Biology AS level

outline a biological test that could be carried out to show the presence of triglyceride in a liquid mixture and describe the positive result for this test.

the solution turns milky for the positive test for this emulsion test.
The test can be carried out by adding alcohol with the mixture and then by adding water.

suggest and explain why respiratory bronchioles do not have any goblet cells,

Because goblet cells secrete mucus and mucus traps pathogens which can lead to the prevention of gas exchage from happening.

In the cell cycle, more mRNA is produced in the G1 phase than during mitosis.
Suggest why this is so.

Because proteins are needed for growth.

state the location in the body where macrophages have their origin.

bone marrow

suggest the role of a meristematic cell and explain the features that help it carry out its role.

Meristematic cells can differentiate and become specialised. It replaces old damaged cells and divides continuously to supply meristemic cells.
Stem cells are not specialised and divides by mitosis to form new genetically identical cells.

state the substances used to synthesise DNA during the s-phase.

-ATP
- DNA polymerase
- DNA ligase

what is the name of the blood vessel that carries blood to the heart from the rest of the body?

vena cava

what is the name of the blood vessel that carries blood to the heart from the lungs?

pulmonary vein

suggest and explain how the presence of mineral ions in the root hair cell can increase the absorption of water by the root hair cells.

Mineral ions are solutes that dissolve in the cytoplasm, this lowers the water potential in the cell. The water potential becomes more negative in the cell, creating a steeper gradient between the soil and the root hair cell.

Describe the role of the spindle during the anaphase stage of mitosis.

The spindle fibre shortens and pulls the chromatids towards opposite poles.

Explain what is meant by a closed double circulation.

Blood flowing through the heart twice for one complete circuit and that blood is kept within blood vessels.

suggest why telomerase activity is important in stem cells.

allows DNA replication to continue and for stem cells to keep dividing.

outline the features of non-self antigens.

• stimulates an immune response

• activates neutrophils

• causes the production of specific antibodies.

What is the name of the blood vessel that carries blood from the heart to the rest of the body?

aorta

outline the similarities and difference between the introns and exons of genes coding for proteins such as carbonic anhydrase.

• both are transcribed

• exons have a coding sequence and introns have a non-coding sequence.

• exons join to form mRNA while introns are not part of mRNA.

explain why the concentration of chloride ions in the blood plasma of deoxygenate blood is lower than in the plasma of oxygenated blood.

because hydrogen carbonate ions pass out of the red blood cells and chloride ions pass into the red blood cells.

Describe the roles of DNA polymerase and DNA ligase in the replication of DNA.

DNA polymerase

• adds activated nucleotides to the growing DNA strand, with matching complementary bases.

• It forms phosphodiester bonds, elongating the new strand.
  
  DNA ligase

• forms okazaki fragments and forms phosphodiester bonds between the fragments.

state what is meant by a sink.

a region of a plant where assimilates are stored.

explain how the properties of water make it suitable as the main component of blood.

water is a good universal solvent and has a high heat capacity, so the temperature of the blood remains constant.