Life Processes

Enzymes

Biological catalysts specific to its specific reaction that speed up chemical reactions, without being used up, by lowering the activation energy required for the reaction to occur.

Induced Fit Model

The substrate enters the active site of the enzyme causing the active site to change shape slightly. An enzyme-substrate complex forms and a reaction occurs, converting the substrate into products. The products are released and the enzyme returns to its original shape.

Factors affecting enzyme activity

Temperature, pH, enzyme concentration, substrate concentration, co-factors, enzyme inhibitors

Co-factors

Non-protein helpers (e.g. metalions) that help complete the active site or aid in binding of substrate.

Inhibitors

Prevents the substrate from binding with the active site, either by occupying the active site (competitive) or binding to the enzyme outside the active site to change the shape of the active site (non-competitive)

Cell membrane

Semi-permeable membrane that defines borders of cells and allows it to interact with environment in controlled way. Phospholipid bilayer: hydrophilic heads and hydrophobic tails. Protein channels and carrier proteins. Fluid mosaic model: flexible and dynamic.

Diffusion

The movement of particles from an area of high concentration to an area of low concentration. No energy is required (passive) and continues until equilibrium is reached. Moves small, non-polar molecules.

Facilitated diffusion

Passive, uses channels or carrier proteins, moves large or charged molecules.

Factors affecting diffusion rate

Concentration gradient, temperature, surface area, distance, molecule size, Sa:V ratio

Osmosis

Diffusion of water through a semi-permeable membrane from high to low concentration. Balance solute concentration.

Tonicity - plant cells

Hypotonic: water into cell (turgid/full)

Isotonic: no movement/normal

Hypertonic: water out of cell (plasmolysed - cell membrane shrinks away from cell wall)

Tonicity - animal cell

Hypotonic - water into cell —> bursts (lysed)

Isotonic - no movement/normal

Hypertonic - water out of cell —> shrinks

Active transport

Movement of molecules from low to high area of concentration (against gradient), requires ATP, vital for life

Photosynthesis

Process that converts light energy into chemical energy (glucose).

Occurs in chloroplast of plant cells