Biology 3a Flashcards
What is osmosis?
The movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration
What is a partially permeable membrane?
A membrane with very small holes in it, so small that only tiny molecules like water can pass through them and bigger molecules like sucrose cant
Why do the water molecules pass both ways through the membrane during osmosis?
Because water molecules move about randomly all the time
If the molecules move about randomly, how is there a steady net flow of water into the region with fewer water molecules?
Because there are more water molecules on one side han on the other
What does this mean if there is a mixture of water and sucrose solution?
The sucrose solution would become more dilute as the water molecules have a steady net movement into that region, the water tries to “even up” the concentration on both sides of the membrane
What is osmosis a type of?
Diffusion-passive movement of water particles from an area of high water concentration to an area of low water concentration
How does water move into and out of cells?
Osmosis
What is tissue fluid?
Water with oxygen, glucose and other things disolved in it. It surrounds the cells in the body and is squeezed out of the blood capillaries to supply the cells with everything they need
The tissue fluid will usually have a different concentration to the fluid inside the cell, what does this mean?
That the water will either move into the cell from the tissue fluid or out of the cell by osmosis
What happens if a cell is short of water?
The solution inside it will become quite concentrated. This usually means the solution outside is more dilute and do water will move into the cell by osmosis
What happens if a cell has lots of water?
The solution inside it will be more dilute and water will be drawn out of the cell and into the fluid outside by osmosis
What is an experiment to show osmosis at work?
Cutting up potato into identical cylinders, adding them into beaker with different sugar solutions in them (one being pure water and another being very concentrated sugar solution and then others in-between) weigh the potato before and after
What does it mean if the potato is heavier afterwards?
It has drawn in water by osmosis
What does it mean if it weighs less after?
Water has been dawn out by osmosis
What is the dependent variable?
The mass of the cylinders at the start of the experiment
What is the independent variable?
The concentration of the sugar solution
Why must all the other variables be kept the same?
To keep it a fair test
Where does gas exchange happen?
In the lungs
What is the job of the lungs?
To transfer oxygen to the blood and to remove waste carbon dioxide from it
How do the lung perform their job?
They 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 a really big surface area (about 75m2), a moist lining for dissolving gases, very thin walls and a good blood supply
What do the villi do?
They provide a really big surface area
Where are villi found?
The inside of the small intestine is covered in them
Why is it good that they increase surface area?
It means that digested food is absorbed much more quickly into the blood
How are villi adapted?
They have a single layer of surface cells and a vert good blood supply to assist quick absorption
What is active transport?
It is the process when substances are absorbed against a concentration gradient (from a lower to a higher concentration)
What are root hair specialised to do?
They are specialised to absorb water and minerals
How are root hairs adapted?
The cells on the surface of plant roots grow until long hairs which stick out into the soil giving 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?
By active transport
Why is active transport used?
Because the concentration of minerals is usually higher in the root cell than in the soil around it so they need to be taken up into the root hair whereas diffusion would take them away into the soil
What does active transport do?
It allows the plant to absorb minerals from a very dilute solution, against a concentration gradient. This is essential for its growth however active transport needs energy from respiration to make it work
How is active transport used in humans?
When taking glucose from the gut and from the kidney tubules
Why do humans need active transport?
It stops us from starving as it is used in the gut when there is a low concentration gradient of nutrients in the gut, but a high concentration of nutrients in the blood
How does this work?
When it is higher in the gut, diffusion works but sometimes its lower in the gut and the concentration gradient is the wrong way so active transport has to be used
What are three ways that substances can be moved?
Diffusion, osmosis and active transport
Why are gases/other disolved needed?
For important life processes
What is an example of this?
Carbon dioxide and water need to get into plant cells for photosynthesis and glucose and oxygen have to get inside cells for respiration
What is an example of when substances are moved out of somewhere?
Waste products need to be taken out of organisms
What is diffusion?
When particles move from an area of high concentration to an area of low concentration e.g. gases diffuse through one another like air freshener, also dissolved particles can diffuse in and out of cells through cell membranes
What are the similarities between diffusion and osmosis?
They both involve things moving from an area of high concentration to a lower concentration
In life processes, where do gasses and dissolved substance need to move through?
An exchange surface
What is an exchange surface?
They are surfaces that are adapted to maximise effectiveness
How are exchange surfaces adapted?
They are thin so substances only have a short distance to diffuse, large surface area so lots of substance can diffuse at once, in animals they have lots of blood vessels to get things in and out of the blood quickly and gas exchange surfaces in animals are often ventilated so air moves in and out
When does exchanging substances become more difficult?
When its in bigger and more complex organisms because the place where the substances are needed (or the waste is made) ends up being a long way away from exchange surfaces
What gas diffuses in leaves?
Carbon dioxide diffuses into the air spaces within the leaf and then diffuses into the cells where photosynthesis happens, the leaf is adapted to do this
Where is the exchange surface on leaves?
Underneath the leaf, its covered in tiny holes called stomata which the carbon dioxide diffuses in through
What else diffuses out through the stomata?
Oxygen from photosynthesis and water vapour, water vapour is lost all over the leaf but mainly through the stomata
What do the guard cells do?
Control the size of the stomata, they close it if the plant is losing water faster than its being replaced by the roots, without the guard cells the plant would wilt
Why is it good that leaves are flat?
It increases the area of the exchange surface so its more effective
What are the cell walls used for?
Inside the leaf, they form another exchange surface, the air spaces inside the leaf increase the area of this surface so theres more chance for carbon dioxide to get into the cells
How does evaporation work?
The water vapour evaporates from the cells inside the leaf then it escaped by diffusion because theres lots of it inside the leaf and less of it in the air outside
Where does evaporation happen quickest?
In hot, dry, windy conditions
What is is the basic description of breathing?
Oxygen goes from air into bloodstream so it can get to your cells for respiration also you need to get rid of carbon dioxide in blood. All happens in the lungs. Breathing is how the air gets in and out of the lungs
Where are the lungs?
The thorax
What is the thorax?
The top part of your body, separated from the lower body (the abdomen) by the diaphragm
Where does the air go?
It goes through the trachea which splits into two tubes called the bronchi (single = bronchus) one goes to each lung.
What do the bronchi do as it gets nearer the lungs?
They split into progressively smaller tubes called bronchioles which finally end at small bags called alveoli where the gas exchange takes place
What are the parts of the breathing system?
Oesophagus, trachea, bronchiole, bronchus, alveoli, diaphragm, rib, heart, intercostal muscle
What is ventilation?
Breathing in and out
How do you breathe in?
Intercostal muscles and diaphragm contract, thorax volume increases which decreases the pressure drawing air in. Air goes in, muscles between ribs pull ribcage and sternum up and out, diaphragm flattens out
How do you breathe out?
Intercostal muscles and diaphragm relax, thorax volume which increases the pressure so air is forced out. Air is forced out, ribcage and sternum drop in and down, diaphragm moves up
What is the definition ventilation?
The movement of air into and out of the lungs
What are artificial ventilators?
Machines that move air and often oxygen into or out of the lungs. They help people who cant breathe by themselves e.g. if they’re under general anaesthetic or have a lung injury or disease
What did artificial ventilators used to be like?
A giant case (iron lung) from the neck to the abdomen with only the patients 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 affect, forcing air out of the lungs. however get could interfere with blood flow to the lower body
What are artificial ventilators like today?
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 cant cope with the artificial air flow
Where does gas exchange happen?
In the lungs
What is the job of the lungs?
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
What are alveoli specialised to do?
Maximise diffusion of oxygen and CO2
What do the alveoli have?
A very big surface area (about 75m2 in humans), a moist lining for dissolving gases, very thin walls and a good blood supply
What do the villi provide?
A really big surface area
Where are the villi?
The inside of the small intestine is covered in millions and millions of these tiny little projections-villi
What are the villi specialised to do?
Increase the surface area in a big way so that digested food is absorbed much more quickly into the blood
What do the villi have?
A single layer of surface cells and a very good blood supply to assist quick absorption?
How would a diagram be labeled of a villi (top to bottom)?
A villus, another villus, network of capillaries, gland cells, circular muscle, longitudinal muscle
What is active transport?
The process when substances need to be absorbed against a concentration gradient i.e. from a lower to a higher concentration
What are root hairs specialised to do?
Absorb water and minerals
How are these cells specialised?
The cells on the surface of the plant roots grow into long hairs which stick into the soil, this gives the plant a big surface area for absorbing water and mineral ions from the soil, most of the water/minerals that get into a plant are absorbed by root hair cells
How do root hairs take in minerals?
Active transport
Why do they need to use active transport?
The concentration of minerals is usually higher in the root hair cell than in the soil around it, so normal diffusion cant explain how minerals are taken up onto the root hair cell
When does active transport happen in humans?
Taking in glucose from the gut and from the kidney tubules. Its used in the gut when there us a low concentration of nutrients in the gut but a high concentration of nutrients in the blood
What does active transport allow?
The plant to absorb minerals from a very dilute solution against a concentration gradient, essential for growth but active transport needs energy from respiration to work
Why do we need active transport?
To stop us starving
What happens when there is a high concentration of glucose and amino acids in the gut?
They diffuse naturally into the blood
What happens when theres a lower concentration of nutrients in the gut than there is in the blood?
The concentration gradient is the wrong way so active transport is used to allow nutrients to be taken into the blood, despite the fact that the concentration gradient is the wrong way
What does the phloem tubes do?
They transport food substances mainly dissolved sugars, made in the leaves to growing regions e.g. new shoots and storage organs e.g. root tubers, of the plant
How do the phloem tubes do this?
They are made of columns of living cells with small holes in the ends to allow stuff to flow through
What way do phloem tubes transport food?
On both directions
What do the xylem tubes do?
They take water upwards. They carry water and minerals from the roots to the stem and leaves in the transpiration stem
How do the xylem tubes do this?
They’re made of dead cells joined end to end with no end walls between them and a hole down the middle
What is transpiration?
The loss of water from the plant
What is transpiration caused by?
The evaporation and diffusion of water from inside the leaves
What does transpiration create?
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 theres a constant transpiration stream of water through the plant
Why does transpiration happen?
Its 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 theres more water inside the plant than in the air outside, the water escapes from the leaves through the stomata
What is the circulatory systems main function?
To get food and oxygen to every other cell in the body. As well as being a delivery service, its also a waste collection service, it caries waste products like carbon dioxide and urea to where they can be removed from the body
What does the first circulatory system do?
Pumps deoxygenated blood to the lungs to take in oxygen, the blood then returns to the heart
What does the second circuit do?
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
What does the heat do?
It is a pumping organ that keeps the blood flowing around the body.
What are the walls of the heart mostly made up of?
Muscle tissue
What do the heart valves do?
They make sure that blood goes in the right direction and prevent it going backwards
What are the four chambers in the heart?
The right atrium, right ventricle, left atrium and left ventricle
What is the process of the circulatory system?
Blood flows into the two atria form the vena cava (right side) and the pulmonary vein (left side). The atria contact pushing the blood into the ventricles. The ventricles contract, forcing the blood into the pulmonary artery (right side) and the aorta (left side) and out of the heart. The blood then flows to the organs through arteries, then returns through veins. The atria fills again and the whole process repeats
What are the three types of blood vessels?
Arteries (carry blood away from heart), capillaries (involved in the change of materials at the tissues) and veins (carry blood to the heart)
What do arteries do?
Carry blood under pressure
How can arteries do this?
The heart pumps the blood out at high pressure so the artery walls are strong and elastics, the walls are thick compared to the size of the hole down the middle (lumen), they contain thick layers of muscle to make them strong, and elastic fibres to allow them to stretch and spring back
What do arteries branch into?
Capillaries
How big are capillaries?
Very small-too small to see
What do capillaries do?
They carry the blood really close to every cell in the body to exchange substances with them
How are capillaries adapted?
They have permeable walls, so substances can diffuse in and out, they supply food and oxygen and take away waste like CO2. Also their walls are usually only one cell thick, this increases the rate of diffusion by decreasing the distance over which it occurs
What do veins do?
They take blood back to the heart
Where are veins from?
Capillaries eventually join up to form veins
Why don’t veins need to be as thick as arteries?
The blood is at a lower pressure in the veins, however they have a bigger lumen 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 do red blood cells do?
Carry oxygen from the lungs to all the cells in the body
How are red blood cells adapted?
Concave shape to give a large surface area for absorbing oxygen, no nucleus so more room for oxygen and they contain a red pigment called haemoglobin
What is haemoglobin?
In the lungs, haemoglobin combines with oxygen to become oxyhemoglobin. In body tissues, the reverse happens, oxyhemoglobin splits up int haemoglobin and oxygen to realise oxygen to the cells
What do white blood cells do?
They defend against disease
How are white blood cells adapted?
They can change shape to kill unwelcome microorganisms, they produce antibodies to fight microorganisms as well as antitoxins to neutralise any toxins produced by the microorganisms, unlike red blood cells, they have a nucleus
What are platelets ?
Small fragments of cells, they have no nucleus
What do platelets do?
They help the blood to clot at a wound to stop losing too much blood and to stop microorganisms getting in
What happens if you have a lack of platelets?
Can cause excessive bleeding and bruising
What is plasma?
The liquid that carries everything in blood
What does plasma carry?
Red and white blood cells, platelets, nutrients like glucose and amino acids (soluble products of digestion absorbed from gut to cells in body), carbon dioxide form organs to lungs, urea from liver to kidneys, hormones and antibodies and antitoxins produced by the white cells
What happens when someone loses a lot of blood e.g. in an accident?
Their heart can still pump the remaining red blood cells around to get oxygen to their organs, as long as the volume of their blood can be topped up
What is artificial blood?
A blood substitute e.g. saline, a salt solution, used to replace the lost volume of blood. Safe is no air bubbles get in blood, and keeps people alive even if they lose 2/3 of their red blood cells, can give them enough to to produce new blood cells
What happens if artificial blood isn’t enough?
They would need a blood transfusion
What are artificial hearts?
Mechanical devices put into a person to pump blood if their own heart fails, usually used as a temporary fix to keep a person alive until a donor heart can be found. In some cases they’re a permanent fix which reduces the need for a donor heart
What is the main advantage of artificial hearts?
Less likely to be rejected by the boys immune system than donor hearts because they’re made from metals or plastics so the body doesn’t recognise them as foreign and attack in the same way as it does with living tissue
What are disadvantages of artificial hearts?
The surgery to fit them can cause infection and bleeding. They don’t work as well as healthy natural ones as parts of it can wear out or the electrical motor could fail. Also blood doesn’t flow through artificial hearts as smoothly, causing blood clots leading to strokes, patient has to take blood thinners to avoid this though can cause problems if they’re in an accident
What happens if its just the heart valves that are defective?
They can be replaced with mechanical valves which is a much less drastic procedure than a whole heart procedure. Fitting them is still a major surgery though and can still be problems with blood clots
What is coronary heart disease?
When the arteries that supply blood to the muscle of the heart gets blocked by fatty deposits causing the arteries to become narrow and blood flow is restricted can result in heart attacks
What are stents?
Tubes that are inserted inside arteries to keep them open, making sure blood can pass through the heart muscles, keeping a persons heart beating
What are the advantages of stents?
Way of lowering the risk of a heart attack in people with coronary heart disease
What are the disadvantages of stents?
Over time, the artery can narrow again as stents can irritate the artery and make scar tissue grow. The patient also has to take drugs to stop blood clotting on the stent
What is the definition of homeostasis?
The maintenance of a constant internal environment
What are the four things that need to be controlled so there is the right amount?
Temperature, water, ion content and blood sugar
What two things need to be controlled as they need to be gotten rid of?
Carbon dioxide and urea
Why does water content need to be controlled?
Cant get too high or too low, too much water could move into or out of cells and damage them
Why does ion content need to be controlled?
If its wrong then cells can be damaged
Why do blood sugar levels need to be controlled?
They need to stay within certain limits
Why does carbon dioxide need to be controlled?
Its a product of respiration and is toxic in high quantities so its got to be removed. It leaves the body by the lungs when you breathe out
Why does urea need to be controlled?
Its a waste product made from excess amino acids
Why must body temperature be controlled?
Enzymes work best at a certain temperature, in the human body they work best at 37 degrees C. If its too hot or too cold, the enzymes wont work properly and some really important reaction could be disrupted, in extreme cases this can lead to death
What is the process of your body responding to your temperature?
Thermoregulatory centre in the brain which acts like a thermostat, contains receptors that are sensitive to the temperature of the blood flowing through the brain, thermoregulatory centre also receives impulses from the skin, giving info about skin temperature, then your body can respond if your too hot or too cold
What is it called when you’re too hot and you don’t cool down?
Hyperthermia
What happens when you get too hot?
Vasodilation-hair lies flat, sweat is produced by sweat glands and evaporates from skin which removes heat. The blood vessels supplying the skin dilate so more blood flows close to the surface of the skin making it easier for the heat to be transferred from the blood to the environment
What is it called when you’re too cold and cant control heat loss?
Hypothermia
What happens when you get too cold?
Vasoconstriction-hair stands up to trap insulating layer of air, no sweat is produced, blood vessels supplying skin capillaries constrict to close off the skins blood supply, when you’re cold you shiver too (muscles contract automatically) which needs respiration that releases some energy to warm the body
What do kidneys act as?
Filters to clean the blood
What are the three main roles of the kidneys?
Removal of urea from blood, adjustment of ions in the blood and adjustment of water content of the blood
How is urea produced?
Proteins cant be stored by the body so any excess amino acids are converted into fats and carbohydrates which can be stored and urea is a waste product of this reaction
Where does this reaction take place?
In the liver
Why and how is urea removed?
Its poisonous, its released into the bloodstream by the liver. The kidneys then filter it out of the blood, its temporarily stored in the bladder in urine an excreted from the body
How are ions taken into the body?
Ions such as sodium are taken into the body in food and then absorbed into the blood
What happens if the ion content (or water content) is wrong?
Can 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 as well as normal
How are excess ions removed?
By the kidneys e.g. a salty meal will contain far too much sodium and so the kidneys will remove the excess sodium ions from the blood, some are also lost in sweat but the balance is always maintained by the kidneys
How is water taken into the body?
As food and drink and is lost from the body in three main ways
What are the three main ways that water is lost?
Urine, swear and in the air we breathe out
We cant control how much we lose in our breath but we control other factors, what is the water balance between?
Liquids consumed, amount sweated out and amount excreted by the kidneys in the urine
Why do you produce more urine on a cold day (pale/dilute)?
Water isn’t lost through sweat
What do sports drinks do?
Replace lost water, sugar and ions to help keep things in order, they replace whats lost in swear and the sugar thats used up by muscles during exercise
What do some manufacturers claim about their sports drinks?
That they rehydrate you faster than plain water or improve your endurance
What are nephrons?
The filtration units in the kidneys
What is ultrafiltration?
A high pressure is built up which squeezes water, urea, ions and sugar out of the blood, into the bowmans capsule. The membranes between the blood vessels and the Bowmans capsule act like filters so big molecules like proteins and blood cells are not squeezed out and stay in the blood
What is inside a nephron
Blood from renal artery, bowmans capsule, capillary network, blood to renal vein, collecting duct and urine
What is reabsorption?
As the liquid flows along the nephron, useful substances are reabsorbed back into the blood, all sugar is reabsorbed involving active transport against the concentration gradient, sufficient ions are reabsorbed but not excess ions and active transport is needed, and sufficient water us reabsorbed
What is the release of wastes?
The remaining substances including urea, continues out of the nephron into the ureter and down to the bladder as urine
What happens if the kidneys don’t work properly?
Problems can be caused in heart, bones, nervous system, stomach, mouth etc. Waste substances build up in the blood and you lose your ability to control the levels of ions and water in your body eventually resulting in death
How can people with kidney failure be kept alive?
Dialysis treatment where machines do the job of the kidneys or they can have a kidney transplant
Why does dialysis need to be done regularly?
To keep the concentration of dissolved substances in the blood at normal levels and to remove waste substances
What happens in a dialysis machine?
The persons blood flows alongside a selectively permeable barrier surrounded by dialysis fluid, its permeable to things like ions and waste substances but not big molecules like proteins (like membranes in the kidney)
What is in the dialysis fluid?
It 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, only waste substances such as urea and excess ions and water defuse across the barrier
How often do people with kidney failure need to have a dialysis session?
Three times a week, each session takes 3-4 hours
What is another disadvantage of dialysis?
It can cause blood clots or infections
Whats the disadvantage of a donor kidney?
It can be rejected by the patients immune system-the foreign antigens on the donor kidney are attacked by the patients antibodies
What can precautions can be taken to prevent this happening?
A donor with a tissue type that closely matches the patient is chosen. Tissue type is based on antigens which are proteins on the surface of most cells. Also the patient is treated is treated with drugs that suppress the immune system, so that their immune system won’t attack the transplanted kidney
What does insulin and glucose control?
Blood glucose levels
How does glucose get into the body?
Eating foods containing carbohydrates puts glucose (a type of sugar) into the blood from the gut
How is glucose usually removed from the blood?
The normal metabolism of cells remove glucose from the blood and also vigorous exercise removes much more glucose form the blood
Why must levels of glucose in the blood be kept steady?
Changes in blood glucose are monitored and controlled by the pancreas, using the hormones insulin and glucagon
What happens when blood glucose levels are too high?
Insulin is added
What is the process of this?
Blood has too much glucose, insulin recreated by pancreas, glucose is removed by liver, insulin makes liver turn glucose into glycogen and blood glucose is reduced
What happens when blood glucose levels are too low?
Glucagon is added
What is the process of this?
Blood has too little glucose, glucagon secreted by pancreas, glucose is added by liver, glucagon makes liver turn glycogen into glucose and blood glucose is increased
What is type 1 diabetes caused by?
A lack of insulin
What is type 1 diabetes?
A condition where the pancreas produces little or no insulin, the result is that a persons blood glucose can rise to a level that can kill them
How can this be controlled?
Living the intake of foods rich in simple carbohydrates i.e. sugars which cause the blood glucose level to rise rapidly, regular exercise which helps to lower the blood glucose level and insulin therapy
What is insulin therapy?
Injecting insulin into the blood. People with type 1 diabetes usually have several injections of insulin throughout the day which are likely to be at mealtimes. This makes sure that glucose is removed from the blood quickly once the food has been digested. This stops the level of glucose in the blood from getting too high and is a very effective treatment
What does the amount of insulin needed to be injected depend on?
The persons diet and how active they are
How did insulin used to be extracted and how is it extracted now?
From the pancreas of pigs or cows but now human insulin is made by genetic engineering, this new insulin doesn’t cause adverse reactions in patients like animal insulin did
Why can there still be long term health problems with insulin injections?
They cant control insulin levels as accurately as a normal working pancreas
What is a pancreas transplant?
Diabetics can have this, a successful operation means they won’t have to inject themselves with insulin again but as with any organ transplant, your body can reject the tissue, if this happens, you have to take costly immunosuppressive drugs which often have serious side effects
How is modern research trying to eliminate organ rejection?
Researching artificial pancreases and stem cell research
