This discussion is now closed.

Check out other Related discussions

AQA BIOL4 ~ 11th June 2013 ~ A2 Biology

Scroll to see replies

Reply 660

flyylikejetz

What do the bacteria in the root nodule of legumes reduce nitrogen to via their nitrogen fixation ?

Reply 661

kdk

Original post by kitkat95

Only one genotype is affected/has decreased- the recessive one. If it were stabilising selection, both the recessive and dominant allele frequency would have been affected.

okay, so does it mean that it is impossible for stabilising selection to occur in allele frequency questions?
becoz the sum of dominant allele and recessive allele is always one, so if one increases the other decreases. ( i.e. they can't increase together!)

Am I right?

Reply 662

krane

Original post by Scienceisgood

Respiration and Photosynthesis brief.

Respiration:
Glycoloysis:
Glucose produced in the light independent reaction comes along and 2 ATP molecules are broken down into ADP and Pi Molecules.
The phosphate ions attach and the glucose molecule splits into 2 3 carbon molecules called Triosphosphate.
Then NAD and FAD come along and are reduced by the Triosphosphate molecules to NADH and FADH.
4 ATP molecules are produced as a result of this reaction.

I thought only NAD was reduced in glycolysis?

Reply 663

kitkat95

Original post by kdk

I'd never thought about that, but yes I guess so :smile:

Reply 664

Nessie133

Original post by lifeisgood2012

are nitorgen fixing bacteria in the soil?

Nitrogen fixing bacteria are either free-living and so live in the soil or are mutualistic and live in the root nodules of certain plants (legumes).

Reply 665

billybobs

Original post by krane

Could anyone tell me how decomposers give back carbon dioxide into the atmosphere?
Is it mainly by respiring but also by breaking down things like starch and not absorbing it all?
Plus how do they give back nitrogen, is it by breaking down proteins etc, absorbing them, and then dieing?

And are saprobiotic microorganisms the same as saprophytic bacteria, and which do they prefer? :biggrin:

Decomposers do indeed give CO2 back mainly through respiration, i'm not sure about starch but your safe option is definitely CO2.

Nitrogen is released as saprobiotic microorganisms/saprophytic bacteria (they dont mind either) break down dead plant matter/faeces from plant/animals and release it as ammonium into the soil, converted to nitrites, nitrates by nitrifying bacteria etc etc.

Reply 666

DELETED ACCOUNT

Original post by lifeisgood2012

are nitorgen fixing bacteria in the soil?

They are present in the nodules of leguminous plants, where they fix nitrogen into ammonium containing compounds in plants. The bacteria in return obtains carbohydrates for respiration.

Reply 667

krane

Original post by flyylikejetz

What do the bacteria in the root nodule of legumes reduce nitrogen to via their nitrogen fixation ?

I think they use it to form amino acids, which the plant acquires from them?

Reply 668

flyylikejetz

Original post by LegendX

Jan 2011 question 2bi.....anyone who can explain?

With 3 & 4 you they are both Rhesus positive meaning they are either (Homozygous dominant or Heterozygous dominant). if you look at 7 & 9 these are rhesus negative so must be (homozygous recessive) they must have got the recessive allele from their parents, who are carriers only possible with a recessive allele.

Hope thats clear

Reply 669

kdk

Original post by kitkat95

I'd never thought about that, but yes I guess so :smile:

Thank you

Reply 670

Tikara

Original post by krane

they are the same, they prefer saprobiotic though :P

They secrete enzymes onto their target to break them down into smaller compounds that are soluble which they then absorb via diffusion - for both nitrogen and carbon containing compounds.
For nitrogen, they release ammonia
for carbon they respire the products of digestion, CO2 :smile:

wait.. what decomposes a decomposer??!?

(edited 10 years ago)

Reply 671

flyylikejetz

Original post by krane

I think they use it to form amino acids, which the plant acquires from them?

so the ones in the soil = nitrogen to ammonium ions
ones in root nodules = nitrogen to amino acids ?

Reply 672

lifeisgood2012

what is the difference between oxaditive phosphorylation, photophosphorylation and substrate level phosphorylation?

Reply 673

flyylikejetz

Original post by lifeisgood2012

what is the difference between oxaditive phosphorylation, photophosphorylation and substrate level phosphorylation?

All methods of synthesis of ATP, or better phosphorylation of ADP ... ADP + P(i) --> ATP

Oxidative phosphorylation in mitochondria, Electron transport chain
Substrate-level phosphorylation cytoplasm of cell (glycolysis) and matrix of mitochondria (Kreb's Cycle)
Photophosphorylation Light dependent reaction in photosynthesis (Thylakoid membranes)

The key is in the name :smile:

Reply 674

Nessie133

Original post by krane

Saprobiotic microogranisms feed on and decompose dead organims by secreting enzymes and then absorbing the products by diffusion. They release carbon dioxide through aerobic respiration.

They give back nitrogen by breaking down ammonium-containing compounds in dead organims,such as urea and amino acids, and releasing ammonia which is converted into nitrite and nitrate ions by nitrifying bacteria.

I don't think it matters whether you use bacteria or microorganisms as long as you say saprobiotic.

Reply 675

jessjess

Original post by flyylikejetz

so the ones in the soil = nitrogen to ammonium ions
ones in root nodules = nitrogen to amino acids ?

it says in my revision guide that it makes ammonia, which is then used by plants to synthesize amino acids :smile:

Reply 676

Tikara

Original post by flyylikejetz

so the ones in the soil = nitrogen to ammonium ions
ones in root nodules = nitrogen to amino acids ?

both of them convert nitrogen to ammonium ions/ammonia only in mutualistic it is then used by the plant to make amino acids to make proteins. and the bacteria gets carbohydrates from the plant in return :smile:

(they aren't so picky about whether you say ammonium ions or ammonia though!)

(edited 10 years ago)

Reply 677

Nessie133

Original post by lifeisgood2012

what is the difference between oxaditive phosphorylation, photophosphorylation and substrate level phosphorylation?

Substrate-level is the formation of ATP by DIRECT linking of an inorganic phosphate to ADP.

Oxidative is the INDIRECT linking of inorganic phosphate to ADP to form ATP using hydrogen atoms and the electron transport chain.

Reply 678

master y

Original post by Tikara

No, and the mark scheme is specific about this

nitrogen fixing bacteria convert nitrogen gas to ammonia, which is then used by the plant to make amino acids to make proteins.

(they aren't so picky about whether you say ammonium ions or ammonia though!)

so ALL nitrogen fixing bacteria conveert nitrogen into ammonium ions? The only difference is what the plant does with it... so what do the free living ones do the plants use the ammonium ions for?