OCR Biology F211 resit - 16th May Watch

abi.tanner
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#41
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#41
(Original post by bulletproof_love)
Does anyone know how to calculate the heart rate from an ECG? I can't find the info anywhere :/
my tutor taught me look along the time and point out the beginning of the P wave and the beginning of the next P wave, and then divide 60 over that time length.

for example, if the length of time between each heart beat is 0.85 seconds you would do 60/0.85 = 70.588 so the heart rate (beats per minute) would be 70.588

or something like that...
this is so confusing, but i hope it helps.
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CocaColaBottle
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#42
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#42
(Original post by laureneb10)
Anyone know why the heart contracts from the base of the heart upwards?
Seriously screwed!
Its like squeezing a water bottle. You squeeze from the bottom to up for water to leave from the top. Apply that to the heart and knowing if it contracted going down it would only, like, extend the Ventricle, not necessarily go anywhere. And we want the blood to go up and out so
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yamamotootsu
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#43
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Am only revising what might come up on the exams

1) Bohr Effect(completely understand it now=) )
2) Blood, tissue fluid and lymph
3) faciliated diffusion(carrier and channel)
4) division of labour
5) Lungs(spirometer)
6) Cardiac Cycle
7) control of cardiac cycle
8) blood vessels
9) Movement of water up the xylem e.g. symplast, apoplast, casperian strip etc
10)Translocation
11) Xerophyte
12) Mosaic model(membrane)and functions
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arcticwombats
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#44
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(Original post by yamamotootsu)
Am only revising what might come up on the exams

1) Bohr Effect(completely understand it now=) )
2) Blood, tissue fluid and lymph
3) faciliated diffusion(carrier and channel)
4) division of labour
5) Lungs(spirometer)
6) Cardiac Cycle
7) control of cardiac cycle
8) blood vessels
9) Movement of water up the xylem e.g. symplast, apoplast, casperian strip etc
10)Translocation
11) Xerophyte
12) Mosaic model(membrane)and functions
Fancy writing up some notes on those? :P
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arcticwombats
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#45
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Having trouble with this spec point -" explain why transpiration is a consequence of gas exchange."

Is it because the water evaporates from surface of mesophyll cells, and then this water vapour diffuses into intercellular spaces and then diffuse out of the leaf via open stomata?
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Niki_girl
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#46
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#46
(Original post by laureneb10)
Anyone know why the heart contracts from the base of the heart upwards?
Seriously screwed!
The heart contacts from the base upwards due to the fact that the wave of excitaton (initiating in the Sinoatrial node, going through the septum, Atrioventricular node, Bundle of HIS and Purkyne tissues first!) is passed along purkyne fibres along the bottom of the ventricles, which causes the heart to contract from the apex (base) upwards
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Niki_girl
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(Original post by arcticwombats)
Having trouble with this spec point -" explain why transpiration is a consequence of gas exchange."

Is it because the water evaporates from surface of mesophyll cells, and then this water vapour diffuses into intercellular spaces and then diffuse out of the leaf via open stomata?
Transpiration is an unavoidable part of gas exchange in plants they leave their stomata open during the day (light + temp etc.) to allow carbon dioxide to enter and oxygen to leave, therefore water vapour can also exit via the stomata down a concerntration gradient - you're right
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lmfw
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WHY is it so impossible to actually get an A on this paper?
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arcticwombats
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#49
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(Original post by Niki_girl)
Transpiration is an unavoidable part of gas exchange in plants they leave their stomata open during the day (light + temp etc.) to allow carbon dioxide to enter and oxygen to leave, therefore water vapour can also exit via the stomata down a concerntration gradient - you're right
Thanks! You sound like you're on track for an A haha!
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yamamotootsu
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(Original post by LisaWilliams)
WHY is it so impossible to actually get an A on this paper?
the mark scheme is PAINFULLY strict that's why

Have you seen June 2010 mark scheme? so many DO NOT ACCEPT
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lmfw
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#51
(Original post by yamamotootsu)
the mark scheme is PAINFULLY strict that's why

Have you seen June 2010 mark scheme? so many DO NOT ACCEPT
They're so tight about things! Yeaah that was the paper i sat F211 with for the first time, got a C, oopsies :P
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jemma2805
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#52
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Hi

Does anyone know where i can get the 25 May 2010 markscheme for OCR can't seem to find it anywhere?
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lmfw
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(Original post by jemma2805)
Hi

Does anyone know where i can get the 25 May 2010 markscheme for OCR can't seem to find it anywhere?
http://www.ocr.org.uk/download/ms_10...0_gce_f211.pdf
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jemma2805
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Thankyou soo much

Really nervous for tomorrow, i'm entering the exam as an external candidate
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Niki_girl
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(Original post by yamamotootsu)
Am only revising what might come up on the exams

1) Bohr Effect(completely understand it now=) )
2) Blood, tissue fluid and lymph
3) faciliated diffusion(carrier and channel)
4) division of labour
5) Lungs(spirometer)
6) Cardiac Cycle
7) control of cardiac cycle
8) blood vessels
9) Movement of water up the xylem e.g. symplast, apoplast, casperian strip etc
10)Translocation
11) Xerophyte
12) Mosaic model(membrane)and functions
(Original post by arcticwombats)
Fancy writing up some notes on those? :P
I'll start if you want,

1. Bohr effect, the effect caused by the fact that the greater the concerntration of carbon dioxide the lower the affinity (attraction) of haemoglobin for oxyen, and therefore in areas of low oxygen tension/ partial pressure more oxygen is released by red blood cells, but in areas of high oxygen tension (lungs!) more oxygen is absorbed by red blood cells, to carry to the respiring cells in the body! On a graph low-->high co2 concerntration is shown, and then there is an increasing partial pressure of oxygen...

ALSO, FETAL HAEMOGLOBIN HAS A HIGHER AFFINITY FOR OXYGEN THAN ADULT HAEMOGLOBIN, so that the fetus can pick up oxygen from the mother's blood in the placenta. (this is shown by the fact that fetal affinity is to the LEFT of adult haemglobin affinity for oxygen on a graph).

2. Blood - complex fluid contained in vessels, pumped by the heart, contains red & white blood cells etc. Tissue fluid, formed by the blood being pumped through capillaries at higher pressure (ultrafiltration), small molecules, like water, amino acids, glucose, pushed out and these bathe cells, giving them nutrients, removing waste. Lymph fluid - contains lymphocytes which are picked up from lymph nodes, formed by tissue fluid drainage.

3. Facilitated diffusion, carries molcules not capable of crossing the cell membrane by diffusion, e.g, charged/ too big. Carrier molecules - can use ATP to change shape and go against a concerntration gradient to carry molecules such as ions. Channel proteins intrinsically embedded in cell membrane, form pores, such as for transporting water across cell membrane - this doesn't require ATP (passive).

4. Division of Labour, the fact that the different cells differentiate (specialise) to their own function, and when combined carry out all of the necessary "labour" (work) required to keep healthy a multicellular organism. (forming tissues --> organs --> organ systems)

5. Lungs, suited to gaseous exchange by being permeable, one cells thick endolthelium cells in alveoli- which are numerous and help provide a large surface area, they are also moist and have a good blood supply owing to the capillaries which surround the alveoli. Spirometer (someone already gave a good answer on this) uses a floating oxygen chamber to measure the total lung capacity and it's components, remember; participant should be in good health, stop if dizzy etc., datalogger measures results, nose plug used to stop air escaping and to get reliable results, also soda lime is used to se up/ neutralise the carbon dioxide which builds up.

6 & 7.Cardiac cycle, atrial systole (atria contract), ventricular systole (ventricles contract), diastole (relax/ filling phase, ventricles fill with blood as atria and ventricles relax), the heart is co-ordinated and intiated by;

Sinoatrial node, "pacemaker" sends out waves of excitation --> Atroventricular node --> delay (impulse cannot pass septum) --> Bundle of HIS ---> Purkyne fibres --> heart contracts from the base (apex) upwards, cycle begins again,

Delay between atrial & ventricular systole, to allow the atria to empty fully before ventricles contract!

*The heart muscle is myogenic (self-starting impulse)

8. Blood vessels (in a closed circulatory system) Arteries (Away from heart, blood under highest pressure, elastic fibres for recoil, smooth muscle for support, epithelial cells for smooth blood flow - narrow lumen compared to diameter) Veins (lowest pressure, deoxygenated blood returning to heart, widest lumen) Capillaries (medium pressure, small diameter, relatively medium lumen, blood to extremities).

9. Movement of water up the xylem e.g. symplast, apoplast, casperian strip etc
Apoplast = water moves between cell walls, pathway of least resistance as water is absorbed from roots
Symplast = through cell cytoplasm/ plasmodesmata
Vacuolar = through plant cell vauoles (least common route I think)
Casparian strip = blocks the apoplast pathway at the endodermis, an impermeable strip of suberin, forces water into symplast pathway, going into the cytoplasm of the cells adjacent to it, water also moves up the xylem by cohesion, tension, transpiration pull and the hydrostatic pressure created by water evaporating from the leaf

10. Translocation = the movement of assimilates up and down a plant by the phloem, an active process requiring ATP, sucrose (the main assimilate) is loaded into phloem at sources (usually photosynthesising leaf) and unloaded at sinks (roots, fruits, areas of growth). Sucrose like water can take an apoplast (H+ Hydrogen ions pumped out by the companion cells into sieve tube elements, takes sucrose with it - transporter protein - and this lowerd water potential, bringing in water by osmosis from the xylem) or symplast (plasmodesmata acts as a valve, after the sucrose is converted into larger sugar, e.g, raffinose, cannot return)pathway.

11. Xerophyte is a plant adapted to live in especially dry, arid (desert) conditions. They aim to reduce water loss by transpirations, using either behavioural or structural adaptations, such as having a reduced surface area of leaves (rolled, needle-shaped) or a shallow but extenisve root system. They have their stomata on the underside of their leaves or sunk into pits, creating an area of high water vapour potential above them, and therefore reducing water loss by transpiration. They can also have accordion-folded stems which store water until it is desperately needed!

12. Fluid mosaic model (membrane) and functions,

Fluid mosaic model = the idea that the cell surface membrane is like a fluid mosaic, it contains many components which fit together and form a sort of "mosaic" but the phospholipid bilayer is also suspended and flexible, "fluid" because it can be penetrated, reform, change shape etc,

Components & Functions

Cholestrol = maintains membrane fluidity whilst stabilising it, holds components in place

Intrinsic Proteins = form channels or carriers to transport different proteins across the membrane, sometimes against a concerntration gradient (active process)

Extrinsic Proteins/ Glycoproteins = cell signalling, recognition, can act as antibodies and attach to water molecules

Phospholipids = form a bilayer that is selectively permeable, in which all other compoenents of the cell surface membrane are embedded, partially hydrophobic - water hating (tail) and hydrophilic - water loving (head)

(*What I think will come up - carbon dioxide tranportation in the blood, through the plasma solution, hydrogencarbonate ions and combined with the haemoglobin...)
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Niki_girl
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(Original post by arcticwombats)
Thanks! You sound like you're on track for an A haha!
I really hope so but to be honest I fall apart in F212 so I basically am hoping to get loads of marks on this paper to compensate...hopefully it'll be a good exam for all of us
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The Smeezington
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(Original post by Niki_girl)
I really hope so but to be honest I fall apart in F212 so I basically am hoping to get loads of marks on this paper to compensate...hopefully it'll be a good exam for all of us
F211 is 30%, F212 is 50% though
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rawr13
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#58
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#58
(Original post by Madmaz)
I always get my conversions wrong so I get the whole question wrong! How do you do yours??

Thank you!!!


hey thats what i usually have difficulty with but ive sorta got better since i do physics and chem aswell.

basically i always convert into metres.

so micrometres= x10^-6 metres
and nanometres = x10-9 metres

i.e. trying to work out the magnification of something when the image size is 6.5cm and the actual size is 7micrometres.

magnification = image size/actual size

6.5cm/7micrometres = 0.065m/7x10^-6m = X9286

get what i mean? just memorize the conversion of micro and nanometres. then you should be fine. ?
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Groat
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#59
(Original post by yamamotootsu)
Am only revising what might come up on the exams

1) Bohr Effect(completely understand it now=) )
2) Blood, tissue fluid and lymph
3) faciliated diffusion(carrier and channel)
4) division of labour
5) Lungs(spirometer)
6) Cardiac Cycle
7) control of cardiac cycle
8) blood vessels
9) Movement of water up the xylem e.g. symplast, apoplast, casperian strip etc
10)Translocation
11) Xerophyte
12) Mosaic model(membrane)and functions
Since when could a topic not come up twice? I wouldn't just ignore the topic because it came up in January 2011. You'll be in for a shock.
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rawr13
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#60
(Original post by laureneb10)
Anyone know why the heart contracts from the base of the heart upwards?
Seriously screwed!

thats only with the ventricles.

its just basically because blood has to be pushed upwards from the ventricles

otherwise it the blood would stay in the ventricles.


i think
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