BIOLOGY 11 (CELL MEMBRANE) 2ND SEM MID TERM

cell membrane

serves as a barrier separating the cell from external environment, controls and regulates passage of needed materials in and out of the cell

phospholipid molecule

consists of phospholipid group, glycerol (head), and two fatty acid chain (tail)

cholesterol molecules

strengthen the cell membrane, making it more flexible

but less fluid, which makes the membrane less permeable to water-soluble substances such as ions or simple sugar.

carbohydrates

serve as identification tags, enabling cells to distinguish one type of cell from another; detect specific chemical signals (ligands) to initiate cellular responses

membrane proteins

transport, channel, cell recognition, enzymatic, cytoskeleton, junction, receptor

transport proteins

- extend from the phospholipid bilayer

- help materials cross the cell membrane

channel proteins

- form tunnels

- help cells import or export needed materials and expel waste

cell recognition proteins

- enable cells to distinguish their own cells from other organisms

- help identify pathogens that may invade the body

enzymatic proteins

- act as catalysts in metabolism

- speed up:

breaking-down reactions (catabolism)

building-up reactions (anabolism)

catabolic (degenerative) reactions

- break down complex molecules into simpler ones

- release energy

anabolic (synthetic) reactions

- build complex molecules from simpler ones

- require energy

cytoskeleton proteins

- act as muscle and skeleton

- maintain cell shape and motility (movement)

junction proteins

- assist in cell-to-cell adhesion

- help with communication between cells

receptor proteins

- receive signals from other cells

- change shape to allow a specific ligand to bind to it

- facilitate signal exchange between cells

ligand

ion molecules which donates a pair of electrons

simple diffusion

movement of molecules from high concentration to low concentration directly through the cell membrane, without energy or transport proteins

facilitated diffusion

movement of molecules from high concentration to low concentration using transport proteins; no energy required.

active transport

movement of molecules against the concentration gradient (low to high) using energy (atp) and transport proteins.

endocytosis

process where a cell takes materials into itself by forming a vesicle from the cell membrane; requires energy.

exocytosis

process where a cell releases materials out of itself when a vesicle fuses with the cell membrane; requires energy.

fluid mosaic model

- the cell membrane is flexible, not rigid.

- phospholipids move side to side and slide past each other.

- the membrane behaves like a fluid similar to a film of oil.

- proteins embedded in the membrane stay in specific areas.

- scattered molecules create a mosaic-like pattern.