VCE Biology Question Thread

[nerdmmb]

This is an interesting question that I somehow stumbled upon while doing a research task sometime ago. 
Firstly, recall that DNA is contained in the nucleus. Hair, skin and nail cells destroy their nuclei as part of their developmental process. They do this in order to maximize the space in the cell filled with the structural protein keratin. This means that the cell nucleus and other internal parts of the cell are destroyed and their space is filled by keratin. MM1 said pretty much the same, I think.

Thank-you!

[Stick]

I'm sorry, this might deviate the thread from its intended purpose for a moment, but this is something I've been wondering for a while now.

How come when you straighten curly hair with a hair straightener, the hair regains its curl when it gets wet? The heat should cause the permanent denaturation of the keratin (and other proteins) present in hair, so I'm not 100% sure as to how it goes back. I guess the reverse also applies regarding curling straight hair with curling irons.

Lol whenever my sister straightens her hair I always start thinking of this. XD

[alondouek]

I'm sorry, this might deviate the thread from its intended purpose for a moment, but this is something I've been wondering for a while now.

How come when you straighten curly hair with a hair straightener, the hair regains its curl when it gets wet? The heat should cause the permanent denaturation of the keratin (and other proteins) present in hair, so I'm not 100% sure as to how it goes back. I guess the reverse also applies regarding curling straight hair with curling irons.

Lol whenever my sister straightens her hair I always start thinking of this. XD

I'd have to hazard a guess (because I no naught about hair-straightening), but I'd say it was because the exposure of the hair to heat is quick and short-lasting enough to only break the disulfide bonds in the hair (which cause the curling) without sufficiently denaturing the keratin structures.

Hence, exposure to water changes the regular environment of the hair, inducing it to return to its original state (as no permanent change by denaturation has occurred).

[alchemy]

I'm sorry, this might deviate the thread from its intended purpose for a moment, but this is something I've been wondering for a while now.

How come when you straighten curly hair with a hair straightener, the hair regains its curl when it gets wet? The heat should cause the permanent denaturation of the keratin (and other proteins) present in hair, so I'm not 100% sure as to how it goes back. I guess the reverse also applies regarding curling straight hair with curling irons.

Lol whenever my sister straightens her hair I always start thinking of this. XD

Funnily enough, I got this question as part of my holiday homework. I'm not sure if this is correct but this is what I wrote:
"Hair is composed of the protein Keratin which is an alpha helix. It is able to stretch and its hydrogen bonds can be broken when heat is applied, but it eventually returns to its original shape as hydrogen bonds form over time."
Would water (H₂O) help in these hydrogen bonds in forming?

[MM1]

Funnily enough, I got this question as part of my holiday homework. I'm not sure if this is correct but this is what I wrote:
"Hair is composed of the protein Keratin which is an alpha helix. It is able to stretch and its hydrogen bonds can be broken when heat is applied, but it eventually returns to its original shape as hydrogen bonds form over time."
Would water (H₂O) help in these hydrogen bonds in forming?

I'm probably incorrect here, but doesn't water, when added, break bonds?

[alondouek]

I'm probably incorrect here, but doesn't water, when added, break bonds?

It can act as a solvent by breaking bonds, but it can also induce formation of new bonds depending on the gaseous H2O saturation of the environment that the hair is in. (That's an answer to your question too, alchemy!)

[nhmn0301]

Funnily enough, I got this question as part of my holiday homework. I'm not sure if this is correct but this is what I wrote:
"Hair is composed of the protein Keratin which is an alpha helix. It is able to stretch and its hydrogen bonds can be broken when heat is applied, but it eventually returns to its original shape as hydrogen bonds form over time."
Would water (H₂O) help in these hydrogen bonds in forming?

In biology, Hydrogen bond is considered to be a quite weak bond, it can easily break and reform (that's why water is cohesive). Hydrogen bond is made from when an H+ attracts an N,O, or F. Hence,  in water, when H+ attracts to OH-, it will create a water molecule. In Keratin, if you look at the alpha helix structure, it's quite flexible, easily stretch since H-bond is weak but easily rejoin since the H+ and O- will try to attract to each other, making the bond cohesive.
Another reason is, keratin contains cysteine amino acids, these amino acid contains Sulfur element. if 2 cysteines meet, they can build a disulphide link between them. Imo, if you add water, then these H+ and O- along the chain will not attract to each other anymore ( or less attract) since there are more H+ and OH- from the added water molecules, therefore, it will break the bond.
These are just my knowledge and might contain some errors , still, hope this makes sense.

[MM1]

I know this varies for every school, but how many SACS are there in Biol generally?

[vox nihili]

I know this varies for every school, but how many SACS are there in Biol generally?

We had 8 each year

[alchemy]

I know this varies for every school, but how many SACS are there in Biol generally?

Stuff have been taken out of the study design, so the word is we will have 6 sacs over the course of this year. However, in class, the teacher said we'll be having 10 

[Yacoubb]

We had 10 SACs on:
• Movement across the membrane
• Enzymes
• Photosynthesis/Cellular Respiration
• Detecting and Responding
• Immunity
• Mitosis/Meiosis
• Monohybrid/Dihybrid crosses
• DNA manipulation
• Evolutionary relationships
• Human Intervention in Evolution

[Jazza12396]

I'm a bit confused with the wording of the stages of Photosynthesis in the textbook. Could someone please explain the stages to me!

[Yacoubb]

I'm a bit confused with the wording of the stages of Photosynthesis in the textbook. Could someone please explain the stages to me!

Light-Dependent Stage:
- Chlorophyll molecules absorb light energy.
- Electrons in the chlorophyll molecules become excited; as a result, the excited electrons enter the electron transport chain.
- To replenish the electrons lost from chlorophyll molecules, water is split to form H+ ions and oxygen gas (a by-product).
- NADPH is formed from NADP+ and H+ ions.
- ATP is formed from ADP + Pi (i.e. Adenosine Di-phosphate + Inorganic phosphate).

Light-Independent Stage:
- Carbon dioxide reacts with H+ ions (provided by NADPH) to form glucose. ATP provides the energy needed to synthesise glucose.
- After the electrons travel through the electron transport chain, they are collected by oxygen atoms, which then become O2- ions. O2- ions then react with excess H+ to form water (a by-product).

[Jazza12396]

Thank you

[nerdmmb]

Is it possible for a monosaccharide to have one carbon atom --> CH₂0