2.5 Cell Membranes

Label each cell membrane component A - E

Learning Objectives
• Describe the role of components of the cell membrane
• Describe factors that affect membrane permeabilty
Success Criteria
• Label the fluid mosaic model
(Grade E)
• Describe the functions of the following components of the plasma membrane (Grade C)
• Describe how temperature affects the cell membrane structure and permeability (Grade C)
• Explain the roles of the components in the plasma membrane (Grade A)
• Apply understanding of membrane structure and permeability to practical investigations (Grade A)

Describe the functions of components of the plasma membrane
(grade C), annotate the diagram.
Glycolipid
Page 128-129 help
Channel protein

• In pairs explain the roles of components within the membrane, using specific examples below (Grade A) Think back to KS4
1) Extrinsic proteins - Glycoprotein/Glycolipid
2) Integral proteins - Channel protein/Carrier protein
Challenge – Explain what is meant by cell signalling

Extrinsic (or Peripheral) proteins may be free on the membrane surface or bound to an intrinsic (or integral) protein.
Glycoproteins
- cell adhesion, when cells join together to from tissues
- Receptors for neurotransmitters at nerve cell synapses
- Receptors for hormones such as insulin and glucagon which affects the uptake and storage of glucose by cells
Glycolipids
- Cell markers or antigens, recognised by cells of the immune system

Many integral proteins are carrier proteins or channels .
Carrier proteins
- root hair cells use active transport via carrier proteins to absorb ions from the soil
- Uptake of glucose and amino acids in the small intestine
- Exchange of Na and K ions in neurons and muscle cells
Channel proteins
- Chloride ions (polar) pass across the lining of epithelial cells, to regulate the composition of mucus in the airways
- Synapses have channel proteins that allow the diffusion of Ca ions into the synapse
membrane, to allow the conduction of nerve
impulses

Membranes control the passage of different substances into and out of cells and organelles. If membranes lose their structure they lose control of this and cell processes are disrupted.
Phospholipids in a cell membrane are constantly moving, increasing the temperature give the phospholipids more kinetic energy, making the membrane more fluid.
Carrier and channel proteins in the membrane will be denatured at high temperatures.
Both of these affect the permeability of membranes

1 ) Describe an experiment by which you could test to see whether temperature affects membrane permeability (6). Beetroot cells contain betalain, a red pigment, because of this it is useful for investigating the effects of temperature on membrane permeability. When membranes are disrupted the red pigment is released and the surrounding solution is coloured.
• Keywords - beetroot, pigment, colorimeter, temperature
Then compare experiment with your neighbour - PA

1.Same volume discs of beetroot
2.Same volume of water
3.Same temperature
4.Same time in waterbath
5.Range of temperatures
6.Use colorimeter to read amount of pigment in solution
6.Graph of colour intensity (% absorbance etc.) over alcohol concentration

• Complete data analysis sheet – Investigating permeability of cell membranes
• Challenge - Application to real life, research into red blood cell membrane disorders, to explain why this leads to anaemia
• PA

Learning Objectives
• Describe the role of components of the cell membrane
• Describe factors that affect membrane permeability
Success Criteria
• Label the fluid mosaic model
(Grade E)
• Describe the functions of the following components of the plasma membrane (Grade C)
• Describe factors that affect the cell membrane structure and permeability (Grade C)
• Explain the roles of the components in the plasma membrane (Grade A)
• Apply understanding of membrane structure and permeability to practical investigations (Grade A)

Multiple-choice quiz
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