Lab 3

Question 1

Enzymes

Answer 1

• are catalysts that speed up chemical reactions but are not themselves consumed or changed by the reactions.
• speed up chemical reactions by lowering the activation energy required to make reactions proceed within the narrow range of temperatures in which living organisms function.
• Without enzymes, most biochemical reactions would take place at a rate far too slow to keep pace with the metabolic needs and other life functions of organisms.
• Most enzymes are proteins. = is a sequence of amino acids (primar y structure) that is folded in a three-dimensional shape.
  –> complex ones

Question 2

Hydrogen bonds in proteins

Answer 2

Hydrogen bonds along the polypeptide backbone (secondar y structure) create coils and folds in the protein that contribute to its overall shape.

Question 3

active site

Answer 3

The complex 3-D structure of enzymes, consisting of one or more folded polypeptide chains, includes the formation of an active site - a special area into which the substrate (material to be acted on by the enzyme) will fit

Question 4

Enzyme specificity

Answer 4

is due to the structure of the enzyme’s active site which must match the shape of the substrate molecule it acts upon. The interaction of the active site with the substrate lowers activation energy.

Question 5

Factors that can change the shape of enzymes

Answer 5

Enzymes are complex proteins , therefore,
- changes in temperature
- alterations in pH
- the addition of certain ions or molecules
- the presence of inhibitors all may affect the structure of an enzyme’s active site

and thus the activity of the enzyme and the rate of the reaction in which it participates.

• rate of an enzymatic reaction can also be affected by the relative concentrations of enzyme and substrate in the reaction mixture.

Question 6

The effect of temperature on the rate of an enzyme

Answer 6

• catalyzed reaction increases as temperature increases, up to a point at which the rate is maximum.
• This temperature is usually close to the optimal temperature for an organism. The rate then declines with a further increase in temperature
• Increased temperature increases molecular movement/ vibration.
• Once the temperature climbs above 50°C, most proteins in living tissue become denatured - their secondary or tertiary protein structure breaks down due to the increased kinetic energy.

Question 7

The Effect of pH on Enzyme Action

Answer 7

• The presence of ions can interfere with the pattern of positive and negative charges within a protein molecule, thus changing the way the protein folds.
• Enzyme: shape of the active site may be changed.
  –> expect, then, that changes in pH (reflecting the concentrations of hydrogen and hydroxide ions) would affect the action of enzymes.
• most favorable pH value (when the enzyme is most active) is the optimum pH.
• Extremely high or low pH values usually result in a complete loss of enzyme activity due to denaturation , the breakdown of the secondar y and tertiary structure of a protein.

Question 8

Lactase

Answer 8

• an enzyme that catalyzes the hydrolysis of lactose.
• Lactose is a disaccharide, made of glucose and galactose, that is found in dairy products.
• When a person consumes dairy products, the lactose is converted into galactose and glucose by the lactase enzyme

Question 9

lactose intolerant

Answer 9

• which means unable to digest lactose.
• People with lactose intolerance do not have enough lactase enzymes to digest lactose.
  –> all depends on how much lactase enzyme each person makes, which is determined by genetics.
• This results in lactose accumulating in the large intestine, where it is fermented by bacteria.
• Fermentation of lactose by bacteria creates a lot of gas, which is the cause of abdominal discomfort for people who are lactose intolerant.

Question 10

over the counter lactase

Answer 10

• over the counter products that contain the enzyme lactase
• The enzyme supplement must first pass through the stomach, where the pH can range from pH 1 (empty stomach) to pH 5 (full stomach), to get to the small intestine (pH 8) where the lactase will hydrolyze lactose into galactose and glucose.

Question 11

Enzyme assay

Answer 11

• Therefore, we will use a substrate that is similar to lactose, ONPG, which can be used in place of lactose.
• ONPG consists of galactose and o-Nitrophenol that are joined by a bond that is cleaved by lactase
• The products are galactose and o-nitrophenolate; o-nitrophenolate is yellow in color and can be measured by spectrophotometry.

Question 12

Renewable energy

Answer 12

• refers to energy created from processes that make energy at the same rate, or faster, than the energy consumed.

Exs: Solar, wind, hydro, and geothermal.

• The development of less harmful and renewable energy sources is critical to the health of our planet. b/c form. Fossil fuels (nonrenewable) are major contributors to greenhouse gas emissions

Question 13

Ethanol fermentation process

Answer 13

• is a combustible fuel that burns cleaner than gasoline and is obtained by the fermentation of sugar by microorganisms.
• source of sugar used for fermentation to produce ethanol comes from plant material.
• ethanol produced via fermentation is distilled and then blended with gasoline to create a cleaner source of fuel.
• Not only does ethanol combustion release less carbon monoxide and dioxide, the CO 2 that is produced will then be absorbed by growing plants used to make the ethanol.
• Overall, this leads to a balance in the amount of CO 2 produced with the amount of CO 2 absorbed, and a renewable source for ethanol production.

Question 14

Ethanol production

Answer 14

• made by the process of fermentation in microorganisms.
• Organisms rely on generating energy from sugar and the first step in this process is glycolysis.
• Glycolysis is accomplished by converting glucose into two molecules of pyruvate and does not require oxygen as a reactant.
• Metabolic pathways for further catabolism can continue to occur anaerobically (in the absence of oxygen) by fermentation or more commonly and efficiently through the use of oxygen (aerobically) by cellular respiration

Question 15

Glycolysis

Answer 15

(glucose catabolism) means “splitting of sugar” and represents an almost universal initial method of liberating the potential chemical energy stored within glucose for cellular work ( ATP)

Question 16

Saccharomyces cerevisiae (Baker’s yeast)

Answer 16

• a facultative anaerobe
• can metabolize sugars under either aerobic (cellular respiration) or anaerobic (fermentation) conditions.
• The process of fermentation in yeast generates ethanol and CO 2 (not ATP).
• The ethanol generated by this process is the product being used in the biofuels industry.
• It is important to note that ethanol is toxic to yeast , which limits how much alcohol can be produced via fermentation.
• Single celled organisms can survive on fermentation alone (i.e.- no oxygen) because the process recycles NAD+ so that glycolysis can continue, where small amounts of ATP can be produced.

Question 17

First-generation biofuels

Answer 17

• The most common sources of plant material to generate biofuel worldwide are corn and sugarcane; known as first-generation biofuels.
• North America climate conditions support the growth of corn which contains a large amount of starch
• starch is first broken down into fermentable sugars (monosaccharides) through enzymatic or acid treatment.
• Yeast don’t have the enzymes to break down starch, therefore this is done prior to fermentation.
• glucose is then converted into ethanol by yeast.

Question 18

starch

Answer 18

is a polysaccharide: carbohydrates of simple sugars linked together

Question 19

The use of corn and sugarcane crops for fuel raises serious ethical and environmental concerns.

Answer 19

• considered the fossil fuel used to produce and harvest the corn and then convert it into ethanol,
• Both sugarcane and corn based production of ethanol have the potential to drive up food prices.
• As demand for corn to supply ethanol refineries rises, so have corn prices, resulting in higher prices for consumers on a wide range of products due to less food availability.
• Although sugarcane ethanol production is more efficient, there are serious environmental concerns with the fact that the sugarcane is being grown on newly cleared land from the rainforest.
• There are serious implications of losing large parts of the rainforest that act as a valuable sink for greenhouse gases (as well as the loss of biodiversity that goes with the forest!).
• Due to these concerns, there are advantages to using non-consumable raw materials for fuel production: cellulose-based biomass.