biology 1 : biological molecules - Carbohydrates

Question 1

what are monomers

Answer 1

smaller units from which large molecules are made from

Question 2

name 3 examples of monomers

Answer 2

monosaccharides
amino acids
nucleotides

Question 3

what are monosaccharides

Answer 3

monomers from which larger carbohydrates are made

Question 4

give examples of monsaccharides

Answer 4

glucose fructose galactose

Question 5

what happens in a condensation reaction between two monosaccharides

Answer 5

forms a 1-4 glycosidic bond

Question 6

what are disaccharides

Answer 6

formed by the condensation of two monosaccharides

Question 7

name all the diassacharides formed by the condensation of glucose

Answer 7

glucose + glucose -> maltose
glucose + fructose -> sucrose
glucose + galactose - > lactose

Question 8

what are isomers

Answer 8

elements with the same chemical formula but different arrangement of atoms

Question 9

what are the two types of glucose and what are they

Answer 9

alpha glucose
beta glucose
isomers

Question 10

how are polysaccharides formed

Answer 10

condensation of many glucose units

Question 11

what is formed at alpha condensation

Answer 11

glycogen and starch

Question 12

what is formed at beta condensation

Answer 12

cellulose

Question 13

what are reducing sugars

Answer 13

acts as a reducing reagent in chemical reactions (donates electrons to other molecules)

Question 14

name all the reducing sugars

Answer 14

glucose fructose
lactose and maltose

Question 15

how to test for reducing sugars

Answer 15

grind food in distilles water than filter out the solid particles
3 cm^3 of food solution into the boiling tube and add 3cm^3 of benedict solution
place boiling tube into boiling water for 5 min
if reducing sugar is present changes the colour will change depending on the amount of reducing sugar
green,yellow,orange,brick red

Question 16

what makes the bendict solution blue

Answer 16

contains copper ion cu2+

Question 17

why is the benedict test unreliable

Answer 17

only gives a very approximent idea of reducing sugar
only gives a narrow range of colour changes
humans perceive colour differently

Question 18

what is the test for non reducing sugars

Answer 18

add dilute hydrochloric acid

heat in a water bath

neutralize it using sodium hydrogencarbonate

complete benedict test

a positive result will form a colourful precipitate

Question 19

why do you need to check if the solution is alkaline for the benedict test

Answer 19

benedict test will not work under acidic conditions

Question 20

how to test for starch

Answer 20

3cm^3 of food solution then add 1cm^3 of iodine and potassium iodide
blue black if starch is present
stays orange is there is no starch

Question 21

how to test for protein

Answer 21

3cm^3 of food solution then add 3cm^3 dilute hydroxide
add 10 drops of dilute copper sulphate
if protein is present solution will turn purple
if not solution will stay blue

Question 22

what is biuret solution

Answer 22

sodium hydroxide and copper sulphate being premixed

Question 23

what does the test for protein also test for

Answer 23

peptide bonds (protein has them amino acids don’t)

Question 24

how to test for lipids

Answer 24

food mixture can not be mixed as lipids can stick to filter paper
leave food mixture to allow particles to settle
add 3cm^3 of food solution then add 3cm^3 of ethanol and water
shake solution
if lipids are present a white cloudy emulsion will form
if not it will stay clear

Question 25

test for iodine

Answer 25

add iodine dissolved in potassium iodide
positive test will be orange to blue black

Question 26

what is the two things starch is made out of

Answer 26

amylopectin
amylose

Question 27

what does amylopectin contain that is useful for its function

Answer 27

long and chained

side branches allow enzymes that break down the molecule to get at the glycosidic bond

Question 28

what does amylose contain that is useful for its function

Answer 28

long, unbranched,coiled shape

this makes it compact which causes it to be good for storage as it can fit more in a small space

Question 29

what is cellulose suited for its functions

Answer 29

long, unbrached and straight cellulose chains(when beta glucose bond)

these chains are linked by hydrogen bonds to form strong fibers (microfibrils)

this means that it provides strong structural support

Question 30

what does glycogen contain that is useful for its function

Answer 30

long and brached
contains alot of side branches so stored glucose can be released quickly
very compact