Biology B3

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  • Created by: tomiaraba
  • Created on: 16-04-16 11:08
When does diffusion take place?
When particles can spread freely from one place to another
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What is a partially permeable membrane?
A membrane that only lets some types of particles through
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Which has a higher concentration of water, a strong salt solution or a weak salt solution?
A weak salt solution as it only has a small amount of salt and lots of water
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What is the cytoplasm of a cell made up of?
Chemicals dissolved in water inside a partially permeable bag of cell membrane
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What direction does water move across a partially permeable membrane?
From an area of high concentration of water molecules (a dilute solution) to an area of low water concentration (a concentrated solution)
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What is this special type of diffusion called?
Osmosis
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What happens if a cell uses up water from inside the cell during chemical reactions?
More water immediately moves in by osmosis (isotonic)
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What happens if a cell produces lots of water inside the cell during reactions?
Water will immediately move out of the cell by osmosis (isotonic)
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What happens if the solution outside the cell is more dilute than the cell content?
Water moves into the cell by osmosis causing the cell to swell and potentially burst (hypotonic)
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What will happen if the solution inside the cell is less dilute than the cell content?
Water will move out of the cell by osmosis and the cell will shrivel up (hypertonic)
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What do plants rely on osmosis for?
To support their stems and leaves
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How does a plant cell become hard and rigid?
Water moves into plant cells by osmosis causing their vacuole to swell and press the cytoplasm against the plant cell walls, when no more water can enter the cell it becomes hard and rigid
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Does the fluid surrounding plant cells need to have a higher or lower concentration of water than the cytoplasm of the cells?
It must be more concentrated (more dilute solution of chemicals)
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What is the movement of dissolved substances called when it moves along a concentration gradient?
Diffusion (or osmosis for water)
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What process do cells use to move dissolved substances against their concentration gradient?
Active transport
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What does the transport system need to carry out active transport?
Energy
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Where does this come from?
Cellular respiration
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What do cells that carry out a lot of transport need? Why?
Lots of mitochondria to make the energy required for active transport
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Why is active transport particularly important in the root of the plant?
The ions the root needs to absorb are often less concentrated in the soil than the root cells so do not move into cells by diffusion; to take up the ions the cell must use active transport
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Where in your body is glucose absorbed against a concentration gradient using active transport?
In your gut and kidney
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What is the main constituent of soft drinks?
Water
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How much was spent on sports drinks last year?
£250 million
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What substances decrease in our cells when we exercise?
Sugar, water and mineral ions
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What happens if you sweat loads?
The body fluids become more concentrated and water leaves your cells by osmosis leaving them dehydrated
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What must you do to continue exercising at your best if you have lost lots of minerals, water and sugar?
You must replace them
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What do sports drinks contain?
Water, sugar (glucose), mineral ions, colourings and flavourings
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What do sports drinks claim to do?
Aid hydration of the tissues, help reduce lost energy, replace lost electrolytes (mineral ions)
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Why can't large organisms do what small organisms can?
For large organisms it is difficult to exchange materials quickly with the outside world. Gases and food molecules cannot reach every cell simply by diffusion
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How can the effectiveness of an exchange surface be increased?
Large surface area, short path for diffusion, efficient blood supply and being well ventilated in animals to maintain concentration gradients
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How is a musk turtle's tongue adapted for gas exchange?
It is covered in tiny buds to increase surface area and it has a very good blood supply
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What are alveoli and how do they increase the effectiveness of gas exchange?
They are tiny air sacs and give the lungs a very large surface area
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What gases are exchanged in the alveoli? Which way do they move?
Oxygen; from air in lungs to blood. Carbon Dioxide; from blood to air in lungs
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Why do alveoli have such a rich blood supply?
To maintain the concentration gradient for gases in both directions
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Why do we want high concentration gradients during gas exchange?
It keeps the process rapid and effective
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Why are the walls of alveoli and capillaries in the lung so thin?
It allows diffusion to take place over the shortest possible distance
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What is the process of moving air in and out of the lungs called?
Ventilating the lungs or breathing
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Where are your lungs found? How are they protected?
In your chest or thorax and are protected by your ribcage
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What separates your breathing system from your digestive organs?
The diaphragm
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What is the difference in function between your lungs and breathing system?
Your lungs provide an efficient surface for gas exchange whereas your breathing system moves air in and out of your lungs
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What two things move to cause ventilation?
Ribcage and diaphragm
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What moves in when you breathe in? What does this do to the concentration gradient?
Oxygen-rich air moves in when you breathe in and this maintains the concentration gradient with the blood
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What benefit does a maintained concentration gradient have?
It means that oxygen continually diffuses into your bloodstream
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What stages are involved when you breathe in?
Intercostal muscles contract and ribs move up and out; the diaphragm flattens; volume of chest increases; increased volume means lower pressure in the chest; atmospheric air is now at a higher pressure than chest and air is drawn into the lungs
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Why do people sometimes struggle to breathe and get enough oxygen into their lungs?
Tubes leading to the lungs may be very narrow so less air gets through them; structure of the alveoli can break down into a few large air sacs (smaller surface area for gas exchange); some people are paralysed by accidents or diseases
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What two ways do artificial aids use to support breathing?
Negative and positive pressure
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What disease was the driving force behind the invention of the 'iron lung'?
Polio
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Is the pressure in the metal container higher or lower in an 'iron lung' when the patient is breathing in?
Lower
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How is this change in pressure achieved?
Air is pumped out of the chamber
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What happens when the vacuum is switched off?
The air moves back out of the chamber increasing the pressure. This assists the patient to force the air out of the lung
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What is the modern version of the 'iron lung' called?
The 'shell'
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How does positive pressure artificial breathing work?
It forces a carefully measured breath of air into your lungs under a positive pressure. When the lungs are full the positive pressure is removed and the air flows out
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What method of positive pressure breathing is often used in emergency treatments?
Positive pressure bag ventilator (squeezed by hand)
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What is the advantage of positive pressure ventilation over negative pressure ventilation?
Patient does not have to be placed inside an iron lung machine so equipment can be used at home or when the patient is moving about; the patients also have some control over their machines
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What are food molecules turned into in the gut?
Simple, sugars, such as glucose, amino acids, fatty acids and glycerol
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Where must digested food molecules move from and to?
Your small intestine to your bloodstream
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What two processes are used to do this?
Diffusion and active transport
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Why do digested food molecules move by diffusion into the blood?
They are small enough to pass freely through the walls of the small intestine and there is a high concentration of food molecules in the gut and a much lower concentration in the blood
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What are villi?
Tiny finger-like projections or folds of the small intestine
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Why do these villi increase the rate of diffusion?
They greatly increase the surface area of the gut lining
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How is the surface area of villi further increased?
Each one is covered in microvilli
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How is a steep concentration gradient maintained in the small intestine?
The small intestine has a very good blood supply that carries away the digested food molecules as soon as they have diffused, this maintains the steep gradient
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When is active transport required to move digested food molecules from your small intestine into your blood?
When time has passed since your last meal and there are more dissolved food molecules in tour blood than in your digestive system. Active transport is used to move these food molecules against its concentration gradient
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What do plants use osmosis to do?
To take water from the soil
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What do plants use active transport to do?
To obtain mineral ions from the soil
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How does carbon dioxide get into plants?
Carbon dioxide diffuses into plants through their leaves
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What adaptations do the leaves have to make them fit for this purpose
They have a flattened shape to increase surface area, they are usually thin so the distance to diffuse is short, and they contain many air spaces in their structure to increase the number of cells that are in direct contact with the gas
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What is the problem with allowing carbon dioxide to freely diffuse all the time?
Water vapour would be lost from the leaves and the plant would die
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When do plants not need carbon dioxide?
During the night when there is no light or when there is only a small amount of light and the carbon dioxide produced in respiration is enough to allow photosynthesis
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What is a cuticle?
A waxy, waterproof and gas-proof layer
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How can carbon dioxide get through the waxy cuticle?
Through stomata; small openings that can open and close when necessary
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What cells control the opening and closing of the stomata?
Guard cells
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How are root cells adapted for taking up water?
They are thin, divided into tubes with a large surface area, root hair cells have tiny projections from the cells which push out between the soil particles
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Once the water has moved into the root hair cells by osmosis where does it go?
To the xylem where it is moved around the plant
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How are root cells adapted for taking up minerals?
They have a large surface area and plenty of mitochondria to provide energy for active transport
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Why do plants open their stomata?
To take in carbon dioxide for photosynthesis
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What is it called when water vapour is lost through stomata
Evaporation
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What is the transpiration stream?
A constant movement of water molecules through the xylem from the roots to the leaves, when water vapour evaporates out of the leaves water is dragged up the plant
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If something increases the rate of photosynthesis what effect will it have on the rate of transpiration?
It will increase this also
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Why are the rates of these two linked?
When the rate of photosynthesis is increased more stomata are opened to let in carbon dioxide, if more stomata are open then more water is lost by evaporation so transpiration also increases
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What conditions will increase the rate of evaporation and hence transpiration?
Hot, dry and windy conditions
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If a plant is in a very hot climate what is its cuticle likely to be like?
Very thick and shiny
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Where on the leaves are the majority of the stomata found?
On the underside
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What does the plant do if it is losing more water than it can take up?
It wilts, this is a protection mechanism to stop further loss of water
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What happens when a plant wilts?
The stomata close which stops photosynthesis and hence any more water loss
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Card 4

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What is the cytoplasm of a cell made up of?

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Card 5

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