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AQA BIOL2~3rd June 2013~AS Biology (Now Closed)

How likely is it that xerophytes comes up do you think? Because it came up in the empa 3 so that should mean not very likely right?

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Reply 2301

Suzanna5678

If there's a question on how water gets from the root hair cells to the xylem do we talk about apoplastic and symplastic pathways and root pressure?

Reply 2302

tumblrgirl

how accurately should you give an answer to a calculation if it doesn't specify?

Reply 2303

zbert

is the apoplastic pathway just cohesive tension pulling the water up the cell walls of the root cortex cells?

Reply 2304

philippawright

You know when water moves through the root cortex.. is it diffusion or osmosis? Everywhere seems to say osmosis but i'm sure we were told diffusion because it never actually crosses a cell membrane so cant be classed as osmosis?
Thanks :smile:

Reply 2305

zbert

Original post by JulianaHiguera

How likely is it that xerophytes comes up do you think? Because it came up in the empa 3 so that should mean not very likely right?

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not likely but then again it's pretty straight forward to remember

Reply 2306

lorobolorolo

7

why do mineral ions move by active transport into the xylem and not by diffusion?

Reply 2307

username985376

2

Original post by Hi, How are you ?

I think so, in some question I v'e done they talked about the fluid moving into the tissue to reduce the diffusion pathway, I think. So technically yes I suppose. Our teachers haven't talked about it either.

Okay thanks

Reply 2308

username985376

2

Original post by blondie24

I think there is but right at the end of the tracheoles but i don't think we need to specifically know about the fluid. I think the respiratory gases diffuse from the tracheoles in to the fluid and then into respiring cells

right okay thanks,

Reply 2309

lorobolorolo

7

Original post by philippawright

You know when water moves through the root cortex.. is it diffusion or osmosis? Everywhere seems to say osmosis but i'm sure we were told diffusion because it never actually crosses a cell membrane so cant be classed as osmosis?
Thanks :smile:

If it moves by the apoplast pathway it moves by diffusion. (through the cell wall)

If it moves by the symplast pathway it moves by osmosis. (Across the cell wall)

Reply 2310

Bixel

5

There's a question in June 2011 that states "Describe how tissue fluid is returned to the circulatory system"

The mark scheme states: "Hydrostatic pressure is lower in capillary, and WATER returns by osmosis"

How comes it mentions water rather than tissue fluid?

Reply 2311

HannahC1996

Original post by zbert

is the apoplastic pathway just cohesive tension pulling the water up the cell walls of the root cortex cells?

The apoplastic pathway is the diffusion of water vapour from an area of high concentration to an area of lower concentration :smile:

Reply 2312

eilish1903

17

Original post by philippawright

You know when water moves through the root cortex.. is it diffusion or osmosis? Everywhere seems to say osmosis but i'm sure we were told diffusion because it never actually crosses a cell membrane so cant be classed as osmosis?
Thanks :smile:

Osmosis IS the diffusion of water

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Reply 2313

HannahC1996

Original post by philippawright

You know when water moves through the root cortex.. is it diffusion or osmosis? Everywhere seems to say osmosis but i'm sure we were told diffusion because it never actually crosses a cell membrane so cant be classed as osmosis?
Thanks :smile:

The symplastic pathway is the movement of water molecules and is therefore osmosis, I think :smile:

Reply 2314

HannahC1996

Original post by lorobolorolo

why do mineral ions move by active transport into the xylem and not by diffusion?

They are moving against a concentration gradient :smile:

Reply 2315

lorobolorolo

7

Original post by Bixel

There's a question in June 2011 that states "Describe how tissue fluid is returned to the circulatory system"

The mark scheme states: "Hydrostatic pressure is lower in capillary, and WATER returns by osmosis"

How comes it mentions water rather than tissue fluid?

Tissue fluid is made up of water and certain things dissolved in it such as salts, amino acids etc.

Therefore it's better to mention water returns rather than tissue fluid returns because tissue fluid does not technically move by osmosis. :smile:

Reply 2316

philippawright

Original post by eilish1903

Osmosis IS the diffusion of water

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Yeah but i'm sure we were told even if it is water, if it doesnt cross a partially permeable membrane it cant be counted as osmosis, its just diffusion? aahhh so confused!