OCR F214 Biology 24/1/11

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Original post by Princess_perfect786

A respiratory substrate is a biological molecule that can be broken down in respiration to release energy (as ATP).
Other substances can also be used to make ATP.

can anyone explain what this statement means? what does it mean by "other substrates". is it saying that glycogen, triglycerides, fats and proteins are not respiratory substrates? if so, then what are respiratory substrates?

Lipids and proteins are also respiratory substrates, they just enter the respiration at different stages (link reaction, krebs cycle) and need to be converted.
cause the RQ (respiratory quotient) for lipids is like 0.7 and for proteins 0.9 :biggrin:

(edited 13 years ago)

Reply 41

Summerdays

Original post by Princess_perfect786

'Other substrates' simply means that many organic molecules can be used to remove the chemical energy in their bonds of the substrates and store that energy in the form of ATP (via respiration). Glycogen, triglycerides, fats and proteins ARE respiratory substrates, but they usually need to be converted into Acetate coenzyme A, in order for them to enter the Krebs cycle. Or they may even be converted to glucose (and then broken down into pyruvate via glycolysis, which then enters the link reaction and the Kreb cycle.) Glycogen, triglycerides and proteins have a lower respiratory index than glucose though (les CO2 is produced during respiration than O2 because they enter respiration via the Krebs cycle, in the form of acetate COA, so the decarboxylation of pyruvate doesn't occur.)

Reply 42

Princess_perfect786

Original post by India27

Hey guys got a question from the specification...compare and contrast the structure and function of a myelinated and non-myelinated neurones? My text book has very little on this, and i've got some info on both structures but not very much on comparisons or contrasting. Thanks :smile:

Around one third of the peripheral nerones in vertebrates are myelinated. That is, they are insulated by an individual myelin sheath. The sheath is created by a series of seperate cells called Schwann cells. These are wrapped around the neurone so the sheath actually consists of several layers of membrane and thin cytoplasm from the Schwann cells At intervals of 1-3mm along the neurone there are gaps in the myelin sheath. These are called nodes of Ranvier. Each node is very short (about 2-3um long).

The remainder of the peripheral neurones and the neurones found in the CNS are not myelinated. Non-myelinated neurones are still associated with Schwann cells, but several neurones may be enshrouded in one loosely wrapped Schwann cell. This means that the action potential moves along the neurone in a wave (continued conduction) rather than jumping from node to node (saltatory conduction) as seen in myelinated neorones.

Because A.P. jumps from node to node in myelinated neurones, transmission of the impulse in these neurones is faster than in non-myelinated neurones. This is useful becuase myelinated neorones are usually very long and carry impulses across long distances, e.g. from sensory receptors to the CNS and from the CNS to effectors, so the speed of transmission needs to be fast. Non-myelinated neurones tend to be shorter and only carry impulses over short distances. They are used in coordinating body functions such as breathing and the action of the digestive system, so a fast speed of transmission is not too improtant.

Edit: the local current in myelinated neurones is elongated, to allow the AP to jump from one node of Ranvier to the next.

(edited 13 years ago)

Reply 43

sc0307

Original post by Princess_perfect786

i understood most of that but what the purpose of having schwann cells on non-myelinated neurones?

Reply 44

Princess_perfect786

Original post by sc0307

i understood most of that but what the purpose of having schwann cells on non-myelinated neurones?

i don't know that either. i used my Heinemann textbook to make these notes but it doesn't say anything about schwann cells around non-myelinated neurones in my Cambridge OCR Advanced Sciences textbook. i don't think its important and you probably won't need to know anything about it for the exam.

do you know if stuff on reflex arcs is going to come up? it doesn't say anything about it in the syllabus but my Cambridge textbook has two pages about it.

Reply 45

sc0307

Original post by Princess_perfect786

It's not on the actual spec but it is mentioned in one sentence in the ocr textbook on the first double page spread on neurones. It doesn't hurt to know a bit about it cos ocr can be really sneaky with stuff like that and have synoptic questions on it. All it is, is a a neurone situated somewhere on the spine i think between a sensory and motor neurone and it bypasses the impulse from having to go up the spine, to the brain and back down again to bring about a much quicker response. Does that sound right?

Reply 46

Summerdays

Original post by sc0307

i understood most of that but what the purpose of having schwann cells on non-myelinated neurones?

Basically it is to protect the neurones from the electrical activity of other near-by neurone and cell, as the schwann cells act as insulators.

Reply 47

joestevens2092

How goes the revision guys? Just had the june 2010 mock and found it nice enough, hopefully our paper on monday will be of equal difficulty

Reply 48

xPixie

Original post by joestevens2092

How goes the revision guys? Just had the june 2010 mock and found it nice enough, hopefully our paper on monday will be of equal difficulty

Let's hope Monday's paper easy :tongue:

& the grade boundaries are low :tongue:

Reply 49

sc0307

can someone explain RQ values to me please

Reply 50

Summerdays

Original post by sc0307

can someone explain RQ values to me please

RQ tell you the ration of CO2 produced in ratio to the amount of oygen used. It infact tells us which stage the respiratory substrates enter respiration (i.e. whether they entered during glycolysis or link reaction or krebs cycle.) Anerobic respiration produce more CO2 than O2 (so have a RQ greater than one.)

Reply 51

sc0307

Original post by Summerdays

so glucose would have the highest rq value compared to lipids and proteins as it can be converted to pyruvate and enter anaerobic as well the other stages of aerobic respiration whereas lipids and proteins cannot do not go through glycolysis and enter directly in krebs?

Reply 52

Summerdays

Original post by sc0307

Yes this is true. Remember that lipids have to be converted into acetate, which then combines with coenzyme A to produce acetate coA, which enter the kreb cycle. And also remember that before the kreb cycle, during the link reaction, decarboxylation of pyruvate (as well as dehydrogenation) occurs (which produces a mole of CO2 per a mole of pyruvate.) But because the acetate coA doesn't entre through the link reaction, the 2 molecules of CO2 that would be produced from the two molecule of pyruvate doesn't occur. So the RQ (CO2 released/O2 input) is less than 1.

Reply 53

sc0307

Original post by Summerdays

are proteins or lipids ever converted to glucose or pyruvate?

Reply 54

Summerdays

Original post by sc0307

are proteins or lipids ever converted to glucose or pyruvate?

Yes, some proteins and lipids are (remember that gluconeogenesis makes glucose from proteins and lipids.)

Reply 55

sc0307

Original post by Summerdays

Yes, some proteins and lipids are (remember that gluconeogenesis makes glucose from proteins and lipids.)

do you take that into account for rq values?

Reply 56

Summerdays

Original post by sc0307

do you take that into account for rq values?

If they are converted to glucose then I believe their RQ value will be the same as that of glucose, 1.

Reply 57

tallysingh

They cannot ask you much about rq values, and if they do they will give you the number. Under anaerobic, rq value with lower number is used most so that is lipids. I went through an examiner report and the chief examiner said most students will not have come across rq. Lipids can be made into acetate, while proteins can be deaminated and the keto acid can respiration Straight.

Reply 58

ibysaiyan

Original post by tallysingh

All you need to know about rq value is the definition itself and range of rq for lipids/c.hydrates/protein =]

Reply 59

sc0307

Original post by ibysaiyan

All you need to know about rq value is the definition itself and range of rq for lipids/c.hydrates/protein =]

I highly doubt they'd ask for the definition, they can't ask you to define terms that aren't on the spec. They would define the term in the question like they did in the june 2010 paper.