Nutrients

Question 1

what are carbohydrates?

Answer 1

organic molecules made up of elements carbon, hydrogen and oxygen

Question 2

why is water important? (6 points)

Answer 2

1) solvent in which chemical reactions take place
2) essential for photosynthesis
3) keeps cells turgid/firm
4) helps in transport of dissolved mineral salts in plants
5) regulates body temperature
6) helps transport dissolved substances around body

Question 3

what is the general formula of carbohydrates?

Answer 3

CₙH₂ₘOₘ

*hydrogen-to-oxygen ratio — 2:1

Question 4

what are is difference between the 2 single sugars?

Answer 4

glucose: found in plants and animals
fructose: common in plants, rare in animals

*single sugars can fit through cell membranes and are basic units of carbohydrates
*both chemical compositions are C₆H₁₂O₆, but atoms are arranged differently

Question 5

what is maltose (malt sugar) made of and what is its enzyme?

Answer 5

glucose + glucose, maltase

Question 6

what is sucrose (cane sugar) made of and what is its enzyme?

Answer 6

glucose + fructose, sucrase

*sucrose is a non-reducing sugar

Question 7

what are 4 sources of carbohydrates?

Answer 7

1) bread
2) rice
3) noodles
4) cereal

Question 7

describe Benedict’s test and its results

Answer 7

steps:
1) add 2cm³ of Benedict’s solution to 2cm³ of food sample in test-tube
2) shake the mixture
3) heat contents in boiling water bath for 2-3min

results:
green precipitate — traces
yellow/orange precipitate — moderate amount
brick-red precipitate — large amount
remained blue — no reducing sugars

Question 7

what are the 4 functions of carbohydrates?

Answer 7

1) provide energy for cell activities
2) form supporting structures (e.g. cell wall)/nucleic acid (e.g. DNA)
3) for conversion into other organic compounds (e.g. amino acids/fats)
4) synthesis of lubricants/nectar in flowers

Question 7

what are the structure, role and occurrence of starch?

Answer 7

several thousand glucose molecules joined together

storage form of carbohydrates in plants, found in storage organs of plants (e.g. potato/tubers/tapioca)

*starch broken down by amylase into maltose, maltose broken down by maltase into glucose

Question 8

what are the structure and role of cellulose?

Answer 8

many glucose molecules joined together but bonded differently from starch

makes up cellulose cell walls to protect plant cells/serves as dietary fibres preventing constipation

Question 9

what are the structure, role and occurrence of glycogen?

Answer 9

branched molecule of many glucose molecules

storage form of carbohydrates in animals, stored in liver/muscles of mammals

Question 10

why are starch and glycogen suitable stores of energy? (4 points)

Answer 10

1) insoluble in water (do not change w.p. in cells)
2) large molecules cannot diffuse through cell membranes (won’t be lost from cells)
3) easily hydrolysed to glucose if needed (for tissue respiration)
4) made of molecules that have compact shapes, occupying lesser space

Question 11

describe the iodine test and its results

Answer 11

steps:
add a few drops of iodine solution to food sample

results:
starch present — iodine solution turns blue-black
starch absent — iodine solution remains brown

Question 12

what are fats?

Answer 12

organic molecules made up of elements carbon, hydrogen and oxygen

*contain less much oxygen than hydrogen, has more than 2 times more energy than carbohydrates

Question 13

what compounds are fats made of?

Answer 13

1 glycerol molecule + 3 fatty acid molecules

*fats broken down by lipase

Question 14

what are 3 sources of fats?

Answer 14

1) butter
2) corn oil
3) olives/nuts and their oils

Question 15

what are the 5 functions of fats?

Answer 15

1) source and store of energy
2) act as insulating material to prevent excessive heat loss
3) solvent for fat-soluble vitamins and some hormones
4) form main parts of cell membranes
5) reduces water loss from skin surfaces

Question 16

describe the ethanol emulsion test and its results

Answer 16

steps:
1) add 2cm³ of ethanol to 2cm³ of food sample in clean test-tube
2) shake contents of test-tube vigorously
3) add 2cm³ of water into test-tube and shake mixture

results:
cloudy white emulsion formed — fats present
remains clear — fats absent

Question 17

what are proteins?

Answer 17

organic molecules made up of elements carbon, hydrogen, exygen, nitrogen and sometimes sulfur

*basic sub-units of proteins are amino acids

Question 18

what are the 3 building blocks of protein?

Answer 18

1) amino group
2) acidic group
3) side chain

Question 19

what is the structure of proteins?

Answer 19

peptide bonds link up amino acids to form polypeptides

two or more polypeptide chains fold to form a specific 3-D molecule called protein

Question 20

what are the 8 sources of proteins?

Answer 20

1) red meat
2) seafood
3) egg whites
4) cheese
5) milk
6) nuts
7) beans
8) lentils

Question 21

what are the 3 functions of proteins?

Answer 21

for the synthesis of:
1) new protoplasm for growth and repair of worn-out cells
2) enzymes and some hormones
3) antibodies

Question 22

describe biuret test and its results

Answer 22

steps:
1) add 2cm³ of sodium hydroxide to 2cm³ of food sample in clean test-tube and shake
2) add 1% copper(II) sulfate drop by drop and shake after each drop

results:
violet solution — proteins present
remained blue — proteins absent

Question 23

what if the food sample for Benedict’s and biuret tests are solids?

Answer 23

add water to crushed food to dissolve nutrients, shake and decant mixture into new test-tube before adding reagent

Question 24

what if the food sample for iodine test is solid?

Answer 24

add the iodine solution directly to the crushed food

Question 25

what if the food sample for ethanol emulsion test is solid?

Answer 25

add ethanol to crushed food to dissolve nutrients, shake and decant mixture into new test-tube before adding water