Topic 1

Question 1

Tests for reducing sugars using Benedict’s reagent

Answer 1

Add Benedict’s reagent to a sample and let it in water bath to 75°C
No reducing sugars —-> higher concentration
Blue (none) > Green > Yellow > Orange > Brick red

Question 2

Biuret test for proteins

Answer 2

Add drops of potassium hydroxide solution to make solution alkaline
Add copper (II) sulfate solution
No protein = solution remains blue
Protein = solution turns purple

Question 3

Emulsion test for lipids

Answer 3

Shake sample with ethanol until it dissolves and pour solution into water
If lipids, they will precipitate out of solution as a milky emulsion
More lipids = more noticeable milky colour

Question 4

Iodine taste for starch

Answer 4

Add iodine solution to test sample
If starch, solution changes from brown to black
No starch = remains brown

Question 5

Energy in food formula (calorimetry)

Answer 5

Mass of water (g) * temp change in water (°C) * 4.2

Energy per gram = energy in food (J) / mass of food (g)

Question 6

Potato cylinder in 0% sucrose solution

Answer 6

OSMOSIS
Water concentration is higher in solution
Water molecules move from solution into potato cylinder, from area of high concentration into low concentration of water
Mass of cylinder increases and cells become turgid

Question 7

Potato cylinder in 80% sucrose concentration

Answer 7

OSMOSIS
Water concentration higher in potato cylinder
Water molecules move from potato cylinder into solution, from a high concentration of water to low concentration of water
Mass of cylinder decreases and cells become less turgid/shrink.

Question 8

Active transport

Answer 8

Movement of particles from an area of low concentration to high concentration, up the concentration gradient, using energy transferred in respiration

Question 9

Diffusion

Answer 9

Movement of particles from an area of high concentration to low concentration, down the concentration gradient
A passive process

Question 10

Nucleus

Answer 10

Contains genetic material that controls activities of the cell. Genetic material arranged into chromosomes.

Question 11

Mitochondria

Answer 11

Where most of the reactions for aerobic respiration take place.

Question 12

Cytoplasm

Answer 12

Gel-like substance where most chemical reactions happen. Contains enzymes that control the chemical reactions.

Question 13

Cell membrane

Answer 13

Holds cell together and controls what does in and out.

Question 14

Ribosomes

Answer 14

Involved in translation of genetic material and synthesis of proteins.

Question 15

Cell wall

Answer 15

Made of cellulose, supports and strengthens cell.

Question 16

Large vacuole

Answer 16

Contains cell sap and maintains internal pressure to support cell.

Question 17

Chloroplasts

Answer 17

Where photosynthesis occurs to make food. Contains chlorophyll.

Question 18

Chromosomal DNA

Answer 18

Controls cell’s activities and replication and floats free in the cytoplasm.

Question 19

Flagellum

Answer 19

Long hair-like structure that rotates to make the bacterium move. Used to move away from harmful substances such as toxins and towards beneficial things such as oxygen and nutirents.

Question 20

Plasmid DNA

Answer 20

Small loops of extra DNA that aren’t part of the chromosome. Contains genes for things such as drug resistance and can be passed between bacteria.

Question 21

Specialised cell

Answer 21

Cells that have structures that make them adapted to their function.

Question 22

How are egg cells adapted to their function

Answer 22

Contains nutrients in the cytoplasm to feed embryo.
Haploid nucleus to fuse with other haploid nucleus to make a diploid zygote.
Membrane changes structure after fertilisation to stop any more sperm getting in so offspring have the right amount of DNA.

Question 23

How are sperm cells adapted to their function

Answer 23

Long tail so can swim to egg.
Lots of mitochondria in middle section to provide energy to swim.
Acrosome at front of head where enzymes stored to digest through membrane of egg cell.
Contains nutrients in the cytoplasm to feed embryo.
Haploid nucleus to fuse with other haploid nucleus to make a diploid zygote.

Question 24

How are ciliated epithelial cells adapted to their function

Answer 24

Line surface of organs and have cilia on their top surface.

Cilia beat to move substances in one direction along surface of tissue.

Question 25

Example where ciliated epithelial cells are

Answer 25

Lining of airways have these to move mucus to the throat to be swallowed.

Question 26

Resolution definition

Answer 26

How well a microscope distinguishes between two points that are close.

Question 27

Light microscopes

Answer 27

Use light to view living cells and can be used to view nuclei and choloroplasts.

Question 28

Electron microscopes

Answer 28

Use electrons rather than light and have higher magnification and resolution so things so smaller things such as inside of mitochondria can be viewed.
Can’t be used to view living cells.

Question 29

How to view specimen with light microscope

Answer 29

Thin slice of specimen.
Use drop of water to keep specimen in place on slide.
Add stain such as iodine.
Place cover slip and press down so no air bubbles and clip it to stage.
Use coarse adjustment knob to move stage up to lens and looking down eye piece, move stage down until its in focus then adjust with fine adjustment knob until clear.
Use clear ruler to find FOV by measuring diameter visible and switch to high magnification lens if necessary.

Question 30

Total magnification formula

Answer 30

Total magnification = eyepiece lens magnification * objective lens magnification

Question 31

Magnification formula

Answer 31

Magnification = Image size / Real size

Question 32

Enzyme

Answer 32

A biological catalyst that increases the speed of a reaction without being changed or used up.

Question 33

Lock and key mechanism

Answer 33

Enzymes only work with one substrate.

For enzyme to work, the substrate has to fit into the active site.

Question 34

Effect of temperature on rate of enzyme-controlled reaction

Answer 34

Higher temp increases rate at first.
Optimum point is where enzyme is most active.
If too hot, bonds holding enzyme together break and active site changes shape so substrate won’t fit anymore. Enzyme is denatured.

Question 35

Effect of pH on rate of enzyme-controlled reaction

Answer 35

If pH is too high or too low, the pH interferes with bonds holding enzyme together so the shape of active site changes and enzyme is denatured.
Most enzymes have optimum pH of 7 but some that work in the stomach works best at pH 2.

Question 36

Effect of substrate concentration on rate of enzyme-controlled reaction

Answer 36

Higher substrate concentration increases rate of reaction as it is more likely that the enzyme will meet up and react with a substrate molecule.
Only true up to a point because all the active sites can become full and adding makes no difference.

Question 37

Investigating effect of pH on enzyme activity

Answer 37

Spotting tile with iodine drop in each.
Keep water at 35C and put test tube with 3cm3 of amylase solution and 1cm3 of buffer solution pH 5.
Add starch at sample the amylase every 10 secs using the iodine. Brown means no starch.
Repeat with different pHs and compare how pH affects time taken for all starch to be broken down.

Question 38

Control variables in investigating effect of pH on enzyme activity

Answer 38

Concentration and volume of amylase solution.

Temp of water

Question 39

Why does the body have enzymes?

Answer 39

The molecules in food are too big to pass through the walls of the digestive system so enzymes break them down into smaller molecules so they pass through the walls of the digestive system easily to enter the blood stream.

Question 40

Why do plants have enzymes?

Answer 40

Energy is stored as starch and when the plant needs energy, enzymes break down the starch into sugars that can be respired to release energy.

Question 41

What does carbohyrase break down

Answer 41

Carbohydrates into simple sugars

Question 42

What does protease break down

Answer 42

Proteins into amino acids

Question 43

What does lipase break down

Answer 43

Lipids into glycerol and fatty acids

Question 44

What else can enzymes do?

Answer 44

Catalyse reactions that synthesise smaller molecules.

Question 45

How to do calorimetry?

Answer 45

Weigh mass of food and skewer it.
Put set volume of warer in tube.
Measure temp of water and set fire to food and hold food underneath tube.
Relight if necessary.
Measure temp of water
Use formula.