Biological Molecules

Question 1

what are biological molecules

Answer 1

essential molecules: carbohydrates, proteins, lipids, and nucleic acids

Question 2

what is a monomer

Answer 2

a building block, the part that make up substances

Question 3

what is a polymer

Answer 3

molecules made from a large number of monomers joined together

Question 4

chemical elements in carbohydrates

Answer 4

C H O

Question 5

chemical elements in proteins

Answer 5

C H O N

(2 amino acids contain Sulfur)

Question 6

chemical elements in lipids

Answer 6

C H O

Question 7

what are reducing sugars in carbohydrates (include examples)

Answer 7

• reducing sugars are soluble
• they include monosaccharides (glucose, fructose, galactose) and disaccharides (maltose, lactose, sucrose)

Question 8

what is maltose made of

Answer 8

two glucose monomers joined together

Question 9

what is lactose made of

Answer 9

a glucose and a galactose joined together

Question 10

what is sucrose made of

Answer 10

a glucose and a fructose joined together

Question 11

examples of carbohydrate polymers

Answer 11

• starch
• glycogen
• cellulose

Question 12

starch

Answer 12

• glucose polymer only found in plants
• acts as storage for carbohydrates

Question 13

glycogen

Answer 13

• glucose polymer only found in animals
• acts as energy store for liver and muscle

Question 14

cellulose

Answer 14

• makes up plant cell walls
• humans cannot digest cellulose as we do not have the enzymes to break it down
• cellulose forms dietary fibre

Question 15

what are proteins

Answer 15

long chains of amino acids

Question 16

what are enzymes made of

Answer 16

enzymes are made of proteins

Question 17

what is a polypeptide chain

Answer 17

a short chain of amino acids

Question 18

how many amino acids are there

Answer 18

20

Question 19

function of proteins

Answer 19

• muscle building
• immune system health
• enzyme building
• gene building.

Question 20

what are lipids (include examples)

Answer 20

fats and oils
(butter, oil, cholesterol)

Question 21

what are the monomers of lipids

Answer 21

a triglyceride
(made of 1x glycerol and 3x fatty acids)

Question 22

importance of lipids

Answer 22

• good insulators (keep us warm)
• good source of long-lasting energy
• can be good to store energy as well after carbohydrates are used up
• lipids make up cell membranes
• protect organs from damage

Question 23

unsaturated vs saturated lipids

Answer 23

unsaturated = has a double bond in fatty acids
saturated = has no double bonds in fatty acids

Question 24

structure of a cell membrane made of lipids

Answer 24

forms a phospholipid bilayer made of a hydrophobic tail (fatty acid) and hydrophilic head (glycerol and phosphate)

Question 25

what happens to unused carbohydrates

Answer 25

• they are turned into fat

Question 26

example of a bad lipid

Answer 26

cholesterol (it is linked to heart disease)

Question 27

test for starch

Answer 27

• Add 2cm3 iodine solution to the food sample
• if starch is not present = yellow/orange
• if starch is present = blue/black

Question 28

test for reducing sugars

Answer 28

• Add 2cm3 benedict’s solution to 2cm3 sample
• Place test-tube in hot water bath (90ºC) for 5 minutes until colours start to change
• If glucose is present = orange/red (depending on how much
• If glucose is not present = stays blue

Question 29

test for proteins

Answer 29

• add 2cm3 biuret test to 2cm3 sample
• shake
• if protein is present = violet
• if protein is not present = blue

Question 30

test for lipids

Answer 30

• 2cm3 of ethanol to 2cm3 of sample (emlusion test)
• Shake
• Add 2cm3 of distilled water
• If lipids are present = layer of fat at the top or droplets of fat (white-ish)
• If lipids not present = clear sample

Question 31

what do enzymes do

Answer 31

act as biological catalysts by speeding up the rate of a specific reaction without being used up

Question 32

example of enzymes as biological catalysts

Answer 32

in metabolic reactions (e.g. digestion) as they break down food into smaller products

Question 33

how do enzymes function

Answer 33

they have an active site which is where the substrate binds and is broken down into products

Question 34

how are enzymes affected by temperature

Answer 34

enzymes are sensitive to temperature. When above the optimum temperature, enzymes will denature causing it to change the shape of the active site so the substrate no longer fits

Question 35

how are enzymes affected by pH

Answer 35

enzymes are sensitive to pH. when above the optimum pH, enzymes will denature, causing it to change shape of active site so the substrate no longer fits

Question 36

what happens to enzymes near optimum temperature and pH

Answer 36

the rate of enzyme activity will increase as they get closer to their optimum temperature/pH

Question 37

what happens to the enzyme if the temperature is too low

Answer 37

• enzymatic activity decreases in colder temperatures.
• if the temperature is too low, there will be no enzymatic activity

Question 38

practical: investigating how enzyme activity can be affected by changes in pH

Answer 38

AIM:
investigate the effect of pH on amylase
(amylase is an enzyme that digests starch into maltose)

METHOD:
1. add a drop of iodine to each of the wells of a spotting tile
2. use a syringe to place 2cm3 of amylase into a test tube
3. use a syringe to add 1cm3 of buffer solution (pH 2) to the test tube
4. use another test-tube to add 2cm3 of starch solution to the amylase and buffer solution; start the stopwatch and mix with pippette
5. every 10 seconds, transfer a droplet of the solution to a new well of iodine solution (which should turn blue-black)
6. repeat this transfer process every 10 seconds until the iodine solution stops turning blue-black (this means the amylase has broken down all the starch)
7. record the time taken for the reaction to be completed
8. repeat the investigation with buffers at different pH (from ph3 to pH11)

RESULTS AND ANALYSIS:
* At the optimum pH, the iodine stopped turning blue-black and remained orange-brown within the shortest amount of time. This is because the enzyme is working at its fastest rate and has digested all the starch

• At higher or lower pH’s (above or below the optimum) the iodine took a longer time to stop turning blue-black or continued to turn blue-black for the entire investigation. This is because on either side of the optimum pH, the enzymes are starting to become denatured and as a result are unable to bind with the starch or break it down

Question 39

practical: investigating how enzyme activity can be affected by changes in temperature

Answer 39

AIM:
investigate the effect of temperature on the activity of amylase (amylase is an enzyme that digests starch into maltose)

METHODS:
1. Add 5cm3 starch solution to a test tube and heat to a set temperature using beaker of water with a Bunsen burner
2. Add a drop of Iodine to each of the wells of a spotting tile
3. Use a syringe to add 2cm3 amylase to the starch solution and mix well
4. Every minute, transfer a droplet of solution to a new well of iodine solution (which should turn blue-black)
5. Repeat this transfer process until the iodine solution stops turning blue-black (this means the amylase has broken down all the starch)
6. Record the time taken for the reaction to be completed
7. Repeat the investigation for a range of temperatures (from 20°C to 60°C)

RESULTS AND ANALYSIS:
* At the optimum temperature, the iodine stopped turning blue-black the fastest. This is because the enzyme is working at its fastest rate and has digested all the starch

• At colder temperatures (below optimum), the iodine took a longer time to stop turning blue-black. This is because the amylase enzyme is working slowly due to low kinetic energy and few collisions between the amylase and the starch.
• At hotter temperatures (above optimum) the iodine turned blue-black throughout the whole investigation. This is because the amylase enzyme has become denatured and so can no longer bind with the starch or break it down