Diffusion – diffusion is the spreading out of cells so that they are evenly distributed over the available space. Diffusion occurs in gases and liquids because the molecules of gases and liquids are constantly moving.
Substances that can enter cells – alcohol, steroids and other fat soluble substances can easily enter cells because they can diffuse through the lipid portions of the membrane. Oxygen and carbon dioxide can also diffuse through the phospholipid bilayer.
Why can oxygen diffuse into cells? – oxygen diffuses into cells because it is continually used up inside the cell for respiration
Production of carbon dioxide in cells – carbon dioxide is continually produced inside the cell by respiration.
Osmosis – osmosis is a special type of diffusion. It is the diffusion of a solvent through a differentially permeable membrane. Osmosis is of particular importance to living cells because the cell membrane is differentially permeable.
Carrier mediated transport – in carrier mediated transport there are special proteins in the cell membrane that bind to an ion or molecule and help it to move across the membrane.
Facilitated diffusion – many substances that a cell needs, such as glucose and amino acids, have molecules that are too large to fit through a cell membrane by simple diffusion. Facilitated diffusion is a passive process that moves substances from a higher concentration on one side of the membrane to a lower concentration on the opposite side.
Active transport – as its name states, active transport is an active process required cellular energy. Active transport is there for the movement of substances across the cell membrane against the concentration gradient using cellular energy.
Vesicular transport – vesicular transport is an active process in which materials move into or out of the cell enclosed as vesicles.
Endocytosis – endocytosis is when a cell surrounds some extracellular material with a fold of the cell membrane.
Exocytosis- if the contents of a vesicle are pushed out through the cell membrane, the process is called exocytosis.
Enzymes – enzymes are proteins that allow chemical reactions to take place at normal body temperature.
Activation energy – the energy needed to get a chemical reaction started is called activation energy
Substrate – the molecules on which an enzyme acts are called the substrate.
Active site – the part of the enzyme molecule that