Cell Transport

Plasma Membrane Composition

The plasma membrane is composed of a phospholipid bilayer.

Arrangement of Phospholipids

The hydrophobic tails face inward, and the hydrophilic heads face outward.

Plasma Membrane Model

The Fluid Mosaic Model.

Fluid Mosaic Model Suggestion

It suggests that the membrane is made of many different molecules that move around.

Types of Membrane Proteins

Integral proteins (embedded throughout the membrane) and Peripheral proteins (attached to one side of the membrane).

Glycolipids

Lipid molecules with carbohydrate chains attached, found on the outer surface of the membrane.

Function of Glycoproteins

Glycoproteins serve as cellular identification markers.

MHC

MHC stands for Major Histocompatibility Complex, involved in immune responses.

Function of Cholesterol

Cholesterol adds fluidity and flexibility to the membrane.

Role of Channel Proteins

Channel proteins create small, uncharged tunnels for substances to pass through the membrane.

Function of Receptor Proteins

Receptor proteins bind to substances in the environment and trigger cell responses.

Function of Carrier Proteins

Carrier proteins transport specific substances, such as glucose, across the membrane.

Enzymes in Plasma Membrane

Enzymes break down molecules and glue molecules together, involved in ATP metabolism.

Glycocalyx

The glycocalyx is a layer of carbohydrate chains that forms a 'sugar coat' on the cell surface.

Role of Carbohydrate Chains

Carbohydrate chains aid in recognition of self vs non-self, immune responses, and protecting the outer surface of the cell.

Selectively Permeable

The plasma membrane allows some molecules to pass while blocking others.

Concentration

Concentration refers to the amount of a specific substance dissolved in a given volume of fluid.

Concentration Gradient

A concentration gradient is the difference in the concentration of a substance between two areas.

Molecules Needing Permission

Macromolecules and charged molecules need permission to move across the cell membrane.

Passive transport

Passive transport is the movement of molecules from HIGH to LOW concentration, driven by kinetic energy.

Goal of diffusion

The goal of diffusion is to reach equilibrium, where concentrations are equal on both sides of the membrane.

Facilitated diffusion

Facilitated diffusion is a type of passive transport that requires a carrier protein to help move substances.

Equilibrium in diffusion

Equilibrium is when the concentration of a substance is the same on both sides of a semipermeable membrane.

Osmosis

Osmosis is the diffusion of water across a semipermeable membrane.

Osmotic pressure

Osmotic pressure is the force that causes water to move in a direction due to the number of non-diffusable particles in a solution.

Cell in isotonic solution

There is no net change in cell size; water moves in and out equally.

Cell in hypertonic solution

The cell shrivels as water leaves the cell (crenation).

Cell in hypotonic solution

The cell swells and may burst as water enters (lysis).

Turgor Pressure

Turgor Pressure is the pressure that builds in a plant cell when water enters, but the cell wall prevents it from bursting.

Plasmolysis

Plasmolysis occurs when a plant cell becomes dehydrated, causing the plasma membrane to pull away from the cell wall.

Active transport

Active transport moves molecules from LOW to HIGH concentration, against the concentration gradient, and requires ATP.

Requirements for active transport

A concentration gradient, ATP, and a carrier protein or 'pump.'

Exocytosis

Exocytosis is the process by which a vesicle fuses with the plasma membrane to release its contents outside the cell.

Endocytosis

Endocytosis is when the cell membrane folds in to surround a substance and forms a vesicle to bring it into the cell.

Phagocytosis

Phagocytosis is a type of endocytosis where the cell engulfs large particles, like bacteria or cell debris, often referred to as 'cell eating.'

Pinocytosis

Pinocytosis is a type of endocytosis where the cell ingests small molecules, such as glucose, often referred to as 'cell drinking.'

Receptor-mediated endocytosis

Receptor-mediated endocytosis is a type of pinocytosis that occurs in response to receptor stimulation on the cell surface.

Difference between phagocytosis and pinocytosis

Phagocytosis involves the ingestion of large particles, while pinocytosis involves smaller molecules.