Biology Unit 2

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Define 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.
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Explain why the water molecules pass both ways through the membrane during osmosis.
This happens because water molecules move about randomly all the time.
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During osmosis, there are more water molecules on one side than on the other, there’s a…
Steady net flow of water into the region with fewer water molecules, i.e. into the stronger sugar solution. This means the strong sugar solution gets more dilute. The water acts like it’s trying to ‘even up’ the concentration either side of the m
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Osmosis is a type of diffusion. Define diffusion.
Passive movement of water particles from an area of high water concentration to an area of low water concentration.
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What is tissue fluid?
Tissue fluid surrounds the cells in the body – it’s 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.
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Describe and explain how tissue fluid helps water move into and out of cells by osmosis.
The 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.
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If a cell is short of water, the solution inside it will become quite concentrated. What does this mean, in terms of osmosis?
This usually means the solution outside is more dilute, and so water will move into the cell by osmosis.
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If a cell has lots of water, explain what happens to the solution inside, in terms of osmosis.
The solution inside it will be more dilute, and water will be drawn out of the cell and into the fluid outside by osmosis.
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Life processes need gases or other dissolved substances before they can happen. State 2 examples to support this.
1) For photosynthesis to happen, carbon dioxide and water have to get into plant cells. And for respiration to take place, glucose and oxygen both have to get inside cells. 2) Waste substances also need to move out of the cells so that the organism c
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In life processes, the gases and dissolved substances have to move through some sort of…
Exchange surface. The exchange surfaces have to allow enough of the necessary substances to pass through.
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When can 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.
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Apart from carbon dioxide, what else is diffused out through the stomata?
Oxygen (produced in photosynthesis) and water vapour also diffuse out through the stomata. (Water vapour is actually lost from all over the leaf surface, but most of it is lost through the stomata).
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Explain how the size of the stomata is controlled by guard cells.
These close the stomata if the plant is losing water faster than it is being replaced by the roots. Without these guard cells the plant would soon wilt.
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Describe the process of how water vapour diffuses out of the cells.
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 less of it in the air outside. Evaporation is quickest in hot, dry, windy conditions.
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Define Ventilation.
The movement of air into and out of the lungs. Remember, ventilation is different from respiration.
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What are ventilators? Include examples.
Ventilators are machines that move air (often with extra oxygen) into or out of the lungs. They help people who can’t breathe by themselves, e.g. if they’re under general anaesthetic, or have a lung injury or disease.
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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.
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Why can’t normal diffusion explain how minerals are taken up into the root hair cell.
The concentration of minerals is usually higher in the root hair cell than in the soil around it. They should go the other way if they followed the rules of diffusion.
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Explain how root hairs take in minerals using active transport.
Active transport allows the plant to absorb minerals from a very dilute solution, against a concentration gradient. This is essential for its growth. But active transport needs energy from respiration to make it work.
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Apart from in root hairs, where else does active transport happen? Include examples.
In humans, for example in taking glucose from the gut, and from the kidney tubules.
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Describe how active transport stops us from starving.
Active transport allows nutrients to be taken into the blood, despite the fact that the concentration gradient is the wrong way.
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When is active transport used in the gut?
When there is a low concentration of nutrients in the gut, but a high concentration of nutrients in the blood.
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Explain why transpiration is just 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, the water escapes from the leaves through the stomata.
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Explain what the circulatory system’s main function is.
To get food and oxygen to every cell in the body. It also carries waste products like carbon dioxide and urea to where they can be removed by the body.
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What is the heart?
The heart is the pumping organ that keeps the blood flowing around the body. The walls of the heart are mostly made of muscle tissue.
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Explain why the heart has valves.
The heart has valves to make sure that blood goes in the right direction – they prevent it flowing backwards.
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Why do capillaries have thin walls – only one cell thick?
Their walls are usually only one cell thick. This increases the rate of diffusion by decreasing the distance over which it occurs.
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What does the haemoglobin in red blood cells do in the lungs?
In the lungs, haemoglobin combines with oxygen to become oxyhaemoglobin. In body tissues, the reverse happens – oxyhaemoglobin splits up into haemoglobin and oxygen, to release oxygen to the cells.
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Explain why people would live in places with high altitudes, in terms of red blood cells.
The more red blood cells you’ve got, the more oxygen can get to your cells. At high altitudes there’s less oxygen in the air – so people who live there will produce more red blood cells to compensate.
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What would an ideal artificial blood product do?
Ideally, an artificial blood product would replace the function of the red blood cells, so that there’s no need for a blood transfusion. These are being developing but currently have problems with side effects.
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The Heart can be repaired with artificial parts. State the disadvantages of artificial hearts.
Surgery to fit an artificial heart can lead to bleeding and infection. Also, artificial hearts don’t work as well as healthy natural ones – parts of the heart could wear out or the electrical motor could fail.
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Blood doesn’t flow through artificial hearts as smoothly. Explain how this can prove to be a disadvantage in artificial hearts.
This causes blood clots and lead to strokes. The patients has to take drugs to thin their blood and make sure this doesn’t happen, which can cause problems with bleeding if they’re hurt in an accident.
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Define Coronary Heart Disease.
Coronary heart disease is when fatty deposits block the arteries that supply the blood to the muscle of the heart. This causes the arteries to become narrow and blood flow is restricted – this can result in a heart attack.
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Define Stents.
Stents are tubes that are inserted inside arteries. They keep them open, making sure blood can pass through to the heart muscles. This keeps the person’s heart beating (and the person alive).
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Stents are a way of lowering the risk of a heart attack in people with coronary heart disease. State what would happen over time.
Over time, the artery can narrow again as stents can irritate the artery and make scar tissues grow. The patient also has to take drugs to stop blood clotting on the stent.
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Define Homeostasis.
Homeostasis is the maintenance of a constant internal environment.
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There is a thermoregulatory centre in the brain that acts as your own personal thermostat. Explain how this controls body temperature.
It contains receptors that are sensitive to the temperature of the blood flowing through the brain. The thermoregulatory centre also receives impulses from the skin, giving info about skin temperature.
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Kidneys basically act as filters to ‘clean the blood’. State the three main roles that the kidneys perform.
1) Removal of urea from the blood. 2) Adjustment of ions in the blood. 3) Adjustment of water content of the blood.
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Kidneys basically act as filters to ‘clean the blood’. One of their main roles is to remove urea from the blood. Describe and explain how the kidneys remove urea fro the blood.
➢ Urea is poisonous. It’s released into the bloodstream by the liver. The kidneys then filter it out of the blood. It’s temporarily stored in the bladder in urine and excreted from the body.
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Ions such as sodium are taken into the body in food, and then absorbed into the blood. What would happen if the ion (or water) content of the body were wrong?
If the ion (or water) content of the body is wrong, this could upset the balance between ions and water, meaning too much or too little water is drawn into cells by osmosis. Having the wrong amount of water can damage cells or mean they don’t work
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Nephrons are the filtration units in the kidneys. Describe and explain the kidney function of releasing wastes.
The remaining substances (including urea) continue out of the nephron, into the ureter and down to the bladder as urine.
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How can people with kidney failure be kept alive?
By having dialysis treatment – where machines do the job of the kidneys. Or they can have a kidney transplant.
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The dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood. This means that…
Useful dissolved ions and glucose won’t be lost from the blood during dialysis.
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Dialysis machines filter the blood. State the disadvantages of this.
Dialysis may cause blood clots or infections.
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Eating foods containing carbohydrates puts glucose (a type of sugar) into the blood from the gut. Suggest 2 factors that remove glucose from the blood.
1) The normal metabolism of cells removes glucose from the blood. 2) Vigorous exercise removes much more glucose from the blood.
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Levels of glucose in the blood must be kept steady. Changes in blood glucose are monitored and controlled by the…
The pancreas monitors and controls the concentration of glucose in the blood. It produces a hormone called insulin.
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Fill in the gap. Insulin blood glucose level.
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What happens when the blood glucose level is TOO HIGH?
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Define Type 1 Diabetes
Type 1 Diabetes is a condition where the pancreas produces little or no insulin. The result is that a person’s blood glucose can rise to a level than can kill them.
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People inject insulin to help control their Type 1 Diabetes. How much insulin should be injected in a person?
The amount of insulin that needs to be injected depends on the person’s diet and how active they are.
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Insulin used to be extracted from the pancreases of pigs or cows, but now human insulin is made by…
Genetic engineering. This human insulin doesn’t cause adverse reactions in patients, like animal insulin.
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Suggest any disadvantages of insulin injections to help control a person’s blood glucose level.
It can’t be controlled as accurately as having a normal working pancreas, so they may still have long-term health problems.
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Other cards in this set

Card 2


Explain why the water molecules pass both ways through the membrane during osmosis.


This happens because water molecules move about randomly all the time.

Card 3


During osmosis, there are more water molecules on one side than on the other, there’s a…


Preview of the front of card 3

Card 4


Osmosis is a type of diffusion. Define diffusion.


Preview of the front of card 4

Card 5


What is tissue fluid?


Preview of the front of card 5
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