AQA Biology Unit 2 with Anon_98.

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Okay, that's haemoglobin stuff done.

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Properties of Starch and Glycogen as energy stores?

−Insoluble = do not affect water potential of the cell, do not diffuse out of the cell

−Coiled/Branched = compact, more can fit into a cell

−Branched/Chained = glucose removed from the ends.

Alright, so there are 3 main properties and those are that both starch + glycogen are insoluble, coiled + branched.

Insoluble is great bc it means that it's presence doesn't affect the water potential of the cell + therefore cannot/does not diffuse out of the cell.

Coiled means it's compact so it can fit a lot of molecules in a small space and overall, more can fit into the cell.

So COILED = COMPACT.

Branched - more ends, therefore more readily hydrolysed so more glucose removed from the ends.

Reply 122

Anon_98

Ohmyg, I just yawned.

Reply 123

Anon_98

Structure of Cellulose?

−Beta glucose arranged in a straight chain (each alternative beta glucose is rotated 180 degrees) = cellulose straight chain

−many cellulose chains are cross linked by hydrogen bonds to form microfibrils

−many microfibrils are cross linked to form marcrofibirils (fibres)

−forms structure of cell wall −strong material (prevents plant cell from bursting or shrinking

Okay so Cellulose is made up of beta glucose and each other glucose molecule is rotated 180 degrees so a straight chain can be formed.

Many cellulose chains are also cross linked by hydrogen bonds to form microfibrils.

Microfibrils are formed due to cellulose chains joining up by hydrogen bonds which they have been cross linked by and then of course, the microfibrils are then cross linked to form macro fibrils.

And that forms the structure of a cell wall which is v strong, rigid material which prevents cell from bursting/shrinking.

Okay so straight cellulose chains form microfibrils and microfibrils form macrofibrils all via cross links + hydrogen bonds + thta's what makes the cell wall v strong.

Reply 124

Anon_98

Why do large organisms need specialised exchange and transport systems?

−have a small surface area to volume ratio

−multicellular (high demand and large diffusion distance)

−impermeable surface (prevent pathogens entering and reduce water loss)

So LARGE organisms need specialised exchange surfaces bc they have a small surface area to volume ratio, multicellular, impermeable surface.

-small SA:VR
-Multicellular
-Impermeable surface.

Mm alright.

Reply 125

Anon_98

Structure of exchange system in insects?

Has openings on body called Spiracles – connects to the trachea which connects to tracheoles which connects directly to the cells.

Okay so the insects exchange system is literally that it has openings on it's body called spiracles. The openings are known as spiracles and they connnect to the trachea and that connects to the tracheoles which connects to the cells.

Spiracles> Trachea > Tracheoles > Cells

STTC.

Reply 126

Anon_98

Adaptation of the gills in fish?

−many gill filaments and gill lamellae = large surface area

−gill lamellae have a thin wall (short diffusion distance) and are permeable

−ventilation brings in pure water (high oxygen, low carbon dioxide) and circulation brings in deoxygenated blood (low oxygen, high carbon dioxide), the water and blood pass over in opposite directions (countercurrent flow), maintains concentration gradient.

Okay, so the gills have 3 MAIN adaptations.

Gill filaments + lamellae have a LARGE SA.

So the filaments and lamellae have a large surface area but the lamellae also have a thing wall which means a short diffusion distance.

THEN

Ventilation brings water high in O2, low in CO2 and circulation brings low O2, high CO2. The water and blood pass in opposite directions and it's known as countercurrent flow.

Countercurrent flow is what maintains the concentration gradient.

SO basically the Ventilation brings water high in O2, low CO2 and circulation does the opposite. = Countercurrentflow = Maintaining concentration gradient.

Alright, so that's ..

-Large SA.
- Short diffusion pathway.
- Maintains conc gradient.

Reply 127

Anon_98

I can hear the birds.- Not sure what time I should be going to bed..

Reply 128

Anon_98

Adaptation of palisade cells for photosynthesis?

−located near top of leaf, closer to light

−large size, large surface area for light

−thin cell wall, short diffusion distance for carbon dioxide

−contains many chloroplasts, site of photosynthesis

−large vacuole, pushes chloroplast to the edge of the cell closer to light

Okay, so unlike a fish- the palisade cells have 5 main adaptations.

So, it's located near the top of the leaf bc obviously near the top means it's closer to the sun + will therefore get more sunlight for photosynthesis.

It is also quite large in size so it can absorb more light/ a large surface area o light, again for photosynthesis.

Thin cell wall, so there's a short diffusion distance for CO2.

Lots + lots of chloroplasts so they cna absorb all that sunlight.

SO the chloroplasts are in great numbers bc it's the site of photosynthesis and the large vacuole pushes the chloroplasts to the edge of the cell closer to light so it can absorb more light. Okay.

One more time:

- Lots of chloroplasts, thin cell wall, large SA, Large vacuole, and near the top of the leaf. --> :leaf:

Reply 129

undercxver

Omg talk about dedication! Keep at it girl. 💪🏼

Reply 130

Anon_98

Okay, well I've still got a great amount to do but I think I'm going to bed for a bit.- I'll be back at, like, 6:30/something.(Hopefully)

It's light outside. )':

Goodnightt.

Reply 131

Anon_98

Original post by undercxver

Omg talk about dedication! Keep at it girl. 💪🏼

Tysm💛 🌞

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Reply 132

username1133132

Original post by Anon_98

Remember to mention maintains concentration gradient across the whole length of lamellae (you probably already know that! :tongue:

)
Good luck x

Reply 133

Anon_98

So it's 6:30 ish, but everything really hurts + I feel pretty sick. + dizzy. Infact, I think I am genuinely going to vomit so .. I'm going back to bed bc I'd still like to think straight. I should be good by 8/9am.

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Reply 134

kkboyk

Original post by Anon_98

Good luck! :tongue:

Reply 135

Fiduciam

Soooo hoping you don't oversleep. :indiff:

ONE.
FINAL.
PUSH. :dumbells:

You've got this Anon, it's probably daunting + exhausting but you've done so incredibly well till now, just get through this last bit of revision and go into that exam with as much confidence as you can okay?

Stay relaxed and well done for everything so far!

You can doooooo ittttttttt! :five:

Okay, well I didn't oversleep - I just decided to get ready + have breakfast + everything else before logging in then I managed to spill water all over my statistics notes and now they're all vile + wrinkly so that was fun + wasted a bit of time. But yes, ummmm, I don't think I have enough time to properly go through everything else so I'm going to spend the next 25 minutes just reading through them then I'll start past papers at 10:00am.

Reply 138

Anon_98

Original post by haj101

Remember to mention maintains concentration gradient across the whole length of lamellae (you probably already know that! :tongue:

)
Good luck x

Thank you for the reminder + no, I didn't. :tongue:

Good luck to you too. <3

Original post by kkboyk

Good luck! :tongue:

Can I just say that your notes were extremely helpful + thanks a whole lot for providing them.

+ ty, good luck to you too if you're also doing the exam! <3