Biomolecues

Question 1

Carbohydrates

Answer 1

has carbon, hydrogen, oxygen

monosaccharides 
water soluble
sweet
all are reducing sugars
glucose fructose galactose

disaccharides 
water soluble sweet
all are reducing sugars except sucrose
glucose + glucose --> maltose
glucose + fructose --> sucrose
glucose + galactose --> lactose
maltose, sucrose (sugar canes), lactose (milk)

polysaccharides 
water insoluble
no sweet taste
non-reducing
starch (storage form in plants)
glycogen (storage form in animals)
cellulose (structural part in plants)

Question 2

Glucose

Answer 2

it is oxidized to release energy by respiration

Question 3

glycogen/starch

Answer 3

excess carbohydrates can be converted to glucose or starch as a storage form in animals and plants respectively

glucose is stored in muscles and liver

they are good storage components because they are :
compact to pack many sugar units into a small volume
water-insoluble and will not upset the osmotic balance of cells

Question 4

cellulose

Answer 4

it forms cell wall for providing support to plant cells

Question 5

deoxyribose/ribose

Answer 5

it forms nucleic acids

DNA: deoxyribose
RNA: ribose

Question 6

lipids

Answer 6

has carbon, hydrogen, oxygen, phosphorus

all are :
insoluble in water
soluble in organic solvents (alcohol and ether)

triglycerides
saturated fat
all fatty acids in a triglyceride are saturated
unsaturated fat
any of the fatty acids in a triglyceride is unsaturated

is oxidized to release energy by respiration
often stored in fat-containing tissues called adipose tissue. The tissue can be found around internal organs and under the skin
act as food reserve
reduce heat loss
shock-absorber for protecting internal organs
transport of fat-soluble vitamins

steroids
as a component of cell membrane
serves as the raw materials for producing sex hormones which are important for sexual development

phospholipids
as the major component of cell membrane

Question 7

proteins

Answer 7

has carbon, hydrogen, oxygen, nitrogen, sulfur

there are 20 different amino acids in the body

• some of them can be made by the human body
• some of them must be obtained from diet

excess amino acids cannot be stored in the body. The excess amino acids are broken down by liver into urea. This process is called deamination

amino acids

peptides

polypeptides

for growth and repair
- it is used to make cell membrane and cytoplasm

for making various important substances in the human body :
enzymes
- as biological catalyst
hormones
- as chemical signals
haemoglobin
antibodies
-for body defence

can be oxidized to release energy by respiration when carbohydrates and fats are in shortage

Question 8

nucleic acids

Answer 8

has carbon, hydrogen, oxygen, nitrogen, phosphorus

nucleotides are the building blocks of nucleic acids

some nucleic acids can act as an energy carrier
- ATP (adenosine triphosphate)

some nucleic acids can act as carriers of genetic information
- RNA (ribonucleic acid) and DNA (deoxyribose)