Hard Stuff Flashcards
What is the definition for osmosis?
- Osmosis is the movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration.
- Osmosis is a type of diffusion - passive movement of water molecules from an area of high water concentration to an area of low water concentration.
What is a partially permeable membrane?
-A partially permeable membrane is just one with very small holes in it. So small, in fact, only tiny molecules (like water) can pass through them, and bigger molecules (e.g. sucrose) can’t.
Which way do the water molecules pass through the partially permeable me,brand in osmosis?
- Water molecules actually pass both ways through the membrane during osmosis this happens because water molecules move about randomly all the time.
- But because there are more water molecules on one side than on the others there’s a steady net flow of water into the region with fewer water molecules, i.e. into the stronger sugar solution.
What happens to the stronger sugar solution in osmosis?
-The strong sugar solution gets more dilute. The water acts like it’s trying to “even up” the concentration either side of the membrane.
Where is osmosis used in the human body?
- Water moves into and out of cells by osmosis.
- Tissue fluid surrounds the cells in the body - basically just water with oxygen, glucose and stuff dissolved in it. It’s squeezed out of the blood capillaries to supply the cells with everything they need.
- Tissue fluid will usually have a different concentration to the fluid inside a cell. This means that water will either move into the cell from the tissue fluid, or out of the cell, by osmosis.
What will happen if a cell is short of water?
- If a cell is short of water, the solution inside it will become quite concentrated (so has a lower water concentration).
- Usually means the solution outside is more dilute (so has a higher water concentration), and so water will move into the cell by osmosis.
What happens if a cell has lots of water in it?
-If a cell has lots of water, solution inside will be more dilute (so will have a higher water concentration), and water will be drawn out of the cell and into the fluid outside by osmosis.
What is an experiment you can do to show osmosis at work?
- Cut potato into cylinders, and get some beakers with different sugar solutions in them. One should be pure water, another should be a very concentrated sugar solution. Then you can have a few others with concentrations in between.
- Measure the length of the cylinders, (made of potatoes) then leave a few cylinders in each beaker for half an hour or so.
- Then you take them out and measure their lengths again.
- If the cylinders have drawn in water by osmosis, they’ll be a bit longer.
- If water has been drawn out, they’ll have shrunk a bit.
What are the different variables in the potato cylinder osmosis experiment?
- The dependant variable is the chip length.
- The independent variable is the concentration of the sugar solution.
- All other variables (volume of solution, temperature, time, type of sugar used, etc.) must be kept the same in each case (control variables) or the experiment won’t be a fair test.
What are the 3 ways substances move?
- Diffusion.
- Osmosis.
- And Active Transport.
In life processes what must the gases and dissolved substances move through?
-Some sort of exchange surface. The exchange. The exchange surface have to allow enough of the necessary substances to pass through.
How are exchange surfaces adapted to maximise effectiveness?
- They are thin, so substances only have a short distance to diffuse.
- They have a large surface area so lots of a substance can diffuse at once.
- Exchange surfaces in animals have lots of blood vessels, to get stuff into and out of the blood quickly.
- Gas exchange surfaces in animals (e.g. alveoli) are often ventilated too - air moves in and out.
Why does exchanging substances get more difficult in bigger and more complex organisms?
-The place where the substances are needed (or the waste is made) ends up being a long way away from exchange surfaces.
How is the structure of leaves adapted for letting gases diffuse in and out of cells?
-Carbon dioxide diffuses into the air spaces within the leaf, then it diffuses into the cells where photosynthesis happens. Leaf’s structure is adapted so that this can happen easily.
-Underneath of a leaf = an exchange surface. It’s covered in biddy little holes called stomata - carbon dioxide diffuses through them.
-Oxygen (produced in photosynthesis)/water vapour diffuse out through the stomata (water vapour lost over surface of leaf too, but most lost through stomata).
-Size of stomata controlled by guard cells. These
close stomata if plant is losing water faster than it is being replaced by the roots. Without these guard cells, plant would soon wilt.
How is the structure of a plant leaf adapted to being an exchange surface?
- Flattened shape of the leaf increases surface area of exchange surface so that’s more effective.
- Walls of the cells inside the leaf form another exchange surface. The air spaces inside the leaf increase the area of this surface so there’s more chance for carbon dioxide to get into the cells (for photosynthesis).
How does water leave the cells inside a leaf?
-The water vapour evaporates from the cells inside the leaf. Then it escapes by diffusion because there’s a lot of it inside the leaf and loss of it in the air outside.
When is evaporation quickest?
-Evaporation is quickest in hot, dry, windy conditions.
What is the thorax?
-The thorax is the top part of the body.
What is the thorax separated from the lower part of the body (the abdomen) by?
-The diaphragm.
What are the lungs protected by?
-The ribs.
Describe the path which air travels (from the mouth to the alveoli).
- Air you breathe goes through the trachea.
- This splits into two tubes called ‘bronchi’ (each one is ‘a bronchus’), one going to each lung.
- The bronchi split into progressively smaller tubes called bronchioles.
- The bronchioles finally end at small bags called alveoli where the gas exchange takes place.
What is ventilation?
-Breathing in and out.
What happens to the thorax when we breathe in?
- Intercostal muscles and diaphragm contract.
- Thorax volume increases.
- This decreases the pressure, drawing air in via the mouth (to balance the pressure in the thorax).
What happens to the thorax when we breathe out?
- Intercostal muscles and diaphragm relax.
- Thorax volume decreases.
- This increases pressure, so air is forced out via the mouth (to balance the pressure in the thorax).
What do artificial ventilators do?
- Ventilators are machines that move air (often with extra oxygen) into or out of the lungs.
- They help people who can’t breathe themselves, e.g. if they’re under general anaesthetic, or have a lung injury or disease.
What were old artificial ventilators like?
- They used to be a giant case (an ‘iron lung’) from the neck to the abdomen, with only the patient’s head poking out.
- Air was pumped out of the case, pressure dropped, the lungs expanded and so air was drawn into the lungs. Air pumped into the case had the opposite effect, forcing air out of the lungs.
- However, they could interfere with blood flow to the lower body.
What are artificial ventilators like nowadays?
- Nowadays, most ventilators work by pumping air into the lungs.
- This expands the ribcage - when they stop pumping, the ribcage relaxes and pushes air back out of the lungs.
- This doesn’t interfere with blood flow, but it can occasionally cause damage (e.g. burst alveoli) if the lungs can’t cope with the artificial air flow.
What is the job of the lungs and how do they do this job?
- The job of the lungs is to transfer oxygen to the blood and to remove waste carbon dioxide from it.
- To do this the lungs contain millions of little air sacs called alveoli where gas exchange takes place.
How are the alveoli specialised to maximise the diffusion of oxygen and CO2?
- They have an enormous surface area (about 75m^2 in humans).
- They have a moist lining for dissolving gases.
- They have very thin walls (shorter diffusion paths).
- They have a good blood supply.
Where are the villi and what do they do?
- The inside of the small intestine is covered in millions and millions of these tiny projections called villi.
- They increase the surface area in a big way so that digested food is absorbed much more quickly into the blood.
How are villi specialised for maximising food absorption?
- They have a single layer of surface cells (shorter diffusion/active transport path).
- A very good supply to assist quick absorption.
- Big surface area - maximise diffusion/active transport.
How does digested food move into the blood?
- Diffusion.
- Active Transport.
What are root hairs specialised for?
-Absorbing water and minerals.
How are root hairs specialised for absorbing eater and minerals?
- The cells on the surface of plant roots grow into long “hairs” which stick out into the soil.
- This gives the plant a big surface area for absorbing water and mineral ions from the soil.
- Most of the water and mineral ions that get into a plant are absorbed by the root hair cells.
How do root hairs take in minerals and why do they use this method?
-Active Transport - the concentration is usually higher in the root hair cell than in the soil around it, so minerals are taken up into the root hair cell by active transport as it goes against the concentration gradient, whereas diffusion is along the concentration, so would not explain why/how minerals are taken up into the root hair cell.
What is active transport?
- The movement of substances against a concentration gradient, so from an area of low concentration to an area of a high concentration.
- Active Transport needs energy from respiration to make it work.
- Active Transport also happens in humans, for example in taking glucose from the gut and from kidney tubules.
What is Active Transport used for in the human body?
- We need Active Transport to stop us starving.
- When there’s a higher concentration of glucose/amino acids in the gut they diffuse naturally into the blood.
- But - sometimes there’s a lower concentration of nutrients in the gut than there is in the blood.
- This means that the concentration gradient is the wrong way.
- So Active Transport allows nutrients to be taken into the blood as concentration gradient is other way around.
- Same process is used in plant roots - “Active transport”.
What are phloem tubes?
- Made of columns of living cells with small holes in the ends to allow stuff through.
- Transport food substances (mainly dissolved sugars) made in leaves to growing regions (e.g. new shoots) and storage organs (e.g. root tubers) of the plant.
- Transport goes in both directions.
What are xylem tubes?
- Xylem tubes take water up.
- Made of dead cells joined end to end with no end walls between them and a hole down the middle (so they are hollow).
- They carry water and minerals from the roots to the stem and leaves in the transpiration stream.
What is transpiration?
- Transpiration is the loss of water from the plant.
- Transpiration is caused by the evaporation and diffusion of water from inside the leaves.
- Transpiration = a side effect of the way leaves are adapted for photosynthesis. They have to have stomata in them so that gases can be exchanged easily. Because there’s more water inside the plant than in the air outside (from photosynthesis), the water escapes from the leaves through the stomata.
What is the transpiration stream?
- Water is lost from the leaves through evaporation and diffusion inside the leaves.
- This creates a slight shortage of water in the leaf, and so more water is drawn up from the rest of the plant through the xylem vessels to replace it.
- This in turn means more water is drawn up from the roots, and so there’s a constant transpiration stream of water through the plant.
What type of circulatory system do humans have?
-Double circulatory system.
What do the two circuits in the human double circulatory system do?
- The first one pumps deoxygenated blood (blood without oxygen) to the lungs to take in oxygen. The blood then returns to the heart.
- The second one pumps oxygenated blood around all the other organs of the body. The blood gives up its oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped out to the lungs again (to gain oxygen again and become oxygenated).
Describe the structure of the heart.
- The heart is a pumping organ that keeps the blood flowing around the body. The walls of the heart are made of muscle tissue.
- The heart has valves to make sure that blood goes in the right direction - they prevent it flowing backwards.
- It is made of four chambers (right atrium, right ventricle, left atrium and left ventricle) to pump blood around.
- It’s left and right side are the opposite way around (so the left side of the heart appears on our right side and vice versa).
How does the heart use its four chambers (right atrium, right ventricle, left atrium and left ventricle) to pump blood around?
- Blood flows into the two atria (right atrium or left atrium) from the vena carva and the pulmonary vein.
- The atria contract, pushing the blood into the ventricles.
- The ventricles contract, forcing the blood into the pulmonary artery and the aorta, and out of the heart.
- The blood then flows to the organs through arteries, and returns through veins.
- The atria fill again and the whole cycle starts over.
What are the three types of blood vessels?
- Arteries - these carry blood away from the heart.
- Capillaries - these are involved in the exchange of materials at the tissues.
- Veins - these carry the blood to the heart.
Describe the structure of an artery and why it is like this?
- The heart pumps blood out at high pressure so the artery walls are strong/elastic to withstand these high pressures.
- Walls are think compared to size of the hole down the middle (the “lumen”).
- They contain thick layers of muscle to make them strong, and elastic fibres to allow them to stretch and spring back.
Describe the structure of a capillary and why it is like this?
- Arteries branch into capillaries.
- Capillaries are really tiny (too small to see).
- They carry the blood really close to every cell in the body to exchange substances with them.
- They have permeable walls, so substances can diffuse in and out.
- They supply food and oxygen, and take away waste like CO2.
- Their walls are usually only one cell thick. This increases the rate of diffusion by decreasing the distance over which it occurs.
Describe the structure of a vein and why it is like this?
- Capillaries eventually join up to form veins.
- Blood is at a lower pressure in the veins so the walls don’t need to be as thick as artery walls.
- They have a bigger lumen (hole in the middle) than arteries to help the blood flow despite the lower pressure.
- They also have valves to help keep the blood flowing in the right direction.
What are the four main components in the blood?
- Red Blood Cells.
- White Blood Cells.
- Platelets.
- Blood Plasma.
What are red blood cells and how are they adapted to maximise their function?
- The job of red blood cells is to carry oxygen from the lungs to all the cells in the body.
- They have a doughnut shape to give a large surface area for absorbing oxygen.
- They don’t have a nucleus - this allows more room to carry oxygen/more room for more of the pigment haemoglobin.
- Contain red pigment called haemoglobin.
- In the lungs, haemoglobin combines with oxygen to become oxyhaemoglobin. In body tissues, the revers happens - oxyhaemoglobin splits up into haemoglobin and oxygen, to release oxygen to the cells.
What are white blood cells and how are they adapted to maximise their function?
- They can change shape to engulf unwelcome/foreign microorganisms.
- They produce antibodies to fight microorganisms, as well as antitoxins to neutralise any toxins produced by the microorganisms.
- Unlike red blood cells, they do have a nucleus.
What are platelets and what do they do?
- They are small fragments of cells. They have no nucleus.
- These help the blood to clot at a wound - to stop all your blood pouring out and to stop microorganisms getting in.
