Unit 4 IB HL Biology

Selective permeability

Only certain substances can cross the cell membrane without assistance.

Permeability

Determined by substance size, charge, and polarity.

Permeable

The hydrophobic bilayer allows small non-polar substances through easily.

Mostly Permeable

Small polar molecules without a charge.

Mostly Impermeable

Large, polar molecules (with no charge) rarely cross the membrane.

Impermeable

Anything with a charge/ions.

Integral proteins

Proteins that span across the entire bilayer.

Peripheral Proteins

Proteins located on the surface of the bilayer.

Transport proteins

Proteins that transport materials across the bilayer.

Channel proteins

Transport proteins that form channels for specific molecules.

Pump proteins

Transport proteins that move molecules against their concentration gradient.

Carrier proteins

Transport proteins that undergo a conformational change to transfer molecules across the membrane.

Recognition proteins

Membrane proteins that serve as "ID tags" for cell-cell recognition.

Receptors

Membrane proteins that receive chemical signals.

Enzymes

Proteins embedded in or associated with the bilayer that catalyze reactions.

Glycoproteins

Proteins with carbohydrate chains linked to them.

Glycolipids

Lipids with carbohydrate chains linked to them.

Cholesterol

Steroids found in animal cell membranes that affect membrane fluidity.

Phospholipid structure

The structure of phospholipids in the bilayer.

Membrane fluidity

The ability of the membrane to move and change shape.

Diffusion

The movement of a substance down a concentration gradient.

Passive transport

Transport that does not require an additional input of energy.

Active transport

Transport that requires an additional input of energy.

Osmosis

The diffusion of water across a semipermeable membrane.

Tonicity

The ability of a solution to make water move into or out of a cell by osmosis.

Isotonic

Solutions with the same solute concentration.

Hypertonic

Solutions with a higher solute concentration.

Hypotonic

Solutions with a lower solute concentration.

Animal cells

Normal, lyse, and crenate in different tonicity solutions.

Plant cells

Turgid, flaccid, and plasmolyze in different tonicity solutions.

Amoeba and Paramecium

Unicellular organisms that use contractile vacuoles to maintain osmotic balance.

IV fluids

Used to deliver fluids to cells and must be isotonic to prevent damage.

Pump proteins

Transport proteins that move molecules against their concentration gradient.

Bulk transport

Exocytosis and endocytosis for the movement of large particles.

Vesicles

Membrane-bound structures involved in transport and compartmentalization.

Surface area to volume ratio

The ratio of surface area to the volume of a cell.

Compartmentalization

The separation of different functions and processes within membrane-bound organelles.

Lysosomes

Membrane-bound organelles found in eukaryotic cells that contain hydrolytic enzymes.

Hydrolytic enzymes

Enzymes that break down molecules by adding water molecules to their chemical bonds.

Packaging

The process of enclosing or organizing something, in this case, the hydrolytic enzymes, to prevent cellular damage.

Cellular damage

Harm or injury caused to the cell, which can disrupt its normal functioning.