B3 Part A Flashcards
1
Q
What are the 3 main processes by which substances move within living organisms?
A
Diffusion, Osmosis and Active transport
2
Q
What is active transport?
A
Active transpiort is the process whereby substances are absorbed against a concentration gradient eg. from an area of lower concentration to an area of higher concentration.
3
Q
What is diffusion?
A
Diffusion is where particles move from an area of high concentration to an area where there’s lower concentration.
4
Q
What is osmosis?
A
Osmosis is a special type of diffusion, which consists of the passive movement of water moleules across a partially permeable membrane, from a region of high water concentration to a region of low water concentration.
5
Q
What is a partially permeable membrane?
A
A membrane with very small holes in it, so only tiny molecules (eg. water) can pass through, and bigger molecules (eg. sucrose) can’t.
6
Q
Water molecules pass both ways through partially permeable membranes in osmosis.
True or false? And why?
A
true because water molecules move about randomly.
7
Q
Fill in the gaps:
Because there will be more water ………… on one side of the membrane than on the other, in ……….. there will be a steady ……. …….. of water into the region with ……… water molecules.
A
Because there will be more water molecules on one side of the membrane than on the other, in osmosis there will be a steady net flow of water into the region with fewer water molecules.
8
Q
If there is a strong concentration of a sugar solution on one side of a membrane, and lots of water on the other side, how will osmosis impact on concentration?
A
The strong sugar solution will become more dilute, the water acts as though it is trying to make the concentration either side of the membrane more even.
9
Q
How is the concentration of substances within cells regulated by osmosis?
A
Tissue fluid (water with oxygen, glucose and other substances dissolved in it) surrounds all the cells in the body. The tissue fluid will have a different concentration to the fluid inside cells, meaning if a cell is short of water and the solution is concentrated, the tissue fluid will be more dilute and will move into the cell by osmosis. If a cell has lots of water, the solution inside it will be dilute and water will be drawn out of the cell and into the fluid outside by osmosis.
10
Q
Outline an experiment that can be conducted to show osmosis at work, using potatoes.
A
- Cut up a potato into identical cylinders, and get a number of beakers with different sugar solutions in them (with one being just pure water).
- Measure the length of the potato cylinders and leave a few in each beaker for half an hour or so. Then take them out and measure their lengths again.
- If the cylinders have drawn water in by osmosis, they’ll be longer than the original length, if the water has been drawn out they’ll have shrunk.
11
Q
How are exchange surfaces adapted to maximise effectiveness?
A
- They are thin, so substances only have a short distance to difffuse
- They have a larger surface so lots of a substance can diffuse at once
- Exchange surfaces in animals have lots of blood vessels, to get stuff in and out of the blood quickly.
- Gas exchange surfaces iin animals are often ventilated too - air moves in and out.
12
Q
Which substances diffuse out of the underside of leaves?
A
Oxygen and Water vapour
13
Q
How are leaves adapted to make them a good exchange surface?
A
- The underneath is covered in small holes called stomata, which are controlled by guard cells
- The flattened shape of the leaf increases surface area
- The walls of the cells inside the lead form another exchange surface, the air spaces inside increase the are of this surface so there’s more chance for carbon dioxide to get into the cells.
14
Q
How does water vapour leave plant leaves?
A
It evaporates from the cells inside the leaf, then escapes by diffusion because there’s lots of water vapour inside the leaf and less of it in the air outside.
15
Q
How are cacti adapted so that they don’t lose water when they absorb gas and photosynthesise more effectively?
A
The cells on the stem of a cactus have stomata-like holes to let gases in. These holes only open at night, when it’s cooler to prevent water being lost. Cacti are adapted so that they can store the CO2 that diffuses in at night until daylight when it’s used for photosynthesis.
16
Q
Where are the lungs situated in your body?
A
In the thorax (the upper part), separated from the abdomen by the diaphragm.
17
Q
What happens to air in your body when you breathe it in?
A
The air travels down the trachea (windpipe), which splits into two tubes called ‘bronchi’, one going to each lung. The bronchi split into progressively smaller tubes called bronchioles, which end at small bags in the lungs called alveoli, where gas exchange takes place.
18
Q
Draw and label a diagram of a cross section of the thorax (12 labels in total)
A
19
Q
Outline the process of ventilation (both breathing in and breathing out)
A
- Breathing in:*
1) Intercostal muscles and diaphragm contract
2) Thorax volume increases
3) This decreases the pressure, drawing air in - Breathing out:*
1) Intercostal muscles and diaphragm relax
2) Thorax volume decreases
3) This increases the pressure, so air is forced out
20
Q
Which two pieces of technology can be used to assist people to breathe?
A
- An ‘iron lung’ (no longer used)
- A modern medical ventilator
21
Q
Describe how an ‘iron lung’/negative pressure ventilator used to work
A
They encased a person from the neck to their abdomen, with only the patient’s head poking out. Air would be pumped out of the case, causing pressure to drop, the lungs of the patient to expand and air to be drawn into them. When air was pumped into the case, air would be forced out of the lungs as the pressure in the iron lung increased.
22
Q
How do modern-day respirators/positive pressure ventilators work?
A
Most ventilators work by pumping air directly into the lungs. This expands the ribcage - when they stop pumping, the ribcage relaxes and pushes air back out of the lungs.
23
Q
What are the advantages of using a modern-day medical ventilator rather than an iron lung?
A
- They’re portable
- Don’t confine the patients
- Useful during operations, when surgeons need access to the body
24
Q
What are the risks of both forms of artificial ventilator?
A
Iron lung/negative pressure: Can interfere with blood flow in the abdomen, leading to the pooling of blood
Modern respirator/psitive pressure: Can occasinally cause damage (eg. burst alveoli) if the lungs can’t cope with the artificial air flow
25
Draw and label a diagram of an alveoli, include the path of oxygen and carbon dioxide diffusion
26
How are alveoli specialised to maximise the diffusion of oxygen and carbon dioxide?
* An enormous surface area (about 75m2 in humans)
* A moist lining for dissolving gases
* Very thin walls
* A good blood supply
27
What are villi and how do they aid digestion?
Villi are tiny projections that cover the inside of the small intestine. They increase the surface are s digested food can be absorbed quicker into the blood.
They have a single layer of surface cells and a very good blood supply to assist quick absorption.
28
Draw and label a cross section of a villus
29
Which plant cells are specialised for absorbing water and minerals?
Root hair cells
30
Why must root hairs absorb minerals using active transport? And why is this a slight disadvantage?
The concentration of minerals is usually higher in the root hair cell than in the soil arund it. Normal diffusion doesn't work because the minerals must be carried against the concentration gradient.
Active transport requires energy from respiration to work
31
Outline one example of active transport being used in the human body
When there's a higher concentration of glucose and amino acids in the gut they diffuse naturally into the blood. However, sometimes there is a lower concentration in the gut than there is in the blood and this is where active transport must come into effect.
32
Phloem tubes in plants transport what substance? What are the tubes made of and in which direction does the transport flow?
Phloem tubes transport food substances (mainly dissolved sugars) made in the leaves to growing regions (eg. new shoots) and storage organs (eg. root tubers) of the plant.
Phloem tubes are made of columns of living cells with small holes in the ends to allow things to flow through.
The transport goes in both directions.
33
What are xylem tubes made of? What do they transport and in which direction?
Xylem tubes are made of dead cells joined end to end with no end walls between them and a hole down the middle.
They carry water and minerals up the plant, from the roots to the stem and leaves in the transpiration steam
34
What is transpiration and what is it caused by?
Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapour and is released to the atmosphere.
It is caused by evaporation and diffusion.
35
Explain why a transpiration stream occurs in plants
When transpiration occurs, it creats a slight shortage of water in the leaf, and so more water is drawn up frm the rest of the plant through the xylem vessels t replace it. In turn, this means more water is drawn up from the roots and so there's a constant transpiration stream of water through the plant.
36
How is transpiration a side-effect of photosynthesis?
Leaves have stomata in them so that gases can be exchanged easily in photosynthesis. Because there's more water inside the plant than in the air outside, the water escapes from the leaves through the stomata.
37
Humans have a double circulatory system. Outline what happens to the blood in each of these circuits.
* The first circuit pumps deoxygenated blood (blood without oxygen) to the lungs to take in oxygen. The blood then returns to the heart
* The second circuit 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.
38
Draw and label a cross section diagram of a heart
39
What are the walls of the heart made of and what is the purpose of their valves?
Walls of the heart are mostly made of muscle tissue. The heart has valves to make sure that blood travels in the right direction, they prevent it flowing backwards.
40
Describe the pathway of blood in the heart
1. Blood flows into the two atria from the vena cava (right atrium) and the pulmonary vein (left atrium).
2. The atria contract, pushing the blood int the ventricles
3. The ventricles cntract, forcing the blood into the pulmonary artery and the aorta, and out of the heart.
4. The blood then flows to the rest of the body's organs through arteries, and returns in veins
5. The atria fill again and the whole cycle starts over.
41
What are the three different types of blood vessel and what are their function?
Arteries - these carry blood away frm the heart
Capillaries - these are involved in the exchange of materials at the tissues
Veins - these carry blood to the heart
42
List three features of arteries
1. The heart pumps the blood out at a high pressure so the artery walls are **strong and elastic**
2. The walls are thick compared to the size of the whole down the middle (the lumen)
3. Arteries contain **thick layers of muscle** to make them strong and **elastic fibres** to allow them to stretch and spring back.
43
Arteries branch into capillaries. Give 5 features of capillaries.
* Capillaries are tiny, too small to see
* They carry 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 (eg. carbon dioxide)
* Their walls are usually only one cell thick, this increases the rate of diffusion as there is a shorter diffusion pathway involved.
44
Capillaries eventually join up to form veins. List three features of veins
1. The blood is at a lower pressure in the veins so the walls don't need to be as thick as artery walls.
2. Veins have a bigger lumen than arteries to help the blood flow, despite the lower pressure.
3. Veins have valves to keep blood flowing in the right direction.
45
What is the purpose of red blood cells?
To carry oxygen from the lungs to all the cells in the body.
46
List 3 features of red blood cells
1. They have a biconcabe shape to give a large surface area for absorbing oxygen
2. They don't have a nucleus - this allows more room to carry oxygen.
3. They contain a red pigment called haemoglobin.
47
What does haemoglobin do when it combines with oxygen?
Haemoglobin forms oxyhaemoglobin with oxygen in the lungs. In body tissues, the reverse happens - oxyhaemoglobin splits into haemoglobin and oxygen, to release oxygen to the cells.
48
What is the purpose of white blood cells?
They change shape to **engulf** 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.
49
What are platelets and what are their purpose?
Platelets are small fragments of cells (with no nucleus). They help the blood to clot at a wound, to prevent blood pouring out and microorganisms from getting in. Lack of platelets can cause excessive bleeding and bruising.
50
What is plasma?
Plasma is the pale straw-coloured liquid which carries everything in blood.
51
List everything that plasma carries
1. **Red** and **white blood cells** and **platelets**
2. **Nutrients like glucose and amino acids** (soluble products of digestion which are absorbed from the gut and taken to all cells)
3. **Carbon dioxide** from the organs to the lungs
4. **Urea** from the liver to the kidneys
5. Hormones
6. **Antibodies and antitoxins** produced by white blood cells
52
What is artificial blood and what is it used for?
Artificial blood is a blood substitute (eg. a saline solution), which is used to replace a lost volume of blood (when a person is severely injured).
53
What are the advantages of using artificial blood?
1. It's safe (if no air bubbles get into the blood)
2. Can keep people alive even if they lose 2/3rds of their red blood cells
3. Can give the patient time to produce enough new blood cells, and therefore reduce the need for a blood transfusion. A blood transfusion increases the risk of spread of disease.
(Artificial blood products that replace the function of red blood cells are being developed, but there are currently problems with side effects.)
54
What are the advantages of replacing a person's heart with an artificial one? (2)
1. They keep the person alive (often until a donor heart can be sourced)
2. Because they're made of metal/plastic, they won't be rejected by the body like 'foreign' living tissue
55
List some disadvantages of using a mechanical device to keep blood pumping round a person's body (4)
1. Surgery to fit one can lead to bleeding and infection
2. Parts of the heart could wear out, or the electrical motor could fail
3. Blood doesn't flow through them as smoothly, which can cause blood clots and lead to strokes
4. The patient has to take drugs to thin their blood, which can cause problems with bleeding if they're hurt in an accident
56
What are the benefits of only replacing a heart valve with an artificial one, rather than replacing a person's whole heart with a mechanical device? (3)
1. They can be very strong and durable, can often last a lifetime
2. The surgery is a much less drastic procedure
3. Artificial hearts have not been very successful in the long term, and are prone to blood clotting
57
What are the advantages of using biological valves (eg. from human or animal) or a donor heart when a person's heart fails? (2)
1. They do not damage red blood cells as they pass through the valves
2. Keep the patient alive, often more durable than artificial devices
58
Give some disadvantages of using biological valves/donor hearts when someon's own heart fails (4)
1. Sourcing donor hearts is a very long process, many people die on the waiting list
2. The body can reject 'foreign' living tissue
3. Biological valves are prone to becoming hardened over the course of several years
4. For patients with long life expectancy, there is a high chance of further operations to replace biological valves
59
What is coronary heart disease and why is it so life-threatening?
Coronary heart disease is when the **arteries** that supply the blood to the muscle of the heart get blocked by **fatty deposits.** This causes the arteries to become **narrow and the blood flow is restricted** - often resulting in **heart attack.**
60
What is a stent?
Stents are metal grids which can be inserted into an artery to maintain blood flow by keeping the artery open.
61
How are stents inserted?
To insert a stent, a *catheter* with a balloon attached to it is inserted into a blood vessel in the leg. The balloon has the metal stent on it. The catheter is directed to the coronary artery. When the narrowed section of artery is found, the balloon is inflated which causes the stent to expand, and it becomes lodged in the artery. The balloon is then removed and stent keeps the artery open so that the heart continues to receive enough oxygen to function effectively.
62
What is homeostasis?
Homeostasis is the maintenance of a constant internal environment.
63
What 6 things must be controlled to maintain homeostasis?
1. Body temperature
2. Water content
3. Ion content
4. Blood sugar levels
Waste products:
5. Carbon Dioxide
6. Urea
64
At what temperature do enzymes in the body work best?
37 °C
65
How does the thermoregulatory centre in the brain detect body temperature?
It contains receptors that are sensitive to the temperature of the blood flowing the brain. it also receives impulses from the skin, which inform it about skin temperature.
66
How will your body respond when you're too hot?
1. The **tiny hairs** on your skin will **lie flat**
2. **Sweat is produced** by sweat glands and evaporates from the skin, removing heat with it.
3. The **blood vessels** supplying to the skin **dilate** so more blood flows closer to the surface of the skin. This makes it easier for heat to be transferred from the blood to the environment.
67
How will your body respond when you're too cold?
1. **Tiny hairs stand up** to trap an insulating layer of air
2. **No sweat** is produces
3. **Blood vessels** supplying skin capillaries **constrict** to close off the skin's blood supply.
4. When you're cold, you **shiver** (your muscles contract automatically). This needs respiration, which releases some energy to warm the body.
68
Why does frostbite occur in people who are exposed to extreme cold for a long period of time?
The blood supply to their fingers and toes is cut off to save heat, killing cells and causing them to go black.
69
What are the three main roles of the kidney?
1. Removal of urea from the blood
2. Adjustment of ions in the blood
3. Adjustment of water content of the blood
70
How is urea produced and why must the kidney filter it out of the bloodstream? How is it removed from the body?
Proteins can't be stored by the body so any excess **amino acids are converted into fats and carbohydrates,** which can be stored. This process occurs in the liver and **urea is produced as a waste product**. Urea is **poisonous**, it's released into the blood stream by the liver. The kidneys then filter it out of the blood, it's **temporarily stored in the bladder in urin**e and excreted from the body.
71
Why must ion content in the body be controlled?
Ions (eg. sodium) are taken into the body in food and then absorbed into the blood. If the ion/water content of the body is wrong, it can mean too little water is drawn into cells by osmosis - causing them not to work as well as normal.
72
Which two ways is ion content controlled?
Excess ions can be removed and overall ion content is maintained by kidneys.
Some ions are lost in sweat.
73
By which three main ways is water lost from the body?
1. Excreted by kidneys in urine
2. In sweat
3. In the air (water vapour) we breathe out
74
How does external temperature affect the amount you sweat and the concentration of your urine?
On a **cold** day, you will **sweat much less** and and produce **more urine** which will be pale and **dilute**.
On a **hot day**, you will **sweat much more** and therefore produce **less urine,** which will be dark-coloured and **concentrated**.
75
Why do sports drinks contain water, sugar and ions?
The water and ions (eg. sodium) replace those lost in sweat, whilst the sugar can replace the sugar that's used up by muscle excersise.
76
Some sports drinks manufacturers claim that they can rehydrate you faster than normal water, what things should you look out for to validate these claims?
* If the claims are based on a scientific study, published by a non-biased body
* If this study used a large enough sample size to get reliable their results
* Have there been other studies, which found similar results?
77
What is the purpose of the nephrons in the kidney? Draw and label a diagram of one
Labels to include: bowman's capsule, glomerulus, collecting duct, blood capillaries
They are filtration units
78
Describe the filtration process, which occurs in the nephrons in the kidneys
1. A **high pressure** is built up, which squeezes water, urea, ions and sugar out of the blood and through the **membranes** between the blood vessels and the **Bowman's capsule**. They act like filters, so big molecules like proteins and blood cells are not squeezed out.
2. As the liquid flows along the nephron, **sugar, sufficent water and sufficent ions are reabsorbe**d into the blood capillaries via active transport.
3. The **remaining substances,** consisting of excess water, excess salts and urea, are **urine.**
4. The **collecting duct collects the urine**, which is then transported in the ureters to the bladder and excreted from the body.
79
What is renal failure and what does it cause?
Renal failure is the loss of function in the kidneys, which can cause waste substances to build up in the blood and can eventually result in death.
80
Which two methods can be used to treat renal failure?
1. Renal dialysis
2. Kidney transplant
81
Describe how a renal dialysis machine works (4 main steps)
1. A person's blood is made to flow out of their body and alongside a **selectively permeable barrier**, surrounded by **dialysis fluid**. It's permeable to things like ions and waste substances, but not big molecules likes proteins
2. The dialysis fluid has the **same concentration** of dissolved ions and glucose **as healthy blood**
3. This means **dissolved ions and glucose won't be lost from the blood during dialysis,** they can't diffuse across the membrance because no concentratin gradient exists.
4. Only **waste substances** (such as urea) and excess ions/water **diffuse across the barrier**, so they are removed from the person's blood and can be disposed of.
82
Why must renal dialysis machines be sterile? And why is dialysis fluid maintainsed at body temperature?
Renal dialysis machines are sterile to prevent infection. Dialysis fluis is maintained at body temperature to prevent the blood losing or gaining heat as it passes through the machine.
83
An anticoagulant (such as heparin) is added to blood as it passes through a renal dialysis machine, why?
Anticoagulants prevents clots forming.
84
What are the disadvantages of kidney dialysis?
* The patient must endure it a few times a week, for a few hours at a time.
* It requires the patient to remain still (often done when they're asleep)
* Can cause blood clots of infections
* Patients must follow a rigid diet
* It's expensive
85
Outline the process of a kidney transplant (3 steps)
1. A donor with a tissue type that closely matches the patient is selected (tissue type is based on antigens, which are proteins on the surface of most cells)
2. The kidney is surgically put into the patient's body.
3. Doctors give transplant patients immunosuppressant drugs that suppress the immune system to prevent it from rejecting the kidney.
86
What are the disadvantages of kidney transplants?
1. All major surgery carries risks
2. The kidney can be rejected by the body if the antigens on the surface are detected by the patient's immune system and white blood cells/antibodies seek to destroy the cells in the living kidney.
3. There is a shortage of donors
4. A precise match of tissue is neded
87
What are the advantages of kidney transplants?
1. They are a more permanent solution than dialysis treatment
2. Even people who are still alive can donate a kidney, as we all have two of them.
88
Which organs control blood glucose levels?
The pancreas and the liver
89
How do the pancreas and liver react when blood glucose levels are too high?
1. Insulin is secreted by the pancreas
2. Glucose will be removed from the blood by the liver
3. Insulin will enter the liver and cause it to convert glucose into glycogen
4. Overall blood glucose levels will decrease
90
What happens when blood glucose levels are too low?
1. Glucagon is secreted by the pancreas
2. Glucagon will cause the liver to turn stored glycogen into glucose
3. Glucose is secreted into the blood by the liver
4. Overall blood glucose levels will increas
91
What is Type 1 diabetes and why is it so dangerous?
Type 1 diabetes is a condition where the pancrease produces little or no insulin. This can result in a person's blood glucose levels rising to a point that can kill them.
92
By which two methods can Type 1 diabetes be controlled?
1. **Avoiding foods rich in simple carbohydrates** (eg. sugars) because the digestion of simple carbohydrates causes glucose levels to rise rapidly. It can even be helpful to **exercise** after eating to use up extra glucose produced during digestion
2. **Injecting insulin.** This will make the liver remove the glucose as soon as it enters the blood from the gut. The amount of insulin that needs to be injected depends on a person's diet and how active they are.
93
Where did insulin for insulin injections used to come from? And how is it producd now?
Insulin used to be extracted from the pancreases of pigs/cows and was purified. Now human insulin can be made by genetic engineering (inserting microorganisms with an insulin creating gene and creating the right conditions for them to duplicate themselves), which doesn't cause adverse reactions.
94
How might a diabetes be permanently cured?
A pancreas transplant, but this comes with all the risks of any other transplant (finding organ donor, rejection, infection, cost of immunosuppressive drugs that can often have side effects etc).
## Footnote
Research into artificial pancreases and stem cell research may eliminate the risk or organ rejection, but there's a way to go yet.
