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AS OCR Biology Depth 07/06/16 Unofficial Mark Scheme

I'm gonna put down the questions, answers and marks available for all the questions I can remember, do the same and we can make a mark scheme together!

Is A or B expiration and why? (2)
A because volume of thorax is decreased, diaphragm bends inwards

Give instructions to find vital capacity (2)
Use spirometer, put mouth on mouthpiece, inhale as deeply as possible and exhale as deeply as possible without nose

Graph, which is which (total lung capacity, residual volume, tidal volume, vital capacity) (4)
-D, from bottom of graph to trough of vital capacity, F, I think E (the one from highest peak to lowest trough)

Describe mechanism of enzymes and how temperature affects its action. (6)
-Lock and key, complementary shape of lipid and lipase active site, substrate fits in and reaction is catalysed
-Induced fit suggests the lipase must also change shape in a way that fits lipid more closely to catalyse reaction.
-As temperature increases, rate of reaction increases
-because the enzyme and substrate gain kinetic energy and collide more frequently therefore higher chance of successful collision and catalysation
-If temperature is too high, hydrogen bonds, ionic bonds break and tertiary structure of enzyme is disrupted and active site changes shape (denatured)
-Therefore can no longer catalyse reactions as active site is no longer complementary to lipid

What can all circulatory systems be described as? (1)
Closed

One difference between fish circulatory system and mammal circulatory system. (1)
Fish is single circulatory, mammal is double

Difference between frog and mammal circulatory system and relative efficiency and why. (6)
-

Which phases are interphase (1)
G0, G1, S, G2

What is chitin monomer most similar to (2)
B-Glucose

Difference between this monomer and typical monosaccharides (1)
Nitrogen

Explain how chitin is made and its structure (4)
-every other monomer is rotated 180 degrees when bonded
-forms 1-4 glycosidic bond by removal of H on OH on one monomer and OH from another
-Condensation reaction, releases water
-Straight, uncoiled chains then form hydrogen bonds with other chains to form strong microfibrils

What is process by which colony evolved (1)
Natural Selection

Why is resistant part of original colonies (2)

What can we deduce about fungal enzymes (2)
-They are extracellular, released into surroundings
-Because the area around fungus has no starch (catalysed into maltose by amylase)

Why isn't pH controlled (1)
-It changes throughout the experiment as alkaline lipid solution is broken down and increases

Name another that isn't controlled (1)
Volume/drops of indicator on white tile

Name one that is controlled (1)
Time/intervals of testing solution

Give 2 alternative methods that increase accuracy (4)
-Take the range of 30-35 and investigate at smaller intervals
-Use lower time intervals to find out more accurate point at which lipid is catalysed

Why isn't indicator added to solution and colour change identified (2)
-Not sure of this one

Where is optimum temperature of lipase (1-2)
- 30-35
-because that is when alkaline solution is broken down and phenopthalein is colourless at lowest time (fastest rate of reaction)

Purpose of rings of chitin (1)
To support trachea and tracheoles from collapsing (high pressure)

Alternative what would happen as a result of chitin (1)
-Mites may be vectors and cause disease
-May bite through tracheoles and leak tracheal fluid (disrupt gaseous exchange)

Degrees of freedom (1)
3

Conclusion (2)
To 0.001 level of significance, our value of 13.85 is higher than critical value (dont remember) therefore results is significant

Why isnt t-test suitable (1)
T test can only be used when 2 groups of data is presented

Calculate chi squared x squared (3)
13.85 (or something similar)

Change in relative proportion of MRSA (2)
-Increases to 52.4%
-Due to decrease in non resistant death and increase in MRSA death

Conclusion since 2007 (3)
-MRSA has decreased
-Non resistant has decreases
-MRSA decreased more rapidly

percentage increase of death from MRSA from 1993 to peak (2)
-3140%

Which divides shortest (1)
Q

Suggest why R stays in G1/G0 (1-2)
-It doesn't replicate or divide as no time is spent in S or M
-Therefore checkpoint may be faulty
-Or cell remains dormant in G0

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Reply 1
Avatar for Jitesh
Jitesh
14
Screenshot_1.png
G0 probably will also be accepted but I assume they were mainly wanting G1, G2 and S
Wasn't the natural selection Q asking how does the bacteria increase in proportion so bascially in increase in size.
My class put binary fission becasue how bacteria increases in proportion
Original post by brodingoson
Wasn't the natural selection Q asking how does the bacteria increase in proportion so bascially in increase in size.
My class put binary fission becasue how bacteria increases in proportion


No, it said how the proportion of bacteria that have resistance increase, binary fission is just how all bacteria replicate.
Original post by IntellectualBoss
No, it said how the proportion of bacteria that have resistance increase, binary fission is just how all bacteria replicate.


hmmmmmm
Natural Selection doesn't make sense to what the question is asking
(edited 7 years ago)
i put binary fission too

Original post by brodingoson
Wasn't the natural selection Q asking how does the bacteria increase in proportion so bascially in increase in size.
My class put binary fission becasue how bacteria increases in proportion
Yes I guess binary fission
Reply 7
Avatar for JStebz
JStebz
8
Original post by brodingoson
Wasn't the natural selection Q asking how does the bacteria increase in proportion so bascially in increase in size.
My class put binary fission becasue how bacteria increases in proportion


I put plasmid transfer lol
Original post by brodingoson
Wasn't the natural selection Q asking how does the bacteria increase in proportion so bascially in increase in size.
My class put binary fission becasue how bacteria increases in proportion


I put binary fission too
Reply 9
Avatar for haes
haes
6
"Why is resistant part of original colonies (2)" is this the question about the evidence because wasn't that only 1 mark?? and was the last question really three marks? damn
i thought it said population not proportion?

Original post by IntellectualBoss
No, it said how the proportion of bacteria that have resistance increase, binary fission is just how all bacteria replicate.
Original post by haes
"Why is resistant part of original colonies (2)" is this the question about the evidence because wasn't that only 1 mark?? and was the last question really three marks? damn


I dont know for sure but don't they tend to give 4 lines when a question is worth 2 marks? I've never seen a 1 mark question where they expect 4 lines of answer.
Also, add in:
Why does P spend double the time in S as Q? (2)
-Because there is double the amount of DNA
-therefore it takes double the time to replicate
and:
What is the purpose of checkpoint Y? (1-2)
-To make sure all DNA has been successfully replicated with no damage or mutation
-So that cell is ready to divide/no mutated polypeptides are synthesised by cell
ITS COMPLETE WITH THIS LAST QUESTION
Tick whether its mitosis or meiosis (3)
-Mitosis, Meiosis, Mitosis
-Both meiosis
for the chi test I accidently divided 13.85 by n (200) and got 0.093 so my conclusion was wrong... do you think I would lose all the marks for the question or get follow through marks for my conclusion?
Why do you look at 0.001 for p. I thought you look at 0.05?
Reply 17
Avatar for Ozil5
Ozil5
8
Original post by IntellectualBoss
ITS COMPLETE WITH THIS LAST QUESTION
Tick whether its mitosis or meiosis (3)
-Mitosis, Meiosis, Mitosis
-Both meiosis


Wasn't it
Mitosis
Meiosis
Mitosis
Meiosis
Mitosis
Original post by lulabellead
for the chi test I accidently divided 13.85 by n (200) and got 0.093 so my conclusion was wrong... do you think I would lose all the marks for the question or get follow through marks for my conclusion?


I think you'd lose the marks because it was only a 2 mark question.
Original post by brodingoson
Wasn't the natural selection Q asking how does the bacteria increase in proportion so bascially in increase in size.
My class put binary fission becasue how bacteria increases in proportion


I put binary fission as well!!!

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