Biology Flashcards
(105 cards)
1
Q
What are primary food substances?
A
Primary food substances are food substances that carry energy value. They include proteins, carbohydrates, and lipids.
2
Q
What are protective food substances?
A
Protective food substances carry no energy value. They include vitamins, minerals, and dietary fibre.
3
Q
What are some examples of carbohydrates and foods rich in carbohydrates?
A
Starch: food rich in starch: bread, rice, potatoes
Sugar: food rich in sugar: fruits, candies, chocolate
4
Q
*What are carbohydrates made of? (extra)
A
*Carbon, hydrogen, and oxygen, with the ratio of hydrogen and oxygen being 2:1.
5
Q
*How can carbohydrates be classified? (extra)
A
*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.
6
Q
What are examples of monosaccharides, disaccharides, and polysaccharides?
A
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
7
Q
*How can monosaccharides become disaccharides or polysaccharides, and how can disaccharides and polysaccharides be decomposed into monosaccharides? (extra)
A
*Monosaccharides undergo condensation to become disaccharides or polysaccharides, and polysaccharides or disaccharides can be broken down to monosaccharides by hydrolysis.
8
Q
*What are the properties of monosaccharides and disaccharides? (extra)
A
*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.
9
Q
What are the uses of glycogen and cellulose?
A
*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.
10
Q
What are the functions of carbohydrates?
A
- They are the main energy source for body activities
- They serve as energy reserves in the form of glycogen in liver or muscles.
- Cellulose is a source of dietary fibre.
11
Q
What are the tests for glucose?
A
- Clinitix test paper: changes from pink to blue in the presence of glucose
- 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.
12
Q
What is the test for starch?
A
Iodine test: iodine solution turns from brown to blue-black in the presence of starch.
13
Q
*What is the test for reducing sugars? (extra)
A
*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.
14
Q
What are types of lipids and food rich in them?
A
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.
15
Q
What is a common example of lipids, and what are the properties of lipids?
A
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. *
16
Q
What are the functions of lipids?
A
- 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.
- Shock absorber: The fat stored in adipose tissues also act as a shock absorber to protect internal organs.
- Heat insulator: subcutaneous fat reduces heat loss from the body.
- 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)
17
Q
What are the differences between lipids and phospholipids? (extra)
A
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.
18
Q
How do phospholipids arrange to become a cell membrane? (extra)
A
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.
19
Q
What is the test for lipids?
A
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.
20
Q
What are the functions of proteins?
A
- For growth and repair of body tissues, as many body tissues are made up of proteins (eg. Muscles, bones, skin, hair, blood)
- 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)
21
Q
What disease is likely when there is a lack of proteins in the diet?
A
Kwashiorkor: causes weak muscles and a swollen abdomen, common among children in developing countries.
22
Q
What are some examples of food rich in protein?
A
Meat, egg, milk
23
Q
What are proteins molecules made up of and what are their building blocks?
A
*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.
24
Q
*How can longer chains be formed by amino acids? (extra)
A
*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.
25
*How do polypeptides form proteins? (extra)
*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.
26
How are the unique shapes of protein important?
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.
27
*What are 5 types of membrane proteins and their functions? (extra)*
*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*
28
How many amino acids are there in our body?
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.
29
What is the test for proteins?
**Protein/Albustix test paper**: it turns from **yellow to green** in the presence of protein.
30
What are characteristics of vitamins?
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**.
31
How are vitamins classified?
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.*
32
What is the importance of vitamin A and what are deficiency diseases of vitamin A?
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).*
33
What are sources of vitamin A?
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.
34
What is the importance of vitamin D, its deficiency disease, and its sources?
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.
35
What are functions of vitamin C and its deficiency disease?
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**.
36
What is the test for vitamin C?
**DCPIP** test: the food sample is added to the DCPIP solution. If the **blue DCPIP solution decolourizes**, it shows that vitamin C is present.
37
What are the properties of minerals?
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**.
38
What are the functions of calcium and what are its deficiency diseases?
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**.
39
What is the function of iron and what is its deficiency disease?
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.
40
What is the function of iodine and what is its deficiency disease?
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)
41
What are characteristics of dietary fibre?
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**.
42
What is the function of dietary fibre?
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**.
43
What are the functions of water?
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.)
44
What are some facts about water?
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**.
45
What is digestion?
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.
46
What are parts of the human digestive system?
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**.
47
What is the difference between physical digestion and chemical digestion?
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**.
48
*What are the steps of obtaining nutrients? (extra)
*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.
49
What is the purpose of chewing?
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.
50
*What are starch, protein, and lipids broken down into after digestion? (extra)
*starch: broken down into maltose and **glucose**
protein: broken down into **amino acids**
lipids: broken down into **glycerol** and **fatty acids**
51
What types of digestion take place in the mouth cavity?
**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.
52
*What are the components and functions of saliva? (extra)*
*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.*
53
What is the purpose of the oesophagus?
It pushes food down to the stomach by **peristalsis**. The rate of digestion there is **insignificant**.
54
What types of digestion take place in the stomach?
**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.
55
What types of substances does the stomach secrete and what are their functions?
***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.
56
What types of digestion take place in the small intestine?
**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.
57
What are the properties of bile?
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.
58
*What are the properties of pancreatic juice? (extra)
*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.
59
*What are the properties of intestinal juice? (extra)
*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.
60
*What are the functions of the gallbladder? (extra)
*The gallbladder temporarily **stores and concentrates bile**. It contracts and controls the **release** of bile into the small intestine.
61
What is absorption?
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**.
62
What are the features of absorption?
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.
63
*What are the characteristics of the small intestine? (extra)
*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**.
64
What are the functions of the large intestine?
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**.
65
What are the types and functions of human teeth?
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.
66
What is the arrangement of human teeth?
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**.
67
How can a tooth be divided into three parts?
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**.
68
What are the five main parts making up a tooth and their functions?
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**.
69
How is tooth decay formed and repaired?
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.)
70
What may be a factor leading to increased risk of tooth decay?
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.
71
What is periodontal disease and how is it formed?
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**.
72
How can we take good care of out teeth and gums to prevent oral diseases?
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.
73
How should we maintain a balanced diet?
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.
74
What is the food pyramid?
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.
75
What are the energy values of food and energy values of primary food substances?
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.
76
What are the factors affecting the daily energy requirement of a person?
**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.)
77
What are the effects of over-eating on body mass and health?
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**.
78
What are the effects of under-eating on body mass and health?
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.
79
How do we calculate BMI?
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)**
80
What are two types of diseases and how do we distinguish them?
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.
81
What are the causes of infectious diseases?
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).
82
List one example of viruses, bacteria, and fungi.
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**.
83
How are infectious diseases transmitted? List an example for each type of transmission.
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.
84
How can we maintain good personal and envrionmental hygiene to prevent infectious diseases?
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.
85
How does vaccination work?
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*
86
*What are the functions of antibodies? (extra)*
*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.*
87
What are non-infectious diseases?
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**.
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How are non-infectious diseases related to lifestyles?
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.
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What causes cardiovascular diseases?
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**.
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What are two health problems caused by the build-up of lipid deposits in blood vessels?
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.
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How is cancer caused?
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.
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What are the risk factors and signs of lung cancer?
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
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What are the risk factors and signs of skin cancer?
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*
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What are the risk factors and signs of breast cancer?
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
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What are the risk factors and signs of cervical cancer?
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
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List 4 risk factors of cancer.
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.
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What is diabetes and how is it caused?
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.
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*What are the functions of insulin? (extra)*
*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.*
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*What are similarities and differences between type I and type II diabetes? (extra)*
*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.*
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What is biotechnology?
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.
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List three examples of geneticlaly modified food.
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.
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*What are potential hazards of biotechnology? (extra)*
*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**.*
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How is biotechnology applied in production of medical products, and what are its advantages?
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**.*
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How is biotechnology applied in testing for genetic diseases?
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.*
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How is biotechnology applied in identifying pathogens?
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.
