In this chapter of AS/A-level Biology, we will study the topic, Genes and Health. We will learn the gaseous exchange and properties related to cell membranes.
Gaseous Exchange
Describe how the mammalian lung is adapted for gaseous exchange
- A large number of alveoli provide a large surface area
- This increases the rate of diffusion
- The alveoli and the capillary have thin walls and are made out of a single layer of flattened cells meaning they are one cell thick
- This creates a short diffusion distance
- In AS/A-level Biology, they have an extensive capillary network that maintains the concentration gradient
- Red blood cells bring a constant supply of carbon dioxide
- Breathing maintains the concentration gradient
Cell Membranes
Structure and properties of cell membranes
Why do phospholipids molecules form a (continuous) bilayer?
- The phosphate heads are hydrophilic
- So they are attracted to water
- The 2 fatty acid tails are hydrophobic
- So they orientate away from water
How does cholesterol affect membrane fluidity?
- The cholesterol combines with fatty acid tails
- Which restrict movement of the phospholipids
- Making the cell membrane more rigid
Fluid mosaic model of cell membranes as interpretations
How does fusing a cell explain the structure of a cell membrane?
- Both types of protein would be found in the fused cell
- Proteins will have intermixed
- There would be the same original number of proteins
- Hence the fluidity in cell membranes
In AS/A-level Biology, temperature effect to the cell membrane
- Increasing the temperature increases the kinetic energy of phospholipids
- The phospholipids move more
- High temperatures disrupt the membrane structure causing more red pigment to escape
- The proteins will denature
Explain the effect of ethanol concentration on the permeability of cell membranes
- It causes the membrane to be disrupted
- Because the phospholipids dissolve in ethanol
- The proteins will then denature
- Pigment will escape easily from a disrupted membrane hence the increase in permeability
Although it may be dull, this part in the topic is important and you managed to finish it! Good job!!
