Download File - A world of biology

The chemistry of life
Key facts
1. The most commonly occurring elements in organisms are carbon, hydrogen, oxygen and nitrogen.
2. Sulfur, calcium, phosphorus, iron and sodium are also in organisms in significant amounts.
3. Sulfur is a component of several amino acids.
4. Phosphorus is essential to ATP and nucleic acids.
5. Iron is present in a group of compounds called cytochromes. These are important in the electron transport
chains of respiration and photosynthesis.
6. Sodium is involved in nerve impulse transmission as well as to help maintain solute concentrations within
cells.
7. Calcium is essential to muscle contraction as well as acting as a coenzyme or a messenger.
8. Water has a high specific heat which allows it to absorb or give off a great deal of energy before it allows a
temperature change. Thus, this thermal property of water allows temperature regulation within organisms as
most organisms are made of a significant amount of water.
9. Water has cohesive properties. This results in attraction between water molecules. Cohesion of water
molecules allows water to move as a column of water in the vascular tissues of plants.
10. Water is a polar molecule, and because of this, it is able to dissolve any other polar substance. Because
most molecules have polar properties, water is often referred as the universal solvent. However, it can not
dissolve non-polar substances. This is especially important in the transport of substances in the blood of
humans. Blood is mostly made up of water.
11. Water is the medium for metabolic reactions.
12. When animals perspire or when plants transpire, water is acting as a coolant.
13. Compounds containing carbon that are found in living organisms (except hydrogencarbonates, carbonates,
and oxides of carbon) are regarded as organic. Therefore, carbon dioxide is not considered an organic
compound.
14. Amino acids contain the following groups: amino group (NH2), carboxyl group (COOH), and an R group
(variable).
15. Glucose is a six carbon ring structure. One carbon is outside the ring.
16. Ribose is a five carbon ring structure. One carbon is outside the ring.
17. Fatty acids contain a carboxyl group and are not a ring structure.
18. Monosaccharides are the simplest carbohydrates and include glucose, galactose, and fructose.
19. Disaccharides include two monosaccharides bonded together. Examples are maltose, lactose, and sucrose.
20. Polysaccharides are long chain carbohydrates, and include starch, glycogen, cellulose and chitin.
21. In animals glucose is carried by the blood to transport energy to cells all through the organism.
22. Lactose in animals provides energy to young mammals until they are weaned from their mothers.
23. Glycogen is used in animals to store energy in the liver and muscles.
24. In plants, fructose makes fruit sweet tasting. This attracts animals, allowing dispersal of the seeds in the
fruit.
25. Sucrose is the form of carbohydrates that is transported by the plant’s phloem (vascular tissue). It represents
an energy source.
26. Cellulose is used in plants to produce fibers that allow the construction of the cell wall.
27. In condensation two simple molecules are joined together to form a larger molecule. When this occurs
water is formed.
28. In hydrolysis larger molecules are broken down into smaller molecules. Water molecules are used up in this
reaction.
29. Four functions of lipids include: energy storage, heat insulation, buoyancy, and they are an essential part of
cellular membranes.
30. Both lipids and carbohydrates serve to store energy.
31. Lipids store twice the amount of energy as an equal mass of carbohydrates. However, carbohydrates are
more easily digested than lipids to release their energy. Also, carbohydrates are water soluble and are easier to
transport.
32. Because lipids are insoluble in water, they do not cause problems with osmosis in cells.
33. A DNA nucleotide contains a sugar (deoxyribose), a nitrogenous base (adenine, thymine, cytosine, or
guanine), and a phosphate group. Nucleotides are the building blocks of DNA.
34. Nucleotides are bonded to one another when the phosphate of one nucleotide forms a covalent bond
(phosphodiester) with the C3 of the other nucleotide.
35. DNA molecules consist of two strands of nucleotides linked together to form a double helix. Hydrogen
bonds between the bases of the two strands allow the linkage. Adenine will only pair with thymine and cytosine
will only pair with guanine. This is called complementary base pairing.
Enzymes
36. The function of enzymes is to lower the activation energy needed for reactions to occur. By doing this, the
reactions may occur faster. Enzymes are organic catalysts. They are proteins.
37. The amino acids that make up these enzymes allow a tertiary and/or quaternary structure. Because each
enzyme has a specific amino acid sequence, enzymes have a specific three-dimensional shape.
38. The molecule an enzyme affects is known as its substrate.
39. The enzyme, because of its three-dimensional shape, has a region called the active site. It is the shape of the
active site that determines which substrate it is specific for.
40. Enzymes may not cause reactions to occur that would not happen on their own.
41. Higher temperatures will increase enzyme catalyzed reaction rates until too high a temperature is reached.
At this high temperature denaturation of the enzyme occurs and the effect of the enzyme is stopped.
42. pH also will affect an enzymes reaction rate. At extreme pH levels, enzymes may be denatured, thus
stopping their effect.
43. Denaturation changes are usually permanent. Temperature and pH are the two most common factors to
cause denaturation.
44. Lactase is an enzyme that speeds up the breakdown of lactose, milk sugar. People without lactase are said
to be lactose intolerant and will experience intestinal distress when they ingest dairy products.
45. By treating dairy products with lactase before ingestion, distress may be prevented in lactose intolerant
people.
46. Increasing the amount of substrate in a chemical reaction will increase the reaction rate as long as there are
available active sites on enzyme molecules.
Complete the following.
1. Name the four most common occurring chemical elements in organisms.
2. Name two compounds that always contain phosphorus.
3. What causes water to be a polar molecule?
4. Describe or diagram how two water molecules could produce a hydrogen bond between them.
5. Explain how water helps to maintain body temperature in humans.
6. Tell whether the following compounds are organic or inorganic:
a. CO2 _________________
b. CH4 __________________________
c. H2O _________________
d. C6H12O6 ________________________
7. Large molecules of organic compounds are called macromolecules and are made up of specific sub-units.
What are the subunits of:
a. carbohydrates ______________________
b. proteins ____________________
c. lipids _______________________
d. nucleic acids ____________________
8. Name three polysaccharides.
9. What monosaccharide is carried by the blood to transport energy to cells throughout the body?
10. What disaccharide provides energy to young mammals before they are weaned?
11. Of what value is cellulose to plants?
12. Where in animals would one find energy stored as glycogen?__________________
13. Explain what, in general, happens in all condensation reactions.
14. Explain what, in general, happens in all hydrolysis reactions.
15. Tell whether the following represents hydrolysis or condensation.
a. amino acid + amino acid --------- dipeptide + water ______________
b. glucose + fructose ----------- sucrose + water ________________
c. glycogen + water ----------- monosaccharides ________________
d. lipid + water ---------------- glycerol + fatty acids ________________
16. What form of lipids provide energy storage in plants?______________ in animals?______________
17. What is the difference between CIS and TRANS fats?
18. What are the three parts of a nucleotide?
19. What bases always connect by complementary base-pairing in DNA?
20. What are the 2 types (shapes) of secondary proteins? (Simple protein folding on website)
21. Using the Types of Proteins on website:
Enzymes: What does lactase do?
Regulatory: What does p53 do?
Motor: What do Dynein and Kinesin do?
Transport: Channel proteins move what ions in a nerve cell?
Storage: Where do we find ovalbumin and gluten?
22. How does an enzyme compare to a catalyst?
23. What is the specific part of the enzyme that attaches to a substrate?
24. How does the induced-fit model of enzyme specificity differ from the lock-and-key model?
25. How do enzymes speed up chemical reactions?
26. What happens in denaturation?
27. What will happen to an enzyme’s effect when denaturation occurs?
28. Name two specific agents that may cause enzyme denaturation. Give an example of each.
29. On the graph to the left, label temperature as the x-axis and enzyme activity as the y-axis, show the general
effect of temperature. On the graph annotate where denaturation occurs.
30. Similarly to number 76, on the graph to the right above, show the effect of substrate concentration.
31. Explain the effect of increasing substrate concentration of the rate of chemical reaction that is being
catalyzed by an enzyme.
32. Explain the action of the enzyme lactase.
33. Some people are lactose intolerant. How might lactase be used to help people with this condition?