Topic 1 - Key concepts

Question 1

prokaryotic cells

Answer 1

cells that do not have a nucleus or membrane bound organelles e.g. bacteria

Question 2

eukaryotic cells

Answer 2

cells that do have a nucleus or membrane bound organelles e.g. animal and plant cells

Question 3

cell membrane

Answer 3

Controls the movement of substances into and out of the cell

Question 4

ribosomes

Answer 4

Where proteins are made (protein synthesis)

Question 5

mitochondria

Answer 5

the organelle where aerobic respiration happens

Question 6

cytoplasm

Answer 6

Most chemical processes take place here

Question 7

nucleus

Answer 7

Contains DNA and controls the activities of the cell

Question 8

chloroplasts

Answer 8

Makes glucose for the plant. They are green and contain chlorophyll, which absorbs light energy for photosynthesis

Question 9

cell wall

Answer 9

Gives the cell structure and support

Question 10

(large) vacuole

Answer 10

Filled with cell sap to help the cell keep its shape

Question 11

plasmid DNA

Answer 11

small loops of extra genetic material

Question 12

flagella

Answer 12

a whip-like tail for movement

Question 13

chromosomal DNA

Answer 13

genetic material which controls the cell’s activities

Question 14

specialised cell: root hair cell adaptations

Answer 14

• increased surface area for faster exchange rate
• no chloroplasts as root hair cells are found underground so there is no sun light for photosynthesis
• thin cell wall for a smaller distance for exchange

Question 15

specialised cell: ciliated epithelial cell adaptations

Answer 15

• tiny hair-like projections called cilia to sweep mucus, with trapped dust and microorganisms
• lots of cilia so increased surface area to absorb water and minerals

Question 16

specialised cell: sperm cell adaptations

Answer 16

• flagella to swim quickly
• lots of mitochondria for energy for movement
• streamline
• acrosome containing enzymes so that the sperm cell can penetrate an egg cell
• haploid nucleus containing the male’s half of the chromosomes needed to make a whole body cell

Question 17

specialised cell: egg cell adaptations

Answer 17

• the egg cell’s cytoplasm contains nutrients for the growth of the early embryo
• the haploid nucleus contains genetic material for fertilisation
• the cell membrane changes after fertilisation by a single sperm so that no more sperm can enter

Question 18

specialised cell: red blood cell adaptations

Answer 18

• no nucleus makes space for haemoglobin
• large surface area (concave) so oxygen can freely move into the cell

Question 19

magnification equations

Answer 19

total magnification = eyepiece magnification × objective magnification

image size = actual size × magnification

Question 20

preparation to look under a microscope

Answer 20

1. place a thin sample on the slide
2. add a stain and a cover slip
3. focus it on the lowest magnification on the objective lens
4. increase the magnification of the objective lens if needed

Question 21

difference between light and electron microscope

Answer 21

• electron microscope uses electrons instead of light
• using electrons means a clearer, higher magnification and more detailed (higher resolution) image
• as microscope technology improved we were able to see the detail of even smaller cells such as bacteria and organelles
• light microscope is cheaper and smaller

Question 22

enzymes

Answer 22

they are made of proteins
biological catalysts to help speed up reactions in the body
help to break down nutrients in digestion
help to build new useful nutrients in the body

Question 23

rate of reaction equation

Answer 23

amount of substrate used (or product formed)/time taken

Question 24

substrate&raquo_space; enzyme&raquo_space; product

Answer 24

proteins&raquo_space; protease&raquo_space; amino acids

starches/carbohydrates&raquo_space; amylase/carbohydrase&raquo_space; glucose/sugars

lipids&raquo_space; lipase&raquo_space; fatty acids and glycerol

Question 25

substrate

Answer 25

the molecule that the enzyme works on

Question 26

active site

Answer 26

the region on an enzyme that binds to a protein or other substance during a reaction

Question 27

rate of enzyme reaction - temperature

Answer 27

1. As the temperature increases the enzyme and substrate again more kinetic energy and so move around more. As they move around more, there is more likely to be a successful collision (the enzyme joins with the substrate) and so the substrate is broken down. The rate of reaction is increasing. 2. The enzyme is at the optimum temperature. The enzymes and substrates have lots of energy and so there are lots of successful collisions happening. This is where the rate of reaction is highest. 3. As the temperature goes above the optimum, the enzyme becomes denatured. This means that its active site changes shape. As the active site is a different shape the substrate is no longer complementary and so no longer fits into the active site. No more reactions can happen. The rate of reaction decreases.

Question 28

rate of enzyme reaction - pH

Answer 28

The fastest rate of reaction is when the pH is at its optimum. Every enzyme has a different optimum pH (6-8 for most). Either side of the optimum the rate of enzyme activity decreases, because the active site changes shape. If the pH is too high or too low the enzyme is denatured.

Question 29

rate of enzyme reaction - substrate concentration

Answer 29

As the substrate concentration increases this means that there are more substrate molecules for the enzymes to bind to. The rate of reaction increases as substrate concentration, until it eventually reaches a maximum rate as all of the enzymes are in use.

Question 30

diffusion

Answer 30

the passive net movement of particles from a high concentration to a low concentration, down the concentration gradient, across a partially permeable membrane

Question 31

osmosis

Answer 31

the passive net movement of water particles from a high water concentration to a low water concentration, across a partially permeable membrane, down the concentration gradient

Question 32

active transport

Answer 32

the movement of particles against a concentration gradient using energy (ATP) from respiration

Question 33

percentage mass change equation

Answer 33

change in mass/initial mass × 100

Question 34

osmosis in potatoes core practical

Answer 34

1. cut, blot and weigh potato cylinders 2. place them into water/sugar solutions of different concentrations for 20 minutes 3. take cylinders out, blot them and reweigh them 4. calculate % mass change

Question 35

enzymes and pH core practical

Answer 35

1. Prepare your reactants: Place starch solution, amylase solution and pH 7 buffer into separate test tubes. Warm them to approximately 40°C for the optimum temperature for enzyme activity 2. Prepare your dropping tile: Place a few drops of iodine solution into each well of a spotting tile. 3. Start the reaction: Mix reactants together, start the stop watch and keep the mixture warm in the water bath. 4. Test for starch: Remove a small amount of mixture and place in a well on the spotting tile. 5. Record your results: Repeat the test until the mixture does not go black (no starch). Record the time. 6. Vary the pH: Repeat with different pH buffers from pH3 - pH10

Question 36

rate calculations for enzyme activity

Answer 36

rate = change ÷ time OR rate = amount of substrate used ÷ time

Question 37

percentage change in mass

Answer 37

(final-initial) ÷ initial