Biology Chapter on Reproduction and Cells

Chapter 1 – Unit 1

• All living things share seven properties: order, sensitivity or response to stimuli, reproduction, adaptation, growth and development, regulation, and energy processing.
• Hierarchy of life (smallest to largest): atoms, molecules, macromolecules, organelles, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and the biosphere.
• Modern cell theory's six statements: All living things are composed of cells, cells are the basic unit of structure and function in living things, all new cells come from pre-existing cells, cells carry hereditary information in the form of DNA, energy flow occurs within cells, and all cells are basically the same in chemical composition in organisms of similar species.
• Eukaryotes possess membrane-bound organelles, whereas prokaryotes do not.
• Matter cycles through a food chain, transferring energy that is eventually lost as heat. This differs from the flow of energy from producer to consumer etc. which is one-way.
• Current domains of life:
• Bacteria: Kingdom Bacteria; Example: Escherichia coli
• Archaea: Kingdom Archaea; Example: Methanobacterium
• Eukarya: Kingdoms Protista, Fungi, Plantae, Animalia; Examples: Amoeba (Protista), Mushroom (Fungi), Oak Tree (Plantae), Human (Animalia)

Chapter 2 – Unit 2

• Four main elements comprising 96% of living organisms: Carbon, hydrogen, oxygen, and nitrogen.
• Trace elements like iron (Fe), iodine (I), and fluorine (F), despite their low abundance, are crucial for various biological functions (e.g., oxygen transport, thyroid hormone production, bone development).
• Isotope: Atoms of the same element that have the same number of protons but different numbers of neutrons.
• Radioactive isotopes are useful:
• Dating rocks and fossils
• Tracing atoms through metabolic processes
• Compounds are formed by chemical bonds between two or more different elements, whereas molecules involve two or more atoms held together by chemical bonds, regardless of element types.
• Bond strengths (decreasing): Covalent (polar and non-polar), ionic, hydrogen
• Covalent (polar): Example: Water (H₂O)
• Covalent(non-polar): Example: Methane (CH₄)
• Ionic: Example: Sodium chloride (NaCl)
• Hydrogen: Example: Water (H₂O) – forming the structure of DNA and protein
• Water's four properties crucial for life:
• High surface tension, cohesion, and adhesion due to hydrogen bonds
• High specific heat
• Excellent solvent
• Ice is less dense than liquid water
• Buffer: Substance that minimizes changes in pH by accepting or releasing hydrogen ions. Example: Bicarbonate system in blood.

Chapter 3 – Unit 2

• All organic compounds contain carbon.
• Carbon skeletons can vary in: length, branching, double bond position, and presence of rings.
• Isomer: Molecules with the same molecular formula but different structural formulas.
• Functional groups:
• Hydroxyl (-OH) Example: Alcohols
• Carbonyl (>C=O) Example: Aldehydes, ketones
• Carboxyl (-COOH) Example: Amino acids, fatty acids
• Amino (-NH₂) Example: Amino acids
• Phosphate (-PO₄³) Example: Nucleic acids, ATP
• Sulfhydryl (-SH) Example: Cysteine
• Dehydration synthesis (Condensation) builds large molecules from smaller ones by removing water molecules. Hydrolysis breaks large molecules into smaller ones by adding water molecules.
• Four major classes of organic compounds: Carbohydrates, lipids, proteins, and nucleic acids.
• Carbohydrates' building blocks are monosaccharides (simple sugars).
• Always attached to a sugar: Hydroxyl (-OH) and Carbonyl (>C=O) groups.
• Monosaccharides' primary function: Provide energy.
• Four major polysaccharides: Starch (energy storage in plants), glycogen (energy storage in animals), cellulose (structural component of plant cell walls), chitin (structural component in fungal cell walls and some animal exoskeletons). Molecular structure and bonding determine the function of polysaccharides.
• All lipids are hydrophobic. Lipids include fats, phospholipids, and steroids.
• Lipids' functions include energy storage, structural components of cell membranes, and hormonal regulation.
• Saturated vs. Unsaturated fats: Saturated fats have no double bonds between carbon atoms, making them solid at room temperature. Unsaturated fats have one or more double bonds, making them liquid at room temperature. Amino acids are the building block of proteins.
• Amino acids share: Amino (-NH₂) and carboxyl (-COOH) groups.
• Amino acids link together to form polypeptides via peptide bonds.
• A protein's function is determined by its shape.
• Four levels of protein structure: primary, secondary, tertiary, and quaternary. Bonds formed at each level affect the overall structure and function.
• Two types of nucleic acids: DNA and RNA. Nucleic acids' building blocks are nucleotides.

Chapter 4 – Unit 3

• Cell size is primarily determined by the surface area to volume ratio.
• Plasma membrane has two leaflets with hydrophilic heads and hydrophobic tails. Proteins (channel) embedded in membrane.
• Only prokaryotic organisms reside in the Bacteria and Archaea domains.
• All cells (prokaryotic and eukaryotic) share: DNA, cytoplasm, and ribosomes.
• Prokaryotic cells lack membrane-bound organelles and a nucleus whereas eukaryotic cells have both. Endomembrane system components:
• Nuclear envelope, endoplasmic reticulum (smooth and rough), golgi apparatus, lysosomes, and vacuoles. Functions include protein synthesis, modification, and transport.
• Nucleolus synthesizes ribosomes.
• Smooth endoplasmic reticulum produces new membrane components.
• Alcoholic or drug user's liver cells have elevated smooth ER for detoxification.
• Golgi apparatus modifies, sorts, and packages cellular products.
• Lysosomes break down cellular waste, while vacuoles store water, nutrients, and waste. Mitochondria and chloroplasts are energy-converting organelles.
• Mitochondria and chloroplasts evidence of their former free-living natures includes: Double membrane, their own DNA & ribosomes, and reproduction independently from the host cell.
• Cell fibers with their functions:
• Microtubules: Organelle movement
• Intermediate filaments: Support cell shape and anchor organelles
• Microfilaments: Support cell, movement

Chapter 5 – Unit 3

• Passive transport molecules include water and nonpolar substances.
• Facilitated transport helps, but does not actively move, larger or charged molecules by using protein channels, while passive transport does not need an energy source.
• Effects of different solutions on plant and animal cells:
• Isotonic: No net movement of water
• Hypotonic: Water moves into cell; Animal cells swell and burst (lysis), plant cells become turgid
• Hypertonic: Water moves out of cell; Animal cells shrink (crenate), plant cells plasmolyze.
• Active transport consumes energy (ATP) to move molecules against their concentration gradient using membrane proteins, contrasted with facilitated which does not consume energy.
• Diagrams showing Exocytosis and Endocytosis.
• Cell utilizes ATP hydrolysis (exergonic reaction) and not endergonic reactions to transfer a phosphate onto another molecule.
• Enzyme selectivity results from complex structure and the active site, which fits the substrate in an induced-fit model.
• Two conditions control enzyme function: temperature and pH.

Chapter 6 – Unit 4

• Cellular respiration converts glucose energy into ATP with 38% capture efficiency.
• Oxidation: Loss of electrons; reduction: Gain of electrons.
• NAD+ accepting electrons and becoming NADH is reduction.
• Main cellular respiration stages: glycolysis (cytoplasm), Citric acid cycle (mitochondrial matrix), and oxidative phosphorylation (mitochondrial inner membrane).
• For each glucose molecule in glycolysis:
• 2 net ATP molecules
• 2 NADH molecules
• 2 pyruvates
• CO2 is released in the Citric Acid Cycle
• Citric Acid Cycle produces: ATP, NADH, and FADH₂.
• CO2 production occurs during the Citric acid cycle.
• O2 consumption happens during oxidative phosphorylation.
• ATP synthase utilizes the hydrogen ion gradient to produce ATP.
• Muscle cells switch to lactic acid production when O2 supply is low.

Chapter 7 – Unit 4

• Two main stages of photosynthesis: Light reactions, Calvin Cycle. Takes place in chloroplasts.
• Light reactions occur in thylakoid membranes, while the Calvin Cycle occurs in the stroma.
• The Light Reactions use water and release oxygen; The Calvin Cycle uses CO2 and produces sugars.
• Light reactions use water and produce ATP and NADPH, that are used to reduce CO2 in the Calvin Cycle, and make sugars, which make their way back to the Light Reactions in their oxidized states.
• Photosynthesis' purpose is to convert light energy to chemical stored energy in sugar
• Hydrogen ion gradient in light reactions drives ATP synthesis; The gradient is used to create ATP.
• Calvin Cycle uses energy from ATP and NADPH to produce sugars.
• Sugars produced by photosynthesis fuel cellular respiration, plant growth etc.
• Photosynthesis is essential as it provides almost all the energy for life on Earth.

Chapter 8 – Unit 5

• Asexual reproduction produces genetically identical offspring, whereas sexual reproduction combines genetic material from two parents.
• Binary fission in prokaryotes resembles mitotic cell division in eukaryotes.
• The cell cycle encompasses stages from chromatin to chromosomes. Sister chromatids form when a chromosome replicates itself.
• A labelled diagram depicting the cell cycle, durations, and key events for all stages.
• Cytokinesis differs between animal and plant cells: animal cells form a cleavage furrow whereas plant cells form a cell plate.
• Reasons for mitotic cell division: growth, repair, and asexual reproduction. Inhibition factors include: lack of growth factors, nutrient depletion, overcrowding.
• Cell cycle controlled by intracellular signalling.
• Mitotic cell division produces identical daughter cells. Meiotic cell division produces four unique haploid daughter cells.