Biology 3 Unit 1
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What is meant by osmosis?
This is the net movement of water from a high concentration, to a lower concentration; through a partially permeable membrane.
Describe 'Active transport'?
Cells use active transport to absorb substances across partially permeable membranes against a concentration gradient. Also requires the use of energy released in respiration.
What are sports drinks?
Sports drinks are solutions of sugar and mineral ions
What 3 things do sports drinks contain and why?
- Water - replace the water lost when sweating, rehydrating body cells
- Sugar - replace the sugars used for energy release in exercise
- Mineral ions - replace those lost in sweating
What are sports drinks designed to do?
They are designed to help balance the concentration of body fluids and the concentration inside the cells.
What are the features of an efficient exchange surface?
- Large surface area
- Thin walls/ thin diffusion path
- Efficient transport system
- Efficient blood supply
Describe how the lung has adapted to be an efficient exchange surface?
- The surface area of the lung is increased by the alveoli
- The alveoli have thin walls, a large surface area and good blood supply
- The lungs are ventilated to maintain a steep diffusion gradient
Describe the gas exchange in the lungs when we breath?
- When we inhale oxygen is diffused into the capillaries surrounding the alveoli, into the blood
- When we exhale carbon dioxide is diffused out of the blood into the lungs to be breathed out
Where is the lungs found?
The lungs are in the thorax, protected by the rib cage and above the diaphragm which separates the lungs from the abdomen
Breathing system: what happens when we breathe in?
- The INTERCOSTAL MUSCLES contract
- The RIB CAGE moves up and out and the DIAPHRAGM flattens
- The VOLUME of the thorax INCREASES
- The PRESSURE in the thorax DECREASES and air is drawn in
Breathing system: What happens when we breathe out?
- The INTERCOSTAL MUSCLES and DIAPHRAGM relax
- The RIB CAGE moves down and in and the DIAPHRAGM becomes DOMED
- The volume of the thorax decreases
- The pressure increases and air is forced out
What is the function of the villi found in the small intestine?
Villi provides a large surface area with an extensive network supply of capillaries to absorb the products of digestion by diffusion or active transport
How are villi an efficient exchange surface?
- Large surface area for diffusion
- Thin walls enables quicker diffusion
- Rich blood supply to produce steep concentration gradient for efficient diffusion
What is the function of the stomata?
- To enable the diffusion of gasses e.g. Carbon dioxide and oxygen.
- Water vapour is also lost through the stomata due to evaporation
What is the function of the guard cell?
To control the size of the stomata
What features of the leaves enable a more efficient diffusion?
Leaves are flat and thin with internal air spaces to increase the surface for easier diffusion of gas
What is the function of the roots?
- To absorb water and mineral ions for food, growth, etc.
- (Root hair cells increase the surface area)
What is meant by transpiration?
Transpiration is the movement of water through the plant.
What occurs in transpiration?
Water absorbed by the roots evaporates from the leaf cells and the water vapour diffused through the stomata
How could the plant dehydrate?
The plant could dehydrate if the rate of evaporation in the leaves is grater than the water uptake by the roots
When is transpiration more rapid?
Hot, dry, windy, bright conditions
How is water loss reduced in the leaves?
- The upper epidermis had a waxy cuticle that stops water loss
- The guard cells can close to prevent excessive water loss
How can wilting reduce water loss?
When the whole plant wilts, the leaves collapse and hang down reducing the surface area
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