Review Questions and Answers

Chapter 1 – Sport and Exercise in the Life Sciences

1) The first ever DNA sequence of a eukaryotic organism was completed in 1996, what was the organism? What further whole organism DNA sequences have been completed since?

The first ever DNA sequence to be elucidated was that of the yeast (saccharomyces cerevisiae; domain – eukarya, kingdom – fungi). The number of completely sequenced genomes has risen rapidly over recent years, with the human genome now completely sequenced, along with that of other eukaryotic organisms such as a nematode (worm) – ceanorhabditis elegans, and other animals such as the mouse and at least two plants. Furthermore, genome sequences currently exist for over one hundred bacteria and archea.

2) What is the difference between genotype and phenotype?

Genotype refers to the genetic make up of an individual at a molecular level comprising the entire gene set, with phenotype being the observable characteristics or attributes resulting from the genotype.

3) Humans share the common feature of life with other organisms. What are the essential characteristics of life?

Humans share common features of life with other organisms. Essential characteristics of life include an ordered structure, adaptability (e.g. to evolutionary pressures), the ability to respond to the environment, the ability to regulate (e.g. body fluid, temperature), to metabolise energy, to grow and develop, and to reproduce.

4) Explain the synthesis of protein from the DNA code to the exit of protein from the cell. Where in the cell do transcription and translation take place?

• Two DNA chains break away from each other and become templates for the formation of further DNA strands.
• The segment of DNA containing a gene is used to produce messenger RNA in a process termed transcription which occurs in the nucleus of the cell.
• RNA is required to read the DNA code and translate it into proteins.
• The messenger RNA strand diffuses out of the nucleus and into the cytoplasm where ribosomes transfer the genetic message into polypeptides.
• Three stages – initiation, elongation and termination.
• A further type of RNA, transfer RNA is required for this process, to transfer amino acids to the polypeptide chain on the ribosome.
• The translation, linking of amino acids in the cytoplasm, stops when a particular sequence of amino acids occurs, this is termination.

5) What are the five most abundant chemical elements in the body? Macromolecules are made up of the four most abundant plus the sixth, phosphorous. What are the main characteristics of each class of macromolecule?

• Carbon
• Oxygen
• Hydrogen
• Nitrogen
• Calcium
  
  
  Macromolecules:
• Carbohydrates: Sugar, starch, use carbon (C), hydrogen (H) and oxygen (O), almost equally, and are often abbreviated as ‘CHO's’.
• Proteins use carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and sulphur (S) for their building blocks, and they are often ‘decorated’ with phosporus (P).
• Fats are almost entirely carbon (C) and hydrogen (H) with very little oxygen (O). The phospholipids that make up the cell walls also contain phosphorus (P) and usually some nitrogen (N).
• Nucleic Acids: DNA and RNA are composed of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P).

6) What are the major components found in human cells and what are their functions?

• Nucleus: the nucleus serves as the cell's command center, sending directions to the cell to grow, mature, divide or die. It also houses DNA (deoxyribonucleic acid), the cell's hereditary material. The nucleus is surrounded by a membrane called the nuclear envelope, which protects the DNA and separates the nucleus from the rest of the cell.
• Ribosomes: organelles that process the cell's genetic instructions to create proteins. These organelles can float freely in the cytoplasm or be connected to the endoplasmic reticulum.
• Endoplasmic reticulum: this organelle helps process molecules created by the cell and transport them to their specific destinations either inside or outside the cell.
• Golgi bodies: the golgi apparatus packages molecules processed by the endoplasmic reticulum to be transported out of the cell.
• Mitochondria: complex organelles that convert energy from food into a form that the cell can use. They have their own genetic material, separate from the DNA in the nucleus, and can make copies of themselves.
• Lysosymes: they digest macromolecules safely withuth allowing digestive enzymes to directly affect the cell. Also act upon foreign bacteria that invade the cell, rid the cell of toxic substances, and recycle worn-out cell components.
• Peroxisomes: protect the cell from its own production of hydrogen peroxide.
• Proteasomes: main engines of non-lysosymal protein degradation and recycling in the cell, focussing on misfolded and short-lived proteins.
  

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