Cell Structure and Function - Part II

Membrane Permeability

ability to allow materials to enter

or leave the cell

Charged Ions

substances that cannot cross the phospholipid bilayer

Polar Molecules

substances with partial charge that can cross membranes slowly

Integral Protein

macromolecules that span the entire membrane and act as pores for the transport of large or charged substances

Transport Proteins

include examples such as channel proteins and carrier proteins

Channel Protein

allows for passive transport across the membrane by creating pores, which can be ungated or gated

Gated Channel Protein

pores that open in the membrane when a specific signal is received

Carrier Protein

membrane protein that binds to specific molecules and undergoes shape changes to allow transport across the membrane

Aquaporin

channel protein in a cell membrane that is specialized for the movement of water

Plasma Membrane

structure in prokaryotes that can be folded inward to create small pockets and compartments for cellular activity

Passive Transport

movement of substances across a cell membrane without the use of energy

Equilibrium

occurs when molecules are equally distributed

Simple Diffusion

movement of molecules through the phospholipid bilayer from high to low concentration

Membrane Pores

spaces in the membrane that permit the movement of substances into or out of the cell

Facilitated Diffusion

passive movement of specific molecules across cell membranes through transport proteins

Osmosis

diffusion of water across a selectively permeable membrane

Impermeable

property of a substance that cannot cross the cell membrane

Solute

any substance that is dissolved in water

Semipermeable

characteristic of a membrane that allows some substances to cross but not others

Selectively Permeable

property of cell membranes that allows some substances to pass through, while others cannot

Hypertonic

any solution that has a higher concentration of solute than another solution

Hypotonic

having a lower concentration of solute and higher concentration of water than another solution

Isotonic

condition that exists when the concentration of two solutions is the same

Hypotonic

solutions that surround a cell and generally cause the cell to collect water, potentially causing the cell to lyse

Hypertonic

solutions that surround cells and are associated with the loss of water by the cell

Plasmolyzed Cell

describes a plant cell in hypertonic solution, which contains a cell membrane that has separated from the cell wall

Crenated Cell

describes a cell that has lost water, giving a crinkled appearance

Turgid Cell

a plant cell that has absorbed water and has cytoplasm that is pressing outwards on the cell wall

Concentration Gradient

difference in the amount of a substance from one location to another

Active Transport

movement of materials through a cell membrane using energy, often leading to the formation of a concentration gradient

ATP

energy-containing molecule that is used to power active transport

Pump Protein

membrane protein that uses energy to move a specific molecule from low to high concentration

Pressure

one of the factors, in addition to concentration, that determines the likelihood that osmosis will occur

Water Potential

tendency of water to leave an area, derived from the effects of solute and pressure

Lower Potential

type of water potential that causes water to join a space

Pressure Potential

component of water potential that consists of the physical force on a solution, which can often be provided by extracellular coverings

Higher Potential

type of water potential that causes water to leave a space

Solute Potential

component of water potential that has an inverse relationship to the solute amount and measures the effect of dissolved substances on the direction of water movement

Osmoregulation

maintaining water balance by controlling the amount of water that enters or leaves the cell

Proteoglycan

major component of the extracellular matrix found on the outside of animal cells

Collagen

elastic, fibrous protein that is found within the extracellular matrix

Cellulose

polysaccharide that is a major component of the plant cell wall

Peptidoglycan

protein-carbohydrate compound that makes the cell walls of bacteria rigid

Chitin

structural polysaccharide found in many fungal cell walls

High Water Potential

describes solutions that surround cells and cause them to swell

Low Water Potential

describes a solution that surrounds cells and causes them to lose water