Chapter 4: Chemical Composition in a Cell ( P2 )

Question 1

What are the importance of carbohydrate in a cell?

Answer 1

• provide energy
• to build cell wall using cellulose
• to form external skeletons ( chitin ) of insects
• as energy storage in the form of glycogen in the liver and as starch in plant cells

Question 2

Are proteins organic compounds?

Answer 2

• Yes and they are found in muscles, hair, and skin

Question 3

What are the elements found in proteins?

Answer 3

• carbon
• hydrogen
• oxygen
• nitrogen

Question 4

Are sulphur, phosphorus, and calcium found in most protein?

Answer 4

• No, only sulphur and phosphorus are found in most proteins

Question 5

What are made up of polypeptide polymers?

Answer 5

• Proteins

Question 6

What is the monomer for proteins?

Answer 6

• amino acids

Question 7

How are amino acids joined?

Answer 7

• they are joined together by peptide bonds through condensation

Question 8

When does a water molecule and dipeptide form?

Answer 8

• it is when two amino acids are joined by a single peptide bond through condensation

Question 9

How are polypeptides formed?

Answer 9

• it is when many amino acids are joined together by peptide bonds to form a long chain of amino acids

Question 10

How many types of amino acids are present in proteins?

Answer 10

• 20

Question 11

What is the importance of protein in a cell?

Answer 11

• build new cells for growth
• regeneration
• to form connective tissues
• to form keratin in the skin
• synthesize of hormones

Question 12

What is in first-class proteins?

Answer 12

• contain all amino acids

- animal proteins

Question 13

Are lipid organic compounds?

Answer 13

• Yes and they are made up of long hydrocarbon chains

Question 14

Elements found in lipids?

Answer 14

• Carbon, hydrogen, and oxygen but with a higher ratio of hydrogen to oxygen atoms

Question 15

What are the properties of lipids?

Answer 15

• hydrophobic
• insoluble in water but soluble in organic solvents such as alcohol, ether, acetone, and chloroform.
• naturally formed in the body

Question 16

Whats are the four types of lipids?

Answer 16

• fats
• waxes
• phospholipids
• steroids

Question 17

Tell one difference between fats and oils?

Answer 17

• fats are solid at room.t because of their high melting points
• oils are liquid at room.t because of their low melting points

Question 18

Which category are fats and oils placed in?

Answer 18

• triglycerides

Question 19

Explain triglycerides.

Answer 19

• made up of one molecule of glycerol and three molecules of fatty acid
• involves condensation to form triglyceride and 3 molecules of water

Question 20

What are the two main types of fats?

Answer 20

• saturated fats

- unsaturated fats

Question 21

Compare and contrast saturated fats and unsaturated fats.

Answer 21

Similarities

• both are lipids that contain carbon, hydrogen, and oxygen
• both are insoluble in water

Difference ( saturated )

• solid at room.t
• increases blood cholesterol
• only single bonds between carbon atoms
• Ex: Butter and full cream dairy products

Difference( unsaturated )

• liquid at room.t
• decreases blood cholesterol
• at least one double bond between carbon atoms
• Ex: Olive oil and fish

Question 22

Explain waxes.

Answer 22

• naturally occurring lipid
• one molecule of alcohol and one molecule of fatty acid
• high melting point and insoluble in water
• candles

Question 23

Explain steroids.

Answer 23

• include sex hormones and cholesterol

- insoluble in water

Question 24

What is the importance of lipids in cells?

Answer 24

• produce bile
• synthesize steroid hormones
• protect organs by acting as a heat insulator
• as a solvent for vitamin A, D, E, and K

Question 25

What are nucleic acids?

Answer 25

• organic molecules consisting of polynucleotide

Question 26

Other than carbon and hydrogen, what are the elements found in nucleic acids?

Answer 26

• oxygen
• nitrogen
• phosphorus

Question 27

Explain the structure of nucleotide?

Answer 27

• consists of a pentose sugar ( 5-carbon sugar ), a nitrogenous base, and a phosphate group
• four types of nitrogenous base: adenine(A), thymine(T), guanine(G), and cytosine(C)

Question 28

Explain the structure of DNA.

Answer 28

• made up of millions of nucleotides to form a polynucleotide
• sugar and phosphate chain forms the backbone of DNA
• DNA molecule consists of two polynucleotide chains intertwined in opposite directions