Issy 3rd Form Biology

Question 1

Give 3 relationships Between Organisms.

Organisms are dependent on one another for these reasons

Answer 1

1) provide a food source (any organism that is consumed).
2) They help with pollination (insects such as bees).
3) They help provide shelter (some species of tree).

Question 2

Some organisms can affect their environment and often impact other species negatively.
Give an example

Answer 2

When a species over hunts a particular population causing them to die out - this can have implications for other organisms.

Question 3

Give 4 examples of impacts that humans have on the environment

Answer 3

1) If pollutants from humans make it into the environment, this can cause an accumulation of toxins in certain apex predators.
2) This can kill the predators.
3) Pollution can also affect habitats such as acid rain killing forests.
4) Large-scale destruction of habitats (e.g. cutting down a rainforest) can have a huge effect on the organisms who live in that environment.

Question 4

Name 5 organelles in an animal cell and explain their function.

Answer 4

1) The cell membrane controls what can go into or out of the cell.

2) The nucleus controls the cell and holds all your genetic material. Your genetic material is called your DNA.

3) The cytoplasm is a jelly-like substance, where the chemical reactions happen inside cells.

4) Mitochondria use up oxygen and nutrients, such as sugar, in order to release energy in respiration.

5) Ribosomes are tiny structures where protein synthesis occurs.

Question 5

Name 8 organelles in a plant cell and describe their function

Answer 5

1) The cell wall gives the plant cell structure and protection, made from cellulose.

2) Vacuoles contain cell sap and can store sugar that has been made from photosynthesis.

3) The chloroplasts contain chlorophyll, which absorbs light energy for photosynthesis, and contains enzymes for photosynthesis.

4) The cell membrane controls what can go into or out of the cell.

5) The nucleus controls the cell and holds all your genetic material. Your genetic material is called your DNA.

6) The cytoplasm is a jelly-like substance, where the chemical reactions happen inside cells.

7) Mitochondria use up oxygen and nutrients, such as sugar, in order to release energy in respiration.

8) Ribosomes are tiny structures where protein synthesis occurs.

Question 6

What is diffusion?

Give two examples

Answer 6

Substances can enter and leave cells in a process called diffusion. They move from areas of high concentration to areas of low concentration.

Question 7

What are cells adaptations?

Answer 7

Cells are adapted to do a particular role for a certain purpose.

This is why life on earth has evolved.

Question 8

What is a flagellum and what type of cells have them?

Answer 8

A flagellum is another word for a tail.
Flagella help some single-celled organisms move around the habitat, lets them find food, move to more favourable conditions, or avoid being eaten.

Question 9

what is a cell?

Answer 9

The basic building block of all organisms.

Question 10

what is an organelle?

Answer 10

A specialised unit within a cell which performs a specific function.

Question 11

What is a tissue?

Answer 11

A group of cells working together to perform shared function, often with similar structure. e.g muscle

Question 12

What is an organ?

Answer 12

A structure made up of groups different tissues, working together to perform specific functions

Question 13

What is an organ system?

Answer 13

A group of organs with related functions, working together to perform certain functions within the body.

Question 14

What is an organism?

Answer 14

When more than one organ system work together to perform a job.

Question 15

How do muscles work?

Answer 15

Muscles work by contracting and relaxing.

Question 16

What are antagonistic muscles?

Answer 16

In an antagonistic muscle pair, one muscle contracts and the other relaxes or lengthens.

the muscle that contracts is called the agonist.

the muscle that relaxes or lengthens is called the antagonist.

Question 17

Name the 5 Functions of the skeleton

Answer 17

1) Movement- bones act as levers and form joints.
2) Protection and support - hard bone protects soft tissues underneath
3) blood cell production in the bone marrow.
4) storage of minerals - bones are made up of and store calcium and phosphorus, which can be used in other parts if the body if required.
5) attachment of muscles. bones provide surfaces for the attachment of muscles.

Question 18

What are connective tissues?

Answer 18

Ligaments connect bone to bone L B B
tendons connect muscle to bone.
cartilage prevents bones from scratching. found on the end of bones.

Tendons connect bone to muscle T B M

Question 19

Identify the 6 Components of a balanced diet.

Answer 19

1) Carbohydrates- starches and sugar
2) Lipids (Fats)- oils and fats
3) Protein- made of amino acids
4) Water
5) Fibre- indigestible plant material
6) Vitamins- organic
Minerals- inorganic

Question 20

Explain the role of the Components of food

Answer 20

Carbohydrates - a slow release energy source.
Lipids (fats) - a fast release energy source.
Proteins - for growth and repair of tissues.
Vitamins - help prevent deficiency diseases.
Minerals - are needed for key chemical processes in your body.
Fibre - helps keep you regular and avoid constipation.
Water - so that you can stay hydrated.

Question 21

Deficiency diseases

Answer 21

Scurvy comes from not eating enough vitamin C. It causes issues in your connective tissues.

Rickets comes from not eating enough vitamin D which is vital for bone development so not consuming enough leads to a softening of your bones. Rickets gives you bowed legs.

Goitre comes from not eating enough iodine. The thyroid gland in your neck swells up.

Anaemia comes from not eating enough iron. It is where you don’t have enough red blood cells. Iron is a key component of haemoglobin, the chemical that transports oxygen around your body. This is why blood has a metallic taste.

Question 22

Factors which affect the amount of food you need

Answer 22

Gender
Age
Energy levels - amount of exercise

Question 23

Average calorie requirement for adults

Answer 23

Men 2500 kcals
women 2000 cals

Women 2000 kcals

Question 24

Define digestion

Answer 24

Breaking down the food you have taken in into small and soluble molecules that can be taken in and processed by the body.

Question 25

What substances enable digestion

Answer 25

Enzymes, which are biological catalysts, help chemically break down the food on its journey through the digestive system.

Question 26

What are the roles of the mouth and oesophagus in digestion.

Answer 26

The mouth is responsible for mechanically breaking down the food (chewing) as well as releasing some enzymes stored in your saliva - amylase

The oesophagus or gullet transports food from the mouth to the stomach.

Question 27

what was the role of the stomach in digestion?

Answer 27

The stomach’s muscular walls contract to mechanically digest the food.
An enzyme is produced to break down proteins - pepsin.
Hydrochloric acid is secreted that kills pathogens and provide correct environment for pepsin.

Question 28

What are the parts of the intestine and what so they do?

Answer 28

The small intestine contains more enzymes.
this is where digested food is absorbed into the blood stream.

The large intestine is where water absorption happens.

The rectum is where waste material (faeces) is stored.

The anus is muscular tissue that acts as the opening to the outside, when faeces leave the body.

Question 29

what is the role of the pancreas?

Answer 29

produces pancreatic juices, which contain lots of digestive enzymes which are released into the small intestine.

Question 30

what is the role of the gall bladder?

Answer 30

stores and releases bile (alkaline) - made in the liver.

bile neutralises stomach acid and emulsifies fats.

Question 31

What is gaseous exchange in animals?

Answer 31

Oxygen passing into the blood and carbon dioxide passing out of the blood.

To exchange gases with the environment, animals have lungs.
The lungs exchange waste carbon dioxide for oxyen from the air.
The oxygen and carbon dioxide are transported to the body in the blood.
Gaseous exchange also happens in the muscles and organs which use the oxygen and diffuse carbon dioxide back into the blood to return to the lungs to be exhaled

Question 32

What are the parts of the respiratory system

Answer 32

The nose/ mouth
The trachea.
The bronchus.
The bronchioles.
The lungs.
The alveoli.
The diaphragm

Question 33

What is ventilation?

Answer 33

Process of breathing in and out in mammals.

Breathing out- exhalation

Question 34

Describe inhalation

Answer 34

Air is inhaled through the mouth or nose.
The diaphragm contracts and moves downwards.
The ribs move up and out as intercostal muscles contract.
The volume of the chest increases.
The increased size of the chest decrease the air pressure inside which sucks air into the lungs.

Question 35

Describe exhalation

Answer 35

The diaphragm relaxes and moves upwards.
The intercostal muscles relax so the ribs move down and in.
The volume of the chest decreases, which increases air pressure in the lungs -
forcing the air out.

Question 36

What is gaseous exchange in plants

Answer 36

Carbon dioxide in oxygen out

Plants need to take in carbon dioxide so that they can photosynthesise. They also produce excess (too much) oxygen in the same process that must be released.

Question 37

Describe how gaseous exchange occurs in plants?

Answer 37

Carbon dioxide moves from the air into the leaf diffusing through small pores called stomata.

At the same time oxygen moves out of the leaf through the stomata.

Question 38

what is the role of guard cells?

Answer 38

Guard cells use osmotic pressure to open and close stomata, regulating the amount of water and solutes within them.

Question 39

What is sexual reproduction

Answer 39

The fusing of different cells to form a new life.

Question 40

What are gametes?

Answer 40

The cells that are given from each partner.
In humans, the male will supply a sperm cell and the female will supply an egg cell.
In plants the male gamete is pollen the female is the egg

Question 41

What is Fertilisation?

Answer 41

what happens when the gametes fuse or join together.

In humans the sperm and egg fuse, this normally happens in the fallopian tubes.

In plants the pollen fuses with the egg in the pistal

Question 42

What are the parts of the human male reproduction organs and what do they do?

Answer 42

Testes - make sperm as well as the hormone testosterone.
Penis - allows urine to leave the body, and transports semen into the female reproductive organs.
Prostate - produces liquids that help the sperm survive outside of the male body.
Sperm duct - tubes that sperm travel down to get from the testes to the urethra.
Urethra -the tube in the penis that sperm passes through in sexual intercourse. It is also the tube in which urine leaves the body.

Question 43

What are the parts of the human female reproduction organs and what do they do?

Answer 43

Ovary - the organ that produces egg cells as well as the hormone oestrogen.
Fallopian tube or oviduct - this tube is where fertilisation takes place. Cells in the fallopian tube transport the egg to the uterus.
Uterus or womb - this is where, if fertilisation has happened, the egg is implanted to develop further. It has a wall lining made of blood that regenerates once per month if the female is not pregnant.
Cervix - the opening to the uterus. It is made of muscular tissue.
Vagina - the opening of the reproductive organs, where the male’s penis goes during sexual intercourse.

Question 44

Describe the role of sperm cells.

Answer 44

Sperm cells spin their tails in a corkscrew motion to move towards their target - the egg.
The sperm fuses with the egg, sharing its genetic information to make a complete genome (all the DNA needed to make a whole organism).

Question 45

What is the menstrual cycle

Answer 45

The menstrual cycle is a monthly cycle which releases a new egg into the female reproductive system.
The egg is transported from the ovaries, along the fallopian tubes to towards the uterus.
If there is no fertilisation, then the blood lining of the uterus breaks down and leaves the body as a period.
If fertilisation does take place, then the fertilised egg then implants itself into the uterus lining to develop during gestation.

Question 46

What is gestation?

Answer 46

The time taken for an embryo to develop from fertillisation to birth.
Gestation takes different amounts of time in different mammals.
Mouse 3 weeks
Human 40 weeks
Elephant 95 weeks

Question 47

What are the female parts of a plant called?

Answer 47

The carpel which contains
The stigma.
The style.
The ovary.
The ovule.

Question 48

What are the male parts of a plant called?

Answer 48

The stamen which is composed of:
The anther.
The filament.

Question 49

How does sexual reproduction in plants occur?

Answer 49

Pollen from the anther on one plant must land on the stigma of another.
Here, it moves down the style towards the ovary and ovule where it will fuse with the egg.
This is called pollination and produces seeds.
Many plants produce sweet nectar to attract insects such as bees, they brush against the stamen collecting pollen and transfer it to the stigma of another plant

Question 50

Why do plants want their seeds dispersed?

Answer 50

in order to move the seed far away from the parent plant so that they aren’t both competing for the same resources such as light, water and minerals.

Question 51

Describe 4 different methods of seed dispersal

Answer 51

Fruit is produced by some plants which contains seeds, animals eat it and deposit their faeces containing seeds.

Animal walks past, the seeds get caught in their fur. The seeds are then transported a long way away from the original site. eg burrs

Wind dispersal. Some plants’ seeds have evolved to be blown in the wind.

Water - seeds blow into to water and carried along a river finding a new germination spot.

Question 52

What are drugs?

Answer 52

Drugs are substances which have a wide range of chemical effects on the body.
Some drugs are legal, rigorously tested, and safe to use. Others have side effects and must be used with caution. Some drugs are illegal.

Question 53

Describe different categories of drugs giving practical examples.

Answer 53

1) Painkillers - reduce the symptoms of pain such as a headache e.g paracetamol
2) Depressants - slow down your reaction time and lower the activity within the brain. eg alcohol
3) Stimulants - improve your reaction time and increases the activity within the brain. eg caffeine
4) Hallucinogens change what you think you can hear as well as see. eg marijuana 5) Performance enhancers are used to improve fat loss and muscle development. eg steroids

Question 54

What is photosynthesis?

Answer 54

Photosynthesis is how plants produce some of the nutrients they need to survive using energy from sunlight
The equation is
Carbon dioxide + water + sunlight → oxygen + glucose

Question 55

What is the chemical and word equation for photosynthesis?

Answer 55

Carbon Dioxide + water + sunlight → glucose + oxygen

6CO2 + 6H2O → C6H12O6 + 6O2

Question 56

Explain 4 importances of photosynthesis.

Answer 56

1) All oxygen is produced by photosynthesis, without it life on earth would not survive.

2) The only way in which energy can enter a food chain.

3) Plants harness the energy from the Sun and store it chemically in their own tissues.

4) When plants are eaten by animals, they take that chemical energy and use it to live and store it themselves.

Question 57

Leaves have some key adaptations to make sure that they photosynthesise efficiently what are the main 5?

Answer 57

1. The waxy cuticle is the waterproof top layer of the leaf, which prevents water from escaping from the upper surface.
2. The stoma are open pores which allow gas exchange with the environment. They can close when water is low to make sure that little is lost, meaning photosynthesis can still happen. Fewer stomata on top surface of leaf.
3. The spongy mesophyll is a layer of cells with air spaces so that gases can diffuse in and around the leaf.
4. The palisade layer is a layer of tightly packed cells that are filled with chloroplasts which makes sure that almost all light is absorbed and little light can pass through.
   5) large surface area to absorb sunlight.

Question 58

What is Respiration?

Answer 58

the process of transferring energy from glucose, which happens constantly in every living cell.

Question 59

Describe the two types of respiration

Answer 59

Aerobic (with oxygen).
Anaerobic (without oxygen)

Anaerobic (this doesn’t use oxygen).

Question 60

Explain aerobic respiration and give the equation.

Answer 60

Aerobic respiration uses oxygen, to break down food molecules.
The equation for aerobic respiration is:
Oxygen + glucose → water + carbon dioxide.

Question 61

Explain anaerobic respiration in animals

Answer 61

doesn’t use oxygen. glucose only partially broken down and produces lactic acid and less energy than aerobic respiration.

The equation for anaerobic respiration in animals is:
Glucose → lactic acid

This lactic acid must be broken down afterwards. This is why you continue to breathe heavily after you have finished strenuous activity.
    You breathe heavily because the lactic acid needs oxygen to be broken down.

Question 62

Explain anaerobic respiration in plants and single celled organisms

Answer 62

Anaerobic respiration in plants produces ethanol and CO2, instead of lactic acid.

The equation for anaerobic respiration in plants and single-celled organisms is:
Glucose → ethanol + carbon dioxide ( + energy)

This is also called fermentation.
This reaction is very useful in industry because it is used to make alcoholic drinks such as wine and beer as well as bread.

Question 63

What is an ecosytem

Answer 63

All the organisms living in a particular area and all the non-living (abiotic) conditions.

Question 64

Explain the use of sampling to discover more about organisms in a habitat

Answer 64

Scientists sample a part of a habitat and use that information to draw conclusions about the whole. It enables them to make judgements without surveying everything which would be inefficient.

Question 65

Describe how quadrats are used for sampling.

Answer 65

A quadrat is a square usually 0.25 square metres.
It is placed on the ground and the organisms within it are recorded in one of 3 ways. It is most useful for collecting information on plants or slow moving animals!
1 the number of individual organisms are recorded
2 the number of different species are recorded
3 the approximate percentage cover of plants can be recorded

Question 66

Describe the method of random sampling using quadrats to estimate the number of daisies in a field

Answer 66

1. Choose a fixed location to start- usually the corner.
2. Use a random number generator or table to tell you how far to walk in each direction to place the quadrat.
3. Count/record the number of daisies in the quadrat.
4. Go back to the fixed point and repeat.
5. The more samples you take the more accurate your results. Usually about 30.
6. Measure the field and calculate the number of quadrats which fit into it
7. Find the mean number of daisies per quadrat from your sampling.
8. Multiply the mean (step 7) by the number of quadrats (step 6) to estimate the number of daisies.

If you are asked to compare two parts of one field you would carry out this method as if the two areas were separate fields

You could be asked to outline this method in a long question, it is important that you are precise and detailed. Marks are given for logical sequencing.

Question 67

Describe the method of systematic sampling using quadrats to look at the distribution of seaweed on the shore.

Answer 67

1. Place a line of quadrats called a transect from the top to the bottom of the shore.
2. Place the quadrat at regular intervals eg every metre along the transect and estimate the percentage coverage of seaweed in each quadrat.

Question 68

What is meant by the term producer.

Answer 68

Any organism which photosythesises (plant or algae)

Question 69

What is biomass?

Answer 69

a measure of the total mass of living material in each trophic level.

Question 70

What is consumer?

Answer 70

organisms that feed on plants or other animals for energy.

Question 71

Describe the different types of consumers using examples

Answer 71

1. Primary consumer- feeds on producers eg aphid feeds on plants
2. Secondary consumer, feeds on primary consumer eg ladybird feeds on aphids
3. Tertiary consumer feeds on secondary consumer eg bird feeds on ladybirds

Question 72

What is an enzyme?

Answer 72

A biological molecule which helps a chemical reaction take place, either digesting or synthesising . It is a catalyst so doesn’t take place in the reaction. Enzymes are specific to the type of food (substrate) they break down. Their name always ends in ase.

Question 73

What is amylase?

Answer 73

It is the enzyme produced by the salivary glands and it breaks down starch into glucose. Therefore it is one of the carbohydratase enzymes.

Question 74

Identify 4 groups of digestive enzymes and explain the substrates they work on and the resulting products.

Answer 74

1. Salivary amylase is produced in the mouth by the salivary glands and breaks down starch into sugars
2. Protease enzymes are produced by the stomach lining and the pancreas and break down proteins into amino acids.
3. Carbohydrase enzymes are produces in the mouth and the pancreas and break down carbohydrates into sugars
4. Lipase enzymes are produced in the pancreas and break down fats

Question 75

Describe how digestive enzymes use the lock and key hypothesis

Answer 75

1. Digestive enzymes are specific to the substrate they work on because they have a specific shape
2. Each enzyme has a part called it’s active site which is the right shape for the substrate this is like a lock.
3. The substrate fits into the active site like a key.
4. The enzyme breaks down the bonds in the substrate which hold it together.
5. When the bonds are broken the enzyme lets the substrate go.

Question 76

What is synthesis? Give an example

Answer 76

Enzymes help to build complex molecules from the simpler food substance molecules.
Eg. Proteins are created by synthesising amino acids
Fats from fatty acid and glycerol
Carbohydrates from sugars

Question 77

What does denaturing of enzymes mean

Answer 77

All enzymes work best at a specific pH and temperature and if it is not right will slow down. Denaturing is when an enzyme has been damaged and will not work any more. The shape has changed so that the key will no longer fit in the lock.

Question 78

Explain the use of bile in digestion

Answer 78

1. Bile is produced by the liver
2. It is stored in the gall bladder.
3. It emulsifies fat- breaking it down into small droplets to increase it’s surface area allowing it to be digested by lipases.
4. It is alkaline and neutralises the hydrochloric acid entering the small intestine from the stomach.

Question 79

Explain diffusion of oxygen in the lungs

Answer 79

1. The alveoli has a thin layer of flattened cells in their wall and the capillary walls are only 1 cell thick as well.
2. The concentration of o2 in the alveoli is higher than in the blood.
3. Therefore there is a concentration gradient and the o2 diffuses from the alveoli into the blood.
4. The red blood cells in the blood carry the o2 to the working muscles.
5. The muscles have a lower concentration of o2 than the blood.
6. There is a concentration gradient and the o2 diffuses from the blood to the muscles.

Question 80

Explain diffusion of carbon dioxide in the lungs

Answer 80

1. There is a high concentration of CO2 in the muscles as a result of tissue respiration.
2. The plasma in blood has a lower concentration of CO2 than the muscles.
3. Therefore there is a concentration gradient.
4. Therefore the CO2 will diffuse from the muscles into the blood.
5. The blood is circulated to the lungs.
6. There is a higher concentration of CO2 in the plasma of the returning blood than the lungs
7. Therefore there is a concentration gradient
8. Therefore the CO2 will diffuse from the blood into the lungs to be exhaled.

Question 81

Describe adaptations of the lungs to allow gaseous exchange.

Answer 81

1. Have a large surface area to allow more o2 and co2 to diffuse.
2. Have moist membranes to allow faster diffusion of gases.
3. Have linings 1 cell thick to allow gases to diffuse easily
4. Has a large network of 1cell thick capillaries to allow more diffusion to take place.
5. Ventilation or breathing moves air with more o2 into the lungs and the air with more co2 out of the lungs.

Question 82

What is blood plasma?

Answer 82

The straw coloured liquid part of the blood which carries blood cells and dissolved substances.
It is 92% water and makes up 55% of the blood. Many substances such as glucose and CO2 are dissolved in the plasma.

Question 83

What are the components of blood?

Answer 83

1. Blood plasma
2. Red blood cells
3. White blood cells- phagocytes and lymphocytes
4. Platelets, small substances which help blood to clot
5. Dissolved substances such as glucose and CO2, urea, hormones.

Question 84

Describe and explain the structure and function of red blood cells.

Answer 84

1. They are biconcave which gives a large surface area for the absorption of oxygen
2. They contain haemoglobin which combines with oxygen in the lungs to make oxyhaemoglobin and releases it for the cells to use to make energy.
3. They don’t have a nucleus which makes more room for haemoglobin.
4. They are produced in the bone marrow of long bones like the femur.

Question 85

Explain the two different types of carbohydrate and their structure

Answer 85

1. Sugars eg glucose, fructose and sucrose simple molecules of one or 2 glucose compounds C6H12O6
2. Starches are complex compounds of many glucose molecules

All carbohydrates are broken down into glucose molecules during digestion

Question 86

Explain how protein is used in the body

Answer 86

Proteins are digested into amino acids which are used mainly for building and repairing muscles.

Question 87

Explain how fats/lipids are used in the body

Answer 87

Broken down into fatty acids and glycerol and are used for nerve function, protection of internal organs and long term energy store

Question 88

How is food moved through the gut?

Answer 88

Peristalsis - the muscles around the gut contract in sequence to squeeze the food along.

Question 89

Describe and explain the structure of a villus

Answer 89

Tiny finger like projections in the intestine. Increase surface area for absorbtion. Each has it’s own blood supply a capillary to enable absorption of molecules through the thin cell wall.

Question 90

Identify the chambers of the heart and describe their function

Answer 90

1. right atrium collects blood from the body
   2 left atrium collects blood from the lungs
2. right ventricle pumps blood to the lungs
3. left ventricle pumps blood to the body

Question 91

What are valves? Identify two parts of the cardiovascular system which contain valves.

Answer 91

1. Structures which allow blood to only pass in one direction
2. The heart and the veins

Question 92

The vascular system consists of 3 types of vessels. Identify each one and relate their structure to their function.

Answer 92

1. Arteries- carry blood away from the heart, therefore they are large and need thick muscular walls due to having higher blood pressure.
2. Veins- carry blood towards the heart, they have thinner walls because of lower blood pressure but contain valves to stop the blood flowing backwards
3. Capillaries- are only one cell thick to enable substances to pass in and out of the blood by diffusion

Question 93

What is blood plasma?

Answer 93

The straw coloured liquid part of the blood which carries blood cells and dissolved substances. It is 92% water and makes up 55% of the blood. Many substances such as glucose and CO2 are dissolved in the plasma.

Question 94

What are the components of blood?

Answer 94

1. Blood plasma
2. Red blood cells
3. White blood cells- phagocytes and lymphocytes
4. Platelets, small substances which help blood to clot

Question 95

Describe the structure and function of red blood cells.

Answer 95

1. They are biconcave which gives a large surface area for the absorption of oxygen
2. They contain haemoglobin which combines with oxygen in the lungs to make oxyhaemoglobin and releases it for the cells to use to make energy.
3. They don’t have a nucleus which makes more room for haemoglobin.
4. They are produced in the bone marrow of long bones like the femour.

Question 96

What is haemoglobin and where is it found.

Answer 96

In the red blood cells it combines with o2 to make oxyhaemoglobin and carries the o2 from the lungs to the cells which need it.

Question 97

Describe the parts of the digestive system?

Answer 97

1. Salivary glands - produce saliva which starts digesting carbohydrates and lubricates the food so it can travel easily
2. Oesophagus - Tube joining the mouth to the stomach
3. Stomach- organ which produces acid to give proteases the right pH for digesting proteins. The acid also helps protect against pathogens in the food.
4. Gall bladder- stores bile which helps break down fats
5. Liver- produces bile which helps break down fats
6. Pancreas- organ which produces the enzymes for digestion, carbohydrase, protease and lipases.
7. Small intestine - about 7m long and covered in villi to increase it’s surface area it absorbs the products of digestion
8. Large intestine- shorter but wider than the small intestine water and salts are reabsorbed here
9. Anus - opening at the end of the system through which waste passes, defecation

Question 98

Describe peristalsis?

Answer 98

Happens in the oesophagus and small intestine, it is the contraction of the smooth muscles which squash the boluses of food and push them along the tubes.

Question 99

Describe the structure of villi and explain their function?

Answer 99

1. Tiny microscopic finger like projections which are in the lining of the small intestine.
2. There are about 4000 villi in a square cm of the small intestine.
3. They contain capillaries which transport the digested food molecules in the blood.
4. They increase the surface area of the small intestine so that more digested food can be absorbed into the blood.

Question 100

why do we need diffusion?

Answer 100

We want oxygen to diffuse into cells because it is needed for life.

We want carbon dioxide to diffuse out of cells as it is a waste product.