Notes for the whole of 'Genes and Health' Topic

Contains summary notes of everything needed to know for Topic 2, Unit 1. 

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Genes and Health: Cystic Fibrosis
Mucus in the lungs
Lungs allow rapid gas exchange between the atmosphere and the blood
Air drawn into the trachea due to low pressure in the lungs (caused by diaphragm)
Trachea ­ two bronchi ­ bronchioles ­ alveoli (sites of gas exchange)
Mucus produced by goblet cells
Any dust, debris or microorganisms are trapped and removed
Removed by cilia, covering the epithelial cells, which beat.
CF: stickier mucus which is harder to move
Stickier mucus increases chance of lung infection and makes gas exchange less efficient
Epithelial Cells
Lining cell
Epithelial cells work together as a tissue called epithelium
Consists of one or two cells sitting on a basement membrane (made of protein fibres in
jelly-like matrix)
Squamous epithelium: lines the walls of the alveoli and capillaries (very thin)
Columnar epithelium: column shaped found in small intestine
Ciliated epithelium: cilia on the free surface ­ appears stratified due to position of nuclei.
This is known as pseudostratified
Sticky Mucus
Microorganisms are trapped in the mucus, some cause illness, these are called pathogens
CF: mucus production continues although mucus cannot be moved by cilia
Low levels of oxygen in the mucus because oxygen diffuses slowly through it, and epithelial
cells use more oxygen, causing harmful bacteria to thrive.
Increase of Size on Surface Area
Surface area to volume ratio: calculated by dividing an organisms total surface area by its
Gas Exchange
Alveoli provide a large surface area
There are numerous capillaries around the alveoli
Thin walls mean a short distance between the alveolar air and blood in the capillaries
Rate of diffusion
- Properties of gas exchange surfaces
1. Surface Area ­ rate of diffusion is directly proportional to the surface area
2. Concentration Gradient ­ rate of diffusion is directly proportional to the difference in
concentration across the gas exchange surface
3. Thickness of the gas exchange surface ­ rate of diffusion is inversely proportional to the
thickness of the gas exchange surface. Thicker = slower
Fick's Law:

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Protein Structure
General Structure
All composed of the same basic unites ­ amino acids
20 different amino acids
Plants can make all these amino acids, animals can only make some
Animals obtain the other amino acids through diet; essential amino acids
Amine group; -NH2
Carboxylic acid group; -COOH
Hydrogen; -H
All attached to a central carbon atom
Each amino acid has a different, variable, side chain (residual group)
Primary Structure:
The specific sequence of amino acids in the polypeptide chain
Two amino acids join in…read more

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Conjugated Proteins:
These have another chemical group associated with their polypeptide chain
Globular Proteins:
Polypeptide chain is folded into a compact spherical shape
Soluble; due to hydrophilic side chains
Enzymes are globular proteins
3-D shape is crucial to ability to form enzyme substrate complexes and catalyse reactions
within cells & binding to other substances
Antibodies are globular
Fibrous Proteins:
Remain as long chains
They can be cross-linked for additional strength
Insoluble; important for structure
Cell Membrane Structure
Phospholipid Bilayer:
CF: caused by a faulty transport…read more

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Glycoproteins; protein molecules with polysaccharides attached
Some proteins span the membrane whilst others are only on the outer/inner layer
Membrane proteins have hydrophobic areas (these are inside the bilayer)
Some proteins are fixed whilst other move around in the fluid (fluid mosaic model)
Old structure; three layer protein-lipid sandwich based on election micrographs (A)
However this structure did not allow the hydrophilic heads to be in contact with water and it
does not allow hydrophobic tails to stay away from water
Phosphate heads are…read more

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Human; red fluorescent
Immediately after fusion the coloured labels remained in their respective halves
After 40 minutes at 370C there was a complete intermixing of proteins
Only possible by diffusion through membrane; proved fluidity of membrane
Unsaturated Phospholipids:
The more unsaturated; the more fluid the membrane
`kinks' in hydrocarbon tail of unsaturated phospholipids prevent them packing tight together
(making more movement)
Protein function:
Carrier and channel proteins
Glycoproteins and glycolipids have important roles in cell-to-cell recognition as receptors
Transport of Substances through Cell Membrane…read more

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Hydrophilic molecules
Insoluble in lipids
Cross the membrane by either diffusing through water-filled pores within channel proteins
that than span the membrane
Different channel proteins for transporting different molecules (each has a specific shape for
a specific ion/molecule)
Some may be opened or closed depending on a signal (hormone or change in voltage across
the membrane) these are GATED CHANNELS
No energy needed
Carrier proteins; ion/molecule binds onto a specific site on the protein which then changes
Movement can occur in either direction; net…read more

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Substances taken into the cell by the formation of vesicles
Part of cell surface membrane engulfs the material to be transported
Substance can also be absorbed by attaching to a receptor in the membrane then
Water Regulation; unaffected lungs
Cells that line the airways produce mucus
Water in the mucus is continuously regulated to maintain a constant viscosity
Must be runny enough to be moved by beating cilia
However it cannot be so runny that the fluid floods the airway
Regulation of water…read more

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Sodium ions diffuse out of the tissue fluid and move down the gradient, passing between
cells into mucus
Movement of ions into mucus draws water out of the cells by osmosis until solutions outside
cell are isotonic (same concentration of water molecules)
People with CF:
CFTR protein may be missing or not functioning properly
When there is too little water; Cl- cannot be secreted across the membrane
No blockage of sodium ions, sodium is continuously absorbed by the cells
This draws chloride ions and water…read more

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Digestive System
People with CF have a high basal metabolic rate
Pancreatic duct becomes blocked with sticky mucus, stop the release of digestive enzymes
Lower concentration of enzymes in the small intestine reduces the rate of digestion
Food is not fully digested so less nutrients are absorbed
Energy loss in faeces; process called malabsorption syndrome
Enzyme Function
Globular proteins that act as biological catalysts
Speed up chemical reactions that would normally be slow at cell temperature
Precise 3-D shape includes a depression surface; active site…read more



Thank you


This is a well presented and detailed set of notes with useful annotated colour diagrams that cover various topics such as protein and lipid structure, cell membranes, transport through membranes, DNA, RNA, cystic fibrosis and inheritance.  It would be a useful exercise to make as set of flashcards of the key terms mentioned in the notes, to be downloaded and used as a self-test.

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