VCE Biology Question Thread

[Scooby]

Thank you I just like to know more as it helps me understand better and makes it easier to grasp new concepts.

Fair enough, I understand that completely. Just make sure it's not something you write on the exam!

[nerdmmb]

Do sodium ions move across the cell membrane by active transport?

[grannysmith]

Do sodium ions move across the cell membrane by active transport?

Depends what kind of situation I suppose. It can either be facilitated or active transport depending on the situation. For example, during an action potential, voltage gated sodium channels open and sodium ions subsequently diffuse into the neuron by facilitated diffusion. However, once the action potential has passed, Na+/K+ pumps actively transport such ions to restore the resting potential.

[winchesteraddict]

Do sodium ions move across the cell membrane by active transport?

Facilitated Diffusion- A carrier molecule is required to move substances such as sodium ions across a membrane, down the concentration gradient via specific integral proteins.
But as grannysmith said it can also be active transport in certain situations.

[Spxtcs]

Hey guys, in my text book there's a section on apoptosis however in the 2014 study design it mentions nothing about apoptosis.  I was just wondering if I still needed to learn about apoptosis or just things in general whereas it mentions it in the text book but not I'm the study design. Thanks!

From my experience and the 2014 study design, you do need to know about it, including what it is, examples of it (e.g. during fetal development to prevent webbing between digits like fingers and toes) and the different types of pathways (intrinsic and extrinsic) that lead to it. This involves signal transduction so I recommend looking at both signal transduction and apoptosis together since it will help in understanding how apoptosis works. A basic definition of apoptosis is 'programmed cell death' and this could come up in SACs, but always know a bit more detail so that you're well prepared for the exam.
What helped me was looking up apoptosis animations online (sites like McGraw and WEHI do really good Biology animations) but be careful because some of these animations go into too much detail since they're usually university resources.

EDIT: here's a cool video http://www.wehi.edu.au/wehi-tv/apoptosis-and-signal-transduction. Note how the cell 'blebs' (does not burst, but becomes smaller blobs instead)

[Scooby]

Hey guys, in my text book there's a section on apoptosis however in the 2014 study design it mentions nothing about apoptosis.  I was just wondering if I still needed to learn about apoptosis or just things in general whereas it mentions it in the text book but not I'm the study design. Thanks!

Check U3 AOS 2

"• coordination and regulation at the cellular level:
– apoptosis (regulated cell death) as an example of a cellular response to specific signals"

In general, just be wary that there is some content you'll need to know that isn't in the study design. Using past exams is a better guide to what you have to know most of the time

[Jay.C]

Just wondering beside protein packaging, transport, import and export what other molecules we need to know in terms of there packaging, transport, import and export?

[nerdmmb]

Just wondering beside protein packaging, transport, import and export what other molecules we need to know in terms of there packaging, transport, import and export?

This will be covered later on but you need to know the process by which molecules are imported/exported - endocytosis, exocytosis which are basically two forms of bulk transport.

You'll also need to know how hormones, neurotransmitters, which are also proteins, enter and leave a cell- this occurs with the help of vesicles. But other than that- you won't need to know about the packaging, transport of other molecules in the same depth as you would need to know about proteins. You'll come across these later on but you can have a look at the study design for some clarification.
Hope that helps.

[doher109]

Hi All

Why doesn't starch want cross linkages between other starch molecules??
(Like, why does it need to present itself in a helix so that no hydrogen bonds can form between?)

 Thankss!

Well to summarise we have 3 carbohydrates to consider in VCE (glycogen/starch/cellulose).

Cellulose does form cross linkages due to it's structure (this allows it to be strong and used as a structural building block essentially.

Starch however isn't used for building. It is for energy storage. If it were in a cross linked structure such as cellulose the SA provided wouldn't be sufficient for energy conversion to occur.

In short (and how you would answer on an exam)

• Starch is an energy storage polysachharide molecule, it is not a structural carbohydrate like cellulose
• Due to the molecular structure of starch it is not able to form crosslinks with other starch molecules. This ensures the molecules of starch have a high surface area to provide an efficient conversion to glucose for respiration 

You don't need to understand the chemistry of it in Biology, if you'd like i can explain though.

Hope it helps 
[/list]

[plants]

To what detail do we have to know the structures of polysaccharides such as cellulose, starch and gylcogen? In my summaries I have only written their function, and whether they're made from alpha/beta glucose. Is this too much? Too little?

Thanks,

[doher109]

Very little

To what detail do we have to know the structures of polysaccharides such as cellulose, starch and gylcogen? In my summaries I have only written their function, and whether they're made from alpha/beta glucose. Is this too much? Too little?

Thanks,

Very little.

VCE Biology is all to with 'structure and function'.

Here is all you need to know.

Starch - energy storage in plants and is a highly branched macro molecule (this creates a high SA for the conversion to glucose)
Cellulose - structural support in plants. Is able to crosslink to adjacent Cellulose molecules to form a very strong structure.
Glycogen - energy storage in humans, highly branched macro molecule.

I've included a copy of some notes i found sufficient. As i did VCE Chemistry as well i was guilty of going to far into the structure of compounds etc. All this does is annoy assessors and waste time.

If you'd like look at the molecular structures online but don't even bother remembering them.

PS ignore Chitin it will likely never appear on an exam, and if it does information will be given.

[nerdmmb]

Just like to add on to what doher109 said,
It's VERY tempting to add extra information in your answer especially because in the beginning, it can get pretty confusing as to how in depth you should get with your answer.

But just have a look at the marks allocated for the question and answer the question according to that. Unfortunately, sometimes that extra bit of information you give can even cost you marks, which in my case, I lost a lot of marks for it and it often pissed my teacher off.

[plants]

Thanks for helping out.
Also regarding apoptosis a user stated:

From my experience and the 2014 study design, you do need to know about it, including what it is, examples of it (e.g. during fetal development to prevent webbing between digits like fingers and toes) and the different types of pathways (intrinsic and extrinsic) that lead to it. This involves signal transduction so I recommend looking at both signal transduction and apoptosis together since it will help in understanding how apoptosis works. A basic definition of apoptosis is 'programmed cell death' and this could come up in SACs, but always know a bit more detail so that you're well prepared for the exam.

There seems to be no specific use the term intrinsic/extrinsic pathways that lead to apoptosis in the NOB textbook. Is this equivalent to signals from inside the cell and signals from out side the cell, respectively?

[grannysmith]

That's correct. Because VCAA has shifted the focus towards signal transduction pathways, we only need to know about the extrinsic pathway ie a ' death' ligand binding to a 'death' receptor, triggering a cascade of intracellular events including the activation of (caspase) enzymes, breakdown of cellular contents into apoptotic bodies, which are then digested by phagocytes. This leads to cell death.
I daresay, that's probably more than you need to know.

[vox nihili]

That's correct. Because VCAA has shifted the focus towards signal transduction pathways, we only need to know about the extrinsic pathway ie a ' death' ligand binding to a 'death' receptor, triggering a cascade of intracellular events including the activation of (caspase) enzymes, breakdown of cellular contents into apoptotic bodies, which are then digested by phagocytes. This leads to cell death.
I daresay, that's probably more than you need to know.

It's more than I know