Exchange with the environment
- Created by: LauraNannini
- Created on: 24-04-20 10:11
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- Topic 8
- Effective diffusion
- Steep concentration gradient
- Short travel distance (squamos cells)
- Large surface area
- Large surface area to volume ratio
- Diffuision in different organisms
- Single cells exchange material with the environment
- Multi cellular organisms have specialised systems fro substance exchange
- Fish have highly vascularised internal gills to draw oxygen from water
- Insects and arthropods have a fine tracheal tubes where gas exchange occurs
- All vertebrates have lungs that connected to the pharynx
- Gas exchange in plants
- Guard cells open and close the stomata
- Plants loose water through the opening of the stomata by the guard cells
- Xerophyte plants have adapted to dry and hot conditions to minimize water loss
- Sunken stomata- maintain humid air around the stomata
- Smaller leaf surface area- prevents more water being evaporated
- Waxy cuticle- makes a water proof layer
- Extensive and shallow root- absorb water from the humus layer of the soil
- Gas exchange in insects
- Exoskeleton made of chitin covered by a impermeable cuticle
- Spiracles are connected to the trachea which runs through the body
- Spiracles can be closed to prevent water loss
- The trachea has lots of water vapour to reduce water loss at the surface
- Tracheoles is at the tips of the trachea and it is where gas exchange occurs
- Some insects pump air in and out of their tracheoles- this is ventilation and leads to mass transport of O2 and CO2
- Gas exchange in fish
- Water passes over the gils to get oxygen that has been dissolved in water
- Lamella provide a large surface area and contain squamous cells for short diffusion rates
- Water and the fishes blood move in a countercurrent system to steepen the concentration gradient and cause a faster rate of oxygen diffusion
- Gas exchange in humans
- The trachea is suported by C-shaped rings of cartilidge to keep our throat open so we can breath
- Alveoli is the site of gas exchange- they have a large surface area and a rich blood supply
- Ventilation allows for a constant supply of air- It is tidal
- Breathing in is an active process- diaphragm contracts and intercostal muscles contract
- Diaphragm move down and increases volume in the thorax
- External intercostal muscles pull the ribcage up to increase volume in the thorax so the air in the lungs is at a lower pressure than that of the air
- Breathing out is a passive process- diaphragm relaxes and the lungs and chest return to the thorax
- Volume in the thorax decreases- pressure inside the lung increases so air can travel out
- Digestion and absorption
- Small intestine have villi and microvilli which increases surface area
- Lipid digestion- bile salts hydrophobic molecules break down the large globule lipids into micelles
- This increases surface area for lipase action
- The mixture of water and micelles is emulsion and is how the lipids can be broken down and absorbed
- Gastric juices break down proteins as they contain pepsin
- Pepsin is a endopeptidasewhich breaks the peptide bonds to make smaller chains
- Trypsin in the small intestine then breaks the protein chains down smaller
- Exopeptidase then break the protein into dipeptides and amino acids and enzymes then further break the dipeptides into amino acids
- Trypsin in the small intestine then breaks the protein chains down smaller
- Pepsin is a endopeptidasewhich breaks the peptide bonds to make smaller chains
- fatty acids resynthesive into triglycerides and associate with proteins to make chylomicrons in the epithelial cells
- Effective diffusion
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