Thursday, 9 May 2013

magnification & real size

Unit 1 quiz & answers

Unit 1 AS biology quiz  Answers - Miss Timms

1.      What kind of bond links amino acids together? Peptide bond.
2.      What type of reaction is involved in linking amino acids together? Condensation reaction
3.      What four different components make up an amino acid? Amino group, carboxyl group, r group and hydrogen atom.
4.      What is a catalyst? Catalysts alter the rate of a chemical reaction without undergoing permanent changes.
5.      Why are enzymes effective in tiny quantities? They can be reused repeatedly and are therefore effective in small quantities.
6.      Explain why enzymes function less well at lower temperatures? A reduction in temperature leads to a reduction in kinetic energy of the molecules within the reaction, so less collision occur and the reaction is slower.
7.      Why is the electron microscope able to resolve objects better than the light microscope? As the electron beam has a shorter wavelength than light.
8.      In which process are ribosomes important? Protein synthesis
9.      What is the overall function of the cell-surface membrane? It forms a boundary between the cell cytoplasm and the environment, allowing different condition to be established inside the cell compared to outside.
10.  What is the name of the blood vessel that supplies the heart muscle with oxygenated blood? Coronary arteries.
11.  List the correct sequence of the four main blood vessels and four heart chambers that a red blood cell passes through on its journey from the lungs, through the heart and body, and back again to the lungs? Pulmonary vein, left atria, left ventricle, aorta, superior and inferior vena cava, right atria, right ventricle and pulmonary artery.
12.  Indicate whether each of the following statements are true or false?
a.       The left and right ventricles contract together? True
b.      Heart muscle is myogenic? False (only in SAN and AVN)
c.       Semi-lunar valves occur between the atria and ventricles? False
d.      The wave of electrical activity from the atrioventricular node is conveyed along the bundle of His? True
e.       The wave of electrical activity from the sinoatrial node directly causes the ventricles to contract? False
13.  What is an antigen? Any part of an organism or substance that is recognised as non-self (foreign) by the immune system and stimulates an immune response.
14.  State two differences between T cells and B cells?
B cells
T cells
·         Matures in bone marrow
·         Matures in thymus gland
·         Involved in humoral immunity
·         Involved in cell-mediated immunity
·         Responds to foreign material outside body cells
·         Responds to foreign material inside body cells
·         Responds to bacteria and viruses
·         Responds to own cells altered by viruses or cancer and to transplanted tissues
15.  Explain how high temperatures (above 60 degrees) may completely prevent enzymes from functioning? Denaturation (protein unfolding and aggregation) may occur which is the permanent change of an enzyme no longer allowing it to function.
16.   Why do specimens have to be kept in a near-vacuum in order to be viewed effectively using an electron microscope? Because electrons are absorbed by the molecules in air.
17.  Name the organelle that is being referred to in each of the following descriptions?
a.       It possesses structures called cristae? Mitochondria.
b.      It contains chromatin? Nucleus.
c.       It synthesises glycoproteins? Golgi apparatus.
d.      It digests worn out organnells? Lysosomes.

Thursday, 2 May 2013

Unit 2 Quiz – The variety of living organisms- Answers

1.      State three ways in genetic variation can be increased in sexually reproducing organisms? Mutations, meiosis, fusion of gametes

2.      How is genetic variation increased in asexually reproducing organisms? Only by mutation

3.      Give definitions for interspecific variation and intraspecific variation? Interspecific – species differ from one another, intraspecific – members of the same species differ

4.      Give two reasons why a sample may not be representative of the populations as a whole? Sampling bias and chance

5.      How may sampling bias be prevented? Random sampling (divide study area into a grid, random number generator and intersection of coordinates)

6.      Draw and label a nucleotide? Phosphate, deoxyribose and organic base

7.      In terms of the structure of the DNA molecule explain why the base pairings are not A with G and T with C? C/T are single ring bases and G/A are double ring bases. The base pairs are always made up of one of each

8.      If the base pairs on one strand of DNA are TGGAGACT what is the base sequence on the other strand? ACCTCTGA

9.      If 19.9% in human DNA are G what percentage of human DNA is T? 30.1%

10.  What is a gene? A section of DNA that contains the coded information for polypeptides.

11.  How many bases of DNA are required for a chain of 6 amino acids? (triplet code) 18 bp

12.  What is the function of the protein found in chromosomes? DNA is wound around protein molecules to keep it in place (histones)

13.  In which two ways does meiosis lead to an increase to a genetic diversity? Recombination by crossing over, independent segregation of chromosomes

14.  Describe the quaternary structure of haemoglobin? Four polypeptides, two alpha, two beta – each with a Haem group containing a ferrous ion.

15.  Why is the process of DNA replication described as semi conservative? Half of the original DNA is saved and built into the new DNA molecules (P165)

16.  What are the three main stages of the cell cycle? Cell division, interphase, nuclear division (mitosis)

17.  What is a tissue? Collection of similar cells that perform a specific function

18.  Name three factors which affect the rate of diffusion of a substance into cells? (Ficks law) SA, conc gradient, diffusion distance

19.  What is meant by counter current flow and why is it an efficient means for transporting gases across fish gills?  Blood and water travel in opposite directions, constant rate of diffusion across length of gill, 80% O2 abs into blood – parallel 50%

20.  Distinguish between horizontal and vertical gene transmission? Horizontal – DNA can be passed from one species to another, vertical – genes passed down from one generation to the next within the same species.