internal membrane and enzymes Flashcards
(24 cards)
membrane bound organelles within EC cells:
mitochondria nucleus golgi apparatus endoplasmic reticulum vesicles vacuoles chloroplasts (in animal cells)
what do internal membranes do?
internal membranes control cell biochemistry. By compartmentalising a cell by having membrane bound organelles creates a specialised enviroment that enables a large number of activities to occur simultaneously in a limited space and under different conditions
Examples of internal membrane
Chemical reactions in Lyosomes break down compounds brought into the cell using strong digestive enzymes in an acidic environment. Enclosing these enzymes in a membrane prevents them from destroying the cell
Membrane bound structures can concentrate reactants and store products
Mitochondria internal membrane
mitochondria increase their internal surface by folding and stacking internal membranes
what does a mitochondria’s inner and outer membrane do?
the outer membrane contains proteins and enzymes involved in the transport of substances in/out of the cell
the inner membrane folds inwards to form extra surfaces for cellular respiration
what is cellular metabolism and enzymes role?
enzymes control biochemical pathways, the sum of chemical reactions that occur in cells is cellular metabolism, the rate of it varying for organelles
metabolic reactions are not random, all are controlled and regulated to maintain cell functions and to meet the energy needs of the cell
Each step is controlled by an enzyme that doesnt undergo any change itself
what happens to enzymes in biological reactions
enzymes are not consumed during the biological reaction and are molecules that act as catalysts to speed up biological reactions, making it easier for a reaction to take place
most enzymes are proteins and like all proteins, enzymes are formed by linking together a sequence of amino aids
enzyme structure
most enzymes have one or more grooves around their surface called active sites which are key to enzyme function
most enzymes are highly specific and can only act on a single substrate some enzymes can act on many substances and can regulate many biochemical reaction
active sites and substrates
active sites are unique in their size and shape, only specific types of molecules will fit, the molecules that fit are substrates
how are enzymes named?
enzymes are often named after the substrate that they act upon and usually have a -ase ending
for example:
the enzyme sucrase breaks down sucrose (a disaccharide) into basic monosaccharides (glucose and fructose)
what do catalysts do?
enzymes are catalysts, they make it easier for a reaction to take place
catalysts speed up reactions by influencing the stability of bonds in reactants. They may provide alternate reaction pathway, thus lowering the activation energy needed for a reaction to take place
without enzyme: the activation energy required is high but with enzyme the ae is low
enzymes and substrates
enzymes have a specific region where the substrate binds and where catalysis occurs. This is called the active sits.
how is an enzyme-substrate complex formed?
enzymes are substrate-specific and when a substrate binds to an enzymes active site, an enzyme-substrate complex is formed
structure of substrate and enzyme reaction
the substrate is drawn to the enzyme’s surface and the subtrate molecule (s) are positioned either way to promote a reaction: either joining two molecules together or splitting a larger one
factors that cause an enzyme to loose its ability to bind to a substrate (4)
enzymes work best in specialised enviroments and the factors below can cause an enzyme to loose its ability to bind to a substrate
- temperature
- pH
- the presence of inhibitors
- concentration of reaction/products
how does temperature effect enzymes
for most plants/animals enzymes there is little activity at low temperatures, enzyme activity increases with temp,
when it is too high for the enzyme to function it is known as enzyme denaturation
an increase in temperature can cause bonds in enzymes to vibrate more, breaking bonds and changing the structure of the active site
how does pH effect enzymes
the extremes of pH (very acidic or alkaline) away from the enzyme optimum can result in enzyme denaturation
effects of enzyme concentration
rate of reaction continues to increase with an increase in enzyme concentration
effects of increasing substrate concentration
rate of reaction increases then plateaus with increasing substrate concentration
what do inhibitors do
enzymes may be deactivated by enzyme inhibitors. Inhibitors slow down the rate of reaction or stop it completely
what do competitive inhibitors do
competitive inhibitors that compete with the substrate for the active site of the enzyme, CI is mainly reversible bc the inhibitor can enter/leave the active site
non-competitive inhibitors role
they either bind permanently to the active site or bind at a site elsewhere on the enzyme causing a change in the shape of the active site. Binding may/may not be reversible. Irreversible inhibitors bind tightly and permanently to the enzymes destroying their catalytic activity eg. arsenic
changes to the shape of the active site
changes to the shape of the active site is known as protein denaturation, resulting in a loss of function and is said to be denatured
denaturation
some enzymes may regain their shape, but most changes are irreversible. When an enzyme is denatured as the active site is altered the substrate can no longer bind or if it binds, the reaction that the enzyme normally catalyses, doesnt occur
denaturation often causes enzymes that were dissolved in water to become insoluble and form a precipitate
