cellular molecules Flashcards
define proteins
large, complex molecules that play many critical roles in body
describe various classes of amino acids
non-polar
polar
acidic
basic
describe functions of proteins
repair and build body’s tissues
allows metabolic reactions to take place
coordinates bodily functions
primary structure of proteins
amino acid sequence
polypeptide sequence
secondary structure of proteins
formed by H bonds between carbonyl and amino groups that make up the polypeptide backbone
alpha helices, beta sheets and random coil
tertiary structure of proteins
overall 3D arrangement of its polypeptide chain in space
quaternary structure of proteins
association of several protein chains or subunits into a closely packed arrangement
subunits held together by H bonds and van der Waals forces between nonpolar side chains
what properties may quaternary structure confer on proteins?
two or more identical or different polypeptide chains
globular v fibrous proteins
fibrous = long, narrow strands , helical like structure, generally structural roles - only soluble in strong acids globular = compact, rounded shape, folded ball like structure, functional roles - soluble in water, acids and bases
examples of globular
haemoglobin,
insulin,
myoglobin, immunoglobulins
and many enzymes
examples of fibrous
keratin
collagen
elastin
fibroin
explain denaturation
primary structure is unaffected, however, shape of protein can be altered so much that the protein becomes dysfunctional = therefore protein considered denatured
this can happen when protein is subject to changes in temp, pH, chemical exposure etc outside optimal range
glycoprotein - what molecules
carbohydrate and protein
lipoprotein - what molecules
lipid (fat) and protein
elastins
ECM protein , fibrous protein function - extensibility and elastic recoil of many vertebrate tissues eg arteries, valves, skin etc
keratins
fibrous structural proteins
main constituents of hair, nails etc
produced by keratinocytes (stratum corneum layer, outermost layer of skin - regenerative)
functions - protect epithelial cells, strengthen internal organs, control growth of epithelial cells, maintain elasticity
define enzymes
biological catalysts, proteins which help speed up metabolism or the chemical reactions in our bodies
naturally produced but can be manufactured
how do enzymes catalyse reactions
enzyme binds to substrate(s) on the active site, substrate molecule changed -> product formed
lowering activation energy necessary for a reaction to occur
discuss rate of an enzyme-catalysed reaction - factors etc
temperature - ^temp, ^rate - however extreme temps can cause denaturation
pH - optimum range, extreme values cause denaturation
enzyme conc - ^conc, ^rate
substrate conc - ^conc, ^rate
define Michaelis constant and explain
describe molecular nature of competitive inhibition
competitive inhibitors bind to enzyme, often at active site, which prevents real substrate from binding , therefore , inhibitor and substrate compete for enzyme
decreases no. of enzyme molecules available to bind to substrate
describe molecular nature of non-competitive inhibition
inhibitor doesn’t prevent substrate from binding , inhibitor and substrate do not affect each other’s binding
however, when inhibitor is bound, enzyme cannot catalyse its reaction to produce a product
decreases no. of functional enzyme molecules that can carry out reaction
why is enzyme activity measured in clinical settings
valuable for clinical diagnosis of several diseases - due to their high sensitivity, specificity and rapid response
what factors can influence enzyme activity in samples
temperature
pH
substrate and enzyme conc
discuss use of enzyme assays in clinical diagnosis
understanding how well a key enzyme functions in a physiological process reveals early signs of disease that has a long latency period
define enzyme assays
lab methods for measuring enzymatic activity within a sample
define cofactor and coenzyme
cofactor - “helper molecules” , can be inorganic or organic , do not bind to enzyme
eg metal ions,
coenzyme - organic, bind loosely to active site of enzyme and aid in substrate recruitment
allosteric proteins
one with an effector which regulates its activity by acting on a site physically distant from protein’s ligand-binding site
define major CHOs in diet
sugars - simple
starch - complex , made of lots of sugars
fiber - complex
describe CHOs digestion
chemical digestion begins in mouth
in the small intestine, pancreatic amylase does the brunt of starch and CHO digestion
after amylases breaks down starch into smaller fragments, brush border enzyme alpha-dextrinase starts working on alpha-dextrin, breaking off 1 glucose at a time
describe and contrast actions/functions of hexokinase and glucokinase
hexokinase - present in all cells, high affinity toward glucose, converts glucose at a faster rate
phosphorylation of glucose to form glucose-6-phosphate, by ATP
glucokinase - only present in liver, low affinity toward glucose
describe synthesis and degradation of glycogen
glycogenesis = synthesis of glycogen from glucose
glucose-6-p converted to glucose-1-p and then converted to uridine diphosphate (UDP)-glucose - inserted into glycogen by either enzyme, glycogen synthase or branching enzyme at the branch points
glycogenolysis = process of liberating glucose from glycogen
glycogen phosphorylase is involved
glucose-1-p is cleaved from glycogen by enzyme which can then be converted to glucose-6-p
glycogen functions in skeletal muscle v liver
skeletal muscle - energy storage
maintain a physiological blood glucose conc
function of glycolysis
breaks down glucose into two pyruvate molecules (3C compounds) and generates energy , NADH and water
functions of lactate dehydrogenase-catalysed reactions
catalyses interconversion of pyruvate and lactate with associated interconversion of NADH and NAD+
fate of blood lactate
in skeletal muscle = oxidation and glyconeogenesis (glycogen synthesis)
define precursors
inactive substance converted to an active one , derived from an available source
describe precursors for, functions of and process of gluconeogenesis
precursors = lactate, glycerol, amino acids
synthesis of glucose from noncarbohydrate precursors, provides glucose when dietary intake is insufficient
fates of absorbed galactose and fructose
removed from blood once in the liver and converted into other metabolites eg glucose, glycogen and lactate
define major lipid classes
triglycerides
phospholipids
steroids
describe processes of lipid digestion and absorption
begins in the mouth
physical action of chewing paired with the action of emulsifiers enables digestive enzymes to do tasks - lingual lipase (and phospholipids) initiates digestion - fats separate from watery components , more accessible to digestive enzymes
within 2-4hrs , roughly 30% of triacylglycerols are converted to diglycerides and fatty acids
bile salts and micelles
describe how lipids are transported in body
lipoproteins in the blood
role of lipoproteins in process of transportation
transport lipids as chylomicrons to most tissues for oxidation and to adipose tissue for storage
and from liver as very low density lipoproteins (VLDL)
synthesis of free fatty acids
from acetyl-CoA and NADPH through action of enzymes called fatty acid synthases - cytoplasm of cell
define ‘essential fatty acid’
polyunsaturated fatty acids provided by foods as they cannot be synthesised in the body
necessary for health
2 families:
omega-3 and omega-6
describe catabolism of fatty acids by beta-oxidation
occurs in mitochondrial membrane
carnitine helps shuttle long-chain fatty acids into mitochondria
2C units are cleaved off at beta-C position (2nd C from acid end) of an activated fatty acid , this forms acetyl-CoA and produces an activated fatty acid (acyl-CoA) with 2 fewer carbons, acetyl-CoA, NADH and FADH2
describe structure and functions of cholesterol
structural component of cell membranes provides stability and fluidity
regulates cell function
building block for synthesising various steroid hormones, vit D and bile acids
27C compound , hydrocarbon tail, central sterol nucleus (feature of all steroid hormones) made of 4 HCO rings and a OH group
structures and functions of eicosanoids and steroid lipids
role in inflammation
reproduction
gastric secretion
regulation of BP
derived from 20C polyunsaturated fatty acids, most frequently arachidonic acid
include prostaglandins, thromboxanes, leukotrienes and lipoxins
what are ketone bodies
produced by liver
alternative source of energy if glucose levels are too low in body
define phospholipid
class of lipids with hydrophilic head - contains phosphate group and 2 hydrophobic tails derived from fatty acids, joined by alcohol residue (usually glycerol molecule) comprise cellular membranes, regulate cellular processes, possess stabilising and dynamic qualities aiding in drug delivery
define prostaglandins
group of lipids made at sites of tissue damage or infection - involved in dealing with injury and illness
control processes such as inflammation, blood flow, formation of blood clots and induction of labour
derived from arachidonic acid
5 absorption mechanisms
1, active transport 2, passive diffusion 3, facilitated diffusion 4, co-transport (or secondary active transport) 5, endocytosis
describe CHOs absorption
all CHOs absorbed in form of monosaccharides , small intestine highly efficient
glucose and galactose are transported into epithelial cells by common protein carriers via co-transport (with Na ions) then leave cells via facilitated diffusion and enter capillaries through intercellular clefts
fructose absorbed and transported by facilitated diffusion alone
monosaccharides combine with transport proteins immediately after disaccharides are broken down
functions of pyruvate dehydrogenase-catalysed reactions
catalysed oxidative decarboxylation of pyruvate with the formation of acetyl-CoA, CO2 and NADH
role of triglycerides in health and disease
high may contribute to hardening of arteries or thickening of arterial walls, increasing risk of stroke, heart attack and heart disease, also cause pancreatitis
role of phospholipids in health and disease
imbalances implicated with many neurological disorders, including bipolar, schizophrenia, and neurodegenerative diseases such as Alzheimer’s, Parkinsons’
role of steroids in health and disease
regulate no. of hormonal events during pregnancy, sex, differentiation, development, reproduction
also exert equally important functions in non-reproductive tissues eg heart, kidney, pancreas, brain
also reduce redness and swelling (inflammation)
