HSC Biology Question Thread

[Mathew587]

Hey guys dotpoint from SFBH what are the distinguish features of every pathogen - e.g. prion's are the only pathogen with no genetic information at all.
Also, what are bigger fungi or macroparasites?

marcoparasites man...
they refer to intestinal worms etc while fungi is smthn like thrush

[angelahchan]

Hi, could someone please help explain the answers for Q19 and 20 for the 2014 paper?
https://www.boardofstudies.nsw.edu.au/hsc_exams/2014/pdf_doc/2014-hsc-biology.pdf

[Opengangs]

Hey guys dotpoint from SFBH what are the distinguish features of every pathogen - e.g. prion's are the only pathogen with no genetic information at all.
Also, what are bigger fungi or macroparasites?

Prions are non-cellular and they are proteins that can fold abnormally. They lack genetic material, such as DNA or RNA.
Viruses are non-cellular and they are made of the genetic material of DNA or RNA, surrounded by an enveloped by a protein coat. The complete package (virus + protein coating) is called a virion. Viruses require a host cell to survive, and reproduce by injecting itself into the host cell. The host cell contains genetic material that then is used to make new viruses, splitting the host cell and exposing the virus.
Bacteria are prokaryotic (meaning they are single celled and do not contain a membrane bound organelle), and they reproduce through a process called binary fission. The bacterial cell splits into two halves, which then produces two new cells that have the capacity to grow to the size of the parent cell. A bacterium is living.
Fungi can be uni or multicellular, and they are eukaryotic organisms. They have a cell wall, composed mainly of chitin. Fungi reproduce by budding, spores, or fragmentation. They are living and motile.
Protozoan are single celled organisms. They are motile, and usually require a vector for transmission.
Macro parasites are the largest pathogens, they can be seen by the naked eye.

[sidzeman]

Prions are non-cellular and they are proteins that can fold abnormally. They lack genetic material, such as DNA or RNA.
Viruses are non-cellular and they are made of the genetic material of DNA or RNA, surrounded by an enveloped by a protein coat. The complete package (virus + protein coating) is called a virion. Viruses require a host cell to survive, and reproduce by injecting itself into the host cell. The host cell contains genetic material that then is used to make new viruses, splitting the host cell and exposing the virus.
Bacteria are prokaryotic (meaning they are single celled and do not contain a membrane bound organelle), and they reproduce through a process called binary fission. The bacterial cell splits into two halves, which then produces two new cells that have the capacity to grow to the size of the parent cell. A bacterium is living.
Fungi can be uni or multicellular, and they are eukaryotic organisms. They have a cell wall, composed mainly of chitin. Fungi reproduce by budding, spores, or fragmentation. They are living and motile.
Protozoan are single celled organisms. They are motile, and usually require a vector for transmission.
Macro parasites are the largest pathogens, they can be seen by the naked eye.

Thank you so much! Could someone also explain the lymph system in the 2nd line of defence for me please
Also, do we have to know the different types of phagocytes e.g. neutrophils, macrophages

[pikachu975]

Thank you so much! Could someone also explain the lymph system in the 2nd line of defence for me please
Also, do we have to know the different types of phagocytes e.g. neutrophils, macrophages

Lymph system has lymph nodes which store lymphocytes.

Lipids are also carried in chylomicrons in the lymph system.

Blood can leak into the lymph system and pass by lymph nodes and if antigens are detected by the lymphocytes then an immune response is started.

I think macrophages can bring debris from consuming a pathogen to the lymph nodes to initiate an immune response.

Also they're called LYMPHocytes because they're in the LYMPH system too!

[archie33]

Could someone quickly give a rundown about all the action potential stuff? (Part of Option topic: Communications)
Thanks!

[sophiegmaher]

For the communication dot point "explain that the response to a stimulus involves a: stimulus, receptor, messenger, effector, response", if we were to draw a diagram for this would it be the same as the negative feedback model? And, for the negative feedback model, do we need to draw a diamond diagram, so the stimulus could be an increase in temperature and the eventual response sweating, but then do we have to show the body ensuring it isn't cooling down too much, so counteracting this stimulus of the body subsequently cooling down...? (the diagram in Naomi's notes)

[sophiegmaher]

Also, what's the difference between photopsin and iodopsin? The text book says one and some youtube videos say the other, but I think they're pretty much the same as they're both describing the photosensitive pigment in cone cells?

[zalihall]

Hey, I've been going through some past papers and i'm so stuck on what is actually required for this question (method? variables? equipment?), any ideas would be greatly appreciated!
"Plant breeders have developed a new variety  of terrestrial plant which has one structure   
that   appears to assist in water conservation in hot, dry environments.
Design a first-hand   investigation the plant breeder could use to determine of this structure   
assists in   water conservation." (4 Marks)

   

[liya1234]

Does someone have a simple definition for recombinant DNA? i'm struggling to understand what exactly it encompasses, is it just DNA which has been genetically altered in some way? Thanks!

[liya1234]

Hi, could someone please help explain the answers for Q19 and 20 for the 2014 paper?
https://www.boardofstudies.nsw.edu.au/hsc_exams/2014/pdf_doc/2014-hsc-biology.pdf

Q19 would be A as this fits the information given the most i.e. the fish have different enzymes that do the same thing but have optimum efficiency at different temperature. this allows to fish to continue normal metabolic processes at a larger range of temperatures (as seen in the graph). however, as this only works when there is a gradual temp change (rather than sudden), we can conclude that it takes time for a different gene producing the enzyme that works in a higher temp to be switched on. thus, if there is a gradual temp change, the fish will be able to survive as different genes can be slowly switched on, but if there is a sudden temp change, the needed genes won't switch on fast enough to produce enough enzymes, decreasing metabolic efficiency

for Q20, I would say B just based on process of elimination. It's not A because substrates are not involved in any way in this case. It's not C as, in this case, the wide range of temperature over which the fish can survive is demonstrated. It's not D as these different enzymes show that metabolic efficiency can be maintained even with changing temperature. Thus, B fits best

[adelaidecruz]

Does someone have a simple definition for recombinant DNA? i'm struggling to understand what exactly it encompasses, is it just DNA which has been genetically altered in some way? Thanks!

Essentially, recombinant DNA is an artificially-made DNA strand formed by the combination of two or more gene sequences.

[adelaidecruz]

Quick question: do we need to know about 2 kinds of artificial blood? Or is 1 enough?

[adelaidecruz]

Could someone quickly give a rundown about all the action potential stuff? (Part of Option topic: Communications)
Thanks!

Hey!

So action potential is the change in electrical potential (or, more explicitly, change in the charge of the neurone's membrane) associated with the passage of an impulse along a neurone. This charge is maintained by a pump that keeps Na+ out and K+ in.

At resting potential, the cell membranes are polarised (unequal charges on either side of the membrane) -- its inside is (-ve) and its outside is (+ve).

At depolarisation, nerve cells are stimulated due to the transient reversal in the membrane potential. Na+ ions move in making the inside (+ve). Consequently, K+ ions move out, creating a wave of (-ve) charge outside the membrane. This electrical wave travels down the axon --> axon terminal.
When an electrical impulse reaches the axon terminals, neurotransmitters (chemical substances) are released which passes across the synapse and to the dendrites of the next cell, causing a new electrical impulse to start in subsequent neurones.

Now some stimuli do not reach said action potential if the stimulus is not 'intense' enough during the refraction period to reach the minimum threshold (minimum amount of voltage needed at which depolarisation becomes "unstoppable") that is required for an impulse to be produced, hence no signal is transferred at all.

[Opengangs]

Quick question: do we need to know about 2 kinds of artificial blood? Or is 1 enough?

Considering the difficulties of the exams this year, I think it's better to know about both kinds: perfluorocarbons, and haemoglobin-based oxygen carriers.
I would also recommend outlining the disadvantages and advantages for each.