concept 8.5: regulation of enzyme activity helps control metabolism

how do cells regulate metabolic pathways

by switching on or off the genes that encode specific enzymes or by regulating the activity of existing enzymes

what is allosteric regulation of enzymes

occurs when a regulatory molecule binds to a protein at one site and affects the proteins function

what would happen if a cells metabolic pathways were operating simultaneously

chemical chaos

what are most allosterically regulated enzymes made of

most are made from polypeptide subunits (quaternary structure), each with its own active site

what are enzymes in catabolic pathways inhibited by

ATP

what are enzymes in catabolic pathways stimulated by

ADP

how does allosteric regulation oscillate

between two shapes: one catalytically active and the other inactive

what does the binding of an activator do

stabilizes the active form of the enzyme

what does the binding of an inhibitor

stabilizes the inactive form of the enzyme

what happens to ATP levels are ADP levels increase

as ATP levels go down, ADP levels go up and stimulate the pathways to replenish the ATP levels

what does the binding of an activator do

it stabilizes the shape that has function active sites

what does the binding of an inhibitor do

it stabilizes the inactive form of the enzyme

difference between active form and active site

active form: activators are activating the enzyme, active site is where the substrate is binding to the enzyme

cooperativity

substrate binding to one active site triggers a shape change in the enzyme that stabilizes the active form for all other active sites on that enzyme

what is cooperativity most like

it is a form of allosteric regulation because it aplifies the response by priming the enzyme to act on addition substrate molecules more readily

example of cooperativity

oxygen binding to hemoglobin causes increased affinity of hemoglobin for O2 and results in O2binding at the remaining sites

feedback inhibition

the end product of a metabolic pathway shuts down the pathway

what does feedback inhibition prevent

feedback inhibition prevents a cell from wasting chemical resources by synthesizing more product than is needed

where is the best place to stop a metabolic pathway

at the beginning so you dont waste energy

how does compartmentalization of the cell help it

it helps bring order to the metabolic pathways

plasma membrane

the boundary that separates the living cell from its surroundings

what allows things to pass through the plasma membrane

its selective permeability

amphipathic

has hydrophilic head region and hydrophobic tail region

transport proteins

often responsible for controlling passage across cellular membrane s

passive transport

no input of energy to move across the cell membrane and may require transport proteins

active transport

required both energy and transport protein to cross the membrane

bulk transport

another form of active transport, exocytosis or endocytosis

exocytosis

large molecules are secreted when a vesicle fuses with the plasma membrane

endocytosis

large molecules are taken in when the plasma membrane pinches inward forming a vesicle

membrane proteins

a membrane is a collage of different proteins, often clustered in groups, embedded in the fluid matrix of the lipid bilayer

what determines most of the membranes specific functions

proteins

how do lipid compositions vary

they adapt to specific temperatures

peripheral proteins

bound to the surface of the membrane

extracellular face

the face of the membrane that faces outward

intracellular face

the membrane face that faces inward

integral proteins

penetrate the hydrophobic core

transmembrane proteins

integral proteins that span the entire membrane

6 major functions of cell surface membrane proteins

1- transport

2- enzymatic activity

3- signal transduction

4- cell-cell recognition

5- intercellular joining

6-attachent to the cytoskeleton and extra cellular matrix(ECM)

what field are surface proteins important

medicine field