biochemistry Flashcards
what are the major carbohydrates of the diet
starch
glycogen
cellulose and hemulose
oligosaccharides
lactose, sucrose and maltose,
glucose and fructose
describe digestion of carbohydrates in the mouth
salivary amylase hydrolyses a1-4 bonds of starch
describe digestion of carbohydrates in the stomach
no carbohydrate digestion
describe digestion of carbohydrates in the duodenum
pancreatic amylase works as in mouth
describe digestion of carbohydrates in the jejunum
final digestion by mucosal cell surface enzymes
how are glucose and galactose absorbed
through and indirect ATP powered process
how is fructose absorbed
fructose binds to the channel protein GLUTS and moves down a concentration gradient
how are cellulose and hemicellulose digested and absorbed
they cannot be digested by the gut but instead increase faecal bulb and decrease transit time
what are hexokinase and glucokinase
enzyme catalysts
synthesis of glycogen step 1
Glycogenin covalently binds Glc from uracil-diphosphate (UDP)-glucose to form chains of approx. 8 Glc residues.
Then glycogen synthase takes over and extends the Glc chains
synthesis of glycogen step 2
The chains formed by glycogen synthase are then broken by glycogen-branching enzyme and re-attached via (α1→6) bonds to give branch points
function of glycolysis
- catabolic pathway that saves some potential energy from glucose-6-phosphate by forming ATP
- the only way energy can be made from fuel molecules when cells lack O2
what does lactate dehydrogenase do
responsible for the production of lactate and regeneration of NAD+
what does pyruvate dehydrogenase do
catalyzes the oxidative decarboxylation of pyruvate with the formation of acetyl-CoA, CO2and NADH (H+)
(1,–3)
what is pyruvate converted to in human cells lacking O2
lactate
what are the different classes of amino acids
- aliphatic amino acids
- aromatic amino acid
- sulphur containing amino acids
- basic amino acids
- acidic amino acids
- polar amino acids
aliphatic amino acid characteristic
R group consisting of hydrocarbon chains
aromatic amino acid characteristic
R group consisting of a hydrocarbon ring
functions of proteins
- structural
- enzymatic
- contractile
- receptor
- defensive
- hormonal
- storage
- transport
STRECHDS
define primary structure
sequence in which amino acid monomers are bonded together to form a polypeptide chain
define secondary structure
- 3D spatial arrangement of amino acids located near each other in a polypeptide chain
forms of secondary structure
alpha helix for example myoglobin
beta pleated sheet form like fatty acid binding protein
define tertiary structure
- functional groups interacting with eachother
- involves van der waals, ionic, hydrogen, disulphide and hydrophobic interactions
define quaternary structure
- several polypeptides interacting with each other
- example: haemoglobin
what are glycoproteins
proteins with less than/or 1 carbohydrate molecule
function of glycoproteins
can cause stability, solubility, cell signalling, orientation
what are lipoproteins
combined with lipids to form lipoproteins
where are lipoproteins found
in cell membranes
function of lipoproteins
transport hydrophobic molecules
what are metalloproteins
protein molecules with metal ions within their structures
functions of metalloproteins
various functions e.g signal transduction, storage, transport
functions of globular proteins
storage, enzymes, hormones, transporters, structural
structure of globular proteins
can be sphere to cigar shape
fibrous proteins location
muscle fibres and connective tissue
structure of fibrous proteins
polypeptide chains organized approximately in parallel along a single axis, producing long fibers or large sheets
how do enzymes reduce entropy
they force the substrate to be correctly orientated by binding them in the formation they need to be in for the reaction to proceed
describe desolvation in enzyme-catalysed reactions
weak bonds between the substrate and enzyme essentially replace most or all of the H-bonds between substrate in an aqueous solution
describe induced fit
conformational changes occur in the protein structure when the protein binds
what is Km
a measure of the affinity an enzyme has for its substrate, as the lower the value of Km, the more efficient the enzyme is at carrying out its function at a lower substrate concentration
what happens to Vmax and Km with a competitive inhibitor
Vmax remains unchanged
Km increases because it takes more substrate to overcome the inhibition
what happens to Vmax and Km with a non-competitive inhibitor
- Vmax is decreased due to enzymes being taken out of action
- Km remains the same as the active site of the enzymes that have not been inhibited is unchanged
why is enzyme activity measured in a clinical setting
- Detection of suspected disease at pre-clinical stage
- Confirmation of suspected disease and assessing severity
- Localisation of disease to organs
- Characterisation of organ pathology
- Assessing the response to therapy
- Organ function assessment
- Assessing genetic susceptibility to drug side effects
- Detection of inherited metabolic diseaseDetection of vitamin deficiency
factors influencing enzyme activity in samples
hypoxia
cellular damage
physical damage
immune disorders
microbiological agents
genetic defects
nutritional disorders
where does the citric acid cycle occur
mitochondrial matrix
how is acetyl CoA produced
made via the decarboxylation of pyruvate dehydrogenase from pyruvate then oxidation then a transfer of the CoA complex
function of pyruvate dehydrogenase sub-units
Each sub-unit catalyses a different part of the reaction to convert pyruvate to acetyl CoA
function of E1
E1 catalyses the first decarboxylation of pyruvate
function of E2
E2 transfers the acetyl group to coenzyme A
function of E3
E3 recycles the lipoyllysine through the reduction of FAD, which is recyled by passing electrons to NAD+
what are the electron carriers of the citric acid cycle
FADH2 and NADH
what is complex 1 in terminal respiration
NADH-Q oxidoreductase
describe complex 1
Oxidises NADH and passes the high-energy e’s to ubiquinone to give ubiquinol
what is complex 2 of terminal respiration
Succinate-Q reductase
describe complex 2
Oxidises FADH2 and like complex I passes high-energy e’s to ubiquinone, which becomes ubiquinol
what is complex 3 of terminal respiration
Q-cytochrome c oxidoreductase
describe complex 3
Takes the e’s from ubiquinol (QH2) and passes them to cytochrome c
what is complex 4 of terminal respiration
cytochrome c oxidase
describe complex 4
Takes the e’s from cytochrome c and passes them to molecular O2
describe chemiosmosis
As e-’s pass through the complexes of the transport chain protons move from the matrix to the outside of the inner mitochondrial membrane
describe proton motive force
When these protons are ‘allowed’ to flow back down their gradient they release energy to do work
what is the binding change mechanism
sequential conformational changed of B subunit
what are the major lipid classes and their role in health and disease
- fatty acids (can be good or bad due to saturation)
- triaglycerols (dietary fuel and insulation)
- phospholipids (membrane signalling)
- steroids (cholesterol, steroid, bile salts)
- eicosanoids
where does lipid digestion begin and by what
stomach acid lipases
where is the main site of lipid digestion
small intestine
describe the absorption of lipids
Ingested lipids (e.g TAG) are cleaved by enzymes (e.g.,pancreatic lipase), absorbed in thesmall intestine, and then transported inchylomicronsviathe lymphatic systeminto the bloodstream, where they reach theliver (for lipoproteins), peripheral tissues (energy) andadipose tissue(storage).
how are lipids transported in chylomicrons
FAs are insoluble so they are packed into chylomicrons which are released by exocytosis into the lymph then blood
describe the steps of beta oxidation
dehydrogenation
hydration
dehydrogenation
thiolysis
energy yield of beta oxidation
32 ATP from 1 glucose molecule
what are ketone bodies
- normal metabolites of fat
- energy source when fasting
synthesis of ketone bodies
- ketone bodies can be oxidised in the mitochondria to yield 2 GTP and 22 ATP
transport of ketone bodies
- ketone bodies are transported from the liver to other tissues and reconverted to acetyl-CoA
main nitrogen-containing molecules of the body
amino acids and nucleotides
fate of dietary protein
synthesised into amino acids and then used for carbon skeletons or cellular respiration
what regulates urea production
CPS1 enzyme
what activates CPS1
N-acetyleglutamate and is allosteric
