SB1

Question 1

What is a prokaryotic cell

Answer 1

A cell that does not have a nucleus

Question 2

What is a eukaryotic cell

Answer 2

A cell that contain a nucleus

Question 3

Function of nucleus

Answer 3

Part of the cell containing all an organisms genetic material

Question 4

Function of cytoplasm

Answer 4

Liquid substance where chemical reactions occur

Question 5

Function of cell membrane

Answer 5

Controls which substances can enter or leave the cell

Question 6

Function of mitochondria

Answer 6

Provides energy for the cell via aerobic respiration

Question 7

Function of cell wall

Answer 7

Cellulose (In plants) that provides structure

Question 8

Function of chloroplasts

Answer 8

Contains chorophyll which absorbes light for photosynthesis

Question 9

Function of vacuole

Answer 9

Contains cell sap to improve the cells rigidity

Question 10

Function of chromosomal DNA

Answer 10

Contains genetic information for bacteria

Question 11

Function of plasmid DNA

Answer 11

Small rings of DNA that carry genes for replication

Question 12

What are specialised cells

Answer 12

Cells that are adapted to carry out a particular function

Question 13

How are sperm cells specialised

Answer 13

• Flagellum allows them to swim
• Acrosome in the head containing enzymes to digest the
  egg cell membrane
• Large number of mitochondria in the mid section to
  release energy for movement
• Contains haploid nucleus

Question 14

How are egg cells specialised

Answer 14

• Cell membrane changes to prevent further sperm entry
• Lots of mitochondria to release energy for the developing embryo
• Haploid nucleus

Question 15

How are ciliated epithelium cells specialised

Answer 15

• Surface contains cilia (microscopic hairs) to sweep substances e.g. mucus
• Large number of mitochondria to release energy

Question 16

What does resolution mean

Answer 16

The ability of a microscope to destinguish two points of a specimen

Question 17

How are electron microscopes more detailed than light microscopes

Answer 17

use beams of electrons, rather than light,
- electron microscopes have a lower wavelegnth which gives them a higher resolution

to produce images. Meaning more can be seen on a microscope slide with greater clarity.

Question 18

What are the negatives of electron microscopes

Answer 18

*Organisms can only be seen in black or white
*Organisms have to be dead

Question 19

What is the equation for magnification

Answer 19

magnification = image size/actual size

Question 20

What is the equation for the magnification of a light microscope

Answer 20

eyepiece lens x objective lens

Question 21

What are the steps for using a light microscope

Answer 21

1. Place slide on stage and look through eyepiece lens
2. Turn focus wheel to obtain clear image
3. Start with lowest objective lens magnification
4. Increase magnification of objective lens and refocus

Question 22

How do you prepare a slide

Answer 22

1. Take thin layers of cells from sample using tweezers and place on slide
2. Add a small amount of iodine as a stain to make cells more visible
3. Apply coverslip taking caution to avoid air bubbles

Question 23

What is an enzyme

Answer 23

A biological catalyst that speeds up a reaction without being used up

Question 24

What is the lock and key hypothesis

Answer 24

That the shape of the substrate is complimentary to the shape of active site and will bond to form enzyme-substrate complexes

Question 25

What is the active site of an enzyme

Answer 25

part of the enzyme where substrate molecules bind and a chemical reaction takes place

Question 26

How can enzymes be denatured

Answer 26

1. Increase beyond optimal temperature 2. Excessive decrease/increase in pH

Question 27

What does denatured mean

Answer 27

when the active site has changed shape and can no longer form enzyme-substrate complexes

Question 28

How does temperature affect enzyme activity

Answer 28

rate of reaction increases with an increased temperature once passing the optimum, bonds that hold the enzyme break, causing it to denature

Question 29

how does the pH affect enzyme activity

Answer 29

if pH is too high or low active site will change shape and therefore denature

Question 30

how does substrate concentration affect enzyme activity

Answer 30

as concentration increases the rate of enzyme substrate complexes formed increases however once at saturation point (ALL THE ACTIVE SITES ARE OCCUPIED) the activity will plateau

Question 31

Practical: how can we investigate the effect of pH on enzyme activity

Answer 31

1. Place 2 drops of iodine solution into each spot of spotting tile 2. Add 2cm³ amylase, 2cm³ starch and 1cm³ of buffer pH into test tube 3. Place solution in water bath of 35 degrees 4. Use pipette to put solution into spotting tile every 20 seconds (should turn blue-black) 5. Repeat until the solution stays orange (shows starch has been broken up) 6. Redo practical with a different pH buffer and compare times

Question 32

What is the equation for rate

Answer 32

Rate = change / time

Question 33

What are carbohydrases

Answer 33

Convert carbohydrates into simple sugars

Question 34

What are proteases

Answer 34

Convert proteins into amino acids

Question 35

What are lipases

Answer 35

Convert lipids (fats) into fatty acids and glycerol

Question 36

What is the test for Starch and how is it done

Answer 36

Iodine test: add iodine solution to food sample if starch is present will turn blue-black if not will stay orange

Question 37

what is the test for reducing sugars and how is it done

Answer 37

Benedict's Solution test: *Add 2cm³ of sample solution and 2cm³ of blue Benedict solution to test tube *Place in boiling water bath for five minutes *Presence of reducing sugars turns solution brick red

Question 38

what is the test for protein and how is it done

Answer 38

biuret test: 1cm³ of 40% potassium hydroxide and 1% copper sulphate to food sample Shake and if protein present colour will go from blue to violet

Question 39

what is the test for lipids and how is it done

Answer 39

Emulsion test: 2cm³ ethanol to food sample and 2cm³ deionised water and shake If lipids are present solutions will turn cloudy

Question 40

how can the energy containing food be measured using calometry

Answer 40

1. Place tube of 50ml cold water 2. Record start temperature 3. Place test tube at 45° and hold burning food sample underneath 4. When food burns up record final temperature

Question 41

What is the equation for energy transferred

Answer 41

Energy transferred = volume of water x 4.2 x temperature increase

Question 42

What is osmosis

Answer 42

The movement of water particles from a concentrated solution to a dilute solution across the selective permeable membrane

Question 43

What is diffusion

Answer 43

The movement of molecules from a high concentration to a low concentration

Question 44

What is active transport

Answer 44

The movement of molecules against a concentration gradient requiring energy

Question 45

Core practical: Investigate osmosis in potatoes

Answer 45

1. Cut potatoes into small discs of equal size 2. Blot discs to remove excess water 3. Measure initial mass of disc 4. Place disks in sucrose solutions of different concentrations 5. Blot with tissue again and record new mass 6. Compre end mass - start mass

Question 46

How do you calculate percentage change

Answer 46

(Change in mass ÷ initial mass) x100