enzymes + proteins Flashcards

Question

what are the reasons that lie behind the high levels of cholesterol?

Answer 1

- no receptors produced - receptors never reach cell surface - receptors can not bind LDL - receptors do not internalise on binding - receptros do not release LDL

Answer 2

[1] Catalyse high reaction rates [2] Have a great reaction specificity [3] Work in mild temperature/pH conditions [4] Can be regulated

Answer 3

a non-protein chemical compound or metallic ion that is required for an enzyme's activity as a catalyst, they can be seen as helper molecules.

Answer 4

Heat-stable substances that can aid enzyme reactions by loosely binding to their active site e.g. FAD from riboflavin

Answer 5

they are enzymes that catalyse the same reaction but vary in structure and other biochemical properties

Answer 6

1. Entropy reduction - Enzymes “force” the substrate(s) to be correctly orientated by binding them in the formation they need to be in for the reaction to proceed 2. Desolvation - Weak bonds between the substrate and enzyme essentially replace most or all of the H-bonds between substrate and aqueous solution 3. Induced fit - Conformational changes occur in the protein structure when the substrate binds

Answer 7

Km (Michaelis Constant) is the substrate concentration necessary to allow an enzyme to function at half its maximal velocity (1/2 Vmax) It is also a measure of an enzyme's affinity/specificity for its substrate under some circumstances: Km tells us how much substrate the enzyme can take on: A lower Km corresponds to a higher substrate affinity (enzyme requires to take on smaller amount of substrate to reach Vmax) A higher Km corresponds to a lower substrate affinity (enzyme requires to take on larger amount of substrate to reach Vmax) -------------------------------------------------------------- Vmax shows how fast a reaction is proceeding when the enzyme is saturated with substrate, it is dependant on enzyme concentration. A lower Vmax corresponds to a slower enzyme A higher Vmax corresponds to a faster enzyme.

Answer 8

it's when an inhibitor binds to the active site of the enzyme and prevents the substrate from binding there. In the presence of a Competitive inhibitor, it takes a higher substrate concentration to achieve the same velocity as no inhibition. It can be overcome by adding more substrate. Vmax is unaffected if there is enough substrate available. To get to 1/2 Vmax more substrate is needed so the Km is larger. Lineweaver-burk plot: The Km increased (the red line on the X-axis) The Km line went down the X-axis because the scale is 1/Km and dividing one by a bigger number will give a smaller number, that's why although it is increased it is closer to zero not further. The Vmax is unaffected (the interception line on the Y-axis).

Answer 9

it's when an inhibitor binds to a secondary site on the enzyme, changing the shape of the active site and preventing the substrate from binding, or it might be able to bind but the rate of product formation is reduced or stopped. In the presence of a non-competitive inhibitor, there is a reduction in the number of functional enzyme molecules that can carry out a reaction so: Vmax is reduced while Km remains the same. That is because the active site of the enzymes that have not been inhibited is unchanged.

Answer 10

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 disease Detection of vitamin deficiencies

Answer 11

There are some enzymes that are secreted from cells, but generally serum enzyme concentrations are low and rise only when there is damage to cells and release of contents.

Answer 12

Hypoxia – loss of oxygen supply due to occlusion, or inadequate oxygenation, or loss of oxygen carrying capacity Cellular damage due to chemicals, drugs Physical damage due to trauma, surgery, burns, radiation etc. Immune disorders – anaphylaxis, autoimmune disease etc Microbiological agents– bacteria, viruses, fungi, protozoa, helminths Genetic defects – many, e.g. Duchenne’s Muscular Dystrophy Nutritional disorders – protein-calorie, vitamin, mineral deficiency

Answer 13

Rate of an enzyme-catalysed reaction is directly proportional to the amount of enzyme present Progress of conversion of the substrate to product is monitored (Fixed-time & Continuous) Spectrophotometry - measurement of an end product Electrophoresis – to determine type of enzyme

Answer 14

Not specific i.e. can be found in more than one tissue in the body. Particular requirements – Optimal temperature, pH etc. Assays must be optimised Enzyme assays are performed to serve two different purposes: (i) To identify a special enzyme, to prove its presence or absence in a distinct specimen, like an organism or a tissue. (ii) To determine the amount of the enzyme in the sample.

Answer 15

it's a hydrolase class enzyme present in the body as an isoenzyme i.e. it catalyses the same reaction but varies in structure and chemical properties. Catalyses the cleavage of orthophosphate from orthophosphoric monoesters under alkaline conditions (don't need to remember this) It can orginate from: Bone & Liver & Kidney & Intestine & Placenta

Answer 16

- Detect Tissue damage e.g. detecting the levels of Creatine Kinase which might indicate skeletal muscle damage - Determine origin of affected tissue e.g. determining the origin of raised levels of Alkaline phosphatase - Notice diseases related to enzyme defects e.g. low/high TPMT activity may be due to genotype mutation e.g. Alpha galactosidase defect due to X-linked disorder which causes Fabry disease. e.g. anaesthesia affected by prolonged apnoea due to AF phenotype which decreases the activity of BChe enzyme.

Answer 17

Allosteric regulation is any form of regulation where the regulatory molecule (an activator or inhibitor) binds to an enzyme in a region other than the active site The place where the regulator binds is called the Allosteric site

Answer 18

1- Activators - molecules that increase the activity of an enzyme 2- Inhibitors - molecules that decrease the activity of an enzyme

Answer 19

allosteric-regulated enzymes are enzymes that have their activities regulated by the binding of modulators or effectors, which can be either activators or inhibitors, at the site other than the active site. Covalently modified enzymes are enzymes that have been modified through processes that involve forming or breaking covalent bonds, which usually occur post-translation.