IB Term 3 Grade 10 DPP Biology

Front

Plasma

Back

Topic 1

Front

solution

Back

solute+solvent

Front

Dissolving substances

Back

Water is slightly polar, and when a non-polar item is added, it can pull apart it.

Front

Plasma Membrane

Back

• The plasma membrane is a phospholipid bilayer that controls substance movement in and out of the cell.

• All cells have a plasma membrane.

• It is selectively (or differentially) permeable.

• Most eukaryotic organelles also have membranes.

Front

Phospholipid

Back

• Phosphate head is hydrophilic (water-attracting).

• Fatty acid tails are hydrophobic (water-repelling).

• The bilayer creates a hydrophobic barrier:

  • Non-polar substances pass through easily.

  • Polar substances cannot pass easily.

Front

Function of Phospholipid Bilayer

Back

• Selectively control entry and exit of molecules.

• Sites of chemical reactions.

• Create compartments in the cell.

• Restrict movement between cell regions.

• Contain protein receptors for communication.

• Involved in cell-cell recognition.

Front

Fluid Mosaic Model

Back

Fluid Mosaic Model

• Also known as Singer-Nicolson Model.

• Integral proteins: penetrate bilayer; function as channels/pumps.

• Peripheral proteins: surface of membrane; involved in recognition/receptors.

• Cholesterol:

  • Decreases membrane fluidity.

  • Lowers permeability to some substances.

Front

Diffusion

Back

• Molecules move from high concentration to low concentration.

• Movement continues until equilibrium is reached.

• The difference in concentration is called a concentration gradient.

Front

Simple Diffusion

Back

• Movement of small, uncharged, or lipid-soluble molecules (e.g. O₂, CO₂).

• Molecules pass directly through the membrane.

• Moves down the concentration gradient.

• No transport protein required.

• Passive process – no ATP needed.

• Stops when concentrations are equal on both sides.

Front

Facilitated Diffusion

Back

• Uses membrane proteins (channels or carriers).

• For large or polar molecules, e.g. glucose.

• Faster than simple diffusion.

• Specific proteins for specific molecules.

• Channels can become saturated.

• Only moves down the concentration gradient.

• Still passive – no ATP used.