2 Biological molecules + Movement of substances into and out of cells

Question 1

What chemical elements are present in carbohydrates?

Answer 1

Carbon, Hydrogen, Oxygen

Question 2

What chemical elements are present in lipids?

Answer 2

Carbon, Hydrogen, Oxygen

Question 3

What chemical elements are present in proteins?

Answer 3

Carbon, Hydrogen, Oxygen, Nitrogen

Question 4

What are carbohydrates used for?

Answer 4

Broken down in respiration, to release energy in form of ATP. Energy used for other reactions and processes in cells

Question 5

Name 3 polysaccharides (polymers of glucose)

Answer 5

Cellulose, starch, glycogen

Question 6

What are the smallest units of carbohydrates?

Answer 6

Simple sugars:
glucose and fructose (monomers)

Question 7

How can sucrose be made?

Answer 7

joining two sugar molecules:
glucose + fructose
Sucrose = plant sugar

Question 8

What are complex carbohydrates? (polysaccharides)

Answer 8

Made up from simple sugars/ many sugar molecules:
Starch - store glucose in plants
Glycogen - store glucose in animals and fungi

Question 9

Why are starch and glycogen better storage molecules?

Answer 9

they are less soluble than simple sugars so have less effect on water movement in and out of cells

Question 10

What are the two main polysaccharides in plants?

Answer 10

cellulose and starch

Question 11

What is a triglyceride made up of? (What are lipids made up of?)

Answer 11

Glycerol and 3 fatty acids

Question 12

What What is the function of lipids?

Answer 12

Energy storage
Part of cell membrane
Thermal insulation
Electrical insulation - around nerve cells
Buoyancy - marine animals such as whales to float

Question 13

Compare carbohydrates and fats as energy sources.

Answer 13

Carbs give instant source of energy while fats take longer to break down so slower release of energy

Question 14

What is the monomer of proteins? (What are proteins made up of?)

Answer 14

amino acids (many joined together)

Question 15

What are the functions of proteins?

Answer 15

Growth and repair of tissues
Structural molecules (collagen, keratin)
Enzymes (controlling chemical reactions)
Hormones
Antibodies
Transport (haemoglobin and cell membrane proteins)

Question 16

What is the chemical test for glucose?

Answer 16

Add Benedict’s solution to food sample in solution
Heat in 85ºC water bath
Turns from blue to brick red
Green/yellow/orange = positive result but lower concentration of the sugar

Question 17

What is the chemical test for starch?

Answer 17

Add a few drops of iodine to sample on spotting tile
Turns from orange to blue-black

Question 18

What is the chemical test for protein?

Answer 18

add Biuret solution to food sample
turns from blue to purple/mauve

Question 19

What is the chemical test for lipids?

Answer 19

Emulsion test:
Add ethanol to food sample in test tube and shake
add equal volume of water
turns from clear to milky white

Question 20

What is an enzyme?

Answer 20

a biological catalyst which speed up reactions. They are made of proteins. They lower the activation energy of a reaction.

Question 21

What is a catalyst?

Answer 21

a substance which increases the speed of a reaction, without being changed or used up in the reaction.

Question 22

What are the chemical reactions in the body that enzymes speed up called?

Answer 22

metabolic reactions

Question 23

How do enzymes catalyse a specific reaction?

Answer 23

Lock and key theory
Substrate and enzyme collide
Substrate binds to active site of enzyme
Forms enzyme-substrate complex
products are then released
Enzyme catalyses next reaction

Question 24

Why can enzymes only catalyse one type of reaction?

Answer 24

Active site has specific shape which is complementary to shape of substrate

Question 25

What conditions speed up enzyme reactions?

Answer 25

• Temperature
• Concentration of enzymes
• Optimum pH
• Concentration of substrates

Question 26

How does temperature change the rate of an enzyme-catalysed reaction?

Answer 26

high temps increase the rate at first
the enzymes have more kinetic energy
they move faster so there are more successful collisions
if too hot, violent collisions break bonds in active site changing its shape so substrate cant fit.
Enzyme is denatured as no longer complementary to substrate

Question 27

How does pH affect the rate of an enzyme-catalysed reaction?

Answer 27

If pH is too high or low, it interferes with bonds holding enzymes together.
Changes shape of the active site and denatures the enzyme. All enzymes have an optimum pH they work best at. Optimum pH is often neutral 7 pH.

Question 28

Describe investigation of temperature affecting enzymes when measuring how fast a substrate disappears

Answer 28

Enzyme amylase catalyses breakdown of starch to maltose
Easy to detect starch using iodine solution - if starch present iodine will turn from browny-orange to blue-black
Put starch solution and amylase enzyme into boiling tube and heat in water bath at correct temperature
Put a drop of iodine solution into each well on spotting tile
Every minute drop a sample of mixture into a well using a pipette
When iodine solution remains browny-orange no starch present Record total time taken
Repeat with water bath at different temperatures to see how it affects time taken for starch to be broken down.

Question 29

PAPER 2 Explain investigation of how pH affects enzyme activity.

Answer 29

Potato contains enzyme catalase, which breaks down hydrogen peroxide, forming water and oxygen gas
Add 10 potato disks (1cm thick cut with cork borer) to hydrogen peroxide in a conical flask with bung on top
attach gas syringe to measure volume of gas produced in 5 minutes
repeat 3 times and calculate mean
pH can be altered by adding different volumes of weak alkali or weak acid

Question 30

What is diffusion?

Answer 30

the net movement of particles from an area of high concentration to low concentration, down a concentration gradient

Question 31

Explain the diffusion of oxygen from cell to cell.

Answer 31

Oxygen particles are moving from an area of high to low concentration, down a concentration gradient. This means particles will spread out more by moving through the cell membrane, particles will move faster if the cell membrane is thin

Question 32

Why does diffusion happen in liquids and gases?

Answer 32

particles are free to move about randomly

Question 33

What is Osmosis?

Answer 33

The net diffusion of water molecules across a selectively permeable membrane, from a region of higher water potential to lower water potential

Question 34

What is water potential?

Answer 34

the ability of water molecules to move freely

Question 35

How does solute concentration affect water potential?

Answer 35

solutes (eg glucose or salt) bond with water molecules. Thus meaning there are less free water molecules that could move.
the more solute present, the fewer water molecules can move freely and the lower the water potential

Question 36

What is a solution with a low solute concentration known as?

Answer 36

hypotonic - weak solution

Question 37

What is a solution with a high solute concentration known as?

Answer 37

hypertonic - strong solution

Question 38

Why is a barrier needed during osmosis

Answer 38

(selectively permeable) to measure movement of water

Question 39

Why does increasing temperature increase diffusion?

Answer 39

Increasing temperature, increases kinetic energy
particles move around faster and spread out faster
diffusion therefore takes place faster at high temperatures

Question 40

Use CORMS to outline investigation of Osmosis in living systems.
(Potato Cylinders)

Answer 40

Change - salt concentration
Organism - same species of swede
Repeat - Do each concentration 10x
Measure - change in mass
Same - temp, time, SA of potato

Question 41

What is active transport?

Answer 41

The movement of particles against a concentration gradient using energy released in respiration

Question 42

How is active transport used in the digestive system?

Answer 42

If lower concentration of nutrients in gut than blood, active transport allows nutrients to be taken into the blood, despite concentration gradient being wrong way. Essential to stop us starving. Needs energy from respiration to happen.

Question 43

How does SA:Volume affect movement of substances?

Answer 43

Rate of diffusion, osmosis, active transport is higher in cells with larger SA:Volume. Substances move into and out of smaller cube faster.

Question 44

How does Distance affect movement of substances?

Answer 44

Short distances increases rate
as substances can move in and out of cells quicker
eg thin cell membrane

Question 45

How does Temperature affect movement of substances?

Answer 45

Increasing temperature, increases rate
particles have more kinetic energy
so they move faster
so move in and out of cells faster

Question 46

How does Concentration Gradient affect movement of substances?

Answer 46

Doesn’t affect rate of active transport
Bigger difference in concentration increases rate of diffusion and osmosis
If lots more particles on one side, more to move across so substances move in and out faster

Question 47

Outline investigation of Diffusion in non-living systems.

Answer 47

Independent - amount of jelly/ size of cell (SA:Volume)
Dependent - Time taken to change colour (pink - colourless as acid diffuses into jelly and neutralises sodium hydroxide)
Control - Same volume of hydrochloric acid, temperature of acid, concentration of acid
Risks - getting acid in someones eye
Do multiple repeats
Equipment:
Measuring cylinder
Stop watch
Teaspoon to handle agar cube
100cm³ glass beaker
Hydrochloric acid
Agar cubes containing alkali and cresol red indicator