Plasma Membrane

Plasma Membrane

- protective barrier that contains the cytoplasm and regulates the transport of substances in and out of the cell.

- allows cell recognition of signals from other cells

- binding site for enzymes

- anchoring for filaments for cytoskeleton

Phospholipid

- lipid molecule that consists of a phosphate group attached to a glycerol, and two fatty acid tails

-semi permeable

kink

- located ON the tail of the phospholipid

- prevent tight packing

Hydrophilic

- attracted to water.

- polar head

Hydrophobic

- repel water

- non polar

cholesterol

-acts as a fluidity buffer

- found between phospholipids

- warm temp: decreases membrane fluidity

- cold temp: increases membrane fluidity

integral protein

-structural support (foundation)

-gateways for molecules to enter and exit

peripheral protein

-found on the surface of the cell membrane

- facilitate communication between the cell and the environment

-where cytoskeleton rests

glycoprotein

- maintains membrane stability

- facilitate cellular recognition (receptors)

glycolipid

-lipids with attached carbohydrates

Fluid Mosaic Model

A model that describes the structure of cell membranes as a mosaic of various components that move fluidly within the lipid bilayer.

Seymour Jonathan Singer and Garth L. Nicolson

proposed fluid mosaic model 1972

Diffusion

The process by which molecules move from an area of higher concentration to an area of lower concentration.

Simple Diffusion

-no energy

-high to low concentration

-Oxygen diffusing into a cell and CO2 diffusing out

Facilitated Diffusion

A passive transport process that uses transport proteins to move molecules across the cell membrane from high to low concentration.

-H2O, glucose, amino acids

carrier proteins

-change their shape to transfer molecules (active)

- prevents hydrophilic or changed molecules to interact with the nonpolar part of the cell

channel proteins

- have pores (passive)

- create a hydrophilic path through the bilayer

Membrane Proteins

These are short branched chains of fewer than 15 sugar units. They facilitate cell-cell recognition and to a lesser extent, maintain structure.

Active Transport

The movement of molecules across a cell membrane from low to high concentration, requiring energy.

Endocytosis

The process by which cells engulf external substances, fluids, or particles by enclosing them in a vesicle formed from the cell membrane.

Exocytosis

- The process of moving large molecules out of the cell by vesicles that fuse with the plasma membrane.

- this is how many hormones are secreted and how nerve cells communicate with one another

Phagocytosis

A type of endocytosis where the cell engulfs large particles, such as bacteria or food, often referred to as 'cell eating'.

Pinocytosis

A form of endocytosis where the cell takes in dissolved molecules as a vesicle, often referred to as 'cell drinking'.

Receptor-Mediated Endocytosis

- A process where cells take in specific molecules based on receptor-ligand interactions.

- only allow certain molecules

water potential

- tendency of water to move from one area to another

tonicity

ability of an extracellular solution to make water move into or out of a cell by osmosis

Isotonic Solution

- concentration of solutes is equal inside and outside

- no net movement of H2O

Hypotonic Solution

- lower concentration of solutes

- H2O will enter the cell

- cell will swell then burst

Hypertonic Solution

- higher concentration of solutes

- H2O will exit

- cell will shrink then crenate

Osmosis

- The diffusion of water across membrane

- high (low solute) to low (high solute)

Cytolysis

The bursting of a cell due to excessive water intake in a hypotonic environment.

Plasmolysis

The process where cells lose water in a hypertonic environment, causing the cell membrane to pull away from the cell wall.

Aquaporins

allow for the passage of water in certain cells