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The potent molecular signal molecule Platelet Activating Factor (PAF) is an example for :

•  Phospholipid

• Ether lipid

• Ceramide

•  Glycolipid

Answer explanation

Platelet Activating Factor is an ether lipid. Its alkyl group is connected by an ether linkage at C1 carbon to a 16 carbon chain. The acyl group at the C2 carbon is an acetate unit as opposed to a fatty acid. The C3 has a phosphocholine head group just like standard phosphatidylcholine. PAF is an unusual lipid in many ways, although it can be considered to be a special case of the more abundant ether lipids.

The enzyme family that transfers H atoms from one substance to another is:

• Dehydrogenase

• Oxidase

• Catalase

• All of the above

Answer explanation

Oxidoreductase, any member of a class of enzymes, commonly known as dehydrogenases or oxidases, that catalyze the removal of hydrogen atoms and electrons from the compounds on which they act. Substances called coenzymes, associated with the oxidoreductase enzymes and necessary for their activity, accept the hydrogen and electrons, which—in metabolic systems of animals—eventually are transferred to oxygen. Other enzymes of this group catalyze such reactions as the oxidation of aldehydes and ketones to carboxylic acids and the dehydrogenation of amino acids.

Enteropeptidase is produced in which part of the body and what is its substrate?

• Small Intestine, Trypsinogen

• Large Intestine, Trypsinogen

• Small Intestine, Triglycerides

• Large Intestine,

  Triglycerides

Answer explanation

Enteropeptidase is an intestinal protease discovered by Ivan Pavlov in Russia. Using surgically modified dogs, Pavlov and colleagues studied the digestive system and found that pancreatic proteases were made as inactive forms. Upon entering the gut, latent pancreatic proteases were activated by another enzyme in the upper section of the intestine. Such an activation mechanism, which occurs outside of the pancreas, is important to prevent autoactivation of pancreatic proteases, thereby avoiding harmful tissue damage. Pavlov named the intestinal enzyme enterokinase for its transformative activation activity. Currently, the enzyme is called enteropeptidase to reflect its proteolytic, but not kinase, activity.

The total ATP yield in the process of respiration is:

• 34

• 32

• 36

• 40

Answer explanation

What is the purpose of the polymerase chain reaction?

• Gene Division

• Gene Recombination

• Gene Expression

• Gene Amplification

Answer explanation

Polymerase chain reaction, or PCR, is a laboratory technique used to make multiple copies of a segment of DNA. PCR is very precise and can be used to amplify, or copy, a specific DNA target from a mixture of DNA molecules. First, two short DNA sequences called primers are designed to bind to the start and end of the DNA target. Then, to perform PCR, the DNA template that contains the target is added to a tube that contains primers, free nucleotides, and an enzyme called DNA polymerase, and the mixture is placed in a PCR machine. The PCR machine increases and decreases the temperature of the sample in automatic, programmed steps. Initially, the mixture is heated to denature, or separate, the double-stranded DNA template into single strands. The mixture is then cooled so that the primers anneal, or bind, to the DNA template. At this point, the DNA polymerase begins to synthesize new strands of DNA starting from the primers. Following synthesis and at the end of the first cycle, each double-stranded DNA molecule consists of one new and one old DNA strand. PCR then continues with additional cycles that repeat the aforementioned steps.

Plasma cells produce thousands of __________ that are released into the bloodstream

• Antigens

• Helper T Cells

• Antibodies

• Virus Fragments

Answer explanation

The plasma cells, produce and secrete large quantities, up to 100 million molecules per hour, of antibody molecules.

An antibody, also known as an immunoglobulin (Ig), is a protein that is produced by plasma cells after stimulation by an antigen. Antibodies are the agents of humoral immunity. Antibodies occur in the blood, in gastric and mucus secretions, and in breast milk. Antibodies in these bodily fluids can bind pathogens and mark them for destruction by phagocytes before they are able to infect cells.

If a person is vaccinated against a disease sometime in the past, which of the following is currently in your body?

• The disease organism itself and antigens for the disease organism

• A very high level of antibodies against the disease antigens

• Memory B lymphocytes for the antigen of this disease organism

• All of the above

Which of the following makes water a liquid at room temperature?

• Noncovalent interactions

• Hydrogen bonds between water molecules

• Van der Waals forces of attraction

• Covalent bonding

Answer explanation

The cohesive forces that keep the water a liquid at normal temperature are provided by hydrogen bonds between water molecules.

For an acid buffer solution the pH is 3. The pH can be increased by ____

• Increasing the concentration of salt

• Increasing the concentration of acid

• Decreasing the concentration of salt

• Independent of concentration of acid & salt

Answer explanation

An acid buffer is a mixture of weak acid and its salt with strong base, its pH increases by increasing the concentration of salt.