Topic 2 - Genes + Health Flashcards
Lungs
Lungs allow rapid gas exchange between the atmosphere and blood.
One bronchus extends into each lung, they branch into smaller air pathways called bronchioles. They each connect to alveolar ducts, that connect directly to alveoli (sites of gas exchange).
Epithelial cells
They line the outer surface of many animals. They line cavities and tubes within animals along with covering sufaces of internal organs.
Basement membrane attaches epithelium to connective tissue below.
Basal membrane
Membrane surface of epithelial cell that faces basement membrane
Apical membrane
Membrane surface of epithelial cell that faces away frkm the basement membrane
Types + location of epithelial cells
Squamous = epithelium in walls of alveolus
Columnar = epithelium in small intestine
Ciliated = found in airways, lungs
Role of cilia, no CF
Mucus is swept by a beating of cilia into the mouth cavity where it is either coughed or swallowed (stomach acid can kill it)
Cilia, with CF
People with CF produce stickker mucus, cilia cannot move this so jt builds up in airways
Pathogens can be trapped in sticky mucus and cause diseases
- white blood cells can fight infection but when they die they release DNA - making mucus stickier
- Low O2 levels in mucus as it diffuses slower due to thickness
- epithelial cells use more O2 as cilia are working harder, requiring more energy.
- anerobic environments perfect for bacteria to thrive
SA:V
Surface area ÷ volume
As an organism increases in size:
- Surface area increases by factor of 4
- Volume increases by factor of 8
SA:V VALUE DECREASES BY A HALF
Unicellular organism’s exchange surface
The whole cell surface membrane is the exchange system
Substances that diffuse into or out of cell move down the concentration gradient (high to low)
Multicellular (larger) organism’s exchange surface
Require more gas exchange in order to meet metabolic needs, harder for them to absorb substances due to the size of their surface compared to their volume
Why cant large organisms rely on simple diffusion
Inner most tissues would be too far from gas exchange site meaning it would not be fast enough.
Organism would die, dehydrate
Gas exchange system features
Large surface area from alveoli
Numerous capillaries associated with each alveolus
One cell thick capillaries and thin alveoli walls reduces distance of air in the alveolus and blood in the capillaries
Cocentration gradient maintained by constant blood flow
Fick’s law
Rate of diffusion = (Surface area x concentration gradient) ÷ thickness of exchange system
Surface area
Directly proportional to rate of diffusion
Concentration gradient
Directly proportional to the difference in concentration across the exchange system
Thickness of gas exchange system
Inversely proportional to the thickness of the gas exchange system
Amino acid structure consists of
amine group (-NH2) carboxylic acid group (-COOH) Hydrogn group (-H) Residual group (R)
Primary structure of protein
The sequence of amino acids in a polypeptide chain
- Amino acids join in condensation reaction to form dipeptide
- Peptide bond formed between two subunits
- Process continues till polypeptide chain is formed
- Proteins consist of two or more polypeptide chains
Secondary structure of protein
Protein folds and coils
- Interactions between R groups of amino acids in polypeptide chain cause it to fold and coil
- They either coil into a-helices or b-pleated sheets
Within a protein molecule there may be sections of both a-helic and b-pleated, and some that are not twisted in any ordered manner
a-helix (secondary structure)
Regularly spaced hydrogen bonds form between amine and carbolxylic groups on different amino acids in the polypeptide chain
b-pleated sheets (secondary structure
Amino acid chains may fold back on themselves or may kink together with the hydrogen bonds holding the parallel chains
Each hydrogen bond is weak but cumulative effect makes structure stabel
Tertiary structure of protein
Protein folds into more precise 3D shape
Chemical bonds and hydrophobic reactions between R groups maintain final tertiary structure
Depression (active site) formed in tertiary structure
Reactions between R groups:
Polar R groups attract other polar molecules
Some amino acids have ionised R groups so ionic bonds can form between + and - R groups
Quaternary structure of protein
Protein has more than one polypeptide chain
Conjulated proteins
Contains other chemical group within their polypeptide chain
Globular protein
Polypeptide folded compactly into spherical shape
Soluble as hydrophillic side chains project on the outside of the molecule
3D structure vital for binding to other substances, such as enzymes and antibodies
Fribrous proteins
Do not fold, remain as long chains
Insoluble proteins
Several polypeptide chains can be cross-linked for strength
Keratin in hair, collogen in bone and tendons
Phospholipid bilayer
Structure of cell surface membrane
Basic structure = two layers of phospholipids
2 fatty acids, 3rd replaced by negatively charged phosphate group
Phosphate heads are polar, hydrophillic
Fatty acid tails are non-polar, hydrophobic
Why do phospholipids arrange themselves in the bilayer
Cells are filled with aqueous cytoplasm and aqueous tissue fluid
Cell surface phospholipids adopt most suitable structure - bilayer
Hydrophobic fatty acid tails have no contact with water on either side of the membrane
Hydrophillic phosphate heads are constantly in an aqueous environment
Fluid mosaic model
Model refers to arrangement of proteins in cell surface membrane
Suggests some proteins are fixed witin the membrane, but some are not and are free to move in the fluid bilayer
Evidence 1 (fluid mosaic model)
Experiment showed two types of proteins:
- Those that can be easily separated from membrane by increasing ionic conc of solution
- Those that required more drastic measures like detergents
This supports the model:
Peripheral proteins are loosely attached to the outer surface membrane
Integral proteins are fully embedded in the phospholipids
Evidence 2 (fluid mosaic model)
Evidende for integral proteins = freeze fracture electron microscopy studies
1) Frozen membrane sections were fractured along weak points between lipid layers
2) Inner fractured surface was coated in heavy metal
Smooth mosaic surfaces were revealed, interspersed with large integral proteins
Evidence 3 (fluid mosaic model)
Mouse/human cell fusion:
1) specific membrane protein in each cell was marked by a colour before fusion
2) light mìcroscope was used to follow protein movement, after fusion no immediate movement
3) after 40 mins at 37°c there was complete intermixing of proteins
4) only way to mix was by diffusion, showing membrane had fluid components
Unsaturated phospholipids + bilayer fluidity
More phospholipids with unsaturated fatty acids, more fluidity
Kinks in the hydrocarbon tails of unsaturated phospholipids prevent them packing closely together - more movement possible
Cholesterol + bilayer fluidity
Cholesterol between phospholipids maintains fluidity of membrane by affecting movement of phospholipids
Diffusion
Passive, no metabolic energy required
Net movement of molecules or ions from a region of high conc to a region of low conc.
Concentration gradient - difference in concentration between two areas, diffuse occurs where there is a gradient
Un-charged molecules like O2 ca diffuse across membrane
