Biology P4 random notes

[abuhantash]

how many layers of podocytes are there?? From what I understand , podocytes wrap around the basement memabrane surrounding the capillaries of the glomerulus. But now I read that podocytes form the wall of the renal capsule too. So, are there two layers of basement membrane and two layers of podocytes? =@

Ok so this is what I know. There r 3 layers, the endothelium of the glomerulus, the basement membrane and then the podocytes. The podocytes are the epithelial cells that kinda modified finger-like projection with gaps in them which allows for substances dissolved in plasma to go through. but ofcourse membrane is a filter.

 

[MukeshG93]

Detail you missed out on:

Higher temperatures --> Larger rates of respiration --> Increased stomatal closure --> Decreased carbon dioxide intake --> Decrease in the rate of photosynthesis

why would an increse in resipration rate increase stomatal closure?

Increased respiration rate means less water inside the plant. Respiration occurs due to the escape of water vapor through the stomata and so it closes to prevent excess water loss. Read the small section about ABA.

 

[zeebujha]

Sympatric speciation, not many questions about this in exams yet, so wanted to explore it:
It is due to reproductive isolation
Some barrier of gene flow occurs between individuals in the same geographical area resulting from different behaviours. The members of the same species may occupy different niche. So, they adapt in different ways specifically for their niche OVER TIME which could lead to:
-evolution of different mating location, mating time or mating rituals
-lack of "fit" between sexual organs: variably shaped genitalia in insects

Adapted to different niches, each section of the specialized population eventually becomes a different new species. This is ADAPTIVE RADIATION

Also, there is the mechanism of polyploidy.

 

[zeebujha]

Botanic gardens:
-Endangered plant species can be grown in botanic gardens
-SEEDS or CUTTINGS collected (not the whole plant itself, lol) from species in the wild and then used to build up a population of plants

Advantages:
-Possible to create ideal growing conditions-either outdoors or in glasshouses, when it is possible to control the growing conditions such as availability of light, nutrients, water and atmospheric conditions. So, growth rate optimised

-Possible to propagate endangered species-either by growing from seed or by some means of vegetative propagation such as cuttings propagations

-Techniques such as tissue culture allow large numbers to be produced very quickly

-suitable for plants which produce seeds with limited longevity

- generating public awareness

-research
ULTIMATELY, ENDANGERED SPECIES OF PLANTS CAN BE RE-INTRODUCED IN A NATURAL HABITAT

Disadvantage:
-Ex-situ conservation. So, not enough emphasis on conservation of the natural habitat of the plants

SEED BANKS:
-Many plants produce seeds which are very long-lived and large number can be stored in a relatively small space. Such COLLECTION OF SEEDS is referred to as seed banks

Advantages:

-LIFE SPAN of seeds INCREASED if they are kept in carefully controlled conditions:
*Low oxygen leves * Low moisture/humidity * Low temperature

-Since seeds contail all genetic information of any given species, it also means that gene pool of that species in maintained

-Such stored seeds can be GERMINATED ANY TIME and seedlings obtained can be grown in Botanic gardens or restored to the wild. They can also be used as a source of more seeds. So, stock of seeds continuously replenished as well.

Disadvantage:
-Some species produce seeds which have a limited longevity (e.g. cocoa, rubber, coconut)-keeping their seeds in seed banks is not possible. Such plants need to be maintained in botanic gardens
-Ex-situ again. So, natural habitat not conserved

 

[zeebujha]

DNA probes:
-A DNA probe is a small fragment of nucleic acid that is labelled with an enzyme or a radioactive tag or a fluorescent dye tag
-It allows the identification of a specific sequence of nucleotides called the target DNA
-The probe will bind to a complementary DNA sequence by base pairing

Fluroescent dye tag: Shows up as fluorescent bonds when gel is exposed to UV source
Radioactive tag: Shows up as a dark band when the gel is exposed to photographic film

Uses:
-To identify restriction fragments containing a particular gene out of thousands of restriction fragments
-To identify the short DNA sequences in DNA fingerprinting
-To identify genetic defects

 

[lillyevans]

hey thanks. u guyz r being real help.
i'll also add few points

why is it important to maintain biodiversity?

ecological role: there is need to ensure survival of potential material from which to develope new varieties of food crops and domestic livestocks in in event of major physical or biotic environment change such as changing pattern of global climate.associated with "greenhouse warming", or emergence of new pest or disease due to natural or human induced mutation. Deforrestation leads to increased co2, floods soil erosion etc.. Organisms of an ecosystem are linked by their energy and nutrient relationships. biochemical cycles like those of carbon and nitrogen are movement of chemical elements throgh living component of ecosystem, as in form of complex organic molecules, along food chain. And then decomposition and break down into inorganic form which can be used again for living material. it is necessary to maintain these cycles for soil fertility due to increasing demands of food production.

economic role: sewage processing is technological use of decay microorganisms and nutrient dried sludge obtained is used as by product. As species have economic importance outside thier habitat eg. pollinating insects, they may also possess undiscovered chemicals or genes with future medicinal importance. Biological control of pest by using more natural predators. to encourage tourism in some countries (ecotourism). improving agriculture:- yeild, hardness, desease resistance. 7000 of drugs prescribed by doctors are derieved from plants growing in rainforrests. biodiversity is also important for studies and research

ethical importance: some natural ecosystems are habitats of indigenous people. We share the planet with species, we have no right to remove them. there is need to recover loss and avoid damage. (extinction is forever!!). loss of biological resources also results in reduced gene pool

 

[lillyevans]

role of insulin in regulation of blood glucose concentration:

normal blood glucse is 80-120mg. after meal glucose from intestine passes into blood. As dis blood passes into pancreas the alpha and beta cells detect raised glucose levels. Alpha cells respond by stopping secretion of glucagon while beta cells respond by secretin insulin. Beta cells contain several types of ion channel including Ca+ and k+.normally k+channels are open k+ diffuse out so inside of cells is -70mv compared to the outside. when glucose level is high in blood, glucose enters beta cells where it is quickly phosphorylated by enzyme glucokinase which is then metabolised to atp. presence of extra atp closes k+ channels and the membrane potential difference reduces to -30mv only. in responce to change in membrane potential ca+ ions rush into cells causing insulin vesicles to release insulin by exocytosis.
insulin esp affects liver and muscle cells. there is increased absorbtion of glucoe from blood into muscle cells, increasd absorbtion of fats by cellmembranes.
Increase in glycogenesis (glucose->glycogen) increase in rate of protein and fat synthesis. Increase in formation of atp, dna, rna.


when glucose level decreases glucagon --> phosphorylase enzyme converts glycogen to glucose. when glycogen finishes ACTH is releasedby hypothalimus.ACTH causes adernal gland to release glucocorticoid hormones eg. cortisol. dis causes liver to convert amino acids and glycerol into glucose. in times of stress another hormone adernaline causes break down of glycogen

 

[zeebujha]

hey thanks. u guyz r being real help.
i'll also add few points

why is it important to maintain biodiversity?

ecological role: there is need to ensure survival of potential material from which to develope new varieties of food crops and domestic livestocks in in event of major physical or biotic environment change such as changing pattern of global climate.associated with "greenhouse warming", or emergence of new pest or disease due to natural or human induced mutation. Deforrestation leads to increased co2, floods soil erosion etc.. Organisms of an ecosystem are linked by their energy and nutrient relationships. biochemical cycles like those of carbon and nitrogen are movement of chemical elements throgh living component of ecosystem, as in form of complex organic molecules, along food chain. And then decomposition and break down into inorganic form which can be used again for living material. it is necessary to maintain these cycles for soil fertility due to increasing demands of food production.

Awesome! Had been looking for the ecological role for some time!

 

[zeebujha]

Promoters:
In prokaryotes, base sequences called promoters are situated just before each gene. These identify the point at which transcription should begin.
In order for the transcription to take place, the enzyme that synthesizes RNA, RNA polymerase, must ATTACH TO THE DNA NEAR THE GENE. Promoters contain specific DNA sequence and response elements that provide a secure INITIAL BINDING SITE for the RNA polymerase and for proteins called TRANSCRIPTION FACTORS that recruit RNA polymerase. These transcription factors have specific activator or repressor sequences of corresponding nucleotides that attach to specific promoters and regulate gene expressions

Response elements: Short sequences of DNA that are able to bind to a specific transcription factors and regulate transcription of genes

So, promoters are required for expression of eukaryotic genes when eukaryotic genes have been placed in a prokaryotic cell

 

[zeebujha]

Current treatment for CF:
-Physiotherapy to dislodge mucus from the lungs
-Antibiotics to fight infection
-DNAse drug to loosen the mucus
-Enzymes to help food digestion
-Heart-lung transplant

Importantly, all of these treatments address the symptoms, not the cause!

 

[zeebujha]

VNTRs:
-Although the introns may seem useless, it has been found that they contain repeated sequences of base pairs. These sequences, called VNTRs, can contain anywhere from twenty to one hundred base pairs
-A given persons VNTR comes from the genetic information donated by his or her parents. One VNTR is inherited from each parent
-If the DNA flanking a VNTR is cut with a restriction endonuclease, the size of resulting DNA fragment can vary, resulting in RFLPs, or "restriction fragment length polymorphisms"

VNTR regions are polymorphic, meaning they have many forms. The number of tandem repeats of a sequence is highly variable in a population.

To map the entire sequence of an individual would be too great an undertaking; so , instead, specific sections of DNA are used, which can be obtained using restriction enzymes. VNTRs would be a perfect choice as they vary enormously between individual (barring twins of course). So, when two samples are compared, it would be possible to tell the differencce between the DNA of two different people.

DNA profiles vary from person to person. When profiles from a single VNTR locus from unrelated individuals are compared, the profiles are normally different. However, it is possible that two individuals have the same profile at one or two loci by chance. But the chance of more than one person having the same DNA profile at 4,5 or 6 different VNTR is extremely small

 

[abuhantash]

You guys are amazing, thank you !
I have some requests please 1) estrogen and progestron, they confuse me!!
2) plant hormones, They asked a 9 mark question about gibrellins in 05 and I had NO idea what to write, seems I dunno as much as I am expected too =[
3) I never heard of VNTRs o.0

May Allah help us all!!

 

[zeebujha]

You guys are amazing, thank you !
I have some requests please 1) estrogen and progestron, they confuse me!!
2) plant hormones, They asked a 9 mark question about gibrellins in 05 and I had NO idea what to write, seems I dunno as much as I am expected too =[
3) I never heard of VNTRs o.0

May Allah help us all!!

Plant growth regulators are basically plant hormones.
We need to know about three plant hormones:
(i) Auxin (specifically IAA)
(ii) Gibberellic acid (GA)
(iii) Abscissic acid (very confusing spelling)


(i) Auxin
There are several chemicals known as auxins, in our case it is IAA. Auxins are produced in apical bud. They move from the apical bud to the lateral buds either from cell to cell or via phloem sap and xylem vessels. Cell to cell movement could involve symplast pathway (via plasmodesmata if I remember correctly) or could be active transport. Coming to the effect of auxin, when auxin is present in high concentration in lateral buds, it inhibits the growth of the lateral buds. So, the plant only grows upward and cannot branch sideways. Removal of apical bud allows lateral buds to grow. This is known as apical dominance. This happens because removal of apical bud means no meristematic region to produce auxin, so concn of auxin in lateral bud decreases eventually. Also, ABA and GA enhance IAA while cytokinins are antagonistic to IAA.

(ii) GA:

We need to know two effects:
(a) Stem elongation:
In plants such as peas, genes are partially responsible for determining how tall the plant grows. The dominant allele codes for an enzyme that catalyses the synthesis of active form of GA whereas recessive allele codes for inactive form of GA. Thus, homozygous recessive plants are relatively short. GA, on its part, induces cell DIVISION and ELONGATION in the STEM, so causing the plant to grow tall

(b) Seed germination:
When seeds absorb water by osmosis, embryo are stimulated to produe GA. This GA passes to the ALEURONE layer where it switches on the gene for transcription of certain enzymes, one of them being amylase. It also results in hydrolysis of proteins to amino acids. The amylase produced diffuses to the endosperm. Here it catalyses the hydrolysis of starch to maltose and then the hydrolysis of maltose to glucose. The glucose diffuses to the embryo plant and provides a source of energy for growth of embryo plant. (Thus, we start with an embryo and end up at the embryo.)

(iii) ABA
We need to know the role of ABA in stomatal closure (role of ABA in leaf abscission not required)
ABA is known as a stress hormone as it is secreted by plants when subjected to difficult environmental conditions (which for A level invariably means low water conditions due to low or high tempr). ABA binds to the ABA receptors on the plasma membrane of the guard cells. On binding, it inhibits the proton pump. This stops hydrogen ions being pumped out, so potassium ions do not enter any further and rather the cell loses K+ ions. Thus the water potential of the guard cells increases and thus the cell loses water to the surrounding cells by osmosis down the water potential gradient. This reduces turgor and makes the guard cells flaccid, eventually closing the stomata

 

[zeebujha]

Role of genetic counsellor: (from mark scheme)
The goals of genetic counseling are to increase understanding of genetic diseases, discuss disease management options, and explain the risks and benefits of testing. Counseling sessions focus on giving vital, unbiased information and non-directive assistance in the patient's decision making process.

-explain the risks of the test before test is carried out. The patients explained about potential psychological impacts of the results of the test and also the increased risk of miscarriage
-explains the outcome of test
-if the outcome predicts a disease:
*suggests about the cost of care
*the drugs available and the expected life span
*if the parents still aren't satisfied , mentions termination of pregnancy
* if termination of pregnancy accepted, discusses the possiblity of the child having the same disease when the parents conceive again. If the parents ask for alternatives, can suggest possibility of pre-implantation diagnosis (PGD), artificial insemination by donor sperm (AID) as possible ways of conceiving next child

 

[zeebujha]

You guys are amazing, thank you !
I have some requests please 1) estrogen and progestron, they confuse me!!

May Allah help us all!!

First of all, both of them are steroid hormones. Both of them help increase the thickness of the endometrium and maintain the endometrium for embryo implntation
However, estrogen is secreted by granulosa cells of a follicle while progesterone is secreted by luteal cells of the corpus luteum. Both of them help increase the thickness of the endometrium and maintain the endometrium for embryo implntation. But during the menstrual cycle, oestrogen is mainly produced in the first 14 days while progesterone in the last 14.

 

[bionology]

You guys are amazing, thank you !
I have some requests please 1) estrogen and progestron, they confuse me!!

May Allah help us all!!

First of all, both of them are steroid hormones. Both of them help increase the thickness of the endometrium and maintain the endometrium for embryo implntation
However, estrogen is secreted by granulosa cells of a follicle while progesterone is secreted by luteal cells of the corpus luteum. Both of them help increase the thickness of the endometrium and maintain the endometrium for embryo implntation. But during the menstrual cycle, oestrogen is mainly produced in the first 14 days while progesterone in the last 14.

point to be added here,
when Oestrogen and progesterone are secreted they have a negative feedback effect on FSH and Lh and both the hormone level of FSH and LH decrese due to increasing oestrogen level

 

[zeebujha]

You guys are amazing, thank you !
I have some requests please 1) estrogen and progestron, they confuse me!!

May Allah help us all!!

First of all, both of them are steroid hormones. Both of them help increase the thickness of the endometrium and maintain the endometrium for embryo implntation
However, estrogen is secreted by granulosa cells of a follicle while progesterone is secreted by luteal cells of the corpus luteum. Both of them help increase the thickness of the endometrium and maintain the endometrium for embryo implntation. But during the menstrual cycle, oestrogen is mainly produced in the first 14 days while progesterone in the last 14.

point to be added here,
when Oestrogen and progesterone are secreted they have a negative feedback effect on FSH and Lh and both the hormone level of FSH and LH decrese due to increasing oestrogen level

that reminds me of something else too, very high level of oestrogen stimulates hypothalamus to produce a high level of LH as evident on day 14

 

[beso2011]

What Are Photons of light ??? can i mention them insted of saying light rays plzzzzzzzzzzz explain them to me

 

[MukeshG93]

how many layers of podocytes are there?? From what I understand , podocytes wrap around the basement memabrane surrounding the capillaries of the glomerulus. But now I read that podocytes form the wall of the renal capsule too. So, are there two layers of basement membrane and two layers of podocytes? =@

You're just confused. The basement membrane of the capillary forms a boundary between the capillary and the inner wall of the renal capsule that exists between it in the glomerulus. So here's how it works:

|glomerulus||epithelium of capillary||basement membrane||podocyte||renal capsule|

So, just one layer!

 

[MukeshG93]

Promoters:
In prokaryotes, base sequences called promoters are situated just before each gene. These identify the point at which transcription should begin.
In order for the transcription to take place, the enzyme that synthesizes RNA, RNA polymerase, must ATTACH TO THE DNA NEAR THE GENE. Promoters contain specific DNA sequence and response elements that provide a secure INITIAL BINDING SITE for the RNA polymerase and for proteins called TRANSCRIPTION FACTORS that recruit RNA polymerase. These transcription factors have specific activator or repressor sequences of corresponding nucleotides that attach to specific promoters and regulate gene expressions

Response elements: Short sequences of DNA that are able to bind to a specific transcription factors and regulate transcription of genes

So, promoters are required for expression of eukaryotic genes when eukaryotic genes have been placed in a prokaryotic cell

JUST AS I THOUGHT! I THOUGHT THE RNA POLYMERASE MUST HAVE SOME WAY OF IDENTIFYING THE PROMOTER IN THE DNA SEQUENCE! Woohoo, my guess was correct! So there is a "transcription factor" that includes a specific complementary sequence to that of the promoter gene in order to bind to the DNA at that point and this is where the Polymerase initiates its business. Very nice. I assume it's the same with operators. Proteins containing specific nucleotide base sequences bind to parts on the gene responsible for the protein synthesis called the operator. When bound here, it doesn't let the transcription of that section proceed.