Energy and Photosynthesis

Week 6: Energy and Photosynthesis

• Active transport involves the movement of molecules across a membrane against the concentration gradient, from low to high concentration, using energy like ATP.
• Three kinds of cellular work that require energy: chemical, mechanical, and transport work.
• Macronutrients (e.g., carbohydrates, proteins, fats) are needed in large amounts for energy and growth, while micronutrients (e.g., vitamins, minerals) are required in smaller amounts.
• Both macronutrients and micronutrients are essential for biochemical processes and are obtained from food; macronutrients must be broken down into monomers before use.
• Relying on a single crop for food can cause malnutrition due to a lack of diverse nutrients, which is especially critical for children under 2.
• Catabolic reactions break down molecules to release energy, whereas anabolic reactions build molecules and require energy.
• Enzymes lower the activation energy needed for a reaction by binding to specific substrates because their shape allow them to do so.
• Enzymes are needed to catalyze the polymerization of monomers into polymers.
• The energy of activation refers to the energy required to start a chemical reaction, which is lowered by enzymes to make reactions occur more easily.
• Enzymes are proteins, and their shape is critical for binding substrates and catalyzing reactions as biological catalysts.
• Exergonic reactions release energy (e.g., breakdown of ATP).
• Endergonic reactions require energy input.
• During the ATP cycle, ATP is broken down to ADP, releasing energy that can be used by the cell, and ADP is then converted back into ATP through cellular respiration.
• An essential mineral cannot be made by the body and must be obtained through the diet.
• In photosynthesis, the "photo" part refers to light reactions capturing light energy and converting it to chemical energy, while the "synthesis" part refers to the Calvin Cycle, where CO2 is used to make sugars.
• Mitochondria convert stored energy in food into ATP but do not create energy from nothing.
• Fossil fuels derive their energy from ancient plants and animals and are considered non-renewable due to their formation taking millions of years.
• Algae-based biofuels are renewable, absorb CO2 during growth, and help reduce the amount of CO2.
• Energy is the ability to do work.
• Kinetic energy is energy of motion, while potential energy is stored energy; chemical energy is a form of potential energy stored in bonds.
• The 1st law of thermodynamics: Energy cannot be created or destroyed, only transformed.
• The 2nd Law of Thermodynamics: Energy transformations increase disorder (entropy).
• Three types of cellular work: chemical, mechanical, and transport work.
• Photosynthesis inputs: CO2, H2O, and light energy.
• Photosynthesis outputs: glucose and O2.
• Photosynthesis occurs in the chloroplast.
• Glucose is used for energy (ATP production), storage (glycogen), and building materials for cellular structures.
• Autotrophs produce their own food (e.g., plants), while heterotrophs obtain food by consuming other organisms.
• Chlorophyll is the pigment in plants that absorbs light energy, with shorter waves having more energy than longer waves.
• In chloroplasts, electrons flow through the electron transport chain, pumping H+ across the membrane, and ATP is generated through facilitated diffusion.
• Carbon fixation entails the process of incorporating CO2 into an organic molecule during the Calvin Cycle.

Week 7: Cellular Respiration & Fermentation

• 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.
• The stages of cellular respiration include 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.
• Electrons for the electron transport chain come from the breaking of covalent bonds in glucose molecules.
• Photosynthesis, with the energy coming from sunlight, produces high-energy C-C bonds in sugar.
• ATP synthase allows H+ to diffuse across the membrane to generate ATP.
• Oxygen is the final electron acceptor in the electron transport chain; without it, aerobic respiration cannot occur, and cells instead rely on fermentation.
• CO2 is produced during the citric acid cycle of cellular respiration.
• The electron transport chain produces the most ATP.
• Fermentation occurs in the absence of O2 and produces much less ATP than cellular respiration.
• Fermentation regenerates NAD+ to allow glycolysis to continue producing ATP.
• NAD+ is oxidized (has lost electrons), while NADH is reduced (has gained electrons).

Week 8: DNA Discovery and Structure

DNA Discovery

• Proteins were initially thought to be the molecules of inheritance due to their complexity and diversity.
• The amount of A always equals T, and G equals C, which suggests that A pairs with T, and G pairs with C, indicating complementary strands.
• The sugar-phosphate backbone is on the outside, consistent with bases being protected inside.
• The uniform diameter of the helix is consistent with base pairing (A-T, G-C) where each pair is of similar size.
• Watson & Crick's model suggests that complementary base pairing (A-T, G-C) allows one strand to act as a template for synthesizing the other.
• The sequence of bases (A, T, C, G) in the DNA accounts for individual differences.
• A nucleotide, which consists of a sugar, phosphate group, and a nitrogenous base (A, T, C, or G), is the monomer of DNA.
• Rosalind Franklin's X-ray crystallography images were crucial in revealing the helical structure of DNA.

DNA Structure, Replication, and Applications

• Covalent bonds are found between the sugar and phosphate molecules in the backbone.
• Hydrogen bonds are found between complementary base pairs (A-T, G-C).
• The sequence of nitrogenous bases in the DNA accounts for genetic variation between people.
• A pairs with T, and G pairs with C when practicing complementary base pairing.
• Antiparallel means that the two strands of DNA run in opposite directions (5' to 3' and 3' to 5').
• DNA polymerase is the enzyme responsible for DNA replication.
• Semiconservative replication means that each new DNA molecule consists of one original strand and one newly synthesized strand.
• 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.
• DNA polymerase adds nucleotides to the growing DNA strand.
• DNA polymerase requires a primer to start synthesis; it cannot begin a new strand without an existing piece of nucleic acid.
• DNA profiling, often used in criminal investigations, identifies individuals based on their unique DNA sequence.
• PCR amplifies small amounts of DNA, making millions of copies of a specific DNA segment.
• Only a small amount of DNA is needed for a successful PCR amplification.

Week 9: DNA Structure, Replication, and Applications

• STRs are highly variable between individuals, making them useful for identifying individuals based on their unique DNA patterns.
• Gel electrophoresis separates DNA fragments based on their size using an electric field and a gel matrix.
• Blood type is not unique to individuals, so it's not useful for identification in criminal cases.
• An allele is a variant form of a gene or genetic marker, such as an STR, that can differ between individuals.
• By multiplying the frequencies of the alleles at each STR locus, we can calculate the probability of a specific combination occurring in the population.
• Homozygous: Having two identical alleles for a particular STR.
• Heterozygous: Having two different alleles for a particular STR.

Gene Expression:

• 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.
• Regulatory region controls when and how much a gene is expressed.
• Coding region contains the instructions for making the protein.
• Replication and transcription occur in the nucleus
• Translation occurs in the cytoplasm (on ribosomes)
• DNA is double-stranded, uses deoxyribose sugar, and has the bases A, T, C, G.
• RNA is single-stranded, uses ribose sugar, and has the bases A, U, C, G.
• 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.
• A codon is a three-nucleotide sequence in mRNA that codes for an amino acid.
• tRNA carries amino acids to the ribosome for protein synthesis, with the anticodon on tRNA binding to the complementary codon on mRNA.
• Ribosomes catalyze the formation of peptide bonds between amino acids during protein synthesis.
• A mutation is a change in the DNA sequence, but not all mutations affect protein function.

Week 10: The Cell Cycle, Cancer, and Mitosis

Cancer and Regulation of the Cell Cycle

• Cancer cells divide uncontrollably and can invade other tissues because they have escaped the regulation of the cell cycle.
• Tobacco use is the most preventable cause of cancer in the U.S.
• A benign tumor is localized, while a malignant tumor is invasive and can metastasize.
• 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.
• Typically, multiple mutations must accumulate in key genes for cancer to develop uncontrolled cell division.

Mitosis

• Somatic cells, such as skin and muscle cells, undergo mitosis.
• The end result of mitosis is two genetically identical daughter cells.
• Prophase: Chromosomes condense.
• Metaphase: Chromosomes align at the center.
• Anaphase: Sister chromatids are pulled apart.
• Telophase: New nuclei form.
• The number of chromatids doubles during mitosis, but the number of chromosomes remains constant.