1.1.3 Cell Membranes/1.1.4 Internal Membranes Flashcards
define osmosis
the passive movement of solvent molecules from region of high water potential to a region of low water potential, across a semi-permeable membrane.
define active transport
the movement of molecules across a membrane from an area of low concentration to an area of high concentration, against the concentration gradient and requiring ATP.
define facilitated diffusion
carrier proteins which change their shape to allow a molecule to pass through, from an area of high concentration to area of low concentration, passively.
What is the structure of an enzyme?
- Tertiary Globular Proteins: protein chain is folded back on itself into a spherical or globular shape
- specialised area of the active site will bind with with a substrate producing an enzyme substrate complex
What is the function of an enzyme?
They lower activation energy (reducing input energy so reactions can take place at lower temperatures) and speed up rate of metabolic reactions
what is the lock and key theory
- only one substrate (key) can fit into the enzyme’s active site (lock) (think puzzle)
- both structures have a unique shape
- the enzyme is not used up
- the two substrates are fused together at the enzyme’s active site, creating an enzyme-substrate complex and finally a product that is separate from the enzyme (which is unchanged).
how does temperature affect enzyme action?
Low Temp = low rate
- enzyme have too little kinetic energy and move slowly –> few successful collisions between enzyme and substrate leads to low rate of reaction
Optimum Temp - high rate
- enzyme have a lot of kinetic energy and move quickly. Lots of successful collisions between enzyme and substrate leads to high rate of reaction
High temp = low rate
- heat breaks the bonds maintaining the tertiary structure of the enzyme. The active site becomes denatured and substrate no longer fits. No successful collisions leads to low rate of reaction.
how does pH affect enzyme action?
low pH = Low rate
- acidity breaks the bonds maintaining the tertiary structure of the enzyme. The active site becomes denatured and substrate no longer fits. No successful collisions leads to low rate of reaction.
Optimum pH = high rate
- many collisions between working enzyme and substrate means high rate of reaction
High pH = low rate
- Alkalinity breaks the bonds maintaining the tertiary structure of the enzyme. The active site becomes denatured and substrate no longer fits. No successful collisions leads to low rate of reaction.
enzymes work best under their ____ conditions, although these conditions can be ___ for _____ enzymes.
- optimum
- different
- different
what are the features of a competitive inhibitor?
- similar shape to substrate
- bind to active site of enzyme
what are the features of a non-competitive inhibitor?
- bind to the enzyme (not in the active site) and change its shape
- substrate no longer fits
What is the impact of competitive and non-competitive inhibitors?
the shape of the active site has changed, so the reactant is no longer able to bind with the substrate.
Explain Temperature enzyme graph
As temp increases, reaction velocity increases until optimum temperature is reached. Beyond this, the reaction velocity lowers.
Explain the pH graph
As pH increases, reaction velocity increases until optimum temperature is reached. Beyond this, the reaction velocity lowers.
explain the substrate concentration graph
As substrate concentration increases, the reaction velocity increases. This is because more substrate molecules increase the chance of successful collisions between enzyme and substrate.
