Biology
The important stuff for Biology: Unit 3
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- Created by: Siobhan Katie Perkins
- Created on: 15-05-09 20:52
Transport Across Membranes
Diffusion:
- Passive process due to a gradient
- High conc. to low conc. because of the random movement of particles until they are evenly spread.
- Equal Conc. = Dynamic Conc. (meaning the particles are still moving)
Osmosis:
- Passive process due to a gradient
- Diffusion of water molecules down a water potential gradient through a membrane
- Net movement of water from a dilute solution to a concentrated solution through a membrane, along a conc. gradient until conc. are equal
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Breathing
Active Transport:
- Allows cells to move substances from an area of low conc. to an area of high conc. because substances move against the conc. gradient
- Cells then absorb ions from very dilute solutions
- Uses energy
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Breathing
Surface Area:Volume
- For a multi-cellular organism:
- Diffusion through surface area is inadequate
- Gills and lungs increase surface area for gas exchange, when SA:V is v. small
- Insects; tracheal system
Inspiration - Breathing In
- Ribs move out and upwards, intercostal muscles contract
- Diaphragm contracts and flattens
- Volume increases, pressure decreases
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Alveolus
Expiration - Breathing Out
- Ribs move in and downwards, intercostal muscles relax
- Diaphragm relaxes and curves
- Volume decreases, pressure increases
Why?
- Ventilation maintains a conc. gradient for diffusion
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The Lungs
Ventilation System of Mammals
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Alveolus
Alveolus
- "air sac"
- High conc. of oxygen -> blood
- High conc. of Carbon Dioxide; blood ->Alveolus
- Constant amount of blood and Carbon Dioxide are exchanged
- Wall = 1 cell thick
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Absortion in Small Intestine
Small Intestine
- Villus -> microvillus = Large surface area
- Area of gut = 2000 meters squared
- Big area is important. Small intestine is where digested food (glucoses, almino acids etc.) enter the blood stream by diffusion and active transport
- Rich blood supply; steep conc. gradient for efficient diffusion
- Large SA for diffusion
- One cell thick wall, short distance for diffusion
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Uptake of Minerals
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Gas Exchange: Fish & Amphibians
Fish
- Bodies; covered in protective scales; prevents oxygen being taken straight from the water
- Thin gills, reduced distance of diffusion
- Moist
- Rich blood supply
- Gills don't work in the air as a lack of water causes gills to stick together, reducing surface area so it's inadequate to take oxygen from the air
Amphibians
- Tadpoles; frilly external gills, large SA, rich blood supply
- Receive oxygen, and rifs Carbon Dioxide through diffusion
- Tadpole -> frog. External gills -> absorbed. Metamporphisis
- Frog's gas exchange, through skin, v.moist, rich blood supply
- Mouth = large, thick skinned. Contains pair of v. simple lungs -> increase SA
- In water, all gas exchange occurs through skin
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Gas Exchange: Insects & Plants
Insects
- Tough outer coating -> little gas exchange
- Need oxygen to power muscles -> internal respiratory system
- Spiracles (system of tubes - cells of tissue) which open and close according to needs (open = need oxygen close = don't need oxygen. Prevents water loss)
- Gas exchange occurs in trachuoles -> tubes
- V. moist are pumped in and out of insect. Maintain conc. gradient
- No blood supply within insect. Tracheoles = v.large SA, close contace with body cells
Plants
- Need Carbon Dioxide (diffusion through leaves) & water for photosynthesis
- SA of leaves, increased by flatness; thin, distance of diffusion is minimal
- Air spaces allow Carbon Dioxide to be in contace with cell -> stomata
- Carbon Dioxide not always needed. Leaves; are covered in a waxy cuticle, a waterproof, gasproof layer
- have stomata; open when Carbon Dioxide is needed, close when not. Prevent water loss
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Uptake of Minerals
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The Circulatory System & Blood Vessels
The Circulatory System
Mammals have a double circulatory system:
- Lungs <-> heart <->body
Fish have a single circulatory system
- Heart -> guts -> body -> heart
Blood Vessels
- Artery- Carry oxygenated red blood at v. high pressure; heart -> lungs
- Thick walls, thick layer of muscle & elastic fibres - Vein- Carry deoxygenated purple blood; body -> heart.
- Valves - prevent backflow - Capillary- No cell is more than 0.05mm away
- narrow, v. think walls, diffusion of oxygen and glucose
- Carbon Diocide cell -? capillary
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The Heart
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- Right side; deoxygenated
- Left side; oxygenated, thickest wall
- Aorta - carries oxygenated blood around the body
- Pulmonary Vein - oxygenated blood from the lungs
- Pulmonary artert - deoxygenated blood to the lungs
- Vena Cava - deoxygenated blood to the heart
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