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

1.) If you read my answer correctly, you'll find that I said volume of indicator not substrate or enzyme which said a few drops indicating they didn't control it.
3.)I guess you'd get the mark for that
4.)That's not negative it's a dash, sorry if thats unclear.

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

for the question about amphibians and mammals, I wrote about the absence of an inter-ventricular septum in the frog and that the oxygenated blood and the deoxygenated blood was mixed meaning less oxygen reached the respiring tissues. i also talked about how the mammals have a thick left ventricle (higher pressure meaning blood carried faster) but the muscular walls in the frog has the same thickness. and i said that frogs have a low metabolic rate so for them this circulation is efficient. and frogs are cold blooded meaning they dont need to maintain warmth and less energy is needed for them.

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

Actually it does make a difference because firstly the indicator is phenopthalein which is a weak acid so if u have varying volumes it can affect the point at which it turns colorless. Also if you have varying amounts it could influence your interpretation of when it's colourless.

hmmmmmm
Natural Selection doesn't make sense to what the question is asking

what on earth is binary fission ..... we never got taught that

"What is the process by which the proportion of resistant bacteria in the population increases"?

I do not think they were looking for binary fission. Not only is it not on the specification, but the answer to that question is much better described as "natural selection" - the wording of the question is clearly hinting towards that as it specifies the fact that more and more are becoming resistant.

Put it this way: if that question was asked about animals becoming resistant, you'd all put natural selection, not meiosis/sexual reproduction

I suppose binary fission could be an ACCEPT on the mark scheme as it's technically correct - who knows. It's only one mark.

for the question about amphibians and mammals, I wrote about the absence of an inter-ventricular septum in the frog and that the oxygenated blood and the deoxygenated blood was mixed meaning less oxygen reached the respiring tissues. i also talked about how the mammals have a thick left ventricle (higher pressure meaning blood carried faster) but the muscular walls in the frog has the same thickness. and i said that frogs have a low metabolic rate so for them this circulation is efficient. and frogs are cold blooded meaning they dont need to maintain warmth and less energy is needed for them.

Wasn't the question about the comparison between fish and mammals?
Or did I just drop 6marks 😭

Apprantley 45 is a a, that's what ocr emailed to our school. They also said they put stuff im that's not on spec to lower the number of a grades as it is the new a level percentage