. leptin which is used in appetite regulation
How low do oxygen levels need to drop to cause damage or even result in death?
<2mmol/L
How long does it take for the brain to adapt to using ketones as an energy source when glucose is low?
3-4 days
How does growth hormone interact with proteins? How does this differ with fats?
GH protects protein reserves & stops us ‘eating’ through them for energy, whereas it has a catabolic effect on fats to release it as energy during periods of starvation
Are catecholamines, cortisol and growth hormone active in fed or fasted states?
fasted/starvation
What pancreatic cells produce insulin?
Beta cells
What pancreatic cells produce glucagon?
Alpha cells
What 3 underlying mechanisms are common in most metabolic syndromes?
1) fat accumulation
2) impaired insulin sensitivity
3) low-grade chronic systemic inflammation
What are the 6 WHO criteria for metabolic syndrome?
1) impaired glucose regulation
2) abdominal obesity
3) hypertriglycemia (high levels of lipids in blood)
4) low levels of HDL cholesterol
5) raised blood pressure
6) microalbuminuria (high levels of albumin in urine)
Why do we see necrosis in adipocytes in metabolic syndrome? How does this contribute to inflammation?
as adipose tissue increases, blood vessels are unable to keep up with the supply due to Fick’s law (same amount of blood vessels, larger cells to service means there is greater distance for molecules to travel)
as cells die, more immune cells enter the area to clean up the dead cells hence an increase in pro-inflammatory markers
What 3 major tissues does insulin target?
skeletal muscle, liver & adipose
Which lipoproteins (cholesterols) are ‘good’ and which are ‘bad’ leading to atherosclerosis?
‘good’ cholesterol is HDL or high density lipoproteins
‘bad’ cholesterol is VLDL or very low density lipoproteins & LDL or low density lipoproteins
these are the ones that lead to cardiovascular disease
What is the functional unit of the pancreas?
Islets of Langerhans or islet cells
these produce insulin (beta cells) and glucagon (alpha cells)
Why are beta cells and alpha cells not technically functional antagonists?
even though they work in opposite ways as functional antagonists do, they work on different receptors to each other
What are the 3 P’s of diabetes mellitus?
polyuria (frequent urination)
polydipsia (increased thirst)
polyphagia (increased hunger)
How does type 1 diabetes contrast with type 2?
type 1: impaired insulin secretion due to destruction of beta cells, early life & rapid onset, accounts for 10-20% of all cases of diabetes and is treated with insulin injections, exercise and diet
type 2: normal insulin production however insulin is resisted by target cells, late life & slow onset, accounts for 80-90% of all cases of diabetes and is treated with weight reduction, exercise, diet and some drugs
Name 4 purposes of metabolic pathways (i.e. glycolysis & citric acid cycle).
1) extraction of energy
2) storage of fuels
3) synthesis of building blocks
4) elimination of waste
True or false… the citric acid cycle only takes place in cells with mitochondria
true
How much of energy in nutrient molecules is converted to energy?
~50%
What is ATP used for?
provides energy for synthesis of macromolecules, transport pumps and muscle contraction
Metabolic process: Glycogenesis
turns glucose to glycogen, decreasing glucose levels in the bloodstream
Metabolic process: Glycogenolysis
turns glycogen into glucose, increasing glucose levels in the blood stream
Metabolic process: Gluconeogenesis
turns amino acids into glucose, increases glucose levels in the bloodstream
Metabolic process: Protein synthesis
turns amino acids into protein, decreasing amino acid levels in the bloodstream
Metabolic process: Protein degradation
turns proteins into amino acids, increasing amino acid levels in the bloodstream
Metabolic process: Lipogenesis
turns fatty acids & glycerol into triglycerides, decreasing the fatty acid levels in the bloodstream
Metabolic process: Lipolysis
turns triglycerides into fatty acids & glycerol, increasing fatty acid levels in the bloodstream
How much ATP is produced in glycolysis? How about the citric acid cycle? And from the electron transport chain?
net +2 ATP, +2 ATP, ~+28 ATP (altogether about 30 ATP)
What happens when there is too much acetyl COA in the bloodstream due to a diet high in fat?
ketogenesis occurs in the liver to form ketone bodies which can be used as fuel when glucose is sparse
What are the 4 major lipid metabolic pathways?
1) lipolysis
2) beta oxidation
3) lipogenesis
4) ketogenesis
Lipolysis is a …bolic reaction that converts … to … & …
catabolic
converts triglycerides to glycerol & fatty acids
Beta oxidation is a …bolic reaction which converts … into …
catabolic
converts fatty acids into acetyl CoA
Lipogensis is a …bolic reaction that synthesises …
anabolic
synthesis of cholesterol
Ketogenesis is a …bolic reaction that synthesises …
anabolic
synthesis of ketone bodies
Where do all 4 of the lipid metabolic pathways converge to?
Acetyl-CoA (to be fed into the cytric acid cycle to produce ATP)
What are the 3 ways that proteins can be metabolised and used?
proteins are digested to form amino acids which are either stored as tissue proteins or plasma proteins
they can also be deaminated and secreted in urine as urea or ammonium or used in metabolic pathways
they can also be turned into neurotransmitters
Describe the pathways of amino acids when they go through transamination (as opposed to being used in tissues or plasma as proteins)
1) transamination: an amine group is switched from an amino acid to a keto acid
2) oxidative deamination: the amine group of glutamic acid is removed as ammonia and combined with Co2 to form urea which is excreted in urine
3) keto acid modifications: the keto acids formed during transamination are altered so they can easily enter the citric acid cycle
Hyperglycemia can lead to other complications down the road like…
1) vascular damage
2) diabetic blindness
3) renal failure
4) neuropathy
