Midcourse Test pt 2

Question 1

Draw the general structure of an amino acid

Answer 1

See Q 11 a

Question 2

Q11 b) calculate the rate of reaction when the standard brown colour was reached in 2 minutes 30 seconds

Answer 2

0.4

Question 3

Q11 b) ii) ( look at graph & read Q 11 b context on prev pg) state how the results shown in fig 11.3 show that the substrate was in excess at all concentrations of catechol oxidase tested

Answer 3

the line continues rising with each concentration and doesn’t reach a plateau

Question 4

Q11 c) i) (read context ad see graph) explain & give reasons for the shape of the curve shown in Fig 3.4 (3 marks)

Answer 4

At low substrate concentrations, man of the enzyme active sites are empty

as more substrate is added, the rate of reaction increases because more enzyme-substrate complexes are formed

At high substrate concentrations, the curve plateaus because more of the active sites are being used

Question 5

Q 11 3) 11) use Fig 3.4 to calculate the value of the Michaelis-Menten constant (Km) for the reaction between catechol oxidase and catechol

Answer 5

0.21 mol dm^-3

Question 6

How do you work out Michaelis-Menten constant?

Answer 6

1/2 Vmax

Question 7

Q11 iii) State what these km values indicate about the relationship between the enzyme and the 2 substrates

Answer 7

The enzyme has a higher affinity for methylcatechol

Question 8

Q 12 ( look at Fig) why doesn’t hormone S need to pass through a transport protein to enter the cytoplasm of the target cell? 2

Answer 8

Hormone S can pass through the hydrophobic core of the bilayer

because they are lipid-soluble

Question 9

The target cell can respond to other cell signalling molecules in addition to hormone
S. The cell has receptors in the cell surface membrane, in the cytoplasm and in the
nucleus.
Explain why hormone S binds only with receptor R in the cytoplasm and not with the
other receptors shown in Fig. 12.1

Answer 9

The hormone S is complementary in shape to receptor R, but not to the other receptors

Question 10

Name the structure through which the hormone‑receptor complex enters the
nucleus.

Answer 10

Nuclear pore

Question 11

Q 12 name structure G

Answer 11

a ribosome

Question 12

Cell signalling by hormone S results in the production of a functioning globular
protein molecule composed of three identical polypeptide chains.
After the synthesis of these polypeptides, changes need to occur to form the
functioning globular protein molecule.
Outline the changes that need to occur to form the functioning globular protein
molecule. 5

Answer 12

The secondary structure must be formed from hydrogen bonding between 2 polar groups

resulting in alpha helices and beta pleated sheets

Then the tertiary structure must be formed from bonding (e.g. hydrogen bonds) between R-groups

This causes the chain to coil

lastly the quaternary structure can form as a result of protein chains being packed together

Question 13

What are the bonds in tertiary structure? 4

Answer 13

Hydrogen, ionic, disulphide, hydrophobic interactions

Question 14

Describe the differences in structure and function between the Rough Endoplasmic Reticulum (RER) and the Smooth Endoplasmic Reticulum (SER) 5

Answer 14

Rough endoplasmic reticulum is covered in ribosomes

and is used to produce proteins

Smooth endoplasmic reticulum lacks ribosomes

and is used to form lipids and steroids

or as a storage site for calcium ions

Question 15

Describe the structure of a phospholipid molecule 3

Answer 15

They have 2 hydrophobic fatty acid tails

attached to a hydrophobic glycerol head

One tail is shorter than the other

Question 16

Describe the features, other than the presence of Golgi vesicles, that would help you identify a Golgi body in a transmission electron micrograph of another area of the same liver cell. 2

Answer 16

The Golgi body is made of cisternae

which look like flattened sacs that bulge at the ends

Question 17

Some Golgi vesicles contain secretory proteins for release from the cell.Describe the sequence of events that occurs following the packaging of a secretory protein into a Golgi vesicle to its release from the cell 2

Answer 17

The vesicle travels to and fuses with the cell surface membrane,

before leaving the cell through exocytosis

Question 18

What is exocytosis 3

Answer 18

the process where the contents of a cell vacuole

are released outside the cell

through fusion of the vacuole membrane with the cell membrane

Question 19

Some Golgi vesicles contain glycoproteins or glycolipids to be added to the cell surface membrane.
Outline the role of glycolipids in the cell surface membrane. 2

Answer 19

They maintain stability in the cell membrane

and are used in cell recognition

Question 20

Q 14 a) complete the table

Answer 20

see memo

Question 21

Q 14 b) calculate the mean value

Answer 21

8.7 + 8.5 + 8.3 + 8.8 = 34.3

34.3/4 = 8,6

exclude 10.5 bc it’s an outlier

Question 22

Q 14 c) ( print a few fresh test papers to do this on) (don’t skip it. It’s important) plot the graph of the mean values shown in table 1.3

Answer 22

See marked paper

Question 23

Use graph in Fig 14.2 to determine the percentage concentration of hydrogen peroxide that produces 7.0cm^3 of oxygen in 30 seconds

Answer 23

1.2 %

Question 24

Q 15 draw diagram ( don’t skip, it’s important)

Answer 24

see marked paper ( remember to do missing beaker I didn’t do)