Science Study Guide PDF: Energy, Photosynthesis, DNA

Study Guide Week 6: Energy and Photosynthesis 1. What is active transport? ◦ Active transport is the movement of molecules across a membrane against their concentration gradient, from low to high concentration, using energy (often in the f...

Study Guide Week 6: Energy and Photosynthesis 1. What is active transport? ◦ Active transport is the movement of molecules across a membrane against their concentration gradient, from low to high concentration, using energy (often in the form of ATP). 2. Name three kinds of cellular work that require energy. ◦ Chemical work (e.g., building molecules), mechanical work (e.g., muscle contraction), and transport work (e.g., pumping substances across membranes). 3. Distinguish between macronutrients and micronutrients. ◦ Macronutrients (e.g., carbohydrates, proteins, fats) are needed in large amounts for energy and growth. Micronutrients (e.g., vitamins, minerals) are required in smaller amounts but are essential for biochemical processes. ◦ We obtain these nutrients from food, and macronutrients must be broken down into their monomers before the body can use them. 4. Why does relying on a single crop for food cause malnutrition? ◦ A single crop may lack the variety of nutrients needed for a balanced diet, leading to de ciencies. Malnutrition is more critical for children under 2, as their growth and development require diverse nutrients. 5. Difference between catabolic and anabolic reactions. ◦ Catabolic reactions break down molecules to release energy. Anabolic reactions build molecules and require energy. 6. How does an enzyme make a chemical reaction possible? ◦ Enzymes lower the activation energy needed for a reaction to occur. Their shape is critical as it determines their ability to bind with speci c substrates. Covalent bonds typically don't spontaneously form or break in a cellular environment without the help of enzymes. 7. Do monomers build up into polymers in the absence of enzymes? fi fi  ◦ No, enzymes are needed to catalyze the polymerization of monomers into polymers. 8. What is the Energy of Activation (Activation Barrier)? ◦ The energy required to start a chemical reaction. Enzymes lower this energy barrier to make reactions occur more easily. 9. Enzymes as biological catalysts. ◦ Enzymes are proteins, and their shape is critical for binding substrates and catalyzing reactions. 10. De ne exergonic vs. endergonic reactions. ◦ Exergonic reactions release energy (e.g., breakdown of ATP). Endergonic reactions require energy input. 11. What is the ATP cycle? ◦ ATP is broken down to ADP to release energy, which can be used by the cell. ADP is then converted back into ATP through cellular respiration. 12. What is an essential mineral? ◦ Minerals that the body cannot make on its own and must be obtained through the diet. 13. Explain the photo vs. synthesis in photosynthesis. ◦ The "photo" part refers to the light reactions, which capture light energy and convert it to chemical energy. The "synthesis" part refers to the Calvin Cycle, where CO2 is used to make sugars. 14. Do mitochondria make energy? ◦ Mitochondria convert energy stored in food into ATP but do not create energy from nothing. 15. Where did the energy in fossil fuels come from? ◦ Fossil fuels derive their energy from ancient plants and animals. They are considered non-renewable because their formation takes millions of years. 16. Why are biofuels from algae a good alternative? fi  ◦ Algae-based biofuels are renewable and can absorb CO2 during growth, helping reduce the amount of CO2 in the atmosphere. 17. What is energy? ◦ Energy is the ability to do work. Kinetic energy is energy of motion, and potential energy is stored energy. Chemical energy is a form of potential energy stored in bonds. 18. Summarize the two laws of thermodynamics. ◦ 1st Law: Energy cannot be created or destroyed, only transformed. ◦ 2nd Law: Energy transformations increase disorder (entropy). 19. Name the three types of cellular work. ◦ Chemical work, mechanical work, and transport work. 20. Inputs and outputs of photosynthesis. ◦ Inputs: CO2, H2O, light energy. Outputs: glucose, O2. ◦ Photosynthesis occurs in the chloroplast. 21. What is glucose used for in cells? ◦ Glucose is used for energy (ATP production), storage (glycogen), and building materials for cellular structures. 22. De ne autotroph and heterotroph. ◦ Autotrophs produce their own food (e.g., plants). Heterotrophs obtain food by consuming other organisms. 23. What is chlorophyll? ◦ Chlorophyll is the pigment in plants that absorbs light energy. Shorter waves have more energy than longer waves. 24. Electron transport chain in chloroplasts. ◦ Electrons ow through the electron transport chain, pumping H+ across the membrane, and ATP is generated via facilitated diffusion. 25. What is carbon xation? fi fl fi  ◦ The process of incorporating CO2 into an organic molecule during the Calvin Cycle. Week 7: Cellular Respiration & Fermentation 1. Explain the relationship between photosynthesis and cellular respiration. ◦ Photosynthesis converts light energy into chemical energy (glucose), while cellular respiration breaks down glucose to release energy (ATP). Photosynthesis occurs in plants, and cellular respiration occurs in both plants and animals. 2. Stages of cellular respiration. ◦ Glycolysis (cytoplasm), Citric Acid Cycle (mitochondria), and Electron Transport Chain (mitochondria). Oxygen is used in the electron transport chain, and CO2 is generated in the citric acid cycle. 3. Electron carriers NAD+/NADH. ◦ Electrons come from the breaking of covalent bonds in glucose molecules. 4. Process producing high-energy C-C bonds in sugar. ◦ Photosynthesis, with the energy coming from sunlight. 5. ATP synthase and H+ diffusion. ◦ ATP synthase allows H+ to diffuse across the membrane to generate ATP. 6. Role of oxygen in cellular respiration. ◦ Oxygen is the nal electron acceptor in the electron transport chain. Without it, aerobic respiration cannot occur, and cells rely on fermentation. 7. Where is CO2 produced? ◦ CO2 is produced during the citric acid cycle of cellular respiration. 8. Which stage of cellular respiration produces the most ATP? ◦ The electron transport chain produces the most ATP. 9. Fermentation vs. cellular respiration. ◦ Fermentation occurs in the absence of O2 and produces much less ATP than cellular respiration. fi  10. Role of fermentation in NAD+ regeneration. Fermentation regenerates NAD+ to allow glycolysis to continue producing ATP. 11. Compare NAD+/NADH. NAD+ is oxidized (has lost electrons), while NADH is reduced (has gained electrons). Week 8: DNA Discovery and Structure DNA Discovery: 1. Why did many scientists think that protein, and not DNA, was likely to be the molecule of inheritance? ◦ Proteins were thought to be the molecule of inheritance because they are complex and diverse in structure and function, which made them appear more likely to carry genetic information. 2. Explain how the following pieces of evidence lead to the model of DNA as a double helix with complementary, antiparallel strands: ◦ 1) The amount of A always equals T, and G equals C – This suggests that A pairs with T, and G pairs with C, indicating complementary strands. ◦ 2) The sugar-phosphate backbone is on the outside – This is consistent with a structure where the bases, which form the genetic code, are protected inside. ◦ 3) The diameter of the helix is uniform – This is consistent with base pairing (A- T, G-C) where each pair is of similar size, maintaining a uniform diameter. 3. Why does Watson & Crick’s model of DNA immediately suggest a mechanism where it can be faithfully copied each time a cell divides? ◦ The complementary base pairing (A-T, G-C) allows one strand to act as a template for the synthesis of the other, ensuring that each strand is accurately replicated. 4. What aspect of the model must account for the variations between individuals? ◦ The sequence of bases (A, T, C, G) in the DNA determines genetic variation, accounting for individual differences. 5. What is a monomer of the DNA polymer? ◦ The monomer of DNA is a nucleotide, which consists of a sugar, phosphate group, and a nitrogenous base (A, T, C, or G).  6. What was Rosalind Franklin’s role in the discovery of DNA structure? ◦ Rosalind Franklin’s X-ray crystallography images were crucial in revealing the helical structure of DNA. She was not awarded the Nobel Prize because of her untimely death, and the award went to Watson, Crick, and Wilkins. DNA Structure, Replication, and Applications 1. Where are the covalent bonds in a DNA molecule? The hydrogen bonds? ◦ Covalent bonds: Found between the sugar and phosphate molecules in the backbone. ◦ Hydrogen bonds: Found between complementary base pairs (A-T, G-C). 2. What aspect of DNA’s structure must account for the variations between individuals? ◦ The sequence of nitrogenous bases in the DNA accounts for individual genetic variation. 3. If given the nucleotide sequence of a single strand of DNA, be able to give the complementary sequence. ◦ Practice complementary base pairing: A pairs with T, G pairs with C. 4. De ne "antiparallel" in the DNA structure. ◦ Antiparallel means that the two strands of DNA run in opposite directions (5' to 3' and 3' to 5'). 5. What enzyme replicates DNA? ◦ DNA polymerase is the enzyme responsible for DNA replication. 6. What is semiconservative replication? ◦ Semiconservative replication means that each new DNA molecule consists of one original strand and one newly synthesized strand. 7. Explain the role of the following in DNA replication: ◦ Helicase: Unwinds the DNA double helix. ◦ Primase: Synthesizes a short RNA primer to initiate replication. ◦ Single-strand binding proteins: Prevent the separated strands from rejoining. fi  ◦ DNA polymerase: Adds nucleotides to the growing DNA strand. 8. Explain the statement: “DNA synthesis cannot occur de novo.” ◦ DNA polymerase requires a primer to start synthesis; it cannot begin a new strand without an existing piece of nucleic acid. 9. What is DNA pro ling? ◦ DNA pro ling is a method used to identify individuals based on their unique DNA sequence. It’s often used in criminal investigations to match DNA samples. 10. What is PCR (Polymerase Chain Reaction)? ◦ PCR is a technique used to amplify small amounts of DNA, making millions of copies of a speci c DNA segment. 11. How much DNA do you need to do a successful PCR ampli cation of a target DNA sequence? ◦ Only a small amount of DNA is needed, often just a few cells worth of DNA, or even a single molecule. Week 9: DNA Structure, Replication, and Applications 1. Why are STRs (Short Tandem Repeats) used as target DNA sequences for DNA testing? ◦ STRs are highly variable between individuals, making them useful for identifying individuals based on their unique DNA patterns. 2. What is gel electrophoresis? ◦ Gel electrophoresis is a technique used to separate DNA fragments based on their size by applying an electric eld to a gel matrix. 3. Why is blood type determination not an acceptable method to positively identify a potential crime suspect? ◦ Blood type is not unique to individuals; many people can share the same blood type, so it’s not useful for identi cation in criminal cases. 4. Review case study questions from the posted slides. ◦ Be sure to review any practice or case study questions provided in your slides for a deeper understanding of DNA testing techniques. fi fi fi fi fi fi  5. Each known STR has many associated alleles. De ne allele in this context. ◦ An allele is a variant form of a gene or genetic marker, such as an STR, that can differ between individuals. 6. If we know the frequency of a particular STR allele in the general population, how can we determine the likelihood that a certain combination of alleles would occur? ◦ By multiplying the frequencies of the alleles at each STR locus, we can calculate the probability of a speci c combination occurring in the population. 7. De ne homozygous and heterozygous in the context of STRs. ◦ Homozygous: Having two identical alleles for a particular STR. ◦ Heterozygous: Having two different alleles for a particular STR. Gene Expression: 1. Do all cells make all the possible proteins at all times? ◦ No, gene expression is regulated so that different proteins are made in different cells at different times depending on the cell's function and environmental conditions. 2. What are the roles of the regulatory region and coding region in gene expression? ◦ Regulatory region: Controls when and how much a gene is expressed. ◦ Coding region: Contains the instructions for making the protein. 3. Where does replication, transcription, and translation occur in a eukaryotic cell? ◦ Replication: Nucleus ◦ Transcription: Nucleus ◦ Translation: Cytoplasm (on ribosomes) 4. Review structural differences between DNA and RNA. ◦ DNA: Double-stranded, uses deoxyribose sugar, bases are A, T, C, G. ◦ RNA: Single-stranded, uses ribose sugar, bases are A, U, C, G. 5. Explain how DNA is the template for RNA production. fi fi fi  ◦ The DNA's coding region serves as a template for RNA polymerase, which synthesizes an RNA strand by matching complementary RNA bases to the DNA template. 6. What is a codon? ◦ A codon is a three-nucleotide sequence in mRNA that codes for an amino acid. 7. What is tRNA? ◦ tRNA is a type of RNA that carries amino acids to the ribosome for protein synthesis. The anticodon on tRNA binds to the complementary codon on mRNA. 8. Did you know that the ribosome is an enzyme? ◦ Yes, ribosomes catalyze the formation of peptide bonds between amino acids during protein synthesis. 9. What is a mutation? ◦ A mutation is a change in the DNA sequence. Not all mutations affect protein function, as some may occur in non-coding regions or lead to silent mutations. Week 10: The Cell Cycle, Cancer, and Mitosis Cancer and Regulation of the Cell Cycle: 1. Cancer cells have escaped the regulation of the cell cycle. What is the result? ◦ Cancer cells divide uncontrollably and can invade other tissues. 2. What is the most preventable cause of cancer in the U.S.? ◦ Tobacco use is the most preventable cause of cancer. 3. What is the difference between a benign and a malignant tumor? ◦ A benign tumor is localized and doesn’t spread, while a malignant tumor is invasive and can metastasize. 4. What is the difference between proto-oncogenes and tumor suppressor genes? ◦ Proto-oncogenes promote cell division, but when mutated, they become oncogenes, leading to cancer.  ◦ Tumor suppressor genes regulate cell division and prevent cancer, but mutations can lead to cancer. 5. How many mutations must accumulate in a cell before uncontrolled cell division results? ◦ Typically, multiple mutations must accumulate in key genes for cancer to develop. Mitosis: 1. What kinds of cells undergo mitosis? ◦ Somatic cells, such as skin and muscle cells. 2. What is the end result of a single mitotic cell division? ◦ Two genetically identical daughter cells. 3. Trace the physical path of chromosomes through the stages of mitosis. ◦ Prophase: Chromosomes condense. ◦ Metaphase: Chromosomes align at the center. ◦ Anaphase: Chromatids are pulled apart. ◦ Telophase: New nuclei form. 4. How many chromosomes and chromatids are present at each step of mitosis? ◦ The number of chromatids doubles during mitosis, but the number of chromosomes remains constant. Week 11: Meiosis 1. What is the difference between a haploid and a diploid cell? 2. What do we mean when we say that two chromosomes are homologous? 3. Meiosis generates haploid daughter cells from a diploid parent cell. Explain what that means in terms of the numbers of chromosomes present in the parent cell vs the daughter cells. 4. Only one kind of cell is produced by meiosis in animals. Which cell type? 5. Understand the steps of meiosis 1 and meiosis 2. In which step are homologous chromosomes separated from each other? In which are the sister chromatids separated? 6. Where does DNA replication occur? (hint: not in m-phase!!) 7. Trace the physical path of the chromosomes/chromatids through meiosis. 8. Compare and contrast the two stages of meiosis. Which stage is very similar to mitosis? 9. What kind of cell can do mitosis (haploid or diploid)? What kind of cells can do meiosis (haploid or diploid)? Inheritance 1. De ne the terms gene, allele, genotype, phenotype, homozygous, heterozygous, dominant, fi recessive. 2. What is meant by the term “gene loci” in the context of homologous chromosomes? 3. In a heterozygote, which allele determines the phenotype (dominant or recessive)? 4. Understand the P, F1, F2 terminology. 5. If given information about the parents, be able to predict the expected pattern of offspring phenotype & genotype 6. If you know information about an organism’s genotype, be able to predict all the possible gametes produced by the organism. 7. Do X-linked recessive genetic diseases affect XX or XY individuals most often? Why? 8. How can a karyotype reveal aneuploidy?