January 2013 wjec Unit 1

Question 1

What happens in prophase?

Answer 1

centromeres split
chromsomes are being pulled to opposite poles
contraction of spinde fibres

Question 2

What indicates interphase?

Answer 2

DNA doubled from 6-12

Question 3

Type of nuclear division?

Answer 3

meiosis
at end of cell cycle, quantity of DNA has been halved and halved again

Question 4

Differences between DNA and RNA?

Answer 4

DNA
double stranded
sugar - deoxyribose
Thymine
helical
1 type

RNA
single stranded
sugar - ribose
uracil
non helical
3 types

Question 5

Describe process stages 1 and 2?

Answer 5

phagocytosis/endcytosis
cell membrane engulfs to form a vesicle around algae

Question 6

Where are vesicles formed?

Answer 6

golgi body

Question 7

Function of organelle mitochondria ?

Answer 7

site of aerobic respiration
+ ATP synthesis

Question 8

3 ways in which prokaryotic cell would differ from amoeba?

Answer 8

Prokaryotes have
No nucleus
No membrane bound organelles
A loop of DNA
Smaller/70S ribosomes;
Cell wall
Capsule/ flagellum/ plasmid;

Question 9

Structure of haemoglobin?

Answer 9

quartnenary

Question 10

2 types of bonds present to maintain 3d shape of polypeptide chain?

Answer 10

Hydrophobic interactions
Disulphide bridges
Ionic bonds
VDW

Question 11

2 waysin which the structure of phospholipids differ from triglycerides?

Answer 11

Triglycerides - dont have phosphate head whereas phospholipids do
triglycerides have 3 fatty acids whereas phosphate heads have 2

Question 12

Describe arrangement of phospholipid molecules?

Answer 12

Phospholipids have hydrophillicheads but hydrophobic tails - attracted to the water
therefore the heads are inside of the water and the tails are out - avoid water

Question 13

The area of phospholipids = 12.2
what would you expect the total surface are of red blood cells to be?

Answer 13

6.1m2
phospholipids are arrangedin a billayer in the membrane

Question 14

How does oxygen enter the cell?

Answer 14

by diffusion
through the phospholipid bilayer

Question 15

How does phospate ions enter the cell?

Answer 15

by facilitated diffusion
through the channel protein
passes through the hydrophilic pore

Question 16

Name process cells use t uptake phosphate ions when external concentration of phosphate ions is between 0-30 au?

Answer 16

Active transport
the concentration of phosphate ions is lower outside (the root)/higher inside (the root)/ Ions are being taken
up against a concentration gradient;
With oxygen present (aerobic) respiration can occur;
Providing {ATP/ energy} (for active transport)/ active transport
needs {energy/ ATP};

Question 17

Explain the shape of curve between concentrations of 30-60 au?

Answer 17

Thereis a limited number of carriers for phosphate ions in the membrane curve levels off

Question 18

Why does the rate of uptake increases on curve Z between concentrations for 30-60 au?

Answer 18

Ions are being taken up by facilitated diffusion;
Uptake only occurs when the external concentration
is higher than the concentration inside the root hair cells

Question 19

1 other reason why the plant needs phosphate ions?

Answer 19

component of nucleotides

Question 20

Type of reaction involved in the breakdown of lactose?

Answer 20

hydrolysis

Question 21

Bond broken during reaction?

Answer 21

glycosidic

Question 22

Molecules when lactose is broken down?

Answer 22

glucose + galactose

Question 23

2 Advantages of using immobilised enzymes?

Answer 23

can be easily reused/ recovered
product is free from contamination
can withstand a wider range of pH and temp

Question 24

Test for reducing sugr?

Answer 24

benedict’s test
use equal amounts of benedict’s reagent and lactose
heat
if positive - blue to brick red

Question 25

What is meant by biosensor?

Answer 25

detects minute concentrations of biologically important molecules

Question 26

What would be main advantage of biosensor?

Answer 26

detects products rapidly
detects minute concentrations
would give quantitative test

Question 27

State and explain the effect of milk being left for 7 years would have on the concentration of reducing sugars detected?

Answer 27

The concentration of reducing sugars would decrease;
Lactose concentration is lower in the sour milk
Lactic acid lowers the pH;
Enzyme would be denatured
Hydrogen (maintaining the 3D shape) would break
This will change the shape of the active site of
lactase
Fewer enzyme-substrate complexes would be
formed/fewer successful collisions;
Benedicts would remain {blue/ change to {orange/
yellow/ green/ brown}/ negative}