Biology Unit 3 Questions Megathread

[shinny]

as humans cannot digest cellulose, how do we get energy from plants? do bacteria digest and release the plants cytoplamsic contents? or do we just 'squish' and squeeze things out of the cell wall?

We get energy from other things within plants. Not all the carbohydrates are in the form of cellulose - not to mention the other nutrients available. The cellulose becomes what we know as dietary fibre.

[WhoTookMyUsername]

so humans can withdraw plant cellular substances without needing to break down the cell wall?

[shinny]

so humans can withdraw plant cellular substances without needing to break down the cell wall?

Well it definitely gets broken down, but I'm not 100% on the main factor involved. There's other components in the cell wall that I'm fairly certain we can break down, and despite that, the mechanical process of chewing and the consequent digestion and stomach acid and whatnot would pretty much tear it apart.

[HERculina]

what does increased metabolic rate mean? 

[WhoTookMyUsername]

Increased cellular activity producing ATP and heat. Giving that metabolism is the sum total of chemical reactions happening in the body, an increase in metabolic rate would simply mean more chemical reactions happening per unit of time

[HERculina]

Increased cellular activity producing ATP and heat. Giving that metabolism is the sum total of chemical reactions happening in the body, an increase in metabolic rate would simply mean more chemical reactions happening per unit of time

ohh ok thanks, this makes sense now
Oh, if your metabolic rate increases too much can their be a fatal build up of products? wat are the consequences of a too fast metabolic rate

[Kaille]

hey guys.

exam question, i don't really agree with the answer.

Evidence that molecule (aquaporin) was a component of cellular water channels came in an experiment with frogs' legs bathed in water solution. One group of eggs were injected with aquaporin RNA while the other group were not. Write a hypothesis based on what you think would happen to the two different groups of eggs.


ANSWER: THAT THE EGGS EXPRESSING AN AQUAPORINE, FOLLOWING INJECTION OG AQUAPORINS RNA, WILL ABSORB WATER, SWELL AND BURST, BUT THE EGGS WITHOUT THE AQUAPORINS WILL NOT BURST.

i thought more aquaporins would enhance water regulation?

[Edmund]

hey guys.

exam question, i don't really agree with the answer.

Evidence that molecule (aquaporin) was a component of cellular water channels came in an experiment with frogs' legs bathed in water solution. One group of eggs were injected with aquaporin RNA while the other group were not. Write a hypothesis based on what you think would happen to the two different groups of eggs.


ANSWER: THAT THE EGGS EXPRESSING AN AQUAPORINE, FOLLOWING INJECTION OG AQUAPORINS RNA, WILL ABSORB WATER, SWELL AND BURST, BUT THE EGGS WITHOUT THE AQUAPORINS WILL NOT BURST.

i thought more aquaporins would enhance water regulation?

Yes aquaporins will make the membrane more permeable to water.

[shinny]

hey guys.

exam question, i don't really agree with the answer.

Evidence that molecule (aquaporin) was a component of cellular water channels came in an experiment with frogs' legs bathed in water solution. One group of eggs were injected with aquaporin RNA while the other group were not. Write a hypothesis based on what you think would happen to the two different groups of eggs.


ANSWER: THAT THE EGGS EXPRESSING AN AQUAPORINE, FOLLOWING INJECTION OG AQUAPORINS RNA, WILL ABSORB WATER, SWELL AND BURST, BUT THE EGGS WITHOUT THE AQUAPORINS WILL NOT BURST.

i thought more aquaporins would enhance water regulation?

Pure water is hypotonic to the cell, so if aquaporins are present, water will rush into the cell and lyse it. Cells which don't have aquaporins will only have water enter by osmosis across the lipid bi-layer itself - a fairly slow and negligible process - meaning that the cell will probably take a long time or never lyse. Not too sure how effectively water crosses a pure membrane. What exactly are they teaching in Bio 3/4 nowadays though? In '07, we were still being taught that water is freely permeable via simple diffusion without any mention of the need for aquaporins o_o

[Kaille]

so osmosis is a relatively slow process in comparison to if aquaporins were present?

eh this was just in an exam paper, never learned anything about aquaporins at school.

[shinny]

so osmosis is a relatively slow process in comparison to if aquaporins were present?

That's my understanding, yes. Perhaps the Biomed students could elaborate. I didn't go very in-depth into biology in first year, and knowledge of aquaporins was quite limited back when I did Bio 3/4.

[Edmund]

so osmosis is a relatively slow process in comparison to if aquaporins were present?

That's my understanding, yes. Perhaps the Biomed students could elaborate. I didn't go very in-depth into biology in first year, and knowledge of aquaporins was quite limited back when I did Bio 3/4.

Didn't you cover this in kidney function? I recall something about aquaporins being stimulated by vasopressin release for fluid reabsorption by the collecting duct. So I'm not sure if this process is any different to frogs legs.

[shinny]

so osmosis is a relatively slow process in comparison to if aquaporins were present?

That's my understanding, yes. Perhaps the Biomed students could elaborate. I didn't go very in-depth into biology in first year, and knowledge of aquaporins was quite limited back when I did Bio 3/4.

Didn't you cover this in kidney function? I recall something about aquaporins being stimulated by vasopressin release for fluid reabsorption by the collecting duct. So I'm not sure if this process is any different to frogs legs.

Kidney physiology and kidneys in general are the death of me. But yeh, I know aquaporins increase the rate of diffusion, but I'm not sure to what extent water can diffuse through the lipid bi-layer, that's all.

[Kaille]

so osmosis is a relatively slow process in comparison to if aquaporins were present?

That's my understanding, yes. Perhaps the Biomed students could elaborate. I didn't go very in-depth into biology in first year, and knowledge of aquaporins was quite limited back when I did Bio 3/4.

Didn't you cover this in kidney function? I recall something about aquaporins being stimulated by vasopressin release for fluid reabsorption by the collecting duct. So I'm not sure if this process is any different to frogs legs.

i only learned about the kidney in 1/2 and in not much depth. and what frog legs?

[Kaille]

another question, in cell mediated immunity, do the macrophages release cytokines that act on t lymphocytes to develop and proliferate into t cytotoxic cells and t helper cells?