A level Biology: Post your doubts here!

[mohmed ahmed soliman]

It asks you to dilute the solution.If you remember there are two types of dilutions we've come across in paper 3.
Serial dilution and simple dilution.
Here they've given you that the total volume of the solution needs to be 50 cm^3.Do keep that in mind.
Make at least five concentrations.You could do serial dilution.
Draw a figure like you would have for paper 3.Add the concentrations and total volume for each.

i want notes for serial and simple dilution
please

 

[My Name]

i want notes for serial and simple dilution
please

Okay just remind me tomorrow if I don't give you today.

 

[My Name]

thanks for all ur help
i hope u continue ur success in higher studies

Welcome.I actually got this from the net only.I too need to revise the tongue part.
Ameen!

 

[My Name]

i want notes for bio informatics please

It is there in the new coursebook.
In the gene tech section.

 

[My Name]

50 to 100 taste receptor cells are for 5 tastes
5types of taste receptors but 50-100 cells in each taste bud

yes

 

[mohmed ahmed soliman]

Describe the structure of a myelinated sensory neurone. [7]
(b) Explain how an action potential is transmitted along a sensory neurone. [8]
[Total18

1 nucleus in cell body ;
2 (long) dendron ; R plural
3 (shorter) axon ;
4 many mitochondria (in cell body) ;
5 many RER/nissl’s granules, (in cell body) ;
6 synaptic knobs ;
7 detail of synaptic knob ;
8 (terminal) dendrites ;
9 Schwann cells ;
10 detail of myelin sheath ;
11 nodes of Ranvier ;
accept points on labelled diagram [7 max]
(b) 12 Na+ channels open ; A sodium channels
13 Na+ enter cell ; R enter membrane
14 inside becomes, less negative/positive/+40mV or membrane depolarised ;
15 Na+ channels close ; A sodium channels
16 K+ channels open ; A potassium channels
17 K+ move out (of cell) ; R of membrane
18 inside becomes negative or membrane repolarised ; A negative figure
max 5
19 local circuits/description ;
20 (myelin sheath/Schwann cells) insulate axon/does not allow movement of ions ;
21 action potential/depolarisation, only at nodes (of Ranvier)/gaps ;
22 saltatory conduction/AW ;
23 one-way transmission ;
24 AVP ; e.g. hyperpolarisation/refractory period

can anyone help me to integrate those marking points to make a proper answer

 

[mohmed ahmed soliman]

Okay just remind me tomorrow if I don't give you today.

ok dont forget

 

[mohmed ahmed soliman]

4 P700/P1, absorbs at 700(nm) ;
5 P680/P11, absorbs at 680(nm) ; what does this means

 

[My Name]

4 P700/P1, absorbs at 700(nm) ;
5 P680/P11, absorbs at 680(nm) ; what does this means

PS I and PS II are the two photosystems.
They both absorb light of different wavelength.
PS I aka PS 700 absorbs light of wavelength 700 nm.
Get it?

 

[My Name]

ok dont forget

In sha Allah yes.
I will find them and give you.Keep reminding me!

 

[My Name]

Describe the structure of a myelinated sensory neurone. [7]
(b) Explain how an action potential is transmitted along a sensory neurone. [8]
[Total18

1 nucleus in cell body ;
2 (long) dendron ; R plural
3 (shorter) axon ;
4 many mitochondria (in cell body) ;
5 many RER/nissl’s granules, (in cell body) ;
6 synaptic knobs ;
7 detail of synaptic knob ;
8 (terminal) dendrites ;
9 Schwann cells ;
10 detail of myelin sheath ;
11 nodes of Ranvier ;
accept points on labelled diagram [7 max]
(b) 12 Na+ channels open ; A sodium channels
13 Na+ enter cell ; R enter membrane
14 inside becomes, less negative/positive/+40mV or membrane depolarised ;
15 Na+ channels close ; A sodium channels
16 K+ channels open ; A potassium channels
17 K+ move out (of cell) ; R of membrane
18 inside becomes negative or membrane repolarised ; A negative figure
max 5
19 local circuits/description ;
20 (myelin sheath/Schwann cells) insulate axon/does not allow movement of ions ;
21 action potential/depolarisation, only at nodes (of Ranvier)/gaps ;
22 saltatory conduction/AW ;
23 one-way transmission ;
24 AVP ; e.g. hyperpolarisation/refractory period

can anyone help me to integrate those marking points to make a proper answer

I remember sharing P4 solved thread's link here.
I'm just gonna copy paste the thing since I actually found it helpful.I know the answer may seem so huge.But it's good incase you can't recall some points.
I hope this helps.

PART A

A sensory neuron has a long dendron and an axon which is often shorter than the dendron. Within the cytoplasm of an axon, all of the usual organelles such as endoplasmic reticulum, Golgi apparatus and mitochondria, are present. Large numbers of mitochondria are found at the tips of the terminal branches of the axon, together with many vesicles containing chemicals called transmitter substances.
The axon and dendron is insulated by the myelin sheath. The myelin sheath is made largely of lipid, together with some proteins, and is formed by a Schwann cell wrapping around the axon many times. This forms many layers of cell membrane surrounding the axon.
At intervals, there are gaps in the sheath between each Schwann cell, called nodes of Ranvier.

PART B

An action potential is generated in the sensory neuron, where an impulse reaches the neuron, leading to the opening of Na+ channels. This causes Na+ ions to move down their concentration gradient and into the neuron, increasing the potential difference of the cell from -70 mV to +40 mV. This is known as depolarization. Once the potential difference reaches +40 mV, an action potential is generated. The Na+ channels then close and the K+ channels open causing K+ ions to move out of the cell. This decreases the potential difference of the neuron (repolarisation) and continues even after the potential difference drops below -70 mV due to the opening of large number of K+ channels. This is known as hyperpolarisation. However, the cell regains its resting potential of -70 mV as the K+ channels close.
The action potential jumps from one node of Ranvier to the next. This is because this is the only place where the sodium ions can pass across the membrane, as the myelin sheath insulates the axon and hence prevents the movement of ions across it. This is called saltatory conduction. The period between one action potential and another, is known as refractory period.

 

[My Name]

Describe the structure of a myelinated sensory neurone. [7]
(b) Explain how an action potential is transmitted along a sensory neurone. [8]
[Total18

1 nucleus in cell body ;
2 (long) dendron ; R plural
3 (shorter) axon ;
4 many mitochondria (in cell body) ;
5 many RER/nissl’s granules, (in cell body) ;
6 synaptic knobs ;
7 detail of synaptic knob ;
8 (terminal) dendrites ;
9 Schwann cells ;
10 detail of myelin sheath ;
11 nodes of Ranvier ;
accept points on labelled diagram [7 max]
(b) 12 Na+ channels open ; A sodium channels
13 Na+ enter cell ; R enter membrane
14 inside becomes, less negative/positive/+40mV or membrane depolarised ;
15 Na+ channels close ; A sodium channels
16 K+ channels open ; A potassium channels
17 K+ move out (of cell) ; R of membrane
18 inside becomes negative or membrane repolarised ; A negative figure
max 5
19 local circuits/description ;
20 (myelin sheath/Schwann cells) insulate axon/does not allow movement of ions ;
21 action potential/depolarisation, only at nodes (of Ranvier)/gaps ;
22 saltatory conduction/AW ;
23 one-way transmission ;
24 AVP ; e.g. hyperpolarisation/refractory period

can anyone help me to integrate those marking points to make a proper answer

Na⁺ ion channels open, Na⁺ ions enter the cell, the inside becomes positive in other words depolarised. Na⁺ channels then close, K⁺ channels open, and K⁺ move out of the cell, the inside becomes negative or repolarised. Local circuits are built up. The myelin sheat insulates the axon so an action potential occurs only at the nodes of Ranvier. The action potential jumps from node to node, this is known as saltatory conduction. There is one-way transmission as the node behind the action potential is still in the refractory period.

This is a simpler and shorter version for part b.

 

[mohmed ahmed soliman]

I remember sharing P4 solved thread's link here.
I'm just gonna copy paste the thing since I actually found it helpful.I know the answer may seem so huge.But it's good incase you can't recall some points.
I hope this helps.

PART A

A sensory neuron has a long dendron and an axon which is often shorter than the dendron. Within the cytoplasm of an axon, all of the usual organelles such as endoplasmic reticulum, Golgi apparatus and mitochondria, are present. Large numbers of mitochondria are found at the tips of the terminal branches of the axon, together with many vesicles containing chemicals called transmitter substances.
The axon and dendron is insulated by the myelin sheath. The myelin sheath is made largely of lipid, together with some proteins, and is formed by a Schwann cell wrapping around the axon many times. This forms many layers of cell membrane surrounding the axon.
At intervals, there are gaps in the sheath between each Schwann cell, called nodes of Ranvier.

PART B

An action potential is generated in the sensory neuron, where an impulse reaches the neuron, leading to the opening of Na+ channels. This causes Na+ ions to move down their concentration gradient and into the neuron, increasing the potential difference of the cell from -70 mV to +40 mV. This is known as depolarization. Once the potential difference reaches +40 mV, an action potential is generated. The Na+ channels then close and the K+ channels open causing K+ ions to move out of the cell. This decreases the potential difference of the neuron (repolarisation) and continues even after the potential difference drops below -70 mV due to the opening of large number of K+ channels. This is known as hyperpolarisation. However, the cell regains its resting potential of -70 mV as the K+ channels close.
The action potential jumps from one node of Ranvier to the next. This is because this is the only place where the sodium ions can pass across the membrane, as the myelin sheath insulates the axon and hence prevents the movement of ions across it. This is called saltatory conduction. The period between one action potential and another, is known as refractory period.

i didnt understand in terminal branches there are synapse

 

[mohmed ahmed soliman]

I remember sharing P4 solved thread's link here.
I'm just gonna copy paste the thing since I actually found it helpful.I know the answer may seem so huge.But it's good incase you can't recall some points.
I hope this helps.

PART A

A sensory neuron has a long dendron and an axon which is often shorter than the dendron. Within the cytoplasm of an axon, all of the usual organelles such as endoplasmic reticulum, Golgi apparatus and mitochondria, are present. Large numbers of mitochondria are found at the tips of the terminal branches of the axon, together with many vesicles containing chemicals called transmitter substances.
The axon and dendron is insulated by the myelin sheath. The myelin sheath is made largely of lipid, together with some proteins, and is formed by a Schwann cell wrapping around the axon many times. This forms many layers of cell membrane surrounding the axon.
At intervals, there are gaps in the sheath between each Schwann cell, called nodes of Ranvier.

PART B

An action potential is generated in the sensory neuron, where an impulse reaches the neuron, leading to the opening of Na+ channels. This causes Na+ ions to move down their concentration gradient and into the neuron, increasing the potential difference of the cell from -70 mV to +40 mV. This is known as depolarization. Once the potential difference reaches +40 mV, an action potential is generated. The Na+ channels then close and the K+ channels open causing K+ ions to move out of the cell. This decreases the potential difference of the neuron (repolarisation) and continues even after the potential difference drops below -70 mV due to the opening of large number of K+ channels. This is known as hyperpolarisation. However, the cell regains its resting potential of -70 mV as the K+ channels close.
The action potential jumps from one node of Ranvier to the next. This is because this is the only place where the sodium ions can pass across the membrane, as the myelin sheath insulates the axon and hence prevents the movement of ions across it. This is called saltatory conduction. The period between one action potential and another, is known as refractory period.

u mentioned nothing about local circuits in part b

 

[My Name]

i didnt understand in terminal branches there are synapse

What? I donb't get your question.
There are alot of mitochondria in the terminal branch.

 

[My Name]

u mentioned nothing about local circuits in part b

All the depolarisation and stuff... that is it.
Rizwan Javed am I right?

 

[mohmed ahmed soliman]

What? I donb't get your question.
There are alot of mitochondria in the terminal branch.

at end of terminal branches are synapse??

 

[mohmed ahmed soliman]

I remember sharing P4 solved thread's link here.
I'm just gonna copy paste the thing since I actually found it helpful.I know the answer may seem so huge.But it's good incase you can't recall some points.
I hope this helps.

PART A

A sensory neuron has a long dendron and an axon which is often shorter than the dendron. Within the cytoplasm of an axon, all of the usual organelles such as endoplasmic reticulum, Golgi apparatus and mitochondria, are present. Large numbers of mitochondria are found at the tips of the terminal branches of the axon, together with many vesicles containing chemicals called transmitter substances.
The axon and dendron is insulated by the myelin sheath. The myelin sheath is made largely of lipid, together with some proteins, and is formed by a Schwann cell wrapping around the axon many times. This forms many layers of cell membrane surrounding the axon.
At intervals, there are gaps in the sheath between each Schwann cell, called nodes of Ranvier.

PART B

An action potential is generated in the sensory neuron, where an impulse reaches the neuron, leading to the opening of Na+ channels. This causes Na+ ions to move down their concentration gradient and into the neuron, increasing the potential difference of the cell from -70 mV to +40 mV. This is known as depolarization. Once the potential difference reaches +40 mV, an action potential is generated. The Na+ channels then close and the K+ channels open causing K+ ions to move out of the cell. This decreases the potential difference of the neuron (repolarisation) and continues even after the potential difference drops below -70 mV due to the opening of large number of K+ channels. This is known as hyperpolarisation. However, the cell regains its resting potential of -70 mV as the K+ channels close.
The action potential jumps from one node of Ranvier to the next. This is because this is the only place where the sodium ions can pass across the membrane, as the myelin sheath insulates the axon and hence prevents the movement of ions across it. This is called saltatory conduction. The period between one action potential and another, is known as refractory period.

u wrote that Na ion move down concentration gradient into sensory neuron
how synapse usually separate receptor from sensory neuron
i think we should say that receptor activates sensory neuron

 

[My Name]

at end of terminal branches are synapse??

yes

 

[kareem22010]

Can anyone see my answer for this question and tell me how many marks I should earn please?( it holds 4 marks)
My answer: amylose is formed by joining multiple glucose units unto unbranched 1,4 glycosidic bonds.amylopectin is formed from joining multiple glucose units into 1,4 glycosidic bonds branching from 1,6 glycosidic bond.