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Answers to the Practice Questions for Midterm 2: Note: Answers are in red. 1. Enzymes are used to activate and speed up all types of cellular reactions, both endergonic and exergonic. a. Explain the difference between these two types of reactions. Endergonic reactions require energy input and result in the conversion of low energy molecules to high energy molecules (i.e. carbon dioxide and water combining to form glucose is an endergonic reaction) Exergonic reactions release energy and result in the conversion of high energy molecules to low energy molecules (i.e. conversion of ATP to ADP) b. Why would enzymes be necessary to activate exergonic reactions? Most reactions, even exergonic ones, require and initial input of energy in order to get the reaction going. This activation energy requires that the cell heat up to very high temperatures in order to proceed, which would harm the cell. Enzymes help lower the activation energy of reactions.
2. Fill in the blank below with the correct term and complete the statement with the correct explanation. Allosteric regulation of enzymes is an example of a _negative_ feedback loop because.... the production of the product subsequently interferes in enzyme function and shuts off the enzyme activity which stops ore product being formed.
3. What is the role of oxygen in cellular respiration? Oxygen is the final electron acceptor in cellular respiration.
4. Where in the cell do the following processes of cellular respiration take place and what are the products of each of these reactions? a) glycolysis - occurs in cytosol and produces ATP and glucose derivatives (pyruvate) b) Kreb's cycle - occurs in mitochondria and produces ATP and carbon dioxide c) electron transport chain - occurs in mitochondria and produces ATP and water
5. Below is a schematic diagram of the two parts of photosynthesis. Fill in the blanks with the appropriate reactants or products. Note: each blank is for a single reactant or product.
6. List the key events that occur during the following phases of cell division/mitosis: a) metaphase - chromosomes line up along the cell center (equator) b) telophase - chromosomes reach the poles, nuclear membrane reforms c) anaphase - separation of sister chromatids towards the poles d) cytokinesis - the cell membrane starts to pinch off and separate the daughter cells e) prophase - chromosomes condense, nuclear membrane breaks down, centrosomes move towards the poles f) interphase - cell growth and DNA replication
7. Fill in the blanks below with either diploid or haploid to correctly complete the statement. During meiosis, the parent cell is _diploid_ and the daughter cells (gametes) are _haploid_.
8. You conduct a cross between two flowers for flower
color and plant height. If the genotypes of the flowers are: PpTT x PPTt, what
are resulting phenotypes and their proportions in the offspring?
9. In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and white (rr) homozygotes. When two roan cattle are crossed, the phenotypes of the progeny are found to be in the ratio of 1 red:2 roan:1 white. Which of the following crosses could produce the highest percentage of roan cattle? a) white x roan b) roan x roan c) red x white d) red x roan e) All of the above crosses would give the same percentage of roan.
10. Why do X-linked conditions appear more frequently in males than in females? Females have two copies of the X chromosome, so they usually have one functional copy which results in a normal phenotype. 11. A person who is heterozygous for the Huntington disease allele has offspring with someone who does not have HD. What proportion of their children will have HD? a) 1/16
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©2003-2004 Dilek Sanver-Wang, MS
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