Biology set 1 revision 3-6-20

What is a phospholipid?

Answer

• A phospholipid is a class of lipids which forms the major part of cell membranes and performs several other functions in the body. Phospholipids have hydrophilic phosphate heads which are water loving and the hydrophobic lipid tails which are water hating. They are composed of three parts; a glycerol molecule, one or two fatty acids and a polar phosphate group

Explanation:

The major types of lipids include fats and oils, waxes, phospholipids, and steroids.

Phospholipids are known as the major component of cell membranes. Our cell membrane has what is called a bilayer, and this bilayer forms because phospholipid has two parts, the part that is hydrophilic hence water loving, and the hydrophobic part which is water hating faces inside thus two layers of these phospholipids come together to make a cell membrane bilayer.

There are also several classes or types of phospholipids. The most common phospholipids are phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and phosphatidylserine.

The existence of barriers that stop members of the two species from producing viable, fertile offpring is called？

1. Reproductive isolation
2. Morphological species concept

Answer

• Reproductive isolation

Explanation:

Reproductive isolation refers to the mechanism that results into separation and individuality of different gene pools which are not compatible and hence inability of two species not of the same pool to reproduce a viable offspring. Reproductive isolation can be caused by pre-zygotic barriers that prevent animals from mating such as ecological isolation, temporal isolation among others. post-zygotic barriers includes hybrid sterility and hybrid invariability.

Gene therapy has been used to treat which of these

A cystic fibrosis

1. familial hypercholesterolemia

c severe combined immunodeficiency

d all above

Answer

• d all above

Explanation:

Gene therapy involves an experimental technique that uses genes to treat a disease or disorder. For gene therapy to be applied, the disorder must be caused by a change in the normal gene or at least treatable by gene changes. All the above conditions are genetic disorders hence can be treated with gene therapy. For instance, Familial hypercholesterolemia is a genetic disorder. It is caused by a defect on chromosome 19. Severe combined immunodeficiency (SCID) is caused by mutations in different genes.

Compare and contrast photosynthesis vs. the complete breakdown of glucose( including glycolysis and cellular respiration). Choose ALL answers that are correct :

1. cellular respiration takes place in chloroplast while photosynthesis in mitochondrion.
2. as far as net energy change is concerned, the complete breakdown of glucose is exergonic and photosynthesis is endergonic.
3. ETC is used both in photosynthesis and in cellular respiration.
4. the reactants of photosynthesis are CO2 and H2O. The products of breaking down glucose are CO2 and H2O too
5. the electron carrier for photosynthesis is NADH and FADH2 for cellular respiration
6. most plants perform photosynthesis during the day when there is sun light. The break down glucose for energy occurs only during the night

Answer

• • as far as net energy change is concerned, the complete breakdown of glucose is exergonic and photosynthesis is endergonic.
  • the reactants of photosynthesis are CO2 and H2O. The products of breaking down glucose are CO2 and H2O too
  • most plants perform photosynthesis during the day when there is sun light. The break down glucose for energy occurs only during the night

Explanation:

During photosynthesis which occurs in the chloroplasts, energy from the sun is used which qualifies the process as endergonic while complete breakdown of glucose produces around 38 ATP molecules which qualifies this as exergonic reaction. Photosynthesis uses water and carbon dioxide as the main reactants forming glucose which undergoes cellular respiration forming carbon dioxide and water in the last steps of ETC. The energy storage molecule ATP and the reduced electron carrier NADPH. Since photosynthesis requires sun light, it takes place during the day while cellular respiration occurs mostly at night for plants.

When tryptophan is present,

1. The Repressor is able to bind to the operator.
2. The repressor is unable to bind to the operator
3. Transcription of structural genes occur
4. Transcription of the structural genes, operator, Promoter occurs.

e both b and c

Answer

• The Repressor is able to bind to the operator.

Explanation:

This entails the prokaryotic gene regulation. When tryptophan is present in the cell, two tryptophan molecules bind to the trp repressor which initiates a series of changes in its shape such that it can bind to the trp operator. When these two - both trp repressor and trp operator - bind, the operator is able to prevent the transcription and eventual expression of genes in the downstream region of the genome by preventing the binding of polymerase enzyme.