Prokaryotic & Eukaryotic Cells

Types of Cells

• Prokaryotes lack a nucleus and membrane-bound organelles; bacteria are an example.
• Eukaryotes possess a nucleus and organelles; examples include plants, animals, fungi, and protists.
• Eukaryotes, unlike prokaryotes, contain membrane-bound organelles such as mitochondria and the endoplasmic reticulum.
• Both prokaryotes and eukaryotes are considered living things.
• Bacteria are classified as prokaryotes.
• Eukaryotes possess a nucleus, a defining characteristic.
• Animals, plants, and fungi are all eukaryotic organisms.
• The absence of a nucleus is a defining feature of prokaryotic cells.
• Both prokaryotic and eukaryotic cells contain genetic material (DNA).
• Proteins are essential for the structure and function of all cells, both prokaryotic and eukaryotic.
• The presence of cells indicates the existence of life.

Cell Transport

• Phospholipids, proteins, and carbohydrates are membrane components.
• Phospholipids form the cell membrane bilayer with hydrophilic heads and hydrophobic tails.
• Proteins facilitate the movement of substances, especially large or charged molecules, across the membrane.
• Carbohydrates on the cell surface act as markers for cell communication.
• Semi-permeable membranes allow only certain molecules to pass through, typically small, nonpolar molecules like oxygen and carbon dioxide.
• Diffusion involves movement from an area of high concentration to low concentration, without energy or protein assistance.
• Facilitated diffusion also moves substances from high to low concentration, without energy, but requires a protein.
• Active transport moves substances against their concentration gradient (low to high), requiring both energy and a protein.
• Osmosis is the movement of water from an area of high water concentration to low water concentration, not requiring energy but sometimes needing a protein.
• Hypertonic solutions cause cells to shrink as water moves out of the cell.
• Hypotonic solutions cause cells to swell as water moves into the cell.
• Isotonic solutions have equal solute concentrations, resulting in no net water movement and no change in cell size.

Viruses

• Viruses are non-living entities that require a host to reproduce.
• Viruses contain either DNA or RNA as their genetic material.
• Protein receptors on viruses bind to host cells to initiate infection.
• Vaccines prepare the immune system to recognize and fight specific viruses.
• Viral reproduction involves attachment to a host, replication of viral DNA, assembly of new viruses, and release from the host.
• Lytic and lysogenic cycles are two methods for viral reproduction.
• The lytic cycle involves fast symptoms and replicating viral DNA.
• The lysogenic cycle involves delayed symptoms and viral DNA hiding in the host DNA.
• Both cycles involve protein receptors attaching and the need to reproduce.
• HIV, is an example of the lysogenic cycle.
• COVID/Flu, is an example of the lytic cycle.
• HIV weakens the immune system, increasing susceptibility to infections.
• Lytic = Quick
• Lysogenic = Long

Cell Cycle & DNA Replication

• Uncontrolled cell division can lead to tumor formation if bad cells escape their checkpoints.
• The cell cycle and mitosis are essential for growth, repair of damaged tissues, and replacement of old/dead cells.
• Interphase consists of G1, S, and G2 phases.
• G1 phase involves cell growth and normal functions.
• S phase is crucial for DNA replication, ensuring daughter cells receive proper instructions.
• G2 phase prepares the cell for mitosis by producing necessary organelles and molecules.
• The S phase is important because it ensures each new cell gets an exact copy of the DNA.
• Mitosis includes prophase, metaphase, anaphase, and telophase.
• Prophase: Chromosomes condense, spindle fibers form, nuclear envelope dissolves
• Metaphase: Chromosomes line up in the center
• Anaphase: Sister chromatids are pulled apart to opposite sides
• Telophase: New nuclei form, chromosomes begin to uncoil
• Cytokinesis divides the cytoplasm, resulting in two identical daughter cells.
• DNA replication occurs during the S phase of interphase.
• The number of chromosomes doubles to 92 after the S phase and is then split evenly during mitosis.
• Base pairing rules: Adenine (A) pairs with Thymine (T), and Guanine (G) pairs with Cytosine (C).
• Helicase unzips the DNA strand, while DNA polymerase adds new bases to build the complementary strand.
• During DNA replication, the template strands must separate so both can be copied.
• DNA replication is semi-conservative, with one old strand and one new strand, ensuring accuracy and stability.

DNA Structure

• DNA (Deoxyribonucleic Acid) carries genetic information and codes for proteins.
• DNA's shape is a double helix.
• The nitrogenous bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G).
• The order of nitrogenous bases determines the order of amino acids in proteins.
• Nucleotide = full unit (phosphate + sugar + base)
• Deoxyribose sugar = middle part of the backbone
• Phosphate = part of the backbone
• Nitrogen base = sticks out and pairs with another base
• Hydrogen bonds = hold base pairs together

Protein Synthesis

• RNA (Ribonucleic Acid) is single-stranded and uses uracil (U) instead of thymine (T).
• mRNA (messenger RNA) carries the genetic message from DNA.
• tRNA (transfer RNA) transfers amino acids to the ribosome for protein synthesis.
• rRNA (ribosomal RNA) makes up the ribosome.
• Transcription (DNA to mRNA) occurs in the nucleus, using RNA polymerase to build mRNA.
• Translation (mRNA to protein) occurs at the ribosome, where mRNA is read in codons, and tRNA brings the correct amino acids.
• rRNA helps form the polypeptide (protein).

Gene Expression & Cell Differentiation

• All start the same, but different genes are activated in different cell types.
• Leads to cell specialization — for example, skin cells, muscle cells, and nerve cells, all with the same DNA but different functions.

Mutations

• A mutation is a change in DNA sequence.
• Mutations might affect how a protein is built.
• Some mutations are harmless or beneficial.
• Any of these can occur with mutations.
• Somatic (body) cells: Diploid (2 sets of DNA).
• Gametes (egg/sperm): Haploid (1 set of DNA).
• If a mutation happens in a somatic cell (like skin), it won’t be passed onto offspring.

Meiosis

• Happens in gametes (egg and sperm).
• Reduce DNA by half to maintain species chromosome number.
• Results: 4 unique haploid cells.
• Genetic diversity in meiosis comes from: 1. Crossing over (exchange of DNA during Prophase I) 2. Independent assortment (random alignment in Metaphase I).

Genetics

• Homozygous = same alleles (EE or ee) → "purebred"
• Heterozygous = different alleles (Ee) → "hybrid".
• Genotype = genetic makeup (e.g., Ee).
• Phenotype = physical trait (e.g., tall).
• Incomplete dominance occurs when traits blend (Red + White = Pink).
• Codominance occurs when both traits show (Red + White = Red + White stripes).

Pedigrees

• To analyze pedigrees, count shaded circles (females) and squares (males) for traits.
• II-5 and II-6 genotypes depend on the trait being dominant/recessive (if both parents have unaffected kids, one must be heterozygous).

Evolution

• Natural selection is how organisms with favorable traits survive and reproduce more successfully.
• Evolution = change over time via common ancestry, not direct transformation.

Evidence:

• Embryology: Similar embryos = shared ancestry.
• Biogeography: Related species on separate continents.
• Molecular: Similar DNA/amino acids = close relation
• Anatomy: Homologous structures = same structure, different function.
• Vestigial = no longer used (e.g., appendix).
• Fossils: Older fossils are deeper; change is slow unless the environment changes quickly.
• Genetic sequences are the most accurate evidence for dogs & wolves vs foxes.
• Anatomical structures like whale fins and bat wings demonstrate common ancestry.
• Vestigial structure example: Human tailbone or whale hip bones.
• Variation: Differences among individuals (e.g., fur color).
• Adaptation: A beneficial trait (e.g., webbed feet in ducks).
• Genetic diversity helps populations survive environmental changes.

Classification

• Binomial nomenclature: 2-name system → Genus + species (e.g., Homo sapiens).
• Remember: Did King Phillip Come Over For Good Soup? → Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
• More closely related? → Same family.
• Most diverse group? → Kingdom.
• If they can mate and produce fertile offspring? → Must be same species.

Cladogram Questions:

• Organism with eggs with shells: Birds and reptiles.
• Organism lacking four limbs: Fish.
• Closest common ancestor to rodents and rabbits: Primates.
• The insect shown = Arthropod (based on exoskeleton & segmented body).

The Six Kingdoms

• Eubacteria: Prokaryotic, causes strep, found everywhere.
• Archaebacteria: Extremophiles (hot, salty, no O₂).
• Protist: Eukaryotic, needs water, very diverse.
• Fungi: Cell walls of chitin, decomposers.
• Plants: Cell walls of cellulose, autotrophic.
• Animals: No cell wall, heterotrophic, multicellular.

Biomolecules

• Carbs: Short-term energy; Monosaccharide; Glucose, starch, cellulose.
• Lipids: Long-term energy, insulation; Glycerol + fatty acids; Fats, oils, phospholipids.
• Proteins: Structure, enzymes, immune defense; Amino acids; Keratin, enzymes, antibodies.
• Nucleic Acids: Genetic info; Nucleotides; DNA, RNA.
• Enzymes = proteins that speed up reactions.
• Active site = specific “lock-and-key” fit.
• Enzymes denature when temperature or pH is extreme.

Photosynthesis & Cellular Respiration

• Photosynthesis: In chloroplasts (plants, some protists/bacteria); Light + CO₂ + H₂O → Glucose + O₂.
• Cellular Respiration: In mitochondria (plants & animals); Glucose + O₂ → ATP + CO₂ + H₂O.
• Energy transfer: Solar → Chemical (glucose) → Chemical (ATP).

Plant vs Animal Systems

• Energy Production: Plant Example: Photosynthesis and Animal Example: Digestive system.
• Response to Stimuli: Plant Example: Tropism and Animal Example: Nervous system.
• Reproduction: Plant Example: Pollen/seeds and Animal Example: Reproductive system.
• Gas Exchange: Plant Example: Stomata and Animal Example: Lungs.
• Protection: Plant Example: Bark/thorns and Animal Example: Skin/immune system.
• Vascularization: Plant Example: Xylem and Phloem and Animal Example: Circulatory system.
• Excretion: Plant Example: Leaf fall/stomata and Animal Example: Kidneys (urinary system).

Ecosystems & Energy Flow

• Producers: Grass, algae.
• Primary consumers: Grasshopper, rabbit, deer.
• Secondary consumers: Frog, snake.
• Tertiary consumers: Hawk, fox.
• Quaternary consumer: Apex predator (e.g., bear, eagle).
• Energy transfer: Solar → Chemical (glucose) → Chemical (ATP).
• If producers have 10,000 J → Primary gets 10% = 1,000 J and Secondary gets 100 J (10% of 1,000).
• Most energy is lost as: Heat.
• Bacteria’s role: Decomposers → recycle nutrients back into the soil.

Symbiosis

• Matching interaction types: → 1 – predation, 2 – parasitism, 3 – commensalism, 4 – competition.

Succession

• Primary succession on moraine: Lichens break down rock to form soil.
• Hardwoods affect ecosystems: They outcompete low plants, provide shelter, and feed decomposers.