Biology

Question 1

What are primary food substances?

Answer 1

Primary food substances are food substances that carry energy value. They include proteins, carbohydrates, and lipids.

Question 2

What are protective food substances?

Answer 2

Protective food substances carry no energy value. They include vitamins, minerals, and dietary fibre.

Question 3

What are some examples of carbohydrates and foods rich in carbohydrates?

Answer 3

Starch: food rich in starch: bread, rice, potatoes
Sugar: food rich in sugar: fruits, candies, chocolate

Question 4

*What are carbohydrates made of? (extra)

Answer 4

*Carbon, hydrogen, and oxygen, with the ratio of hydrogen and oxygen being 2:1.

Question 5

*How can carbohydrates be classified? (extra)

Answer 5

*They can be classified into monosaccharides, disaccharides, and polysaccharides. Monosaccharides are the simplest form of carbohydrates, disaccharides consist of two monosaccharides joined together, and polysaccharides consist of more than 2 monosaccharides joined together.

Question 6

What are examples of monosaccharides, disaccharides, and polysaccharides?

Answer 6

Monosaccharides: glucose and fructose found in fruits and honey, galactose found in milk and dairy products
Disaccharides: maltose (glucose+glucose) found in germinating barley, lactose (glucose+galactose) found in milk and dairy products, sucrose (glucose+fructose) found in sugar canes, sugar beets, and table sugar
Polysaccharides: starch, glycogen, cellulose (made of glucose molecules arranged in different ways

Question 7

*How can monosaccharides become disaccharides or polysaccharides, and how can disaccharides and polysaccharides be decomposed into monosaccharides? (extra)

Answer 7

*Monosaccharides undergo condensation to become disaccharides or polysaccharides, and polysaccharides or disaccharides can be broken down to monosaccharides by hydrolysis.

Question 8

*What are the properties of monosaccharides and disaccharides? (extra)

Answer 8

*They are called sugars, taste sweet, and are soluble in water. All except sucrose are reducing sugars and can be detected using Benedict’s test.

Question 9

What are the uses of glycogen and cellulose?

Answer 9

*Glycogen is a the main storage form of carbohydrates in animals, which is abundant in livers and muscles, *while cellulose is a major component of cell walls in plants.

Question 10

What are the functions of carbohydrates?

Answer 10

1. They are the main energy source for body activities
2. They serve as energy reserves in the form of glycogen in liver or muscles.
3. Cellulose is a source of dietary fibre.

Question 11

What are the tests for glucose?

Answer 11

1. Clinitix test paper: changes from pink to blue in the presence of glucose
2. Diastix test paper: changes from blue to green in the presence of lower concentrated glucose and from blue to brown in the presence of higher concentrated glucose.

Question 12

What is the test for starch?

Answer 12

Iodine test: iodine solution turns from brown to blue-black in the presence of starch.

Question 13

*What is the test for reducing sugars? (extra)

Answer 13

*Benedict’s test: after adding an equal volume of Benedict’s solution to the food sample, the mixture is boiled for 5 minutes. If there are traces of reducing sugar, the mixture turns from blue to green or yellow with precipitate. If there are moderate amounts of reducing sugar, the mixture turns from blue to orange with orange precipitate. If there is an abundance of reducing sugar, brick-red precipitate forms.

Question 14

What are types of lipids and food rich in them?

Answer 14

Two types of lipids are fat and oil, with fat being a solid at room temperature found in animals and oil being a liquid found in plants. Food rich in lipids include cheese, butter, and lard.
*Oils are generally healthier than fats; this is because fats typically consist of saturated fatty acids while oils consist of unsaturated fatty acids. Excess intake of fats increases risk of cardiovascular disease, however intake of oils may lower the risk of heart disease.

Question 15

What is a common example of lipids, and what are the properties of lipids?

Answer 15

One example of lipids is triglycerides, which consists of 1 glycerol molecule condensed with 3 fatty acid tails.
*Lipids are made up of carbon, hydrogen, and oxygen, with the ratio of hydrogen to oxygen being way larger than 2. They are insoluble in water but soluble in organic solvents. *

Question 16

What are the functions of lipids?

Answer 16

1. Energy reserves: lipids are stored in adipose tissues, which are found under the skin. As subcutaneous fat or around internal organs. 1g of lipid provides 38.9kJ of energy.
2. Shock absorber: The fat stored in adipose tissues also act as a shock absorber to protect internal organs.
3. Heat insulator: subcutaneous fat reduces heat loss from the body.
4. As a component of cell membranes
   *(They are also used for absorption, transport, and storage of lipid-soluble vitamins, as well as the production of hormones)

Question 17

What are the differences between lipids and phospholipids? (extra)

Answer 17

A phospholipid molecule is structually similar to a triglyceride molecule, but one fatty acid tail is replaced by a phosphate group. The phosphate group is polar and attracted by water, while the fatty acids are non-polar and repelled by water.

Question 18

How do phospholipids arrange to become a cell membrane? (extra)

Answer 18

Phospholipid molecules are arranged in a bilayer and can move laterally. The hydrophillic “head” is in contact with aqueous solution outside the cell/extracellular fluid, and the hydrophobic “tail” points inward, not being in contct with aqueous envrionments.
In between phospholipid molecules are protein molecules interpersed among them. Some are attached to the phspholipids, some embedded half-way, and some span the entire bilayer.

Question 19

What is the test for lipids?

Answer 19

Grease spot test: a drop of food sample is dropped onto a piece of filter paper. After it dries, a translucent spot forms. After the filter paper is immersed into an organic solvent, the spot disappears, which indicates the presence of lipids.

Question 20

What are the functions of proteins?

Answer 20

1. For growth and repair of body tissues, as many body tissues are made up of proteins (eg. Muscles, bones, skin, hair, blood)
2. For providing energy when carbohydrates and lipids are used up: 1g of proteins provide 18.2kJ of energy.
   *(For producing enzymes, antibodies, haemoglobin, and some hormones)

Question 21

What disease is likely when there is a lack of proteins in the diet?

Answer 21

Kwashiorkor: causes weak muscles and a swollen abdomen, common among children in developing countries.

Question 22

What are some examples of food rich in protein?

Answer 22

Meat, egg, milk

Question 23

What are proteins molecules made up of and what are their building blocks?

Answer 23

*Carbon, hydrogen, oxygen, nitrogen, while some also contain sulphur. *The building blocks are called amino acids *consisting of a amino group and a carboxyl group.

Question 24

*How can longer chains be formed by amino acids? (extra)

Answer 24

*Two amino acids undergo condensation to form a peptide with a peptide bond, while three condense to from a tripeptide. More than 3 amino acids condensed together form polypeptides.

Question 25

*How do polypeptides form proteins? (extra)

Answer 25

*A polypeptide is first formed by joining many amino acids. The attraction forces in the polypeptide causes it to coil and fold in a specific way into a 3D structure. Then, it may combine with other coiled polypeptides to form a protein. The amino acid sequence determines the shape of the protein, and the unique shape of proteins allows different proteins to perform different functions in our body.

Question 26

How are the unique shapes of protein important?

Answer 26

They are important for the functions of enzymes, receptors, and antibodies. Especially for enzymes, the changes in shapes of active sites cause them to lose their functions.

Question 27

What are 5 types of membrane proteins and their functions? (extra)

Answer 27

1. channel proteins: provide channels for substances to move across the membrane
2. carrier proteins: bind to certain substances and transports them across the membrane
3. receptors: bind to chemical messengers outside cells
4. antigens: for cell recognition
5. enzymes: to catalyse chemical reactions

Question 28

How many amino acids are there in our body?

Answer 28

Proteins in our body are made up of 20 amino acids.
*12 are non-essential amino acids which can be produced in our body, and 8 are essential amino acids to be obtained from diet.

Question 29

What is the test for proteins?

Answer 29

Protein/Albustix test paper: it turns from yellow to green in the presence of protein.

Question 30

What are characteristics of vitamins?

Answer 30

Vitamins have no energy value, but they help promote growth, regulate metabolism, and strengthen immunity. The lack of any vitamin in our diet may lead to deficiency diseases.

Question 31

How are vitamins classified?

Answer 31

They are classified into lipid-soluble vitamins, with examples being vitamins A, E, K that can be stored in large amounts, and water-soluble vitamins with examples being vitamins B and C that cannot be stored in large amounts and are easily lost when exposed to water, high temperatures, and oxygen.

Question 32

What is the importance of vitamin A and what are deficiency diseases of vitamin A?

Answer 32

Vitamin A is important for vision in dim light as it is used to form a pigment in the retina, and for strengthening immunity by keeping the cornea, skin, lining of the alimentary canal and breathing system healthy. Its deficiency disease is night blindness (and easy infection of lining of the lungs and trachea).

Question 33

What are sources of vitamin A?

Answer 33

Vitamin A can be found in margarine, liver, eggs, milk, fish liver oil, dairy products, and in carotene that can be transformed into vitamin A in the liver. Foods containing carotene include carrots, sweet potatoes, pumpkins, spinach, mango, and kale.

Question 34

What is the importance of vitamin D, its deficiency disease, and its sources?

Answer 34

Vitamin D is for maintaining strong bones and teeth. Its deficiency disease is rickets, where the patient’s bones become soft and bent especially in children’s legs. It can be produced by the skin under sunlight.

Question 35

What are functions of vitamin C and its deficiency disease?

Answer 35

Vitamin C is for the growth and repair of connective tissues and for healing wounds. It promotes the absorption of iron from plants and helps the immune system to work properly. Its deficiency disease is scurvy, where the patient’s gums bleed and wounds heal poorly.

Question 36

What is the test for vitamin C?

Answer 36

DCPIP test: the food sample is added to the DCPIP solution. If the blue DCPIP solution decolourizes, it shows that vitamin C is present.

Question 37

What are the properties of minerals?

Answer 37

Minerals have no energy value. Some of them form body tissues, and some help regulate metabolism. The lack of minerals our diet may lead to deficiency diseases.

Question 38

What are the functions of calcium and what are its deficiency diseases?

Answer 38

Calcium is used to build bones and teeth, help with blood clotting, and send messages in the nervous system. Its deficiency diseases include rickets in children and osteoporosis in adults, where the bones become porous and brittle, resulting in them being easily broken.

Question 39

What is the function of iron and what is its deficiency disease?

Answer 39

Iron is used to make haemoglobin, which is a red pigment in red blood cells that carries oxygen. Its deficiency disease is anaemia, where the patient faints easily because there is not enough haemoglobin to carry oxygen to the brain.

Question 40

What is the function of iodine and what is its deficiency disease?

Answer 40

Iodine is used to maintain the functions of the thyroid gland (thyroxine, thyroid hormones). Its deficiency disease is goitre, where the patient’s thyroid gland becomes swollen. *(may also be caused due to excessive intake of iodine)

Question 41

What are characteristics of dietary fibre?

Answer 41

Dietary fibre is a substance found in the cell wall of plant cells, found in fruits, vegetables, and cereals. It has no energy value, and cannot be either absorbed or digested.

Question 42

What is the function of dietary fibre?

Answer 42

Dietary fibre adds bulk to food and stimulates peristalsis to ensure the food is pushed forward in the intestines. It also holds water which keeps faeces soft and prevents constipation.

Question 43

What are the functions of water?

Answer 43

1. It is the main component of the cytoplasm of cells, which is the medium for chemical reactions.
2. It is the main component for blood, which transports substances around the body.
3. It is a solvent for wastes like urine and sweat.
4. It makes up body secretions like digestive juices.
5. It also helps to regulate body temperature/acts as a coolant by evaporation of sweat.
6. *(It is a major component of many lubricating fluids.)

Question 44

What are some facts about water?

Answer 44

Water makes up about 70% of our body. Our body loses water through urination, sweating, and breathing out, therefore, we must drink 6-8 glasses of fluids every day to replace water loss through water, milk, juice, tea, soup etc. A lack of water causes poor digestion and constipation.

Question 45

What is digestion?

Answer 45

Digestion is the action of food being broken down into small, simple, and soluble substances that can be absorbed and used by our body cells.

Question 46

What are parts of the human digestive system?

Answer 46

The digestive system is made up of the alimentary canal and digestive glands that produce digestive juices. The alimentary canal is made of the mouth cavity, the oesophagus, the stomach, the small intestine, the large intestine, and the anus.

Question 47

What is the difference between physical digestion and chemical digestion?

Answer 47

Physical digestion refers to the food being ground (grinded) into smaller sizes but no chemical changes are made, while chemical digestion refers to the process of food being catalysed to break down chemically under the action of enzymes.

Question 48

*What are the steps of obtaining nutrients? (extra)

Answer 48

*1. ingestion: eat food
2. digestion: breaking down food using mechanical/physical digestion and chemical digestion
3. food absorption: the completely digested food are transported by blood or lymph to absorb the nutrients.
4. assimilation: the nutrients absorbed are used to build new cells to build the body
5. egestion: indigestible food substances or unabsorbed food are mixed with bacteria from the large intestine to excrete from the large intestine.

Question 49

What is the purpose of chewing?

Answer 49

Chewing is a process of physical digestion which grinds the food into small pieces. This increases the surface area of the food in-taken and maximises the efficiency of digestive enzymes in chemical digestion, and reaches a much higher rate of chemical digestion.

Question 50

*What are starch, protein, and lipids broken down into after digestion? (extra)

Answer 50

*starch: broken down into maltose and glucose
protein: broken down into amino acids
lipids: broken down into glycerol and fatty acids

Question 51

What types of digestion take place in the mouth cavity?

Answer 51

physical digestion: chewing of teeth grinds the food into smaller pieces, increasing the surface area and the efficiency of enzymes.
The tongue rolls the food into a bolus/ball structure to help to swallow the food. Saliva makes food moist and easier to swallow.
chemical digestion: salivary amylase secreted by the salivary glands is an enzyme that catalyses the breaking down of starch into maltose.

Question 52

What are the components and functions of saliva? (extra)

Answer 52

Saliva consists of water, mucus, and salivary amylase. Mucus in the saliva acts as a lubricant for the food while salivary amylase is an enzyme that catalyses the breaking down starch into maltose.

Question 53

What is the purpose of the oesophagus?

Answer 53

It pushes food down to the stomach by peristalsis. The rate of digestion there is insignificant.

Question 54

What types of digestion take place in the stomach?

Answer 54

physical digestion: by the churning of the stomach to turn the food into chyme (congee-like, small pieces and soft) and for mixing with gastric juice
chemical digestion: proteins are partially digested by proteases (pepsin) in gastric juice secreted by the stomach.

Question 55

What types of substances does the stomach secrete and what are their functions?

Answer 55

mucus glands: they produce mucus to separate the gastric juice from the walls of the stomach, preventing damage done to stomach cells.
gastric glands: they secrete highly acidic gastric juice, which is made of water, aqueous hydrochloric acid, and proteases. Proteases (pepsin) are enzymes that catalyse the breaking down of protein into amino acids.
The acid in gastric juice provide an acidic pH of around 2, killing bacteria in food and allowing pepsin to work.
*Salivary amylase is denatured at this pH.

Question 56

What types of digestion take place in the small intestine?

Answer 56

Physical digestion: action of bile that emulsifies fat droplets to make them decrease in size, peristalsis pushing food and mixing them with digestive juices
chemical digestion: enzymes in pancreatic juice and intestinal juice
All carbohydrates, lipids, and proteins are digested completely into small, simple, and soluble substances. The digestion is complete in the small intestine and nutrients are ready to be absorbed.

Question 57

What are the properties of bile?

Answer 57

It is produced in the liver and stored in the gallbladder. It does not contain enzymes. It produces bile salt that emulsifies lipids into smaller oil droplets, which increases the surface area for enzymes to work on.
*It also produces mineral salts (alkaline sodium hydrogencarbonate) to neutralise the acid in gastric juice.

Question 58

*What are the properties of pancreatic juice? (extra)

Answer 58

*It is produced in the pancreas. It contains pancreatic amylase to digest starch into maltose, proteases to digest proteins into peptides and peptides into amino acids, and pancreatic lipase to digest lipids into fatty acids and glycerol. It also contains sodium hydrogencarbonate (alkalis) to neutralise gastric juice, ensuring that the digestive enzymes in the small intestine work properly.

Question 59

*What are the properties of intestinal juice? (extra)

Answer 59

*Intestinal juice is produced by glands in the wall of small intestine, and by specialized cells on the epithelium of the small intestine. It contains water, mucus, sodium hydrogencarbonate, carbohydrases, and proteases. Carbohydrases break down disaccharides into monosaccharides while proteases break down peptides into amino acids.

Question 60

*What are the functions of the gallbladder? (extra)

Answer 60

*The gallbladder temporarily stores and concentrates bile. It contracts and controls the release of bile into the small intestine.

Question 61

What is absorption?

Answer 61

Absorption is the process of food in the lumen of the intestine being transported through the epithelium of the intestinal wall by diffusion and active transport into food in the blood or lymph.

Question 62

What are the features of absorption?

Answer 62

Absorption of food and water takes place mostly in the small intestine (90%), while a small amount of food substances are absorbed in the stomach and large intestine. Most water is absorbed in the small intestine (by osmosis), and the remaining water is absorbed in the large intestine.

Question 63

*What are the characteristics of the small intestine? (extra)

Answer 63

*It consists of the duodenum, jejunum, and ileum. It is around 7m long and 2.5 cm in diameter, having a large surface area of 250m^2. Its walls have folds and contain structure called villi, which are fingerlike projections of epithelium. The villi are covered with microscopic projections called microvilli on the epithelial cells. These features help the small intestine to increase food absorption rate by providing a large surface area.

Question 64

What are the functions of the large intestine?

Answer 64

The undigested food (eg. dietary fibre) enters the large intestine. The large intestine absorbs minerals and most of the remaining water, leaving a semi-solid waste called faeces. Faeces are temporarily stored in the large intestine until they are passed out of the body through the anus in egestion.

Question 65

What are the types and functions of human teeth?

Answer 65

Our teeth take part in physical digestion because they are used to break food into smaller pieces. Humans have four types of teeth: incisors, canines, premolars, and molars.
Incisor: chisel-shaped, flat sharp edge, for biting and cutting food.
canine: pointed and curved, for tearing food like flesh.
premolar: broader chewing surface, have cusps for crushing and grinding food.
molar: the broadest chewing surface, the largest in size with more cusps, for crushing and grinding food.

Question 66

What is the arrangement of human teeth?

Answer 66

The arrangement is symmetrical both left-to-right and up-to-down. For each jaw, 4 incisors are located in the middle, followed by 1 canine on each side, 2 premolars on each side, and 3 molars on each side. Humans have a total of 16 teeth for each jaw and 32 for both jaws.

Question 67

How can a tooth be divided into three parts?

Answer 67

It can be divided into the crown, the neck, and the root. The crown is the part that is exposed, while the neck is the part embedded inside the gum. The root is the part embedded inside the jawbone.

Question 68

What are the five main parts making up a tooth and their functions?

Answer 68

The outer part of the crown is made up of a non-living tissue called enamel. It is made of non-living calcium salt, therefore, it is hard and can protect the tooth from damage.
Under the enamel is a bone-like living material called dentine, which has stands of living cytoplasm throughout its structure. It is not as hard as enamel, and makes up a large part of the tooth.
The centre of the tooth is the pulp cavity, which contains blood vessels and nerve fibres. Blood vessels supply oxygen and nutrients, while removing waste like carbon dioxide in respiration. Nerve fibres detect temperature and pressure/pain.
The root of each tooth is covered by a layer called cement. It attaches the root to the jawbone through the periodontal membrane.

Question 69

How is tooth decay formed and repaired?

Answer 69

Tooth decay is caused by the action of bacteria in our mouth. After eating, the bacteria and food debris in our mouth form a sticky and invisible layer called plaque on the surface of the teeth. Bacteria in the plaque act on the sugar in the food debris to produce acid. The acid may dissolve the enamel and make a hole, resulting in the beginning of tooth decay.
Tooth decay starts from the surface of the enamel and gradually spreads to the dentine and pulp cavity. The acid irritates the nerves and causes toothache.
In serious cases, the decayed tooth may have to be removed. *(Often, tooth decay is also repaired with dental fillings, where the decayed part is removed and cleaned, and the hole is filled with a filing material like amalgam or composite resin. If the decay reaches the pulp cavity, root canal therapy is carried out, where nerves and blood vessels are removed.)

Question 70

What may be a factor leading to increased risk of tooth decay?

Answer 70

Frequent snacking: our saliva is slightly alkaline, which helps neutralise the acid in our mouth. After we eat, it takes about 30 minutes for the pH value in our mouth to return to normal. Therefore, if we eat snacks frequently, the environment in our mouth will frequently become acidic. This will lead to a higher risk of tooth decay.

Question 71

What is periodontal disease and how is it formed?

Answer 71

Periodontal disease is a common oral disease. If we do not brush our teeth properly, plaque may accumulate between the teeth and gums and gradually harden to form calculus. The rough surface of the calculus leads to the build up of more plaque.
Bacteria in the plaque secrete toxins, causing the gums to become red and swollen. The gums may bleed easily during brushing. The calculus spreads downwards, deepening the pocket and pushing gums away form the tooth. If periodontal disease is not treated, the periodontal membrane and the jawbone may be destroyed and the tooth may become loose and fall out.

Question 72

How can we take good care of out teeth and gums to prevent oral diseases?

Answer 72

1. Brush our teeth twice a day.
2. Use toothpaste containing fluoride to strengthen the enamel and increase its resistance to acid attack.
3. Use dental floss to remove plaque accumulated between adjacent teeth.
4. Chew sugar-free gum to stimulate the secretion of saliva.
5. Have a balanced diet with sufficient calcium and vitamin D to maintain strong teeth.
6. Avoid frequent snacking to reduce plaque formation.
7. Go to dental check-ups at least once a year.

Question 73

How should we maintain a balanced diet?

Answer 73

We should include the six main types of food substances in the right amounts and proportions in a diet. This balanced diet can provide us with appropriate amounts of energy and nutrients.

Question 74

What is the food pyramid?

Answer 74

The food pyramid is designed to help us plan a balanced diet. It shows the different types of foods in the right proportions the we should eat.
We should eat fat/oil, salt, and sugar the least, as eating too much may result in health problems.
We should eat dairy products and intake proteins moderately; we should drink 2 glasses of dairy and eat 4-6 ping-pong sized portions of protein a day.
We should eat more vegetables and fruits to avoid constipation and regulate metabolism/strengthen immunity. We should eat at least 1.5 bowls of cooked vegetables a day and at least 2 medium-sized fruits a day to ensure we have enough dietary fibre/vitamin C.
We should eat the most grains as the main energy source, which is 4-6 bowls a day. They are stored as chemical energy by body cells during respiration.
We should drink 6-8 glasses of fluids every day to get enough water.

Question 75

What are the energy values of food and energy values of primary food substances?

Answer 75

Food provides us with energy. Different foods have different energy values; the higher the energy value, the more energy the food contains. The energy values is measured in kilojoules per gram or kilocalories per gram.
The energy value of food is mainly determined by the amounts of primary food substances it contains: carbohydrates contain about 17 kJ/g energy, lipids contain 39kJ/g, and proteins 18kJ/g.
One gram of lipids provides about twice as much energy as the same amount of carbohydrates. Therefore, foods rich in lipids usually have higher energy values.

Question 76

What are the factors affecting the daily energy requirement of a person?

Answer 76

Age: children and teenagers generally require more energy per kilogram of body mass than older people. This because children and teenagers are more active and are growing rapidly. They require a large amount of proteins and calcium for building body tissues.
Sex: Men generally require more energy than women. This is because men have a higher ratio of muscles to fat than that of women. They require more energy to support muscle contraction.
Activity level and occupation: People who do more physical work require more energy than those who do less physical work because they need more energy for muscular activities.
*(Special body status: Pregnant women need more energy and protein for the growth of the foetus, and more iron for formation of foetal blood cells. Breastfeeding mothers need more nutrients for milk production but less iron, as menustration stops during breastfeeding.)

Question 77

What are the effects of over-eating on body mass and health?

Answer 77

If we take in more energy than we need by eating too much, the energy will not be used up. The energy intake becomes greater than the energy expenditure. The excess energy will be stored in the body as fats. This leads to an increase in body mass. A person becomes overweight when their body mas exceeds the normal level. A person is considered to be obese if they are seriously overweight.
Being overweight and obese increases the risks of many health problems, such as high blood pressure, cardiovascular disease and diabetes.

Question 78

What are the effects of under-eating on body mass and health?

Answer 78

If we take in less energy than we need by eating too little, our body will use the stored subcutaneous fats or muscle proteins to release energy to support body activities. This leads to a decrease in body mass. A person becomes underweight is their body mass is below the normal level.
Being underweight may lead to health problems such as poor growth, weak muscles and bones, and a weak immune system. If our diets lack certain food substances for a long time, we may suffer from deficiency diseases.
One possible disease is anorexia, where patients refuse to eat for fear of gaining weight. Patients may have a distorted body image and consider themselves to be fat even though they are thin. This may lead to severe health problems or even death.

Question 79

How do we calculate BMI?

Answer 79

BMI, or body mass index, is used to determine whether a person’s body mass is within the normal range.
BMI = body mass (kg)/height² (m²)

Question 80

What are two types of diseases and how do we distinguish them?

Answer 80

A disease occurs when parts of the body cannot function properly. They can be classified into two types: infectious diseases, which are caused by pathogens and can be transmitted from person to person, and non-infectious diseases, which involve no pathogens and cannot be transmitted to others.

Question 81

What are the causes of infectious diseases?

Answer 81

Infectious diseases are caused by microorganisms. Microorganisms that cause diseases are called pathogens. When pathogens enter our bodies, they may cause us to become sick by directly damaging body tissues or by secreting toxins. There are many different types of pathogens, including viruses, bacteria, fungi, *(and protists).

Question 82

List one example of viruses, bacteria, and fungi.

Answer 82

Virus: Influenza virus infects the upper respiratory tract and causes influenza.
Bacterium: M. tuberculosis infects the lungs and causes tuberculosis.
Fungus: T. rubrum grows on skin of the foot and causes athlete’s foot.

Question 83

How are infectious diseases transmitted? List an example for each type of transmission.

Answer 83

Through air/droplets: the infected person releases droplets or aerosols when coughing or sneezing, infecting people who inhale the droplets/aerosols. An example is influenza.
Through animals: dengue fever is transmitted through mosquitos.
Through body fluids: AIDS is transmitted through body fluids including blood, semen, breast milk, but not saliva nor sweat. It can also be transmitted through sharing of needles, transfusion of contaminated blood, and through giving birth.
Through direct contact: athlete’s foot is transmitted by contact of contaminated floors, towels, etc.
Through water or food: cholera is transmitted through water and food. The vomit and faeces of patients diagnosed with this type of disease are contaminated as well.

Question 84

How can we maintain good personal and envrionmental hygiene to prevent infectious diseases?

Answer 84

Air/droplets: wear a surgical mask, cover mouth and nose when coughing and sneezing, close the toilet lid when flushing, wash hands, maintain good ventilation.
Water/food: boil drinking water and cook food thoroughly to kill microorganisms, wash hands after using the toilet and before eating, keep food refrigerated below 4C.
Direct contact: avoid close contact with infected patients, wash hands with soap frequently, clean objects and surfaces in public areas frequently.
Bodily fluids: Do not share needles, razors etc, wear gloves when handling wounds, use condoms during sexual intercourse.
Animals: kill or avoid contact with animals that carry pathogens by using insecticides or insect repellent, prevent the growth of animals that carry pathogens.

Question 85

How does vaccination work?

Answer 85

Our bodies have an immune system that protects us from infectious diseases. However, it takes time for the immune system to respond when the body encounters a new kind of pathogen for the frist time. Vaccination works by preparing the immune system so that it can respond quickly when we are infected by the pathogen the vaccine caters for.
A vaccine, containing weakened or dead pathogens, is introduced. It stimulates the immune system to produce antibodies by the white blood cells to destroy the vaccine.
If pathogens of the same kind enter our bodies, the immune system can quickly recognise them and produce a larger amount of antibodies to destroy them. We develop immunity against the disease.
some vaccines only contain parts of the pathogen/antigens. Most vaccines offer long-term protection, but for pathogens that undergo genetic changes frequently, the antigens are changed and we need to re-take the vaccines from time to time. eg. influenza

Question 86

What are the functions of antibodies? (extra)

Answer 86

1. They group pathogens together so that white blood cells can engulf pathogens through a process called phargocytosis.
2. They bind with toxins and act with antitoxins to make them harmless to the body.

Question 87

What are non-infectious diseases?

Answer 87

Non-infectious diseases are not caused by microorganisms and do not spread from one person to another. They usually develop slowly and last for a long time. Non-infectious diseases are becoming more common in many parts of the world, with examples being cardiovascular diseases, colorectal cancer, lung cancer and diabetes.

Question 88

How are non-infectious diseases related to lifestyles?

Answer 88

Most non-infectious diseases do not have a single cause, but are related to more than one risk factor. A risk factor increases a person’s risk of developing a disease, such as alcohol drinking which damages the liver, smoking which damages the lungs and heart, unbalanced diet, being overweight etc.
Many risk factors of non-infectious diseases are related to unhealthy lifestyles. Developing a healthy lifestyle can prevent non-infectious diseases.

Question 89

What causes cardiovascular diseases?

Answer 89

Cardiovascular diseases are a group of disease that affect the heart and blood vessels. They are usually caused by the build-up of lipid deposits in the blood vessels. If there is a high level of lipids in our blood, these may be deposited on the inner walls of the blood vessels. This narrows the blood vessels and decreases the rate of blood flow. In serious cases, the blood vessels may become blocked.

Question 90

What are two health problems caused by the build-up of lipid deposits in blood vessels?

Answer 90

1. Coronary heart disease: if teh blood vessels supplying blood to heart muscles are blocked, the heart cannot get enough oxygen and nutrients. This results in coronary heart disease. The heart cannot pump blood effectively and may even stop beating, causing death. in severe cases of coronary heart diseases, severe chest pain occurs, the heartbest becomes irregular, and the heart may stop beating. It can be trested by balloon angioplasty or coronary bypass surgery.
2. Stroke: if the blood vessels supplying blood to the brain are blocked, the brain cells cannot get enough oxygen and nutrients and may die. This results in stroke. Depending on which parts of the brain are damaged, the patient may lose ability to control some body parts. It may result in death.

Question 91

How is cancer caused?

Answer 91

Normally, cells in the body divide in an orderly way. However, if the mechanisms that control cell division fail, cells may divide in an uncontrolled way, forming a tumour. Tumours can be benign or maligant, where benign tumours grow slowly and do not spread to other parts of the body.
Maligant tumours are cancers. They can invade nearby tissues and spread to other parts of the body to form more maligant tumours. Cancer may form in different parts of the body, resulting in different cancers. Examples are colorectal cancer, lung cancer, skin cancer, and cervical cancer.

Question 92

What are the risk factors and signs of lung cancer?

Answer 92

Risk factors:
1. smoking
2. air pollution
3. family history
4. weakened immunity
5. exposure to harmful chemicals, eg. radon gas, asbestos (used as insulation)

Signs:
1. persistent coughing, coughing blood
2. shortness of breath
3. chest pain
4. losing weight
5. bone pain

Question 93

What are the risk factors and signs of skin cancer?

Answer 93

Risk factors:
1. exposure to ultraviolet light
2. radiation
3. having fair skin
4. HPV infection
5. weakened immunity
6. family/personal history of skin problems

Signs:
1. waxy bump/red nodule/crusted lesion
2. a large spot with inconsistent colour
3. colour-changing mole
4. lesions with red/pink/white/blue/blue-black colours and irregular border

types of skin cancer: melanoma, basal cell carcinoma, squamous cell carcinoma

Question 94

What are the risk factors and signs of breast cancer?

Answer 94

Risk factors:
1. lack of physical activities
2. drinking alcohol
3. obesity
4. age
5. genetic factors; family history

signs:
1. breast lump/thickening
2. change in size, shape, or appearance of breast
3. peeling, scaling, crusting/flaking
4. redness/pitting

Question 95

What are the risk factors and signs of cervical cancer?

Answer 95

Risk factors:
1. HPV infection
2. having STDs (sexually transmitted diseases)
3. having multiple sex partners
4. smoking
5. weakened immunity

Signs:
1. vaginal bleeding after intercourse, between periods, or after menopause
2. watery, bloody vaginal discharge that may have a foul odour
3. pelvic pain/pain during intercourse

Question 96

List 4 risk factors of cancer.

Answer 96

1. genetic factors: people who carry certain genes in their DNA have an increased risk of some cancers like breast cancer.
2. infection by viruses eg. infection by Human papillomavirus increases the risk of cervical cancer.
3. exposure to chemicals: exposure to asbestos increases risk of lung cancer.
4. exposure to radiation: exposure to UV radiation for a long time increases the risk of skin cancer.

Question 97

What is diabetes and how is it caused?

Answer 97

Diabetes is a disease in which the patient’s blood glucose level is too high because the body cannot effectively regulate the amount of glucose in blood. Diabetes patients may become thirsty and tired easily. The high blood glucose level may cause damage to many organs, including the heart, eyes and kidneys.
Blood glucose level is regulated by insulin, which is a hormone produced by the pancreas to decrease blood glucose level. In a diabetes patient, the body does not produce enough insulin or does not respond to insulin properly. They need to inject insulin to control their blood glucose level.
Diabetes may be related to genetic factors, but most cases are caused by unhealthy lifestyles and can be prevented by having a balanced diet and exercisign regularly.

Question 98

What are the functions of insulin? (extra)

Answer 98

1. to stimulate liver cells to convert excess glucose into glycogen and store them in liver and muscles
2. to stimulate body cells to use more glucose in respiration to reduce glucose content in blood.

Question 99

What are similarities and differences between type I and type II diabetes? (extra)

Answer 99

Type I diabetes patients are insulin-dependent. They do not produce insulin and need to inject insulin.
Type II diabetes patients are non-insulin-dependent. Their body cells/liver cells do not respond to insulin well, or they do not produce enough insulin. This type of fiabetes is more common and caused by unhealthy lifestyle like imbalanced diets or lack of exercise. It can be managed by controlling diet and weight.
Both diabetes patients have an increased risk of amputations from reduced blood flow or nerve damage, usually in the lower limbs. Wounds are also harder to heal, causing amputations.

Question 100

What is biotechnology?

Answer 100

Biotechnology is then use of living organisms or biological processes to make useful products or to develop new technologies. It is applied through the production of genetically modified food.
Modern biotechnology often involves changing the genetic materials of living things. For example, genetically modified food is produced by changing the genetic materials of the crops or livestock to give them desirable traits like resistance to chemicals or diseases, improved nutrition value or higher growth rate.

Question 101

List three examples of geneticlaly modified food.

Answer 101

1. soya can be genetically modified to make them resistant to herbicides.
2. Rice can be genetically modified to contain beta-carotene, which can be converted to vitamin A and offer higher nutritional value.
3. Salmon can be generically modified to grow twice as fast, increasing productivity and food supply.

Question 102

What are potential hazards of biotechnology? (extra)

Answer 102

The long-term effects of intaking genetically modified food is unknown. In addition, new genes or products in genetically modified food may cause allergic reactions.

Question 103

How is biotechnology applied in production of medical products, and what are its advantages?

Answer 103

Biotechnology can be used to make medical products such as medicines and vaccines. For example, scientists have successfully made genetically modified E. coli bactera that can produce human insulin for patients with type I diabetes.
The advantages of producing insulin this way is that insulin produced is structually identical with that produced in human bodies, which will not be rejected by the immune system. The efficiency of pure insulin production is increased, yield increases, and cost decreases, since bacteria has a high growth rate and produces insulin continuously.

Question 104

How is biotechnology applied in testing for genetic diseases?

Answer 104

Genetic diseases are the result of abnormal changes (mutations) in our DNA which affects the normal functions of the body. They can be tested using biotechnology, since DNA nutations in a person’s cells or blood can be detected through biotechnological means.
Down syndrome, where the patient has an extra 21st chromosome, causes decreased/poor muscle tone, short neck, flattened facial profile and mental disabilities. It can be detected in a foetus.
new-born screening checks newborn babies for genetic diseases like G6PD, where red blood cells break down prematurely and cause anaemia. Early detection prevents symptoms or minimises disease severity.
Carrier testing helps couples find out if they carry vulnerable genes. One example is a genetic disease thalassaemia, where little or no haemoglobin is produed, and the red blood cells are malformed.

Question 105

How is biotechnology applied in identifying pathogens?

Answer 105

Each type of pathogen has a unique DNA sequence and unique proteins. Biotechnology can be used to detect these DNA or proteins, identifying the pathogen.
For example, to determine if a patient has influenza, a sample can be taken from the patient’s nose or throat for testing. If the test shows that influenza DNA or proteins are present from colour changes, doctors can conclude that the patient has influenza. Then, antiviral drugs that specifically target influenza can be prescribed.