Biology P4 random notes

[MukeshG93]

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

Further detail to be added:
Oestrogen (made during the development of the Graafian follicle) inhibits the secretion of FSH only. Progesterone (made AFTER ovulation when LH has caused the formation of the corpus luteum), on the other hand, inhibits the secretion of FSH and LH, to make sure LH doesn't have any other weird effects on the developing ovum (which excessive levels of hormones usually tend to).

Further point to be added:
High levels of oestrogen and progesterone thus cause the inhibition of the development of any more Graafian Follicles, so no more ovulation occurs, only one ovum per cycle. Also, this is how birth control pills work. They make the levels of oestrogen and progesterone in the body go way up during the start of the menstrual cycle to inhibit the secretion of FSH initially, which results in no ovulation at all; meaning no chance of pregnancy at all.

 

[zwitterion7]

Can someone please post a note on sympatric speciation and COC's.

 

[zeebujha]

@mukesh:
Oestrogen inhibits the secretion of BOTH FSH and LH. It inhibits the Gonadotrophin Releasing Hormone production by hypothalamus. GnRH is the hormone that makes the the anterior pituitary gland release gonadotrophic peptide hormones called FSH and LH. Pills lower the level of both FSH and LH.

 

[zeebujha]

Can someone please post a note on sympatric speciation and COC's.

I don't know what COC means and I have already posted note on sympatric speciation somewhere in this thread

 

[zeebujha]

Bioleaching:
-Some bacteria are chemoautotrophic i.e.they derive their energy via breakdown of inorganic chemicals. The microbial oxidation process involved in bioleaching occurs at the cell membrane of the bacteria. The electrons pass into the cells and are used in biochemical processes to produce energy for the bacteria while reducing oxygen to water.

 

[zeebujha]

Metabolite: Intermediates and products of metabolism.

(i) Primary metabolite: Directly involved in growth, development, and reproduction. Alcohol is an example of primary metabolite produced in large scale by industrial microbiology. Produced during the active growh phase known as exponential phase
(ii) Secondary metabolite: Not directly involved in these processes, but usually has an important ecological function. These are produced in the times of stress and not during the active growth phase. Produced during the stationary phase. Examples: antibiotics and pigments

 

[zeebujha]

Inhibition of the active site of the enzyme transpeptidase by penicillin is irreversible competitive inhibition. Now, why is it irreversible?

 

[zeebujha]

Horizontal transfer:
Horizontal gene transfer (HGT), also lateral gene transfer (LGT), is any process in which an organism incorporates genetic material from another organism without being the offspring of that organism. By contrast, vertical transfer occurs when an organism receives genetic material from its ancestor, e.g., its parent or a species from which it has evolved.
In case of bacteria, the genetic material mostly refers to plasmid. Means of horizontal transfer:
1. Transduction: Process by which DNA is transferred from one bacterium to another via a virus. It also refers to the process whereby a foreign DNA is introduced into another cell via a viral vector.
2. Bacterial conjugation: Transfer of genetic material between bacterial cells by direct cell to cell contact or by a bridge like connection
3. Transformation: Genetic alteration of a cell resulting from direct uptake, incorporation and expression of exogenous genetic material from its surrounding and taken up though cell membranes. This may occur naturally or artificially

The plasmid may contain alleles providing resistance to a single or even multiple antibiotics

 

[zeebujha]

Why enzyme immobilisation enhances enzyme stability:
Stability of an enzyme: Its ability to retain its tertiary structure so that it can be effective under a wide range of conditions

The surface on which the enzyme is immobilized is responsible for retaining the structure in the enzyme through hydrogen bonding. These links will prevent vibration of the molecules in the amino acids of the enzyme and thus increase thermal stability.
The micro environment of surface and enzyme has a charged nature that can cause a shift in the optimum pH of the enzyme of up to 2 pH units. This may be accompanied by a general broadening of the pH region in which the enzyme can work effectively, allowing enzymes that do not normally have similar pH regions to work together.

 

[zeebujha]

I am SERIOUSLY confused about how a biosensor works. Different books and mark schemes seem to present different methods. Which one are we supposed to stick to??

- Enzyme glucose oxidase immobilised in a protective gel matrix made of cellophane acetate
- glucose oxidised to gluconic acid and hydrogen peroxide

1st:
- H+ ions released from gluconic acid
- give positive charge
- size of current proportional to concn of H+ and thus on the concn of glucose

2nd:
-platinum electrodes
-detects oxygen concentration
-electrode generates an electrical signal

3rd:
- electrode recognizes the no.of electron transfer due to hydrogen peroxide/oxygen coupling
-the electron flow is proportional to the no. of glucose molecules

 

[zeebujha]

Treatment of cancer using MAb:
-MAbs can be bonded to molecules of cancer drugs (MAbs bonded to drugs known as "magic bullets")
-The MAb then injected into the patient
-They attach only to the surface of the cancer cells, delivering the drug to them. The drug therefore destroys the cancer cells but not other cells
-Also less drug is needed if only the tumour cells are targeted

 

[zeebujha]

The main aim of the adaptations of wind pollinating flowers is to maximise exposure to the air of the pollen producing anthers and the pollen collecting stigmas

 

[zeebujha]

Outbreeding depression: Offspring from crosses betn individuals from population have lower fitness thatn progeny from crosses between individual of the same population (as opposed to inbreeding depression)

Outbreeders are plants that do not normally self pollinate. If they are dioeciour or hermaphrodite there are structural and physicological methods of preventing self pollination

Inbreeders are plants that normally self pollinate

Heterozygoisty: Possession of different alleles of a gene on the homologous chromosomes in a diploid

Advantages of outbreeding:
-Results in heterozygosity
-Lessens the chance of offspring receiving two recessive alleles of the same gene, which may be harmful
-Avoids inbreeding depression
-May confer hybrid vigour
-May result in variation amongst the offspring
-Variation increases likelihood of at least some individuals surviving in difficult conditions such as disease. So, the species has a greater chance of survival

 

[zeebujha]

Structure of a maize grain (grain is a fruit and not a seed):
- The fruit is called "caryopsis and conatins a single monocotyledonous seed. In maize, each ovary contained a single ovule, so each fruit contains a single seed.

In maize, the fruit wall (pericarp) and the seed coat (testa) are fused together to form the HULL. Thu hull encloses the endosperm and the embryo and is rich in cellulose.

Just below the hull, there is an ALEURONE layer. It contains proteins which are converted into hydrolytic enzymes which digest food stored in the endosperm at the time of germination of seed (gibberellin anyone?)

The greater part of teh remaining portion forms the endosperm. It is a large yellow mass situated outside the embryo but inner to the aleurone layer

The embryo lies on one side of the endosperm, and consists of a single cotyledon called the SCUTELLUM
The scutellum lies in close contact with the endosperm. During germination, it absorbs the stored food from the endosperm. The embryonic axis consists of a RADICLE and a PLUMULE. The radicle, which eventually develops in to the root, is protected by a sheath called COLEORHIZA. The plumule, which eventually develops into the shoot, is also covered by a sheath called COLEOPTILE

 

[Sheeny112]

jee..wat do u guys use to study for bio? i just read the OCR book nd memorized the mary jones revision guide....reading all the notes here i feel so unprepared nd scared nd omg im ganna die

 

[fatema]

heyy
for the application topic : biodiversity and conservations, we need to know an example of an endangered species so can we use an example of an african elephant as mentioned in the application books, or tiger as mentioned in mary jones book?

 

[ivorydale]

can anyone tell me the role of synapses for section B type questions. Because i dont think i have enough points to fill up all that space they give

 

[zeebujha]

heyy
for the application topic : biodiversity and conservations, we need to know an example of an endangered species so can we use an example of an african elephant as mentioned in the application books, or tiger as mentioned in mary jones book?

there is no restriction on the choice of the endangered species. You could choose a plant if you wanted to!

 

[zeebujha]

can anyone tell me the role of synapses for section B type questions. Because i dont think i have enough points to fill up all that space they give

do you mean the need for the synapse such as summation, one directional impulse etc. If that is the case then we share the same boat. Am not very sure about that section either!

 

[ivorydale]

can anyone tell me the role of synapses for section B type questions. Because i dont think i have enough points to fill up all that space they give

do you mean the need for the synapse such as summation, one directional impulse etc. If that is the case then we share the same boat. Am not very sure about that section either!

exactly. Right now, a detailed answer can really help