VCE Biology Question Thread

[The Usual Student]

Hey,

So basically, your textbook is trying to say that when the temperature of water decreases (example -12 Celsius), the volume of the water seems to decrease, as the molecules are moving slower (taking up less space) and causing the volume to shrink. However, when the water is heated, the molecules are moving at a much faster rate, and will take up more space causing the material to seem a little more larger.

I have attached a picture at the bottom, hopefully that helps you. 

ah that makes sense
so molecule movement is the movement of the actual water molecules and they move more obviously when the temperature increases, meaning they would expand and take up more space when heated? that makes sense man!
thanks!

[geminii]

I'm reading ahead for 3/4 Bio before school starts and I came across this question:

"If an amino acid is involved in the formation of a sulfur bond, what can you conclude about the molecular formula of that amino acid?"

I have no idea what this means, if someone could help explain it then that would be great!

[cosine]

I'm reading ahead for 3/4 Bio before school starts and I came across this question:

"If an amino acid is involved in the formation of a sulfur bond, what can you conclude about the molecular formula of that amino acid?"

I have no idea what this means, if someone could help explain it then that would be great!

Well you know how each amino acid is composed of Hydrogen, Nutrigen, Oxygen and Carbon, well there's one amino acid which contains Sulfur atoms in its R group chain. So if this amino acid par takes in Sulfur bonds, then it must have a Sulfur atom in its R group side chain!

[sunshine98]

I'm reading ahead for 3/4 Bio before school starts and I came across this question:

"If an amino acid is involved in the formation of a sulfur bond, what can you conclude about the molecular formula of that amino acid?"

I have no idea what this means, if someone could help explain it then that would be great!

Afaik when their is sulfur involved in a bond in a protein it is a S-S bond meaning its a sulfur bonding with another sulfur. Hence, you would say that the amino acid in question would contain a sulfur (or the molecular formula would include sulfur)
Hope this helps 

[Callum@1373]

I'm reading ahead for 3/4 Bio before school starts and I came across this question:

"If an amino acid is involved in the formation of a sulfur bond, what can you conclude about the molecular formula of that amino acid?"

I have no idea what this means, if someone could help explain it then that would be great!

cysteine and methionine are the only amino acids that contain a sulfur atom, but only cysteine forms sulfur bonds so the molecular formula would be the formula for cysteine.

[sunshine98]

cysteine and methionine are the only amino acids that contain a sulfur atom, but only cysteine forms sulfur bonds so the molecular formula would be the formula for cysteine.

Just adding you don't actually need to know about specific amino acids for bio , but its great to know nonetheless

[geminii]

I'm reading ahead for 3/4 Bio before school starts and I came across this question:

"If an amino acid is involved in the formation of a sulfur bond, what can you conclude about the molecular formula of that amino acid?"

I have no idea what this means, if someone could help explain it then that would be great!

Ah I see, thanks so much!

Just adding you don't actually need to know about specific amino acids for bio , but its great to know nonetheless

That's what I thought as well

Afaik when their is sulfur involved in a bond in a protein it is a S-S bond meaning its a sulfur bonding with another sulfur. Hence, you would say that the amino acid in question would contain a sulfur (or the molecular formula would include sulfur)
Hope this helps 

Thanks!

I also have another few questions I came across that I don't quite understand...

1. What is a characteristic of fats that makes them energy dense?
(I wrote that they are hydrophobic, but I don't know why being hydrophobic makes fats energy dense)

2. During an experiment, you analyse a compound that has a chemical composition of carbon, hydrogen and oxygen in the ratio of 1:2:1 and a six-sided molecular shape. What predictions would you make with regard to classification of the compound?

3. How many water molecules would be required to completely hydrolyse a carbohydrate polymer that contained 100 monomers? (I know what hydrolysis is but I don't know how to go about solving the problem).

Thanks again!

[sunshine98]

I also have another few questions I came across that I don't quite understand...

1. What is a characteristic of fats that makes them energy dense?
(I wrote that they are hydrophobic, but I don't know why being hydrophobic makes fats energy dense)

2. During an experiment, you analyse a compound that has a chemical composition of carbon, hydrogen and oxygen in the ratio of 1:2:1 and a six-sided molecular shape. What predictions would you make with regard to classification of the compound?

3. How many water molecules would be required to completely hydrolyse a carbohydrate polymer that contained 100 monomers? (I know what hydrolysis is but I don't know how to go about solving the problem).

Thanks again!

1) They have more C-H bonds that can be broken for energy
2) As soon as you see only  C, H, O you can narrow down your options to  carbohydrates or lipids. The six-sidedness clarifies that its a carbohydrate as well as the fact that its in the 1:2:1 ratio. The ratio is something  you should know about carbohydrates or you may have learnt that the empirical formula is this- CnH2nOn ( glucose as an example which is C6H12O6 where n=6)
3) you can think of it as one water molecule to each bond. When u think about it the number of bonds is always one less than the number of monomers (try it with smaller numbers , a polymer with 10 monomers has 9 bonds hence 9 water molecules). So you would need 99 water molecules

[geminii]

1) They have more C-H bonds that can be broken for energy
2) As soon as you see only  C, H, O you can narrow down your options to  carbohydrates or lipids. The six-sidedness clarifies that its a carbohydrate as well as the fact that its in the 1:2:1 ratio. The ratio is something  you should know about carbohydrates or you may have learnt that the empirical formula is this- CnH2nOn ( glucose as an example which is C6H12O6 where n=6)
3) you can think of it as one water molecule to each bond. When u think about it the number of bonds is always one less than the number of monomers (try it with smaller numbers , a polymer with 10 monomers has 9 bonds hence 9 water molecules). So you would need 99 water molecules

Awesome, thank you! For question 1, is that because they are hydrophobic, or just because they are fats and has nothing to do with the fact they are hydrophobic? And for question 2, would I just write that it's a glucose molecule or would I need to elaborate on anything?

[sunshine98]

Awesome, thank you! For question 1, is that because they are hydrophobic, or just because they are fats and has nothing to do with the fact they are hydrophobic? And for question 2, would I just write that it's a glucose molecule or would I need to elaborate on anything?

Yh as far as I know  it doesn't have to do with the fact that the hydrophobic. That they are hydrophobic arises from their non polar structure. That it has more energy comes from the fact that it has more C-H bonds  which increases the amount of energy.
For question two I would explain what I've said above, how the ratio and atoms involved and even the structure hints at a glucose molecule. And the amount of explanation you provide obvs has to do with the number of marks the question is worth so you can figure that out accordingly.

[vox nihili]

Ah I see, thanks so much!

That's what I thought as well

Thanks!

I also have another few questions I came across that I don't quite understand...

1. What is a characteristic of fats that makes them energy dense?
(I wrote that they are hydrophobic, but I don't know why being hydrophobic makes fats energy dense)

2. During an experiment, you analyse a compound that has a chemical composition of carbon, hydrogen and oxygen in the ratio of 1:2:1 and a six-sided molecular shape. What predictions would you make with regard to classification of the compound?

3. How many water molecules would be required to completely hydrolyse a carbohydrate polymer that contained 100 monomers? (I know what hydrolysis is but I don't know how to go about solving the problem).

Thanks again!

1. Like sunshine said, nothing to do with hydrophobicity. Has to do with the bonds involved in fats and lipids. They have lots of high energy C-H bonds, more so than proteins and carbohydrates (which have about the same amount of energy density; whereas lipids are twice as dense)

2. They're hinting at glucose, or more broadly a hexose. The ratio is consistent with a monosaccharide and six-sided indicates that it's a hexose. A lipid wouldn't have the same six-sided shape

3. What sunshine said

[robertsona12]

Some one Please help with this Question!!

During an experiment, you analyse a compound that has a chemical composition of carbon, hydrogen and oxygen in the ratio of 1:2:1 and a six sided molecular shape. What Predictions would you make with regard to classification of the compound?

Cheers, 

[Biology24123]

It would be a carbohydrate as they have those elements in 1:2:1 ratio and the monomers (glucose) are six sided molecules

[vox nihili]

Some one Please help with this Question!!

During an experiment, you analyse a compound that has a chemical composition of carbon, hydrogen and oxygen in the ratio of 1:2:1 and a six sided molecular shape. What Predictions would you make with regard to classification of the compound?

Cheers, 

Remember to have a quick scroll through the last through pages to make sure your question hasn't been answered; it was answered right above your post

[geminii]

Remember to have a quick scroll through the last through pages to make sure your question hasn't been answered; it was answered right above your post

Haha yeah I was just gonna say that