Essay Links To Make Flashcards
Links to make for photosynthesis
This is important because, without …………….. there would be less glucose converted to sucrose. As a consequence, less
sucrose will be actively loaded into the phloem, less mass flow to the roots, less glucose available for aerobic respiration and less
ATP used for active transport of nitrates which are essential for protein synthesis and the production of essential Rubisco enzyme
for the LIR in new palisade mesophyll cells. Less growth means more competition for light and water.
Links for muscles
This is important because, without …………….. there would be weaker muscle contractions and fatigue/cramps can be caused by
a build-up of lactate through anaerobic respiration. As a consequence, muscle fatigue may result in a prey organism being unable
to escape predation. Fast-twitch muscles can overcome this through a store of phosphocreatine which is hydrolysed into
phosphate and creatine using phosphocreatine kinase, the energy released is used to phosphorylate ADP into ATP.
Links for the synapse, then link this to inhibitory neurotransmitters
This is important because, without …………….. there would be weaker muscle contractions and fatigue/cramps can be caused by
a build-up of lactate through anaerobic respiration. As a consequence, muscle fatigue may result in a prey organism being unable
to escape predation. Fast-twitch muscles can overcome this through a store of phosphocreatine which is hydrolysed into
phosphate and creatine using phosphocreatine kinase, the energy released is used to phosphorylate ADP into ATP.
Links for receptors
This is important because, without …………….. the medulla oblongata would not be able to coordinate a response to reduce higher
than normal blood pressure. Excess tissue fluid will form and may build up in tissues and organs as the excess fluid, not returned
to the capillary (via osmosis) or drained by lymph. Extended periods of hypertension will lead to increased risk of stroke and kidney
failure.
OR
Extended periods of hypertension may result in damage to the endothelial layer of the arteries. Over time the collective damage
and weakening of the elastin and muscle fibres may lead to the formation of an aortic aneurysm.
Links for protein synthesis
This is important because, without ……………. there would be less haemoglobin produced which may lead to anaemia. This
would reduce the total oxygen saturation and may not meet the oxygen demands of the organism. As a consequence, this
may lead to fatigue, heart palpitations, hair loss and shortness of breath.
• Sickle-celled anaemia is a genetic disease which may lead to various acute and chronic complications, several of which have a
high mortality rate e.g., haemolytic crisis. This is when red blood cells break down at a faster rate. This is particularly common
in patients with coexistent G6PD (Glucose-6-phosphate dehydrogenase) deficiency.
• Hemoglobin has the essential role of oxygen transport to respiring tissues so that oxygen can act as the final electron acceptor
and yield significant amounts of ATP through the complete oxidation of glucose and prolong the formation of lactate which can
denature cellular proteins.
Links for meiosis
This is important because, without ……………..the formation of haploid gametes would not be possible.
Increased variation is essential for the long-term reproductive success of a species. Over many generations, changes to the
environment and abiotic/biotic factors create different selection pressures. Variation in phenotype ensures the survival of a species
as the advantageous alleles are passed on from one generation to the next.
OR
Down Syndrome is caused by non-disjunction of homologous chromosomes during Meiosis I, each of the gametes formed will
have an unequal number of chromosomes. This leads to a trisomy of chromosome 21. Maternal age is associated with greater risk
of meiotic nondisjunction leading to Down syndrome. This may be associated with the prolonged meiotic arrest of human oocytes
potentially lasting for more than four decades.
Links for the nitrogen cycle
Nitrifying aerobes (autotrophs) oxidise ammonia to nitrates to gain high energy electrons to meet their energy demands. This
process is beneficial to plants as it produces a source of nitrates that can be actively transported into root hair cells. This lowers the
water potential of the cytoplasm and establishes a water potential gradient that allows the uptake of water from the soil to maintain
a continuous column of water in the xylem vessels. Nitrates will also be assimilated into nitrogen containing compounds e.g. DNA
nucleotides and amino acids
Links for stomatal opening mechanism
When environmental conditions are favorable to stomatal opening (e.g., high light intensity and high humidity), a proton
pump drives protons (H+) from the guard cells. This means that the cells’ electrical potential becomes increasingly negative. The
negative potential opens potassium voltage-gated channels and so an uptake of potassium ions (K+) occurs. To maintain this
internal negative charge chloride ions, enter (or the organic ion malate is produced) the guard cells.
This increase in solute concentration lowers the water potential inside the cell, which results in the diffusion of water into the cell
by osmosis. This increases the cell’s volume and turgor pressure. Then, because of rings of cellulose microfibrils that prevent the
width of the guard cells from swelling, so elongate the guard cells. The two guard cells lengthen by bowing apart from one another,
creating an open pore through which gas can diffuse.
Regulation of transcription in prokaryotic
• E. Coli can metabolise glucose and lactose
• Bacteria only synthesise lactose-metabolising proteins in the absence of glucose and lactose is detected in the environment.
• Expression of Lactose permease rapidly transports lactose across the membrane & expression of β-Galactosidase hydrolyses
lactose into glucose & galactose.
• The genes coding for these enzymes/proteins are found in the Lac operon region of bacterial DNA
The process/mechanism:
1. In the absence of lactose: a repressor protein (RP) is produced by the expression of a regulatory gene.
2. This is located upstream of the operon region.
3. The RP binds to the DNA at the promoter region of the lac operon and inhibits transcription.
4. RNA polymerase is unable to bind to the promoter and initiate transcription.
5. This is important because, unrequired proteins are not translated so less ATP is wasted.
6. In the presence of lactose: Lactose binds to the repressor protein;
7. (RP) changes tertiary structure and is no longer complementary;
8. (RP) detaches from the promoter region (of the lac operon)
9. RNA polymerase can now bind, and transcription of β-Galactosidase and Lactose permease is initiated.
10. mRNA for β-Galactosidase and Lactose permease is translated by 70S ribosomes.
11. This increases permeability of cell membrane to lactose and increases rate of hydrolysis of lactose into glucose and
galactose.
Menstrual cycle links
Menstrual cycle:
1. Regulated by Gonadotropin Releasing Factor (GnRF) from the hypothalamus.
2. This peptide hormone is secreted into the blood and binds to receptors on the gonadotrope cells of the anterior
pituitary body where it causes secretion of FSH.
3. FSH stimulates the development of primary ovarian follicles into mature ovarian follicles, and the secretion of increasing
quantities of oestrogen.
4. Oestrogen stimulates the growth of the glandular tissue and blood vessels of the endometrium (lining of uterus).
5. High level of oestrogen in the blood around the time of ovulation has two effects:
• It inhibits the release of GnRF , and hence of FSH (by negative feedback).
• It stimulates the anterior pituitary to release increasing quantities of LH (by positive feedback).
6. The increase in LH concentration stimulates three things:
• ovulation
• development of follicle into the corpus luteum
• corpus luteum to secrete increasing quantities of oestrogen and progesterone
7. The oestrogen and progesterone together maintain and cause further growth of the endometrium.
Link for respiration
This is important because, without …………….. there would be less ATP to meet the energy demands of the cell. ATP has 3
important uses in muscle cells: the breaking of the actin-myosin cross bridge when it binds to the myosin head; providing energy
for the change in shape (recovery stroke) so that the myosin head can perform the power stroke and the active transport of
Calcium ions back into the sarcoplasmic reticulum.
As a consequence of this not happening, diaphragm muscle contraction to increase the volume of the thoracic cavity may not occur
and the concentration gradient during gas exchange (ventilation) will not be maintained.
