Transport across the cell membrane

Passive

does not require energy, substances move with concentration gradient.

Active

does require energy, substances move against the concentration gradient

Osmosis

The diffusion of a solvent (water) through a differentially (semi) permeable membrane, the solvent can move through the membrane, but the solute is not able to fit through, the only way to reach equilibrium is for the solvent to move

Tonicity definition

The concentration of a solution as compare to another solution

What defines an isotonic solution

extracellular and intracellular ion concentration equal

What defines a hypotonic solution

extracellular concentration ion is less than intracellular

What defines a hypertonic solution

extracellular ion concentration is more than intracellular

What happens when a cell is placed in a hypotonic solution?

A cell placed in a hypotonic solution would result in movement of solvent (water) into the cell.
This is because the ion concentration is higher in the cell so water moves to move in the reach equilibrium, as solutes are not able to move through the semi permeable membrane.
This will lead to the cell swelling and possibly bursting.

simple Diffusion

the spreading out of particles from areas of high concentration to areas of low concentration to areas of low concentration resulting is even distribution of particles

Collision mechanism diffusion

• This ‘spreading out’ of particles is brought about due to more collisions happening between particles at high concentrations.

• This forces them to move away from each other into areas of low concentration where they experience less collisions.

Diffusion – Gradient and Rate

• The difference in concentration that brings about diffusion is known as a concentration gradient (diffusion gradient).

• The greater the difference between the two concentrations, the faster the rate of diffusion

Facilitated Diffusion – Core Definition

The spreading out of particles from areas of high concentration to areas of low concentration resulting in even distribution of particles.

Facilitated Diffusion – Selectivit

• Occurs through integral proteins such as carrier and channel proteins, therefore it is selective.

Facilitated Diffusion – Polar Molecule

• Generally used for water molecules and ions as they are polar molecules (polar molecules cannot pass through the phospholipid bilayer)

Endocytosis – Core Definitio

The taking in of solids or liquids through vesicles.

Endocytosis – Membrane Action

• Cell membrane folds around the substance (solid or liquid) until it is completely enclosed.

• Vesicle then pinches off within the cytoplas

Term: Endocytosis – Types

• Pinocytosis – taking in liquids (Cell drinking)

• Phagocytosis – Taking in solid particles (Cell eating)

Which of the following groups correctly lists molecules which undergo facilitated diffusion?

• ) Water, oxygen and glucose

• (b) Amino acids, glucose and sodium ions

• (c) Glucose, fatty acids and oxygen

• (d) Sodium ions, amino acids and carbon dioxide
  

b

Cell Membrane – Structure
or the cells of a body to function normally, they must remain in a stable environment.
Describe the structure of the cell membrane and explain how it allows the exchange of ions to occur (14 marks)

• Made of phospholipid bilayer

• 

  Arranged in a bilayer/double layers

• Hydrophilic heads and hydrophobic tails

• Proteins embedded in membrane (channel and carrier proteins)

• Cholesterol presentGlycoproteins and glycolipids present

• Site of cell signalling, chemical reactions, recognition, attachment, and selective transport

• Processes include diffusion, facilitated diffusion, osmosis, active transport, endocytosis, exocytosis

• Vesicles formed

• Membrane is fluid

Term: Endocytosis
Definition:
Organelle E entered the cell via a process known as endocytosis.
Describe this process 5marks

• Vesicular transport

• Active process / requires energy/ATP

• Cell membrane folds around material until enclosed

• Vesicle is formed and pinched off

• Pinocytosis takes in liquids

• Phagocytosis takes in solids

  

Exocytosis Describe how the structure of the cell membrane allows for transport of materials via exocytosis.
✅ Key Points:

• Vesicles are made of the same phospholipid bilayer as the cell membrane, allowing for attachment

• Membrane is fluid (contains cholesterol), so it can change shape

2 marks

• Vesicles are made of the same phospholipid bilayer as the cell membrane, allowing for attachment

• Membrane is fluid (contains cholesterol), so it can change shape