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AQA AS Unit 1 Biology Exam 21st May 2015

Reply 980

vuvuzela

3

Sodium Potassium pump please anyone?

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Reply 981

shiney101

10

Do you think we'd need to know how exactly TEM and SEM work? Like with the electron beams etc?

Reply 982

jackmichaeljmh

2

Original post by thesuperdark

Has anyone got any tips for the data questions? The rest of the paper is fine for me, apart from the two long data questions on every paper that seem to completely screw me!

Just slow down and think about the numbers logically. I always see people panicking on these - especially if it asks you to calculate the rate of something. Also, if it asks you to evaluate a claim, make sure you say reasons it could be true as well as false. Think about things like sample size, previous medical conditions, length of study (time), etc. as well as the data itself. Good luck!

Reply 983

username1533709

5

Original post by swinglow2003

do we need to know the test for non-reducing sugars? never heard of it before.

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Yes. If you don't get a red precipitate in a test for reducing sugars,you will have to do the non reducing sugars test to see if a non reducing sugar is present.

Basically, dilute HCL and sodium hydrogencarbonate is added to the sample,and then Benedicts reagent is added.If a red precipitate forms,a non reducing sugar is present.

Reply 984

nina_96

Original post by Kadak

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I'm uploading a hiv doc.I ll tell you when I'm done.When I give you the link,watch from 14:00 to 20:00.Good animation of how immune system works.

Okay! Thank you!!

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Reply 985

randoms132

2

Original post by jackmichaeljmh

Can someone please explain sodium-potassium pump??? Literally the only thing I can't get!! :angry:

1. Sodium ions are actively transported out of the epithelial cells and into the blood (while at the same time potassium ions move into the epithelial cells) via a protein carrier molecule called 'the sodium potassium pump'
2. There is now a much higher concentration of sodium ions in the lumen than in the epithelial cells, so as a result sodium ions move into the epithelial cells down the concentration gradient AND it is couple with glucose molecules this involves a different carrier protein called the co transport protein
3. Glucose, then passes into the blood via facilitated diffusion from the epithelial cells through a different type of carrier

anyone correct me if im wrong !!

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Reply 986

Eviekelly

1

Does anyone know how to answer this question please:
Describe how you would use a 1.0 mol dm–3 solution of sucrose to produce 30 cm3 ofa 0.15 mol dm–3 solution of sucrose.

Reply 987

jackmichaeljmh

2

Original post by shiney101

Do you think we'd need to know how exactly TEM and SEM work? Like with the electron beams etc?

No. I've found that saying just that EM's have a shorter wavelength, and therefore give a higher resolution image with more detail. I hate these q's too but that's always got full marks for me. They aren't usually more than 2-3 marks anyway

Reply 988

samwillettsxxx

3

Original post by vuvuzela

Sodium Potassium pump please anyone?

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Do you mean the whole glucose absorption?

Reply 989

samwillettsxxx

3

Ok so if I've done average on the biology EMPA for AQA is it possible to get better grade with a good exam paper mark

Reply 990

Alex13579

Could somebody help me with how science work question like the use of control group, and something like what is meant by randomly assigning patients into 2 group

Reply 991

shiney101

10

Original post by kandykissesxox

can someone explain the cardiac cycle please and the digestive system xx

Cardiac cycle:

Deoxygenated blood enters the right atrium through the vena cava
When the atrium contracts (atrial systole) the atrioventricular valves open, filling the right ventricles with blood.
Ventricle then contracts causing AV valves to close since pressure below is greater than above, and opens the Semi lunar valves open.
Blood then flows through the pulmonary artery into the lungs.
Oxygenated blood then enters left atrium through pulmonary vein
Atrium then contacts, Av valves on the left side opens, blood enters left ventricle
Left ventricle contracts, semi lunar open (AV closes) allowing blood to move through Aorta to the rest of the body

I think that's it, if any one picks out anything I've missed etc please let me know.

Reply 992

nishofficial

3

Original post by jackmichaeljmh

No. I've found that saying just that EM's have a shorter wavelength, and therefore give a higher resolution image with more detail. I hate these q's too but that's always got full marks for me. They aren't usually more than 2-3 marks anyway

Do you not think they could ask a five marker on it? In my school, we were set a paper written by a teacher with a five marker comparing light with electron microscopes!

Reply 993

samwillettsxxx

3

Original post by Alex13579

Could somebody help me with how science work question like the use of control group, and something like what is meant by randomly assigning patients into 2 group

Control groups are treated exactly the same as the other group however they take a placebo (has no effect) instead of the drug
And it is to compare to show the effects

Reply 994

Eviekelly

1

Original post by Alex13579

Could somebody help me with how science work question like the use of control group, and something like what is meant by randomly assigning patients into 2 group

Using a control group allows a comparison to be made between the two groups so you can see the effect of a drug or inhaler...
Assigning patients randomly stops experimenter bias because they can't influence which people go in which group, eg. can't decide that healthier thinner people going in the drug group and unhealthy go in the control group as this would influence the results

Reply 995

Mr_Cupcakes

2

Original post by shiney101

Cardiac cycle:

Deoxygenated blood enters the right atrium through the vena cava
When the atrium contracts (atrial systole) the atrioventricular valves open, filling the right ventricles with blood.
Ventricle then contracts causing AV valves to close since pressure below is greater than above, and opens the Semi lunar valves open.
Blood then flows through the pulmonary artery into the lungs.
Oxygenated blood then enters left atrium through pulmonary vein
Atrium then contacts, Av valves on the left side opens, blood enters left ventricle
Left ventricle contracts, semi lunar open (AV closes) allowing blood to move through Aorta to the rest of the body

I think that's it, if any one picks out anything I've missed etc please let me know.

It's actually a double circuit, as the left atrium contracts so does the right one etc

Reply 996

Ozy96

5

Question:

Does atheroma lead to thrombosis then aneurysm then myocardial infarction?

Reply 997

jackmichaeljmh

2

Original post by Alex13579

Could somebody help me with how science work question like the use of control group, and something like what is meant by randomly assigning patients into 2 group

These q's are very annoying as we all always overthink the answers.

Control group: shows that any observations are caused by the independent variable and not something else that each group had in common.
Random assignment: avoids bias, whether deliberate or accidental.

Thats literally it! They're almost too easy so we always complicate it more than we need to

Reply 998

randoms132

2

Original post by kandykissesxox

can someone explain the cardiac cycle please and the digestive system xx

Cardiac cycle:
(a) The heart is myogenic it initiated its own contraction. In the right atrium there are a specialised group of cells called the SAN these send a wave of electrical activity across both atrium causing them to contract
(b) non conductive tissue between atrium and ventricles to stop wave of electrical activity pass through the ventricles
(c) the wave of electrical activity reaches the AVN, AVN delays to allow any remaining blood to flow from atrium to ventricles before ventricles contract
(d) AVN send a wave of electrical activity along the Bundle of His
(e) the wave of electrical activity then passes through the muscular walls of ventricles causing them to contract (from the apex upwards)
:smile: