B3.1 Movement of molecules in and out of cells Flashcards
What is osmosis?
Osmosis is diffusion of water molecules from a region of high water concentration (a dilute) to a region on low water concentration (more concentrated solution) through a PARTIALLY PERMEABLE MEMBRANE
What is a partially permeable membrane?
a membrane with very small holes in it so that only small molecules (such as water) can pass through it
What causes water to move to move into and out of cells by osmosis?
difference in the concentrations of the solutions inside and outside a cell
What do most soft drinks contain?
water, sugar, ions
Why do sports drinks contain sugars?
to replace the sugar used in energy release during the activity
What do sports drinks contain ions and water?
to replace the water and ions lost during sweating
What happens if the water and irons are not replaced after having done exercise?
the iron/ water balance of the body is disturbed and the cells do not work as efficiently.
Describe what happens if a cell is short of water
the solution inside the cell will become more concentrated. This means that the solution outside the cell is more dilute.
therefore water will move into the cell by OSMOSIS
Describe what happens if a cell has lots of water
the solution inside it will be more dilute. water will be drawn out of the cell by OSMOSIS
What is active transport?
the process where substances are absorbed against a concentration gradient.
they move from a region of low concentration to a region of high concentration
this requires the use of energy from respiration
What does active transport enable?
enables cells to absorb ions from very dilute solutions
What does active transport require?
energy from respiration
Many organisms are …….. for exchanging materials
specialised
The effectiveness of an exchange surface is increased by:
4 factors
1) having a large surface area - so lots of a substance can diffuse at once
2) being thin, to provide a short diffusion path
3) (in animals) having an efficient blood supply- lots of blood vessels to get substances into and out of the blood quickly
4) (in animals, for gaseous exchange- eg alveoli) being ventilated - so air can move in and out
Gas and solute exchange surfaces in humans and other organisms are ….. to maximise effectiveness
adapted
Why does exchanging substances get more difficult in bigger, more complex organisms?
as the place where the substance is needed is further away from the exchange surfaces
In humans, how is the surface area of the lungs increased by?
increased by the alveoli
In humans, how is the surface area of the small intestine increased by?
by villi
How do the villi in the small intestine allow substances to diffuse through more easily?
- provide a large surface area - so digested food is absorbed faster into the blood
- have an extensive network of capillaries- to absorb products of digestion by diffusion and active transport
- have a single layer of surface cells- short diffusion and active transport path
How are the alveoli in the lugs specialised to maximise the diffusion of oxygen and carbon dioxide?
- large surface area
- a moist lining for absorbing gases
- thin walls
- good blood supply
What is the upper part of the body called?
the thorax
What are lungs protected by?
the ribcage
What is the lower part of the body called?
the abdomen
How are the lungs separated from the lower part of the body (the abdomen)?
separated by the diaphragm
Describe the function of the 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
What is ventilation?
The movement of air into and out of the lungs
Describe the changes that happen when we breathe in
- diaphragm contracts and becomes flatter
- the ribcage moves out and up
- thorax volume increases
- this decreases the pressure, drawing air in
Describe the changes that happen when we breathe out
- Diaphragm relaxes and moves up
- ribcage moves in and down
- thorax volume decreases
- this increases the pressure, so air is forced out
By what process does carbon dioxide enter the plant?
by diffusion
In plants, where are most water and mineral ions absorbed?
the roots
How is the surface area of the roots increased by?
root hairs
Describe how root hairs take in minerals
using ACTIVE TRANSPORT
- concentration of minerals is usually higher in the root hair cell than in the soil around it
- active transport allows the plant to absorb minerals from a very dilute solution, against a concentration gradient.
low concentration of minerals ——-to———high concentration
Give an example of when active transport is used in humans
in the GUT - when there’s a lower concentration of nutrients in the gust than there is in the blood.
How is the surface area of a leaf increased by?
the flattened shape
internal air spaces
Why do plants have stomata?
to obtain carbon dioxide from the atmosphere and to remove oxygen produced in respiration
Where do plants mainly lose water vapour?
from their leaves.
Most of the loss of water vapour takes place through the stomata
In what conditions does evaporation occur faster?
in hot, dry and windy conditions
How do dissolved substances move by?
by diffusion and active transport
What happens if plants lose water faster than is replaced by the roots?
The stomata close to prevent wilting
What is the size of the stomata controlled by?
guard cells which surround them
By what process does water vapour escape from the plant?
by diffusion
Describe artificial ventilators
HELP PEOPLE TO BREATHE
they are machines that move the air into and out of the lungs
used to be a giant case (an ‘iron lung’) with only the patients head sticking out. Air was pumped out of the case, pressure dropped, lungs expanded and air was drawn in. - could interfere with blood flow
Now, most work by pumping air into the lungs which expands the ribcage and when you stop pumping, the ribcage relaxes and pushes air back out of the lungs - does not interfere with blood flow but could damage (eg burst alveoli).
What provides the lungs with a large surface area?
alveoli
What provides the small intestine with a large surface area?
villi
What are 4 factors that increase the rate of transpiration?
sunlight- causes stomata to open
high temperature- increases the rate of evaporation
High winds- increases diffusion gradient
Low humidity/dry conditions- larger diffusion gradient
What provides roots with a large surface area?
root hair cells
How does water get into plants?
by osmosis into the roots
How do mineral ions get into the plant?
By diffusion or active transport into the roots
What is diffusion alone a sufficient means of transport in simple organisms but not large multicellular organisms?
As surface area to volume is too small in big organisms for substances to reach all cells quickly enough to meet metabolic demands
Why do villi have lots of mitochondria and microvilli?
Mitochondria- To release energy for active transport by respiration
Microvilli- increase surface area so speeds up exchange
How does an iron lung help a patient to breathe?
The iron lung creates a vacuum that causes the patient’s lungs to expand so air rushes in
Why do plants wilt in dry conditions?
it reduces the surface area from which water can be lost
Name some features of the breathing system
rib
trachea
bronchus
bronchiole
alveoli
diaphragm
Name the gas that moves from the alveolus into the blood
oxygen
Describe the changes in the volume of the lungs in one breathing cycle
volume rises when we breathe in
and falls when we breathe out
Explain how the diaphragm and ribcage cause changes in lung volume
air moves into the lungs caused by upward and outward movement of the ribcage and by flattering of the diaphragm
air moves out of the lungs caused by the return of the ribcage to original position (moves downwards)
An iron lung and a modern ventilator cause the patient to inhale in a very different way
explain this difference
in an iron lung- outside pressure forces air into lungs
modern ventilator- air is forced mechanically into the lungs
Give advantages and disadvantages of using the modern ventilator rather than the iron lung ventilator
advantages- more freedom of movement of the patient, more portable, does not affect blood flow of lower body
disadvantages- tube in trachea is uncomfortable, more difficult to eat/talk
Explain why routes need to use active transport and osmosis to absorb water and ions
- solution in soils is more dilute than in root cells
- so water moves from the dilute to more concentrated region (osmosis)
- concentration of ions in soils is less than in root cells
- so energy is needed to move ions against the concentration gradient (active transport)
What are some possible effects f the balance between ions and water is not correct
cells will work inefficiently
absorb too much water
lose to much water
Explain how oxygen moves into the blood
by diffusion
from a high concentration of oxygen to a low concentration
What is a disadvantage of a leaf having lots of stomata?
increased water lost
Why is very little water lost when the lower surfaces of leaves were covered in grease?
lower surface has more stomata
stomata are now covered in grease
so water can not evaporate from stomata
