Biology EOC Review - Cells and Genetics

Cells

• Homeostasis:

  • Definition: The way a body or cells maintain a stable internal environment, such as temperature or water level.

• Mitochondria and Chloroplasts:

  • Chloroplasts use sunlight to produce glucose (food) through photosynthesis.
  • Mitochondria use glucose to produce ATP (energy) that the cell can use.

• Nucleus and Ribosomes:

  • The nucleus contains DNA, which provides instructions for making proteins.
  • Ribosomes read the DNA instructions and build proteins (protein synthesis).

• Central Vacuole and Cell Wall:

  • The central vacuole stores water and exerts pressure against the cell wall.
  • The cell wall provides strength and prevents the cell from bursting, helping the plant maintain its structure.

• Macromolecules:

  • Carbohydrates: Includes glucose, used by mitochondria to produce ATP.
  • Nucleic Acids: Includes DNA and RNA; store and transmit genetic information.
  • Proteins: Includes enzymes, which speed up chemical reactions. Consist of amino acid monomers that form peptides. Contains nitrogen.
  • Lipids: Forms the selectively permeable cell membrane.
  • Nucleic Acids: Consist of nucleotide monomers. Contains nitrogen and phosphorus.

• Enzymes:

  • Function like a lock-and-key:
    • A substrate binds to an enzyme at its active site.
    • An enzyme-substrate complex is formed, and a shape change occurs, allowing the chemical reaction.
    • The substrate is broken down into products, and the enzyme remains unchanged to be reused.
  • Function as catalysts by lowering the activation energy required to start a reaction, thus speeding up the reaction rate.
  • Optimal pH levels:
    • Pepsin: 2
    • Sucrase: 6
    • Trypsin: 8
  • Denaturation: When an enzyme changes shape and loses its functionality due to environmental changes (e.g., pH level). Pepsin, which functions best in acidic conditions, will not work at a pH of 9 (basic).

• Passive vs. Active Transport:

  • Passive Transport:
    • Does not require ATP.
    • Particles move from high to low concentration (with the concentration gradient).
    • Examples:
      • Simple Diffusion: Particles move freely across the membrane.
      • Facilitated Diffusion: Particles move through a protein channel.
      • Osmosis: Water moves across the membrane.
  • Active Transport:
    • Requires ATP.
    • Particles move from low to high concentration (against the concentration gradient).
    • Examples:
      • Protein Pump: Uses energy to move particles across the membrane.
      • Endocytosis: Cell takes in large materials.
      • Exocytosis: Cell pushes out large materials.

• Types of Cell Transport:

  • Simple Diffusion: Moves straight through the membrane.
  • Facilitated Diffusion: Uses a protein channel.
  • Active Transport: Requires energy to move particles from low to high concentration.

• Tonicity:

  • Hypertonic:
    • Solution has a higher solute concentration than the cell.
    • Water moves out of the cell.
    • Animal Cell: Shrinks.
    • Plant Cell: Shrinks (Plasmolysis).
  • Hypotonic:
    • Solution has a lower solute concentration than the cell.
    • Water moves into the cell.
    • Animal Cell: Swells (may burst).
    • Plant Cell: Swells (good for structure).
  • Isotonic:
    • Solution has the same solute concentration as the cell.
    • No net water movement.
    • Animal Cell: Stays the same.
    • Plant Cell: Stays the same.

• ATP-ADP Cycle:

  • ATP is a high-energy molecule with 3 phosphate groups; energy is stored in the bonds between the phosphate groups.
  • Energy is released when a phosphate group is removed from ATP, converting it to ADP (a lower energy molecule with 2 phosphate groups).
  • Energy is absorbed when a phosphate group is added back to ADP, regenerating ATP.

• Photosynthesis:

  • Equation: Sunlight + CO2 + H2O _rightarrow C6H{12}O6 + O2
  • Reactants: Sunlight, Carbon Dioxide (CO2), Water (H2O)
  • Products: Glucose (C6H{12}O6), Oxygen (O2)

• Cellular Respiration:

  • Equation: C6H{12}O6 + O2 _rightarrow CO2 + H2O + ATP
  • Reactants: Glucose (C6H{12}O6), Oxygen (O2)
  • Products: Carbon Dioxide (CO2), Water (H2O), ATP

• Interdependence of Photosynthesis and Cellular Respiration:

  • Products of photosynthesis (glucose and oxygen) are the reactants of cellular respiration.
  • Products of cellular respiration (carbon dioxide and water) are the reactants of photosynthesis.
  • This cycle balances energy and gases in living things and the environment.

• Organelles:

  • Photosynthesis takes place in Chloroplasts.
  • Cellular respiration takes place in Mitochondria.

• Cell Division:

  • Mitosis:
    • Results in 2 genetically identical daughter cells.
  • Meiosis:
    • Results in 4 genetically different daughter cells.
  • Diploid vs. Haploid:
    • Diploid cells contain 2n chromosomes.
    • Haploid cells contain n chromosomes.
  • Gametes:
    • Haploid cells produced through meiosis.
  • Somatic cells:
    • Diploid cells produced through mitosis.

• Gametes vs. Somatic Cells:

  • Gametes: Sex cells (sperm or egg), haploid (n), half the number of chromosomes.
  • Somatic cells: Body cells (e.g., skin or muscle), diploid (2n), full set of chromosomes.

Genetics (Molecular Genetics - Protein Synthesis & Mutations)

• Central Dogma of Biology:

  • DNA \rightarrow RNA \rightarrow Protein

• DNA Replication:

  • Process: A cell makes a copy of its DNA before it divides.
  • Semi-conservative: Each new DNA strand consists of one old strand and one new strand.
  • Example:
    • Original DNA sequence: ATG CAA GCC AGT
    • New DNA strand: TAC GTT CGG TCA

• DNA vs. RNA:

  • Both consist of monomers called nucleotides.
  • DNA:
    • Nucleotide: phosphate, deoxyribose, and nitrogenous base.
    • Adenine (A) bonds with thymine (T).
    • Cytosine (C) bonds with guanine (G).
    • Double-stranded.
  • RNA:
    • Nucleotide: phosphate, ribose, and nitrogenous base.
    • Uracil (U) bonds with adenine (A).

• Structures and Functions:

  • DNA: Stores genetic information.
  • mRNA: Copies DNA information and carries it to the ribosome.
  • tRNA: Makes proteins by reading mRNA.

• Protein Synthesis Diagram:

  1. DNA
  2. Transcription
  3. mRNA
  4. tRNA
  5. Amino acid
  6. Polypeptide chain (protein)
  7. Translation

• Transcription:

  • Process: A cell makes a copy of messenger RNA (mRNA) from a DNA template; the first step in making proteins.

• Translation:

  • Process: A cell uses the information in messenger RNA (mRNA) to build a protein by linking together amino acids in the correct order.

• Transcription and Translation Example:

  • DNA: TAC ACA CTA ACC ATG
  • mRNA: AUG UGU GAU UGG UAC
  • Amino Acid Sequence: Methionine – Cysteine – Aspartic acid – Tryptophan – Tyrosine

• Chargaff’s Rule:

  • DNA:
    • Adenine (A) = Thymine (T)
    • Cytosine (C) = Guanine (G)
  • Example:
    • Sample A: Adenine (15%), Cytosine (35%), Guanine (35%), Thymine (15%)
    • Sample B: Adenine (23%), Cytosine (27%), Guanine (27%), Thymine (23%)
    • Sample C: Adenine (19%), Cytosine (31%), Guanine (31%), Thymine (19%)

• Mutations:

  • Causes: Mistakes during replication or transcription, exposure to mutagens (chemicals, radiation, viruses, etc.).

  • Types:

    • Substitution (point mutation): A nucleotide base is swapped out for another.

      • Original: ATC GCC TAT CCG
      • Mutated: TTC GCC TAT CCG

    • Insertion (frameshift mutation): A nucleotide base is added to a DNA sequence, causing the DNA sequence to shift (example missing in original text)

      • Original: ATC GCC TAT CCG
      • Mutated: ATC GGC CTA TCC G

    • Deletion (frameshift mutation): A nucleotide base is removed from a DNA sequence, causing the DNA sequence to shift (example missing in original text)

      • Original: ATC GCC TAT CCG
      • Mutated: ATCG CCT ATC CG

  • Frameshift mutations are generally more harmful than point mutations because they alter more of the amino acid sequence.

• Nondisjunction:

  • Definition: When chromosomes do not separate evenly during meiosis.
  • Occurs during meiosis II if the chromosomes split evenly in the first division, but not in the second division.
  • Impact on chromosome number:
    • Cell A (Trisomy): The gamete has an extra chromosome.
    • Cell B (Monosomy): The gamete has one less chromosome.

Genetics (Mendelian Genetics)

• Crossing Over:

  • Process: Homologous chromosomes (one from mom, one from dad) swap genetic information before forming gametes.
  • Significance: Creates genetic variation; ensures all gametes are genetically different from one another.

• Mendel’s Laws of Heredity:

  • Law of Segregation: Offspring randomly inherit one allele from each parent.
  • Law of Independent Assortment: Traits are not inherited together; hair color does not affect eye color.

• Genetic Definitions:

  • Gene: A sequence of DNA on a chromosome that codes for a particular trait.
  • Allele: Different versions of a gene or trait (e.g., eye color, hair color).
  • Homozygous: Two of the same allele for a given trait (e.g., AA, cc, MM, ss).
  • Heterozygous: Two different alleles for a given trait (e.g., Aa, Cc, Mm, Ss).

• Phenotype vs. Genotype:

  • Genotype: Genetic makeup for a given trait.
  • Phenotype: Physical expression of a trait.

• Patterns of Dominance:

  • Mendelian: Complete Dominance
    • Simple definition: One trait is dominant, and one trait is recessive.
  • Non-Mendelian: Incomplete Dominance
    • Simple definition: Two traits are expressed partially; Black + White make Grey.
  • Non-Mendelian: Codominance
    • Simple definition: Two traits are expressed equally; Black + White make Black AND White.

• Camellia Flower Example (Codominance):

  • Red camellias crossed with white camellias produce flowers with red AND white petals.
    • RR x WW -> All offspring RW
  • Phenotypic ratio: 100% will have red AND white petals (RW).
  • Codominance: Red + White = Red AND White.

• Tulip Flower Example (Incomplete Dominance):

  • Red tulips crossed with yellow tulips produce orange flowers.
  • To produce only orange and yellow tulips, cross an orange tulip (RY) with a yellow tulip (YY).
    • RY x YY -> 50% RY (Orange), 50% YY (Yellow)
  • Incomplete dominance: Red + Yellow = Orange (an “in-between” phenotype).

• Lily Flower Example (Complete Dominance).

  • Purple flowers are dominant to white flowers.
  • Cross in which a purple flower and white flower produce other white flowers: Pp x pp
  • Genotypic ratio: 50% Pp and 50% pp.
  • Two white flowers cannot produce a purple flower because white is a recessive trait, and both flowers only have the recessive gene.

• Dihybrid Cross Example:

  • Pea plants heterozygous for two traits (YyRr x YyRr), where yellow (Y) is dominant to green (y) AND round (R) is dominant to wrinkled (r).
  • Phenotypic ratio: 9:3:3:1
    • 9 are yellow and round
    • 3 are yellow and wrinkled
    • 3 are green and round
    • 1 is green and wrinkled. (9 YR, 3 Yr, 3 yR, 1 yr)