ch 3 Food

Question 1

what are the elements present in food ?

Answer 1

c, h, o, n, (p, s)

Question 1

why is food necessary?

Answer 1

as a source of energy
growth and repair etc.

Question 2

what are the elements present in dissolved salts?

Answer 2

sodium, magnesium, chlorine, potassium, calcium.

Question 3

what are the three trace elements?

Answer 3

iron, copper, zinc
only required in tiny amounts

Question 4

what are biomolecules?

Answer 4

chemicals that are made inside a living thing.

Question 5

carbohydrates - elements
what is the ratio?
formula?
example?

Answer 5

c, h, o
2:1
Cx(H2O)y
glucose C6H12O6

Question 6

what are the three types of carbs?

Answer 6

monosaccharides
disaccharides
polysaccharides

Question 7

what are monosaccharides?

Answer 7

single sugar unit, simplest carb, water soluble

Question 8

what is a disaccharide?

Answer 8

composed of two sugar units joined together, water soluble e.g. maltose

Question 9

what is a polysaccharide?

Answer 9

composed of many sugar units, insoluble in water, very large molecules, e.g. starch

Question 10

structural role of carbs

Answer 10

cellulose is used to form plant cell walls.

Question 11

metabolic role of carbs

Answer 11

glucose is broken down in respiration to produce energy.

Question 12

lipids - elements
ratio?
temp?
structure?

Answer 12

c, h, o
no simple ratio, very little oxygen
fats = SOLID at room temp
oils = LIQUID at room temp
triglyceride - glycerol linked to three fatty acids

Question 13

what is a phospholipid?

Answer 13

fat like substance in which one of the fatty acids is replaced by a phosphate group.

Question 14

what is the structural role of lipids?

Answer 14

lipids are important food stores in plants and animals.

Question 15

what is the metabolic role of lipids?

Answer 15

lipids can be broken down in respiration to release energy.

Question 16

Protein- elements
ratio?
structure?
sources?

Answer 16

c, h, o, n
no ratio but they are very large and complex
composed of amino acids, held together by peptide bonds
meat, eggs etc.

Question 17

how many common amino acids is there ?

Answer 17

20

Question 18

what is a polypeptide?

Answer 18

has more than 20 amino acids
a protein is a long polypeptide (at least 200 amino acids)

Question 19

what are the two types of proteins? explain

Answer 19

fibrous- show little to no folding. they form long fibres, strong and tough e.g. keratin in hair and nails

globular- show lots of folding, form rounded shapes, e.g. enzymes.

Question 20

what is the structural role of proteins?

Answer 20

fibrous proteins such as keratin are found in skin and hair.

Question 21

what is the metabolic role of protein?

Answer 21

they form antibodies to fight infection.

Question 22

vitamins- types, explain

Answer 22

water soluble- B,C soluble in water.
fat soluble- A,D,E,K

Question 23

what is the metabolic role of vitamin c?
deficiency?

Answer 23

the formation of connective tissue, such as the gums, skin
causes scurvy

Question 24

what is the metabolic role of vitamin d?
deficiency?

Answer 24

helps to absorb calcium, healthy bones and teeth
rickets, osteomalacia

Question 25

minerals- why are they needed?

Answer 25

to form rigid bone structures such as bone, to form biomolecules such as haemoglobin.

Question 26

water- why is it needed?

Answer 26

it is a liquid in which all metabolic reactions take place,
it provides the basis of transport systems in organisms

Question 27

where id water mainly found?

Answer 27

the cytoplasm

Question 28

why is water a good solvent?

Answer 28

it is able to dissolve a wide range of molecules.

Question 29

energy transfer reactions- types?

Answer 29

anabolic reactions- use energy to convert smaller molecules into larger ones. e.g. protein synthesis

catabolic reactions- release energy when a complex molecule is broken down to a simpler form. e.g. respiration.

Question 30

what is the test for reducing sugar?
colour change?

Answer 30

benedict’s solution
negative result = blue
positive result = red

Question 31

what is the test for starch?

Answer 31

iodine test
if starch is present- blue/black/purple
if starch is absent- red/yellow

Question 32

what is the test for lipids?

Answer 32

brown paper

Question 33

what is the test for protein?
results?

Answer 33

biuret test
a negative result= blue
a positive result= purple