In depth Triple Biology (1b)

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  • Created by: HarveyCB
  • Created on: 09-09-18 12:47
What is diffusion
The spreading out of particles from an area of higher concentration to an area of lower concentration
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In what substances does diffusion occur
Both solutions and gases, because the particles are free to move about randomly
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What is the simplest type of diffusion
When different gases diffuse through each other
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Where does diffusion occur in your body
Across cell membranes
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What can diffuse across cell membranes
Dissolved substances, but only small molecules
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Name some examples of substances that can diffuse across a cell membrane
Oxygen, glucose, amino acids and water
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What cannot diffuse across cell membranes
Big molecules such as starch and proteins
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Particles move randomly, what does this mean about diffusion
Particles can move from an area of low concentration to high
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Define net movement
The direction in which the majority of particles are moving in diffusion
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What is the rate of diffusion
How fast diffusion occurs
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What are the three factors that affect diffusion rate
Concentration gradient, temperature and surface area
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What is the concentration gradient
The difference in the concentration of particles (larger difference, steeper concentration gradient)
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How does concentration gradient affect rate of diffusion
The steeper the concentration gradient the faster the rate of diffusion, as the net movement from one side is greater
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How does temperature affect the rate of diffusion
The higher the temperature the faster the particles move, therefore increasing the rate of diffusion
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How does surface area affect the rate of diffusion
The larger the surface area, the faster the rate of diffusion, as more particles can pass through at once
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Give an example of cells specialised for diffusion
Epithelial cells. They have lots of small projections on the surface, formed from folds in the cell membrane. This increases surface area and therefore the rate of diffusion
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What is osmosis
The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
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What must always be included in the definition of osmosis
Partially permeable membrane
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What is a partially permeable membrane
A membrane with very small holes in it
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What can pass through a partially permeable membrane
Water
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What can't pass through a partially permeable membrane
Sucrose (a sugar)
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Water molecules move randomly, what does this mean about osmosis
The water particles can move from an area of low concentration to high
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What is osmosis a type of
Diffusion
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Which types of cells lose and gain water through osmosis
Both plant and animal cells
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What happens when a cell is short of water
The solution inside becomes concentrated (low concentration of water molecule), which results in osmosis into the cell
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What happens when the solution surrounding a cell is short of water
Osmosis from the cell into the solution occurs
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What are the dangers of over hydrated cells
They burst
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Why do sports drinks contain water and ions
To replace those lost by sweat
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What happens when your cells have too little water inside them
They can be permanently damaged
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What is the textbooks example experiment for osmosis
Placing potato into sugar solutions of different concentration to see the affect on the potatoes mass
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In the textbooks example, what should happen to the mass of the potato in pure water
It increases
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In the textbooks example, what should happen to the mass of the potato in a highly concentrated sugar solution
It decreases
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What is active transport
The movement of particles against the concentration gradient using energy from respiration
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What does active transport allow
The absorption of ions from very dilute solutions
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Give an example of a cell adapted for active transport
Root hair cells
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How are root hair cells adapted for active transport
They have a large surface area, and a thin cell membrane
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How are root hair cells also adapted, that makes osmosis easier
A large permanent vacuole with a highly concentrated solution in it (steeper concentration gradient)
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Where does active transport occur in humans
In the gut (but only sometimes), and the kidneys
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Why does active transport in the digestive system only sometimes occur
Because there is sometimes a higher concentration of glucose and amino acids in the gut than the blood
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Why is active transport in the gut necessary
To stop us from starving
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What do diffusion and osmosis not require that active transport does
Energy
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What are exchange surfaces
The surface across which diffusion, osmosis or active transport occur in multicellular organisms
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Give two examples of diffusion being used to get rid of waste products
Gas exchange and the diffusion of urea into blood plasma
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What is gas exchange
The transference of oxygen and carbon dioxide between cells and the enviroment
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What affects the ease with which an organism exchanges substances with its surrounding
The surface area to volume ratio (SA:V)
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A smaller surface area in comparison to volume means what
Any substance exchange is less efficient
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How does an organisms size affect the SA:V ratio
The larger an object the smaller its surface area is compared to the volume
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What units must the surface area and volume be in
It's does not matter as long as surface area is measured in x squared, and volume in x cubed
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What must you ensure when calculating the SA:V
The ratio is simplified (64:32 becomes 2:1)
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Why are exchange surfaces needed
Multicellular organisms have a smaller surface area compared to volume, so they need an exchange surface for efficient diffusion
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How are exchange surfaces adapted to maximise efficiency
Thin membranes, large surface area, lots of blood vessels, and for gas exchange surfaces in animals, they are ventilated
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Give three examples of gas exchange you need to know
Human (alveoli), plants (stomata) and fish (gills)
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What is the function of the lungs
To transfer oxygen to the blood and remove waste carbon dioxide
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What do the lungs contain to carry out gas exchange
Alveoli
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What is the singular of alveoli
Alveolus
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What surrounds the alveoli
A network of capillaries
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What gases diffuse in each direction
Oxygen from the air into the blood, and carbon dioxide from the blood into the air
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How does air leave the lungs
Through small tubes called bronchioles
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How are the alveoli adapted
Enormous surface area, moist lining for dissolving vases, thin walls and a good blood supply
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What is the approximate surface area of the alveoli in humans
75 m squared
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Where are the products of digestion absorbed
The small intestine
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What aids absorption in the small intestine
Tiny projections called villi
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What is the singular of villi
Villus
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How are villi adapted
They have a large surface area, a single layer of surface cells, and a good blood supply
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Why do plants need carbon dioxide
For photosynthesis
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Where is the gas exchange surface in leaves
Underneath the leaf
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What is a leafs exchange surface covered in
Tiny holes called stomata
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What is the singular of stomata
Stoma
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What diffuses through the stomata
Carbon dioxide, water vapour and oxygen
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How is the area of the exchange surface of a leaf increased
Through the flattened shape of the leaf
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Where is another exchange surface in a leaf
The walls of the cells inside the leaf, where there are lots of air spaces to increase surface area, and therefore the chance of carbon dioxide entering the cells
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How is water loss controlled in cells
Through the guard cells
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How do the guard cells work
They are on either side of the stomata, and open and close them
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What would happen without the guard cells
The plant would lose so much water it would begin to wilt
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Where does gas exchange occur in fish
In the gills
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How do the gills work
Water enters the fish's mouth, and leaves through the gills, through which oxygen from the water diffuses into the blood, and carbon dioxide into the water
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What is the gill made up of
Gill filaments, which are covered in tiny structures called lamellae
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What is the singular of lamellae
Lamella
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What is the purpose of the gill filaments and lamellae
To increase the surface area
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How are the lamellae adapted for gas exchange
They have a thin surface layer of cells, and lots of blood capillaries
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How is a large concentration gradient maintained in the lamellae
The blood and water flow in the opposite direction
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Other cards in this set

Card 2

Front

In what substances does diffusion occur

Back

Both solutions and gases, because the particles are free to move about randomly

Card 3

Front

What is the simplest type of diffusion

Back

Preview of the front of card 3

Card 4

Front

Where does diffusion occur in your body

Back

Preview of the front of card 4

Card 5

Front

What can diffuse across cell membranes

Back

Preview of the front of card 5
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