Movement of Molecules prompt cards

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Ways in which dissolved substances move in and out of cells
diffusion and active transport
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Explain osmosis
The movement of water molecules from a dilute (high water to solute ratio) to more concentrated solution (low water to solute ratio) through a partially permeable membrane (allows water molecules through but not solute molecules as they're too big)
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Water can move...
... in or out of a cell depending on differences in concentrations inside and outside of cell
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General effect of osmosis and example
gradually dilutes a solution eg root hair cell
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Most soft drinks contain
water, sugar and ions
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Explain effect of sports drinks when we exercise
In exercise, glucose used to release energy, water and ions (salts) lost in sweat. Sports drinks replace ions, water and sugars so that cells can function efficiently.
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If water, ions and sugars aren't replaced
the ion/water balance of body is disturbed and cells don't work as efficiently
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Explain active transport
Substances sometimes move against a concentration gradient. This requires energy from respiration. Active transport enables cells to absorb ions from very dilute solutions.
8 of 31
The size and complexity of an organism
increases the difficulty of exchanging materials
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Many organ systems are adapted for exchanging materials. Gas and solute exhange surfaces...
are adapted to maximise effectiveness
10 of 31
The surface area of the lungs increased by the
alveoli
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The surface area of the small intestine increased by
villi (line walls of small intestine)
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Explain villi
provide a massive surface area for exchange to take place, has extensive network of blood capilleries (efficient blood supply) maximising absorption of products of digestion, thin walls for short diffusion path
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Absorption of products of digestion in the villi is by
diffusion and active transport
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Surface area of lungs increased by
alveoli (tiny air sacs where exchange of oxygen and carbon dioxide takes place by diffusion)
15 of 31
Explain alveoli
millions in each lung so large surface area, excellent blood supply, thin capilleries supply blood so short diffusion path, well ventilated
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Summary: generally, effectiveness of exchange surface increased by
large surface area, thin, efficient blood supply, well ventilated for gaseous exchange
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Lungs are in the
upper part of the body (thorax (heart and lungs))
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Ribcage
Protects the contents of the thorax
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Diagphram
muscular 'sheet' dividing throax and abdomen
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Breathing system
takes air into and out of the body so that oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into the air
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Describe mechanism by which ventilation takes place: inspiration
Ribcage moves outwards and upwards due to inter costal muscles contracting, diagphram contracts/flattens, space within thorax increases which decreases air pressure. Air drawn in due to decreased pressure.
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Describe mechanism by which ventilation takes place: expiration
Ribcage moves inwards and downwards due to inter costal muscles relaxing, diagphram relaxes and moves upwards , space within thorax decreases which increases air pressure. Air forced out due to increased pressure.
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Movement of air in and out of lungs is called
ventilation
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How substances enter plants
Carbon dioxide enters leaves by diffusion, most of water and mineral ions are absorbed by roots
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Surface area in roots increased by
root hairs
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Surface area in leaves increased by
flatterned shape (providing large surface area for efficient photosynthesis), internal air spaces
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Function and position of stomata
On undersurface of leaves. They obtain carbon dioxide from the atmosphere and remove oxygen produced in photosynthesis (by diffusion)
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Main site of water vapour loss in plants
the leaves, mostly through the stomata
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Evaporation more rapid in
hot, dry, windy conditions
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Explain transpiration
Water vapour from internal leaf cells evaporates through stomata. Size controlled by guard cells. If plans lose water faster than replaced by roots, stomata can close to prevent wilting and eventual dehydration.
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Other cards in this set

Card 2

Front

Explain osmosis

Back

The movement of water molecules from a dilute (high water to solute ratio) to more concentrated solution (low water to solute ratio) through a partially permeable membrane (allows water molecules through but not solute molecules as they're too big)

Card 3

Front

Water can move...

Back

Preview of the front of card 3

Card 4

Front

General effect of osmosis and example

Back

Preview of the front of card 4

Card 5

Front

Most soft drinks contain

Back

Preview of the front of card 5
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