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AQA BIOL1 Biology Unit 1 Exam - 16th May 2011

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yeahh
i wrote

Cholera is transmitted through water that is contaminated with the bacterium. This can be spread by preparing/eating food with hands that have faecal contamination with the bacterium. The cholera bacterium produces a toxin that binds to chloride ion protein carriers on the epithelial cells of the small intestine. This changes the shape of the protein carrier and chloride ions are released into the lumen of the small intestine. This lowers the water potential of the small intestine causing water to travel by osmosis from epithelial cells, blood and surrounding tissue which have a relatively high water potential compared to that of the lumen. This loss of water from the blood and tissue causes dehydration in the individual and diarrhoea.

i always forget to write about ORS and all that stuff

Don't need to include ORS cos the question didn't ask for it. Just included it for the sake of it so in case anybody wasn't sure about ORS.

Reply 381

EffKayy

Original post by gunit123

advantages and limitations of tem and sem anyone????

advantages of tem
*small objects can be seen, also internal details
*higher resolution
*small wavelength of electrons
disadvantage
*staining process has to occur, and yet it is still black and white
*2d??
*artefacts may occur from prep.
*has to be in a vacuum
*living specimens cant be tested
*specimen has to be extremely thin

SEM ADVANTAGE - specimen doesnt have to be thin.

Reply 382

??????????????????

Original post by emmaaa65

describe the risk factors involved with coronary heart diesease and include in your answer how smoking can cause a myocardial infarction (5marks)

Risk factors:
-Genetic
-Smoking
-Lack of exercise
-High blood pressure

Smoking causes tar build up in the arteries so they are smaller. This increases pressure. If there are arethroma's in the body, they can become dislodged from the pressure and end up clotting the Coronary arteries which reduced/stop blood flow to the heart so less oxygen. This causes the muscle tissues to die as they have no oxygen to respire with so no ATP produced to contract muscle to the heart tissue dies leading to a MI.

Reply 383

TlanTlan

Original post by gunit123

advantages and limitations of tem and sem anyone????

Overall advantages of electron microscopes:

- Both types have much higher resolution(and thus magnification) compared to optical microscopes due to the (de broglie) wavelength of electrons being much shorter than that of visible light.

Overall disadvantages:

-Both types cannot produce a colour image.
-Both types require a vacuum, so living specimens cannot be observed.

TEM:

Advantages:

-Higher resolution than SEM microscopes
-Allows density of specimen to be evaluated.

Disadvantages:

-Requires very thin specimens.
-Complex staining and preparation process required which can result in artefacts.
-Produces only a 2d image.

SEM:

Advantages:

-Can produce a 3d image of the surface of the specimen
-Specimen does not need to be prepared and sliced first

Disadvantages:

-Lower resolution than TEM

Reply 384

??????????????????

Original post by EffKayy

Yeah its 2d.
Also SEMs can have colour or is 3d. I forgot which one.

Reply 385

canthardlywait

Anyone know best way to achieve full marks, when asked to:
-Describe graph
-Explain graph

and also whats the best way to answer an "Evaluate" question.

Any help is much appreciated.

Reply 386

emmaaa65

Original post by ??????????????????

yeah thats pretty much what i put aswell

The risk factors involved in CHD include factors such as high blood pressure and high cholesterol, which can be caused by a diet high in salt or saturated fat. High blood pressure can cause the artery walls to weaken and form an aneurysm, whilst high blood cholesterol can result in an atheroma. Smoking contributes to CHD as the nicotine in tobacco increases adrenaline, which results in high blood pressure. The nicotine also has a ‘sticky’ effect meaning red blood cells stick together and form blood clots, which can restrict the blood flow and hence the supply of oxygen to the heart muscle. Smoking also increases carbon monoxide concentration which binds to haemoglobin irreversibly meaning insufficient oxygen is supplied to the heart muscle. These factors result in the heart muscle from dieing, therefore leading to a myocardial infarction.

Reply 387

liviaaa

Original post by ??????????????????

I don't think atheroma becomes dislodged? Atheroma is a built up of fatty substances and cholesterol in the lining of the artery, narrowing it. This increases the chance of an embolous getting jammed or a blood clot forming.

Reply 388

??????????????????

Original post by canthardlywait

Anyone know best way to achieve full marks, when asked to:
-Describe graph
-Explain graph

and also whats the best way to answer an "Evaluate" question.

Any help is much appreciated.

Describing should show the trends. Use terms like positive/negative correlation. Refer to the date. Eg at 0.4 concentration to 0.6 the rate of reaction increases then the gradient drops after 0.6 to 0.8.

When explaining just say what caused the results.

Evaluate needs both views. Go pros and cons.

Reply 389

??????????????????

Original post by liviaaa

Look up thrombosis.

Reply 390

LiviD

Original post by liviaaa

Some random Q:

-Define disease

-What's the biochemical test for a lipid?

- What is the role of the nucleus?

a disease is when an infection causes recognisable symptoms...
i think

Reply 391

liviaaa

Original post by canthardlywait

Anyone know best way to achieve full marks, when asked to:
-Describe graph
-Explain graph

and also whats the best way to answer an "Evaluate" question.

Any help is much appreciated.

Describe, just say what you see - include figures!

Explain - say why the described bit ^ happened

Evaluate - the answer is normally no, and it's because it's only a correlation, not cause and effect, so may have been caused my other named factors. (May be yes for once though...)

Reply 392

emmaaa65

Original post by liviaaa

an atheroma can rupture and increase the risk of a thrombosis, which can become dislodged and block other arteries

? i think

Reply 393

liviaaa

Original post by ??????????????????

Look up thrombosis.

Thrombosis is the process when a blood clot forms.

Reply 394

liviaaa

Original post by emmaaa65

an atheroma can rupture and increase the risk of a thrombosis, which can become dislodged and block other arteries

? i think

Yes the blood clot can become dislodged, but not the atheroma I don't think.

Reply 395

??????????????????

Original post by liviaaa

Thrombosis is the process when a blood clot forms.

They can become dislodged or rupture causing more blood clots or moving to other areas. If it moves to coronary arteries it will lead to M.I as it block the C. arteries.

Reply 396

anna258

Hey

can anyone answer the question in the QP given at the beginning of the thread (11th Jan 2011)
-QUESTION 4 (c) (iii)

It's so confusing!!!!!!!

Reply 397

emmaaa65

Original post by liviaaa

Yes the blood clot can become dislodged, but not the atheroma I don't think.

ahh yeah okay. the atheroma and thrombosis are two different things, but an atheroma can increase the risk of a thrombosis. i was starting to get all confused and ahhh lol

Reply 398

oHellno

Original post by canthardlywait

Anyone know best way to achieve full marks, when asked to:
-Describe graph
-Explain graph

and also whats the best way to answer an "Evaluate" question.

Any help is much appreciated.

The others have answered your question, but in terms of the evaluate question try and think about if it was reliable, so the sample size, if there was a control, how many variables were changed. If it's about a drug or something for humans and it was only tested on animals, mention that too.

Reply 399

??????????????????

Original post by liviaaa

Yes the blood clot can become dislodged, but not the atheroma I don't think.

CGP says, the atheroma can rupture which damages artery walls giving it a rough surface. Platelets and firbin accumulate there making a blood clot which can block another artery or dislodge.