Circulation and Response

Question 1

Respiration

2.33 understand that the process of respiration releases energy in living organisms

Answer 1

Respiration is a reaction that occurs in all cells, in all organisms, all of the time to release energy from organic molecules such as glucose and lipid (fat).

Many organic molecules can be respired to release energy, but human normally use glucose, and resort to respiring fat when the glucose runs out.

Question 2

2.34 describe the differences between aerobic and anaerobic respiration

Answer 2

Aerobic respiration

Glucose + oxygen > carbon dioxide + water + energy

In this form of respiration all of the energy is released from the glucose as it is fully broken down. It is used for day to day life processes- like movement and reproduction- and keeping warm.

Anaerobic respiration

Glucose > lactic acid + energy

Anaerobic respiration takes place when the heart and lungs cannot work fast enough to provide to oxygen needed for aerobic respiration: for example when exercising The energy released is less in anaerobic respiration because the glucose cannot be fully broken down.
The lactic acid produced accumulates in muscles and can be painful as it changes the pH in the muscles. Once the exercise has stopped, blood will deliver oxygen to the muscles, which is used to break down the lactate (lactic acid) into carbon dioxide and water. This is known as the oxygen debt. Note that the time taken for the lactic acid to be removed and for the breathing and heart rate to return to normal is called the recovery period.

Question 3

2.35 write the word equation and the balanced chemical symbol equation for aerobic respiration in living organisms

Answer 3

Glucose + Oxygen > Carbon dioxide + Water + Energy

C6H12O6 + 6O2 → 6CO2 + 6H2O (+ energy)

Question 4

2.36 write the word equation for anaerobic respiration in plants and in animals

Answer 4

Glucose > Lactic acid + Energy

C6H12O6 > 2C3H6O3 + energy

In plants:
Glucose > ethanol + carbon dioxide + energy

C6H12O6 > 2C2H5OH + 2CO2

Question 5

2.37 describe experiments to investigate the evolution of carbon dioxide and heat from respiring seeds or other suitable living organisms.

Answer 5

To test for Carbon Dioxide Produced During Respiration

1. Put a small amount of red hydrogen-carbonate indicator into a test tube.
2. Lower a gauze platform into the tube with tweezers.
3. Put some living organisms (e.g soaked germinating seeds, small insects like woodlice) onto the platform. Seal the tube.

In a control tube, either put dead organisms in it or none at all. You can then be sure that the carbon dioxide is coming from the living processes in the organisms.

Hydrogen-carbonate indicator is usually red. When it mixes with carbon dioxide, the indicator will turn yellow.

To test for the effect of Temperature on the Rate of Respiration

• Using above method, set up the tube in a water bath at a controlled temperature.
• Time how long it takes for the hydrogen-carbonate indicator to turn yellow and then repeat the experiment at different temperatures.

To test for the Energy Released During Respiration

Germinating peas produce heat energy, whereas boiled (dead) peas do not.

1. Soak peas in water and mild disinfectant to start germination and kill microorganisms on the peas.
2. Boil half the peas.
3. Set up two thermos flasks, one with germinating peas and one with boiled peas. insert a digital thermometer, surrounded by cotton wool, into both flasks and connect them to a data logger supplied with power.
4. Record the temperature of both flasks after one week. as the germinating peas can respire, the heat will be higher whilst the boiled ones can’t therefore they remain at the same temperature

Question 6

5.5 understand the role of yeast in the production of beer

Answer 6

Yeast is added to ferment sugars into alcohol in beer.

Brewing Beer

1. Extracting sugar - barley seeds are mixed with water and allowed to sprout, turning the starch in the seeds into sugars.
2. Hops are added to give flavour to beer.
3. Yeast is added to ferment the sugars into alcohol. The mixture is kept warm so the yeast reproduces and respires.
4. The tank is sealed so the yeast can respire anaerobically producing alcohol. This also stops unwanted microorganisms spoiling the beer.
5. A chemical is added to make the yeast settle, leaving a clear liquid. This is called clarifying or clearing.
6. The beer is pasteurised by heating it to 72 degree C for 15 secs. This kills harmful microorganisms but doesn’t affect the taste.
7. The beer is bottled or put in sealed casks (bottling or casking)

Yeast must be filtered out (or killed by heat treatment) if the beer is going to be bottled. Otherwise it would continue to respire, producing carbon dioxide that would make the bottles explode.

Question 7

5.6 describe a simple experiment to investigate carbon dioxide production by yeast, in different conditions

Answer 7

Investigating Respiration Rate in Yeast

Apparatus: flasks, gas syringe, stopclock

Count the number of bubbles given off over a period of time, e.g. 1 min, 10 min etc. This experiment can be repeated at a range of different temperatures by standing the flask in a water bath.

The effect of varying the concentration glucose on the rate of respiration can aslo be tested by settling up flasks with a range of glucose concentrations. The same apparatus can be used to investigate the rate of respiration in different varieties of yeast.

Variables

The dependent variable is the rate of respiration, indicated by the number of bubbles of carbon dioxide per minute. Independent variables that can be tested are: temperature, concentration of glucose, type of sugar, and variety of yeast. Other variables that should be kept constant are: volumne of solution, mass of yeast used, time that you counted from start of experiment, and diameter of the delivery tube.

Control

A control flask can be set up, which contains boiled yeast that is then cooled, instead of using living yeast. The control should be tested in the same conditions as the experiment tube. Because the yeast is dead you can use it make sure that any gas produced in the experiment is from the respiration of the yeast, not from any other chemical reaction happening in the tube.

Improvement

The gas given off can be collected in a gas syringe to measure the volume of carbon dioxide produced per minute, as a more accurate way of investigating respiration rate.

Question 8

5.7 understand the role of bacteria (Lactobacillus) in the production of yoghurt

Answer 8

A live bacterial (Lactobacillus) culture is added to the warm milk. The mixture is incubated for several hours. The bacteria reporduce and feed on the lactose sugar in the milk, producing lactic acid, which gives a sharp taste to the yoghurt and thickens and preserves it.

Question 9

Making yoghurt

• Put milk in a saucepan and heat the milk to 80 degree celcius
• Pour the hot milk into a bowl and leave to cool to 46 degree celcius
• add the organisms needed to change the milk into yohurt
• pour yoghurt into glass jars and put them into a warm place for 8 hours
• pour the yoghurt into a sterile, airtight container and put it in the fridge.

Answer 9

Name an organism added to change the milk into yoghurt.

Lactobacillus/Streptococcus

Explain why the milk must be heated to 80 degree celcius

to kill the bacteria in the milk

Explain why the milk must be cooled to 46 degree celcius

to avoid killing the Lactobacillus organisms that make yoghurt
it’s the optimum temperature for the enzymes before they can be denatured

Explain why yoghurt is kept in a warm place for 8 hours

during this time, lactic acid is produced
warm temperature is optimum condition for enzymes and bacteria reproduction

Changes take place to the pH of the yoghurt when it is kept warm for 8 hours. Describe and explain how the change in pH helps to preserve the yoghurt.

• the bacteria produce and feed on the lactose sugar in the milk, producing lactic acid which changes the yoghurt to low pH. The lactic acid in the yoghurt also stops the growth of the bacteria and preserves it. The low pH denature the enzymes that caused the respiration.

Question 10

2.44 describe the structure of the thorax, including the ribs, intercostal muscles, diaphragm, trachea, bronchi, bronchioles, alveoli and pleural membranes

Answer 10

Thorax is a chest cavity that contains:

the trachea - a flexible tube, surrounded by rings of cartilage to stop it collapsing

bronchi - branches of the trachea

bronchioles - branches of a bronchus

lungs - to inhale and exhale air for gas exchange

alveoli (air sacs) - microscopic air sacs at the ends of bronchioles, where gases are exchanged

intercostal muscles - to raise and lower the ribs

pleural membranes - to protect and lubricate the surface of the lung

the diaphragm - a muscular ‘sheet’ between thorax and abdomen

Once air is breathed in through the mouth or nose it travels down the trachea. The trachea splits into two- one going into the left lung and one going into the right lung- these pipes are called bronchi. Each bronchus will then divide further into many bronchioles: each ending in a sac called an alveoli.

The trachea and bronchi have walls of muscle that are supported by cartilage. The cartilage is in partial rings so that the tubes can be moved in any direction. Cilia on the walls move mucus out of the breathing system and into the stomach.

Question 11

2.45 understand the role of the intercostal muscles and the diaphragm in ventilation

Answer 11

Breathing in: The diaphragm and intercostal muscles contract, so the ribs rise and the diaphragm flattens. The pressure inside the thorax falls and so air enters the lungs.

Breathing out: The diaphragm and intercostal muscles relax, so the ribs move down and the diaphragm moves up in the thorax. This increases the pressure inside the thorax, which pushes air out of the lungs.

Question 12

2.46 explain how alveoli are adapted for gas exchange by diffusion between air in the lungs and blood in capillaries

Answer 12

• There are millions of alveoli, surrounded by a dense network of blood capillaries, which provide an enormous surface area for gas exchange. Both the alveolus and the capillary wall (called the endothelium) are very thin, so short distance for gases to diffuse.
• Water lines the alveolus, so gases can dissolve, making diffusion easier.
• ** Rich blood** supply maintain concentration gradient, making diffusion in both direction more efficient.

Question 13

What is Gas Exchange?

Answer 13

Carbon dioxide diffuses from the blood into the alveolus, and oxygen diffuses from alveolus into the blood. This is called gas exchange.

Question 14

2.47 understand the biological consequences of smoking in relation to the lungs and the circulatory system, including coronary heart disease

Answer 14

• Stops the cilia in the trachea working, so dirt and pathogens get into the lungs
• Nicotine in smoke makes your heart beat faster and increases your blood pressure. Your heart then has to work harder.
• Carbon monoxide takes up haemoglobin, so smoker doesn’t have enough oxygen and can be breathless. The heart then has to pump harder to get oxygen needed around the body
• tar can cause the alveoli to break down, leading to emphysema
• Lung cancer- tar and other chemicals cause cells to mutate and form cancers in the lungs and throat.
• Substances in smoke increase the risks that arteries will become narrowed by fatty material (atheroma). This can cause heart attacks and strokes.
• Coronary heart disease is when atheroma narrows the coronary arteries. The coronary arteries then cannot supply as much oxygenated blood to the muscle of the heart.
• Smoking increase the risk that blood will clot - another cause of heart attacks and strokes.

Question 15

2.49 understand why simple, unicellular organisms can rely on diffusion for movement of substances in and out of the cell

Answer 15

Unicellular organisms- including fungi and bacteria- have a large surface area to volume ratio and they are small and so the diffusion distance is short, meaning diffusion happens very quickly.

Question 16

2.50 understand the need for a transport system in multicellular organisms

Answer 16

Multicellular organisms have a small surface area to volume ratio and the distance for diffusion would be very large and so very slow. This wouldn’t support the organism; so they have developed transport systems, like the ventilation system and the circulatory system which speed up diffusion enough to support themselves.

Question 17

2.48 describe experiments to investigate the effect of exercise on breathing in humans.

Answer 17

During exercise cells respire more quickly (to provide more energy for movement) this means oxygen has to be delivered more quickly and carbon dioxide taken away more quickly. As a result of this the lung muscles contract and relax more rapidly and the heart beats faster.

Simple experiment to investigate the effect of exercise on breathing rate

1. Sit still for five minutes and then count your breaths for one minute.
2. Now do some exercise for four minutes. e.g standing on and off a step, skipping or jogging on the spot, etc.
3. Immediately after you’ve finised exercising, count how many breaths you take in one minute
4. Record the change in number of breaths per minute before and after exercise.
5. Repeat the experiment a few times with different people.

Variables that you should keep the same include the time spent exercising and the type of exercise you do.

You should find that number of breath per minute increase during exercise. You’ll also find that the breathing rate stays higher than normal for serveral minutes after the exercise stops.

Question 18

2.64 explain how the heart rate changes during exercise and under the influence of adrenaline

This is a good source:
http://www.livestrong.com/article/355672-why-adrenaline-speeds-up-heart-rate/

Answer 18

During exercise, the muscle cells are respiring faster. They need more oxygen to do this and produce more cabon dioxide as a result. The heart rate increases to speed up the flow of blood and deliver oxygen faster, and to remove the extra carbon dioxide more efficiently.

Adrenaline is also secreted during exercise or when frightened. The adrenaline hormone, from adrenal glands, increases the heart and breathing rate, the blood sugar level and the rate of respiration. More energy is released in the muscles, so the body is ready for ‘action’.

Question 19

2.57 describe the composition of the blood: red blood cells, white blood cells, platelets and plasma

Answer 19

The blood has several different components.
55% of the blood is plasma: yellow liquid containing water with different things dissolved in it.
There are many red blood cells (Erythroeytes.)
There are less white cells: Phagosytes; lymphosytes.
Platelets (cell fragments) which play an important role in clotting.

Question 20

2.58 understand the role of plasma in the transport of carbon dioxide, digested food, urea, hormones and heat energy

Answer 20

Water- which is 90% of plasma- is a solvent and a liquid; so plasma carries carbon dioxide, digested food, urea, hormones and heat around the body disolved in water:

• digested food such as glucose, amino acids, fatty acids, glycerol, vitamins and minerals ( think of food pyramid)
• waste products. Amino acids are broken down in the liver to make urea. The kidney extract the urea, which we excrete in the urine.
• carbon dioxide, mainly carried as hydrogencarbonate ions HCO3-
• Hormones, and blood clotting factors
• heat. Water also carries heat, which is important in regulation of the body temperature.

Question 21

2.59 explain how adaptations of red blood cells, including shape, structure and the presence of haemoglobin, make them suitable for the transport of oxygen

Answer 21

• Red blood cells transport oxygen from lungs to the tissues. Red blood cells are small and flexible, so they can pass through narrow blood vessels.
• They don’t have nucleus, so they can be packed with haemoglobin.
• The small size and biconcave shape of red blood cells gives them a large surface area to volume ratio for obsorbing oxygen. When the cells reaches the lungs, oxygen diffuces from the lungs into the blood.
• The haemoglobin modules in the red blood cells binds easily with the oxygen to form oxyhaemoglobin.
• The blood is then pumped around the body to the tissues, where the reverse reaction takes place.
• Oxygen is released which diffuses into cells.

Question 22

2.60 describe how the immune system responds to disease using white blood cells, illustrated by phagocytes ingesting pathogens and lymphocytes releasing antibodies specific to the pathogen

Answer 22

If the microorganisms get into your body, your immnue system is activiated.

Two types of white blood cell are important in this response - phagocytes and lymphocytes.

Phagocytes

Phagocytes is activiated when the microorganism gets into the body.

• The phagocyte finds the microorganisms and engulfs them.
• The phagocytes ingests the microorganisms.
• The microorganisms have been digested and destroyed.

Lymphocytes

• Lymphocytes make antibodies. Antigens are markers on the surface of the microorganism.
• The lymphocyte becomes sensitised to the antigens and produces antibodies.
• The antibodies then lock onto the antigens.
• This cause the microorganism to clump together, so that phagocytes can digest them.

Some lymphocytes form memory cells so that if the pathogen gets into your body again it can be dealt with quickly before your are affected by the symptoms of illness. This secondary immune response is much faster and stronger than the first one.

Question 23

2.62 understand that platelets are involved in blood clotting, which prevents blood loss and the entry of micro-organisms

Answer 23

If the skin is cut, the exposure to the air stimulate the platelets and damaged tissue to produce a chemical. The chemicals in platelets cause soluble plasma protein fibrinogen in the blood into a insoluble fibres of another protein called fibrin. The network of fibrins forms a clot and then a scab as red blood cells become trapped in it.

Platelets are produced in the bone marrow- they are fragments of cells.

Question 24

2.63 describe the structure of the heart and how it functions

Answer 24

The heart can be thought of in four sections: the right atrium; the right ventricle; the left atrium; the left ventricle. A description of the workings of the heart:
The right atrium fills with blood (from the vena cava) and the valve is closed; This area is squeezed forcing the blood through an atrio-ventricular valve into the right ventricle; This area contracts forcing the blood through the pulmonary artery where it is oxygenated at the lungs; the pulmonary vein fills the left atrium with blood; This contracts forcing the blood into the left ventricle; when the left ventricle contracts the blood is forced out through the aorta.

Things to remember:

• Veins lead to the heart; arteries lead away.
• Atrium means entrance hall in Latin; hence the atrium is where blood enters the heart.
• The left side is bigger than the right as it has to pump blood through the whole body.
• You talk about the heart from right to left, as if you were examining someone’s heart and using their own left and right.

Question 25

2.65 describe the structure of arteries, veins and capillaries and understand their roles

Answer 25

Arteries, 10mm diameter on average

• Arteries carry blood away from the heart.
• Substances from the blood can’t pass through artery walls.
• They have thick, muscular, elastic walls in order to cope with the high pressure created when the heart beats.

Veins, 4mm diameter (average)

• Veins return blood to the heart.
• They have thinner walls than an artery and have less elastic muscular fibre because they do not have to cope with high pressure.
• They have valves to prevent blood flowing backwards.

Capillaries (0.005mm diameter), very narrow lumen

• Capillaries are tiny blood vessels whose walls are one cell thick so substances can diffuse easily
• The walls are permeable to allow exchange of substances between blood and the body cells.

Question 26

2.66 understand the general structure of the circulation system to include the blood vessels to and from the heart, the lungs, the liver and the kidneys

Answer 26

Vein- to the heart
Artery- away from heart
Lung- pulmonary
Liver- hepatic
Kidney- renal
Stomach- gastric
Between the gut and liver is the hepatic portal vein.