VCE Biology Question Thread

[tiff_tiff]

Animal cells do not have cell walls. They have an outer membrane (boundary) which is known as the phospholipid bilayer. Plant cells have a phospholipid bilayer, as well as a cell wall on top of it. The cell wall is not another phospholipid bilayer, though. It is composed of cellulose and it a rigid boundary which further protects and shapes plant cells. No eukaryotic cells have cell walls besides plant cells, some fungal and protists, but there are also some prokaryotic cells that also have them such as some bacteria.

Hope it clarified things!

Fungal cells and some protists have cell walls.

thank u!!!!!

[tiff_tiff]

1) Cell division uses ATP??
in the book it says
kinetochores contain molecular motor proteins, including kinesins and cytoplasmic dynein (see Figures 5.18 and 5.19), which use energy from ATP hydrolysis to do the work of moving the chromosomes along the microtu- bules.
how do chromosomes move along the microtubules???
i thought microtubules just connect to the kinetochores and are pulled to the centrosomes

2) what is independant assortment in meiosis?

[grannysmith]

Anything that otherwise wouldn't move/occur requires energy. Cell division is one such example.

You don't need to know this, but microtubules are constituents of  the cytoskeleton and assists in what is known as cytoplasmic streaming. Recalling from unit 1, this essentially refers to the facilitated movement of the cytoplasm. Given this, it's reasonable that the separation of chromatids during cell division is helped by microtubules.

[mahler004]

It comes from activated phosphorylated glucose molecules. Does this mean that an inorganic phosphate group is attached to glucose before it can bind with another glucose monomer to form maltose?

The phosphate comes from ATP (or an NTP - nucleotide triphosphate,) but yes.

[cosine]

Can someone explain to me the process of cellular respiration in simple terms, and how exactly it is the opposite of photosynthesis? Also this is a bad question but when plants photosynthesise glucose, do the glucose molecules then go through cellular respiration?

[TheAspiringDoc]

Can someone explain to me the process of cellular respiration in simple terms, and how exactly it is the opposite of photosynthesis? Also this is a bad question but when plants photosynthesise glucose, do the glucose molecules then go through cellular respiration?

Ok, to start off: cellular respiration is the process by which cells break down sugars to create useable energy sources. It takes place in the mitochondria (hence them sometimes being referred to as the 'powerhouse' of the cell) and needs oxygen to occur.
Represented as an equation, cellular respiration looks like this:
C6H12O6 + 6O2 -> 6O2 + 6CO2 + Energy (ATP)
This can be resented in a worded equation as:
Glucose + Water -> Oxygen + Carbon Dioxide + Energy (in the form of ATP)
ATP or adenosine triphosphate has three phosphate groups attached and when it releases one, it also releases energy and the remaining molecule is now called ADP or adenosine diphosphate.

For your second question (cellular respiration = photosynthesis?) my answer is that they are both the same on a chemical level, and are simply reversed ( as photosynthesis is represented as: 6O2 + 6CO2 ----> (using sunlight energy) C6H12O6 + 6O2). also photosynthesis are also rather opposite in that they occur in different organelles (photosynthesis occurs in the chloroplasts), a catalyst is needed for photosynthesis (chlorophyll) but not for cellular respiration, photosynthesis is anabolic, whereas cellular respiration is catabolic, they (as already shown in the chemical equations) do opposite things with oxygen and carbon dioxide; photosynthesis turns carbon dioxide into oxygen and  cellular respiration turns oxygen into carbon dioxide.
So theoretically, if we put an organism which uses cellular respiration (all animal cells do) into a sealed, glass jar with a plant that photosynthesises (most do, although onion, for example, doesn't) then they could actually live together if also equipped with water sunlight food, ect.   how cool is that?!
However, they are not exactly opposite, because although they are reversed chemical equations, they are not reversed processes (for example, at no point does cellular respiration require sunlight for an energy source). 

And for your third question, the glucose produced by photosynthesis is sometimes used for cellular respiration, although it may also be converted to sucrose and then transported around the plant for other uses, i.e. sweetening the fruit of the plant or it may be stored as starch for later needs (including cellular respiration)

Hope I helped
tl;dr no, just read it, too hard to exlain any shorter

[cosine]

Two questions:

Do we need to know how many of each product is produced for one molecule of glucose in aerobic respiration?

Aerobic respiration is the breakdown of glucose in the presence of oxygen. In which stage, out of the 3, is oxygen actually involved in?

[Jay.C]

Aerobic respiration is the breakdown of glucose in the presence of oxygen. In which stage, out of the 3, is oxygen actually involved in?

Oxygen is used up in Electron transport. The hydrogen ions carried by NADH and FADH are combined with oxygen to synthesise water.

[Rishi97]

Two questions:

Do we need to know how many of each product is produced for one molecule of glucose in aerobic respiration?

Yes there are always questions on that even if it is MC

[grannysmith]

Oxygen is used up in Electron transport. The hydrogen ions carried by NADH and FADH are combined with oxygen to synthesise water.

Yep, oxygen is essentially the terminal electron acceptor.

Yes there are always questions on that even if it is MC

This is true, although you aren't required to know the quantity of each product produced except ATP. So just know that 4 ATP produced in glycolysis but a net of 2 ATP, 2 ATP in Krebs cycle, 32-34 ATP in ETC.

[cosine]

Yep, oxygen is essentially the terminal electron acceptor.
This is true, although you aren't required to know the quantity of each product produced except ATP. So just know that 4 ATP produced in glycolysis but a net of 2 ATP, 2 ATP in Krebs cycle, 32-34 ATP in ETC.

I thought it was only 2 ATP produced during glycolysis?

[wobblywobbly]

I thought it was only 2 ATP produced during glycolysis?

(Stealing this metaphor from Crashcourse), you use two ATP in glycolysis as an investment to make four ATP (so two is made overall). Though I'm quite sure that 2 ATP would be a sufficient exam answer (but if your teachers are pedantic in your SACs, that might be a different story)

[tiff_tiff]

can someone please list the organelles with double membrane?

when i google it different websites say different things....

I know mitochondria and chloroplasts do have a double membrane

what about the nucleus, vacuole, ER, golgi apparatus, lysosomes and ribosomes?



Also: do plants cells NOT have centrioles?

Thank u in advance ~

[Jay.C]

can someone please list the organelles with double membrane?

when i google it different websites say different things....

I know mitochondria and chloroplasts do have a double membrane

what about the nucleus, vacuole, ER, golgi apparatus, lysosomes and ribosomes?

The organelles that have double membranes are; Mitochondria, Chloroplasts, Endoplasmic Reticulum, Golgi Body, and Nucleus.
Vacuoles have a singular membrane, ribosomes can be free and without a membrane or can be attached to the ER and have a singular membrane and lysosomes have singular membranes.
 

[cosine]

The organelles that have double membranes are; Mitochondria, Chloroplasts, Endoplasmic Reticulum, Golgi Body, and Nucleus.
Vacuoles have a singular membrane, ribosomes can be free and without a membrane or can be attached to the ER and have a singular membrane and lysosomes have singular membranes.
 

How does the nucleus have a double membrane?