Intro to metabolism Flashcards
describe ATP
coenzyme, that is acted in by other enzymes
hydrolysis of atp releases energy
what are the standard and actual free energies of hydrolysis
the standard free energy of hydrolysis is the amount of energy you get from a mole of ATP, when all the concentrations of ATP, ADP and phosphate are 1 molar (-31kJ/mol)
the actual free energy takes the actual ATP, ADP and phosphate values (-60 kJ/mol)
what is the metabolic role of ATP
during oxidation, atp is generated and consumed by energy-consuming reactions
oxidation of glucose, fatty acids and amino acids are broken down to CO2 by the various pathways, liberating energy
ATP is then used in muscle contraction, biosynthetic reactions, ion-pumping, and some of the energy is lost as heat
describe NADP
acceptor of hydrogen
derived from vit B3
NADP+ - oxidised form
NADPH - reduced form
anabolic pathways require both energy and reducing power in the form of NADPH
metabolic role of NADP
acts as oxidising agent and gets reduced throughout respiration
reduced NADP is reduced and is reoxidised in biosynthetic
what are the 4 main categories of dietary requirements
energy (main sources included carbohydrates, fat and protein)
macronutrients
electrolytes and minerals
vitamins
how is fat broken down
by the beta-oxidation pathway in the mitochondria
how are carbs broken down
glycolysis in cytoplasm and then enters into the mitochondria as pyruvate to be further oxidised
how are proteins broken down
digested to 20 differnt amino acids, each of which has at least 1 breakdown pathway, these pathways all end with the intermediate acetyl-CoA, which is the fuel for the citric (tricarboxylic) acid cycle
what does the citric acid cycle do
oxidises the acetyl groups into CO2
undergoes oxidative phosphorylation
what are starch’s two subcomponents
amylose contains straight chains, in which the glucose units are linked 1-4
amylopectin contains alpha 1-4 linked straight chains with the occasional alpha 1-6 branch
overview of starch digestion
begins in saliva where amylase (synthesised by the parotid gland)breaks alpha 1-4 links, this process is interrupted in the stomach because the pH is low but resumes in the small intestine, where salivary amylase resumes and amylase from the pancreas also acts on starch
starch is broken down into smaller shorter chain glucose polymers (disaccharides)
in the small intestine isomaltase and glucoamylase break these down even further so all of the starch is converted to glucose
glucose is absorbed in the small intestine by active uptake
disaccharide digestion
sucrose (glucose and fructose) is broken down by sucrase to glucose
lactose (galactose and glucose) is broken down by lactase to glucose
galactose and fructose are broken down in the liver
distribution of the lactase persistence phenotype
65% of the world is lactose intolerant
lactase is expressed in infants , but normally this switches off by adulthood, due to exposure in many parts of the world which means it doesn’t not switch off
being unable to digest lactose leads to a lot of digestive problems
anaerobic and aerobic glycolysis
always phosphorylated to to glucose-6-phosphate
in the muscle and liver there are storage form of glucose (glycogen) this can be broken down to glucose-1-p which interconvertible to glucose-6-p
in the cytoplasm glucose 6p becomes pyruvate
in aerobic the pyruvate can enter into the mitochondria
in anaerobic pyruvate becomes lactate
what are fatty acids
components of fat
tissues store it triacylglycerol (adipose, but also liver and muscle)
double bond causes a kink in a straight chain
describe digestion of triacylglycerol
insoluble so it has to be solubilised by bile acids and salts
these are produced in the liver and stored in the gallbladder and then secreted into the small intestine
they are hydrophobic on one side and hydrophilic on the other, they act to bring TAG into solution in the form of micelles where it is acted on by pancreatic lipase to be digested
describe chylomicrons
TAG is packaged by the intestinal cells and secreted via the lymphatic system into the blood in the form of chylomicrons
they are the digested and transported form of TAG
overview of the digestion and transportation of dietary fat
TAG is solubilised by bile to monoacylglycerol (glycerol with a single fatty acid attached), this is taken up by intestinal enzymes and reassembled to TAG and packaged into chylomicrons
these then circulate the blood and are then hydrolysed by lipoprotein lipase to fatty acids and glycerol, they can then be taken up and oxidised or reconverted to TAG
what happens to TAG during starvation and exercise
TAG is broken down to liberate free fatty acids in the plasma, they travel bound to albumin as they are not very soluble, these can be taken up and oxidised to yield energy
overview pf protein turnover
proteins in the body are constantly being broken down and resynthesised
when its broken down the constituent amino acids are released into an amino acid pool to resynthesise proteins or drained by removal of amino acids to make the biosynthetic products or for energy production
amino acids can be broken down, amino group is removed and excreted as urea, then the carbon skeleton can be metabolised (completely oxidised to CO2 or can be changed to other circulating intermediates such as glucose or ketone bodies)
what is nitrogen balance
the net total of nitrogen in your body
nitrogen balance - excreting the same volume as ingesting
positive nb - synthesising more than excreting, possibly due to growing or being pregnant
negative nb - excreting more than ingesting, occurs during starvation and diseases
nitrogen balance results in a requirement for dietary protein
overview of protein digestion
principle enzyme in stomach is pepsin, has a very low ph, it unfolds proteins and denatures them, also makes them more susceptible to proteolytic attack and halts bacterial growth
pancreatic proteases (trypsin, chymotrypsin, elastase, carboxypeptidases and bicarbonate) and peptidases secreted by small intestine also help break down proteins
overview of zymogens
trypsinogen is activated by enteropeptidase in the small intestine to become trypsin
trypsin then activates itself, chymotrypsin, elastase and carboxypeptidase
theses are all zymogens which have different specificities (hydrolysed different peptide bonds
how are amino acids excreted during protein turnover
transamination (the removal of the amino group) to form amino acid glutamate
that leaves the carbon skeleton of the amino acid which are broken down to C02
the amino group is dealt with by excretion via urea, glutamate is converted to alanine during transport, then glutamate is reformed in the liver
how are amino acids metabolically classified
some are broken down to form glucose, very important during starvation, they are used to maintain the plasma glucose concentration
some are converted to ketone bodies
large amino acids are broken into both, part of the backbone form glucose and part to ketones
