AQA GCSE Biology unit 3- Exchange of materials

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Give a definition of Osmosis.
The diffusion of water across a partially permeable membrane.
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Give a definision of active transport?
The movement of substances across a partially permeable membrane against the concentration gradient using energry from respiration (ATP).
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Give examples of things tat can be absorbed by active transport.
Ions from dilute solutions, and other substances such as sugar can be absorbed.
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Why does ative transport need energy?
Because substances must be moved against the concentration gradient.
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Why is glucose, water and minerals lost during exerise?
glucose- used in respiration to produce energy, water- lost through sweat to cool down the body, minerals- gets lots with water in sweating
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What do sports drinks contain?
water, glucose and minerals to rehydrate the body
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Why do some scientists think that sports drinks are unessicary?
Because for normal amounts of exercise water is enough to rehydrate the body.
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What is an isotonic solution?
A solution that's concentration matches that of the body's fluids.
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Why do large organisms need exchange surfaces?
To obtain all the food and oxygen they need.
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What qualitiese make an exchange surface effient?
a large surface area, thin wall, a short diffusion path, and an effienct transport system e.g the bloodstream
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How are the lungs adaped to be an efficient exhange surface?
Their surface area are increased by the alveoli, they have thin walls, and a good blood supply. The lungs are ventilated which creates a large diffusion gradient.
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What happens when we breathe in?
The intercostal muscles between the ribs and the diapram contract. The rib cage moves up and out and the diaphram flattens. The volume of the thorax increases, and the pressure there decreases and air is drawn in.
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What happens when we breathe out?
The interostal muscles of the ribcage and diaphram relax. The ribcage moves down and in and the diaphram becomes domed. The volume of the thorax decreases, and the pressure increases and air is forced out. This is known as ventilation.
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Why might someone need an artificial breathing aid?
If the alveoli are damaged- the surface area for gas exchange would be reduced. If the tubes leading to the lungs are narrowed- less air can pass through them. If a person is paralysed- their muscles will not work to pull the ribage up and out.
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Give an example of a negative pressure breathing aid and how it works.
The 'iron lung'- a person's chest is sealed in a metal cylinder, air is drawn out and the persons chest is moved out and they breath in. Air is then pumped in and the air is forced out of the persons lungs.
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Give an example of a positive pressure breathing aid and what they do and why they might be better than a negative breathing aid.
A Bag of air linked to a gas mask. A positive pressure breathing aid forces air into the lungs and is better as they are smaller and less expensive, easier to controle at home and can be used with computers to be more accurate and to have controle.
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Where are the villi situated and what are they the exchange surface for?
In the small intestine. They are exchange surfaces for food molecules.
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Why are the villi effiecient at being an exchange surface?
They have very thin walls and have many capillaries close to the wall. They are finger-like projetions which inreases their surface area. The an absorb through active transport and diffusion.
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Gases diffuse in and out of leaves through tiny holes called the___________.
stomata
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The stomata are controlled by ________ cells which __________.
guard, surround
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What gasses are exchanged and why?
Oxygen: needed for respiration and is a waste product of photosynthesis. Carbon Dioxide: needed for photosynthesis and is a waste product of respiration.
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Plants loose water _____ through the stomata due to _________ in the leaves.
vapour, evaporation
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Leaves are ______ and very ______ so the gases do not need to diffuse very far . There are aslo internal _______ pockets.
flat, thin, air
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What happens when a plant uses water faster than it can be replaced?
The stomata an close to prevent wilting.
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Look at a cross section of a leaf write a six mark answer as to how they are adapted.
1. Waxy cuticle- waterproof which stops water loss 2. Air spaces 3. Cells not tightly packed- have a large surface area available for gas exchange 4. Guard cells open and close the stomata to preent water loss. 5. Stomata allow gasses to move in/out
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What can wilting prevent?
excess water loss as it reduces surface area
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The stomata open to allow what gas in?
Carbon dioxide.
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What increases evaporation? what could happen if there is too much evaporation?
hot, dry, windy and bright conditions. the plant could dehydrate.
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what is the transpiration stream?
The movement of water through a plant.
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Other cards in this set

Card 2

Front

Give a definision of active transport?

Back

The movement of substances across a partially permeable membrane against the concentration gradient using energry from respiration (ATP).

Card 3

Front

Give examples of things tat can be absorbed by active transport.

Back

Preview of the front of card 3

Card 4

Front

Why does ative transport need energy?

Back

Preview of the front of card 4

Card 5

Front

Why is glucose, water and minerals lost during exerise?

Back

Preview of the front of card 5
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