VCE Biology Question Thread

[melons]

I've heard that bacteria can carry out metabolic processes such as photosynthesis and respiration. But how can they do this without membrane bound organelles such chloroplasts and mitochondria?

[jessica666]

I've heard that bacteria can carry out metabolic processes such as photosynthesis and respiration. But how can they do this without membrane bound organelles such chloroplasts and mitochondria?

I think that bacteria carry out anaerobic respiration in the cytosol. Also, most bacteria do not photosynthesis, but some bacteria contain free floating chlorophyll in their cytosol which allows them to carry out photosynthesis

[melons]

Thank you.

[grannysmith]

Also, some bacteria can undergo oxidative phosphorylation in their plasma membrane, as they contain proteins embedded within.

[vox nihili]

I've heard that bacteria can carry out metabolic processes such as photosynthesis and respiration. But how can they do this without membrane bound organelles such chloroplasts and mitochondria?

Chloroplasts and mitochondria are actually bacteria. Early eukaryotic cells ate them both but didn't manage to digest them, so they went on doing photosynthesis and oxidative phosphorylation in our cells. Over time, they have become reduced to the bare bones. Explains part of the reason that antibiotics can make us quite sick—they hurt mitochondria.

Incidentally, blue green algae is actually just cyanobacteria (which can photosynthetise).

[walkec]

Hi everyone,
I have a question about transmission of nerve impulses. I know that when a signal is transmitted along the axon of a neuron it is a electrical signal, but when it reaches the synapse does the neurotransmitter convert the electrical signal to a chemical signal so it can cross the synapse to the receptors on the dendrite of the next neuron?

[jessica666]

Hi everyone,
I have a question about transmission of nerve impulses. I know that when a signal is transmitted along the axon of a neuron it is a electrical signal, but when it reaches the synapse does the neurotransmitter convert the electrical signal to a chemical signal so it can cross the synapse to the receptors on the dendrite of the next neuron?

Basically, when it reaches the synapse, it triggers the release of neurotransmitters (protein based) by exocytosis.The neurotransmitters cross the synapses and bind to receptors on the next neuron.

[melons]

Hi everyone,
I have a question about transmission of nerve impulses. I know that when a signal is transmitted along the axon of a neuron it is a electrical signal, but when it reaches the synapse does the neurotransmitter convert the electrical signal to a chemical signal so it can cross the synapse to the receptors on the dendrite of the next neuron?

Neurotransmitters are chemical molecules that are released by exocytosis at the axon terminals and travel across the synapse to the dendrites of the next neuron.

[Reus]

3 questions for you guys! 

• Why are clotting factors not normally present in plasma?
• Name one inherited disease caused by the absence of a clotting factor
• Name the clotting factor involved.

Thanks

[jessica666]

Is someone able to help me out with the inflammatory response?

I understand that mast cells release histamine which causes blood vessels to dilate, drawing more blood to the region and increasing heat, redness and swelling.

What I don't understand is how this actually kills the pathogen?

Thanks

[grannysmith]

It facilitates the process

[Reus]

Is someone able to help me out with the inflammatory response?

I understand that mast cells release histamine which causes blood vessels to dilate, drawing more blood to the region and increasing heat, redness and swelling.

What I don't understand is how this actually kills the pathogen?

Thanks

Exactly what grannysmith said, it literally makes the blood vessels more permeable and hence the phagocytic cells are easily transported to the damaged tissue.

[jessica666]

Thanks! So do both inflammation and phagocytosis usually occur in non-specific immune responses?

[Reus]

Thanks! So do both inflammation and phagocytosis usually occur in non-specific immune responses?

Yes, they are both subclassifications of the second line of defence (non-specific/innate).

[Scooby]

Is someone able to help me out with the inflammatory response?

I understand that mast cells release histamine which causes blood vessels to dilate, drawing more blood to the region and increasing heat, redness and swelling.

What I don't understand is how this actually kills the pathogen?

Thanks

Local dilation of capillaries --> blood flow through area is more rapid (which may cause erythema) --> phagocytes can be transported to area more rapidly and destroy

Release of histamine increases permeability of local capillaries --> phagocytes more rapidly able to diffuse out into the interstitial spaces. Plasma also leaks excessively from the capillaries and accumulates in the interstitial spaces (plasma leaks more rapidly from capillaries than it can be returned to circulation via the lymph vessels), which causes swelling