Some bio questions

davidche SG

Yup i am chionging bio topic by topic TYS now cos i suck in bio. Ill finish the book in one day tho dont worry.

Since the answer keey is highly unreliable, i have to post my doubts here XD

1) How does oxygen pass out through the stomata of leaves? Diffusion or transpiration. Why not transpiration?

2) How does most carbon dioxide reach the photosynthesising cells of a green leaf? Diffusion through the epidermis or stomata?

NG QIBO AARON AUBREY SG

Yup i am chionging bio topic by topic TYS now cos i suck in bio. Ill finish the book in one day tho dont worry.

Since the answer keey is highly unreliable, i have to post my doubts here XD

1) How does oxygen pass out through the stomata of leaves? Diffusion or transpiration. Why not transpiration?

2) How does most carbon dioxide reach the photosynthesising cells of a green leaf? Diffusion through the epidermis or stomata?

1) transpiration

2) stomata

enirtep SG

1) it diffuses out through stomata. gaseous exchange takes place at stomata, remember that (carbon dioxide in, oxygen out or vice versa)

2) refer to 1)

recap diffusion: it is the movement of molecules from a region of higher concentration to a region of lower concentration. so when there is high concentration of carbon dioxide in the air, it diffuses in. there is a lot of oxygen in the plant (photosynthesis produces oxygen) so it diffuses out.

transpiration is water loss, nothing to do with gaseous exchange. hths! :D

davidche SG

1) it diffuses out through stomata. gaseous exchange takes place at stomata, remember that (carbon dioxide in, oxygen out or vice versa)

2) refer to 1)

transpiration is water loss, nothing to do with gaseous exchange. hths! :D

o yar thanks. And thansk for registering just to answer my qn. XD

davidche SG

Fitness training increases the conc. of lactic acid that athletes can tolerate in their muscles. What is a consequence of this increase?

a) Blood flow to muscles is increased

or b) more anaerobic respiration can take place in muscles.

eagle SG

Fitness training increases the conc. of lactic acid that athletes can tolerate in their muscles. What is a consequence of this increase?

a) Blood flow to muscles is increased

or b) more anaerobic respiration can take place in muscles.

heh, fitness and health corner

davidche SG

lol i tot more anaerobic means more lactic acid as product?

UltimaOnline SG

lol i tot more anaerobic means more lactic acid as product?

Yes, you see, the idea is - once you (as an athlete) has conditioned your body to tolerate greater concentrations of lactic acid (by having training sessions in which you cheong anaerobic respration until you kena high lactic acid concentrations in your muscles, but you keep cheonging, shouting gloriously in Hokkien, "要拼才会赢!!!" like a raving lunatic), your body will then eventually be conditioned to tahan greater concentrations of lactic acid from anaerobic respiration which translates to you eventually being able to cheong and sprint your 2.4km the entire stretch while running over your opponent's collapsed corpses along the way.

eagle SG

lol i tot more anaerobic means more lactic acid as product?

yup

And as UltimaOnline has explained... That's why seasoned gym goers can last longer in the gym than newcomers :D

And you growl out loud as you do a heavy deadlift :D

davidche SG

oh i see. lol. btw, the gym forum is as inactive as a corpse.

davidche SG

Some more questions( i am doing new questions simultaneously you see)

Which process does not require energy? Tissue respiration or transmission of nerve impulse. If it is the former, How does respiration not require energy?

UltimaOnline SG

Some more questions( i am doing new questions simultaneously you see)

Which process does not require energy? Tissue respiration or transmission of nerve impulse. If it is the former, How does respiration not require energy?

Both require energy. However, net result of tissue respiration is that you produce more energy (ie. ATP molecules) than you invest in during the respiration process.

SBS n SMRT SG

Yup i am chionging bio topic by topic TYS now cos i suck in bio. Ill finish the book in one day tho dont worry.

Since the answer keey is highly unreliable, i have to post my doubts here XD

1) How does oxygen pass out through the stomata of leaves? Diffusion or transpiration. Why not transpiration?

2) How does most carbon dioxide reach the photosynthesising cells of a green leaf? Diffusion through the epidermis or stomata?

1. The oxygen potential is higher in the cells in the spongy mesophyll layer than the layer of moisture outside the cell, therefore, oxygen would move down a concentration gradient by diffusion. The oxygen potential in the layer of moisture is higher than the intercelluar air space, therefore, oxygen would diffuse out of the layer of moisture to the intercelluar air space. By diffusion of molecules, the oxygen molecules would slowly move its way out of the leaf through a stomata. Transpiration only applies to osmosis of water( through liquid water or water vapour)

2. It is the same as question 1 except in this case carbon dioxide moves to the cell as compared to question 1 oxygen moving out. Carbon dioxide would allow a plant to photosynthesize in the present of chlorophyll, light energy and water.

Equation of photosynthesize is

Water + Carbon Dioxide+Energy ==Light energy+Chlorophyll==> Glucose+Water+Oxygen

In symbols

12(H2O)+6(CO2)+X(ATP)==Light energy+Chlorophyll==> C6H12O6+6(H2O)+6(O2)

X could be anything as ATP is energy

H2 means a diatomic covalent molecule of hydrogen not 2 molecules of hydrogen

OT: Finally, a bio qns for me to answer.....

Garrick_3658 SG

If you wanna write ATP at O level (which you don't have to) then write it together with the light energy and chlorophyll. ATP is not a raw material... ... ...

At first when I see it, I was like "Simi ATP, mai luan luan lai leh"...

How does most carbon dioxide reach the photosynthesising cells of a green leaf? Diffusion through the epidermis or stomata?

If you really wanna know, it is about the CO2 becoming H2CO3 (carbonic acid) then diffusing through the cells. If you really want to know how then ask UltimaOnline because, well because, erm, I don't have the facts with me right now... Bio next week what...

eagle also can la, if he doesn't suck at bio as much as he did in chemistry :P PSPS :D

UltimaOnline SG

If you wanna write ATP at O level (which you don't have to) then write it together with the light energy and chlorophyll. ATP is not a raw material... ... ...

At first when I see it, I was like "Simi ATP, mai luan luan lai leh"...

eagle also can la, if he doesn't suck at bio as much as he did in chemistry :P PSPS :D

ATP is the chemical form of energy.

Photosynthesis first uses light energy in the presence of chlorophyll to produce energy (in the form of ATP), which then uses this energy to rearrange the atoms of CO2 and H2O to give you glucose (which is also immediately used to synthesize amino acids, fats, etc).

Aerobic (and anaerobic) Respiration is breaking apart glucose to get energy (in the form of ATP). Aerobic occurs in presence of oxygen (and takes place partly in mitochondria and partly in cytoplasm of cell) and you get more energy (more ATP molecules), compared to anaerobic respiration which occurs in absence of oxygen (and takes place wholy in cytoplasm of cell).

Notice that photosynthesis and aerobic respiration are macham opposites, but in both cases, energy is worked with mainly in the form of ATP (there are other energy-rich molecules, you'll learn at 'A' level).

>>> it is about the CO2 becoming H2CO3 (carbonic acid) then diffusing through the cells <<<

Yes, carbon dioxide dissolves in water for form carbonic acid, H2CO3, which may be deprotonated (loss of proton or H+ ion) to form HCO3-. It is usually in this form, monohydrogencarbonate ion, that plants and animals (including humans) transport dissolved (ie. aqueous) carbon dioxide within the blood, within the film of water on mesophyll cells, on alveolar/alveoli walls, etc.

Also, if asked to explain why acids react with carbonates to give you carbon dioxide gas, it is related to the discussion above.

CO3 2- + 2H+ --> H2CO3

(carbonate ion gets protonated to form carbonic acid)

H2CO3 --> CO2 + H2O

(carbonic acid exists in equilibrium with carbon dioxide and water. Since carbon dioxde is a gas (at r.t.p.) and leaves the reaction mixture/solution, you get your 'efferverscence' observation.)

Any further qn?