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Chapter 1: Cell Membrane and TransportFluid Mosaic Model

(Week 3)PowerPoint® Slides

by Ms Lina Tang

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Learning Objective (s)

2

• Understanding the fluid mosaic model

• Understanding the roles of different components on theplasma membrane

• Different transport processes

Learning Outcome (s)

3

• Understanding the fluid mosaic model and the underlying reasons for the structure

• Be able to describe the roles of different components onthe plasma membrane

• Be able to describe and different transport processes – diffusion, facilitated diffusion, osmosis, active transport, exocytosis and endocytosis

Fluid Mosaic Model• Membrane -

Phospholipid bilayer

▫ Hydrophobic tail (fatty acid

chains)▫ Hydrophilic head (glycerol

and phosphates)

Figure 1: Structure of a Phospholipid

Figure 2: Fluid Mosaic Model – Components of semi-permeable cell

membrane

• Solution = solute + solvent• Three terms are used to describe a solution:

▫ Hypertonic One of the two solutions that has a higher concentration of a solute

▫ Hypotonic One of the two solutions having lower concentration of a solute

▫ Isotonic Two solutions having the same concentration of a solute

1. Simple Diffusion

Net movement of molecules (or ions) from a region of their higher concentration to the region of their lower concentration

▫ Moving down a concentration gradient to reach an equilibrium▫ Usually for small substances▫ Cross freely anywhere along the membrane▫ Eg. Gases diffused in water and cross through the bilayer

Figure 1.3 Simple Diffusion

2. Facilitated Diffusion

▫ Protein channel or carrier protein

▫ Cross at specific place

▫ Water soluble substances, eg Na, K, Cl, Ca, amino acids

3. Osmosis

Solute + Solvent = SolutionSyrup)

(Sugar + Water =

- Movement of water molecules alone, and not of solutemolecules, resulting in equilibrium

Figure 1.4 Osmosis

4.

•

Active Transport

Uses ATP energy produced during respiration to move molecules across the membrane

• Crossing a gradient in the opposite direction ofconcentration, solutes are transported from lower concentration to higher concentration

Figure 1.5 Active Transport: Sodium-Potassium Pump

5. Bulk transport- Large quantities of materials

- Into cells (endocytosis)- Phagocytosis – cell eating- Pinocytosis – cell drinking

- Out of cells (exocytosis)

Figure 1.6 Endocytosis and

Exocytosis

References:

Jones, M. 2007, AS/A Level Biology (Cambridge 2ndInternational Examinations),University Press.

edn, Cambridge

Lee, S.C. & Liew, S.L. (2011). Success in BiologySTPM (vol 1). Fajar Bakti.

For

Lee, S.C., Liew, S.L. & Choong,Biology For STPM (vol 2). Fajar

N.M. (2011). SuccessBakti.

in

15

Key terms:

phospholipid A substance whose molecules are made up of aglycerol molecule, two fatty acids and a phosphate group

Term Definition