EXAM 2 Focus Points pt 1

Plasma Membrane

selectively permeable membrane that is made of phospholipids, membrane proteins, cholesterol, and carbohydrates

Phospholipid bilayer

Hydrophilic heads face the water environment inside and outside the cell and hydrophobic tails face inward

Transmembrane proteins

Extend through the lipid bilayer, can function as channels, carriers, receptors, or anchors, and have regions compatible with the membranes interior and water environment

Peripheral Proteins

Attach to one surface of the membrane or to other membrane proteins, often support the membrane, anchor the cytoskeleton, or participate in signaling, usually associate with the membrane surface rather than crossing the hydrophobic core

Passive transport

Energy is NOT directly required, down the concentration or electrochemical gradient, allows the substances to move down the gradients, examples are simple diffusion, facilitated diffusion, and osmosis

Active Transport

Energy is required directly through an energy coupled process, moves against the gradient, builds or maintains gradients and moves substances against them, examples are sodium potassium pump, coupled transport

Simple diffusion

Small, nonpolar molecules pass directly through the lipid bilayer

Moves from higher concentration to lower concentration

Requires NO ATP and NO transport proteins

EX) Oxygen and CO2

Facilitated diffusion

Moves substances down their gradient with the help of membrane proteins

Requires NO direct ATP

Channel mediated and carrier mediated

EX) Glucose transport through GLUT carriers, ions through ion channels

Osmosis

Passive net movement of water across a selectively permeable membrane

Water moves toward the side with the higher effective solute concentration

Primary active transport

Uses energy DIRECTLY from ATP to move substances against their gradients

Secondary active transport

Uses energy STORED in an ion gradient created by primary active transport

Symport and antiport

Symport v Antiport

two substances move in the same direction v substances move in opposite directions

Exchange pumps

Move substances in opposite directions across the membrane

EX) Sodium potassium pump

maintains sodium and potassium gradient, helps regulate cell volume, and supports electrical signaling in nerve and muscle cells

Vesicular transport

Large substances or bulk quantities can move in membrane bound vesicles

Requires cellular energy and membrane remodeling

Multiple types

Endocytosis

Vesicular transport where material enters the cell in a vesicle

Phagocytosis

Vesicular transport: a type of endocytosis that engulfs large particles

Pinocytosis

Vesicular transport: A type of endocytosis that takes in extracellular fluid and dissolved substances

Receptor mediated endocytosis

Vesicular transport: Specific molecules bind receptors before being brought inside

Exocytosis

Vesicular transport: A vesicle fuses with the membrane and releases contents outside

Concentration gradient

A difference in the concentration of a substance. Diffusion moves a substance from high concentration to lowE

Electrical gradient

A difference in electrical charge across a membrane. Positive ions are attracted to negative charge; negative ions are attracted to positive charge

Electrochemical gradient

The combined influence of the concentration gradient and electrical gradient on an ion

Isotonic

Cell stays the same size, no net movement

Hypertonic

Cell loses water and shrinks, higher relative effective solute concentration outside of the cell

Hypotonic

Cell gains water and swells, lower relative effective solute concentration outside the cell