Considering the following;
I. Heat is not readily available to all living cells.
II. Heat at excessive amounts denatures proteins.
III. Heat does not provide the activation energy for their reactions.
IV. When a critical temperature is reached, proteins no longer function
Answer;
I and IV
Explanation;
Living cells cannot use heat to provide the activation energy for biochemical reactions because heat is not readily available to all living cells and also when a critical temperature is reached, proteins no longer function.
Too much heat can kill an organism by rendering its organelles, cells, tissues and organs permanently inoperable and un-salvageable. The same process can be observed in tissues at low temperatures, and is the cause of frostbite. This is because enzymes are denatured by high temperature and inactivated by low.
Answer:
False
Explanation:
The blood brain barrier (BBB) is a selective border that prevents the entry of foreign substances into the brain. It is made up of different components including endothelial cells, astrocytes, and pericytes etc.
Of all these mentioned three, the endothelial cells are directly responsible for the selectivity of the BBB. The endothelial cells are bound together by the tight junctions situated between them, impeding the passage of foreign materials e.g. solutes, pathogens etc.
Astrocytes help to maintain the BBB by surrounding the endothelial cells, providing biochemical strength.
The pericytes are located in the basement membrane, where they communicate with endothelial cells. They help to sustain the BBB by stabilizing and monitoring the maturation of endothelial cells via communicating directly between cell membrane as well as paracrine signalling.
Answer:
c. binds to allolactose and becomes inactive, allowing lac gene expression to occur.
Explanation:
Interaction between allolactose and repressor leads to allosteric repulsion which makes repressor inactive leading to the lac gene expression. This is the reason why allolactose is known as the inducer of lac operon becasue it causes gene expression in lac operon.
In the absence of allolactose, the repressor binds the operator and does not allow RNA polymerase to do transcription.
Answer:
Endocrine disruptors are the synthetic or natural chemicals that may interfere with the functioning of the endocrine system in the human body. These chemicals mimic the naturally occurring hormones produced in the body like estrogen (a female sex hormone) and androgen (a male sex hormone) also these interfere with the production of the thyroid hormone. They bind to the receptors present in a cell and prevents the endogenous hormone from binding. The normal signaling process fails to respond properly.
Chemicals that functions as endocrine disruptors include dioxine, polychlorinated biphenyls (PCBs), pesticides and DDT.
Answer:
The correct answer is option c. "The basic function of fermentation is the regeneration of NAD , which allows continued ATP production by glycolysis".
Explanation:
For bacteria, the basic function of fermentation is not the production of ATP or ethyl alcohol, the basic function of fermentation is the regeneration of NAD+ , which allows continued ATP production by glycolysis. Bacteria normally uses glycolysis for ATP production, it only undergoes fermentation in the absence of oxygen. During bacterial fermentation, a small organic compound as an electron acceptor is used for NADH and regenerates NAD+, this NAD+ is later used in glycolysis for ATP production.
