Overview of Topics for the Upcoming Test

• Discussion of various biological concepts and mechanisms relevant for the test.

Bacteria

• Shapes of Bacteria: Important to recognize the various shapes (e.g., coccus, bacillus, spiral).
• Differences between Prokaryotes and Eukaryotes:
  • Prokaryotes (including bacteria) do not have organelles.
  • Nucleus: Bacteria possess no nucleus; instead, their DNA is organized in a region called the nucleoid, which is a single loop of circular DNA.
  • Common Features: Both prokaryotes and eukaryotes share common features critical for protein synthesis, including:
  • Ribosomes: Present in both cell types.
  • Plasma Membrane: Essential for maintaining cell integrity.
  • Genetic Material: DNA and RNA serve as the genetic blueprint for both.
  • Cytoplasm: The site for many cellular processes.

Transport Mechanisms

• Types of Transport:
  • Passive Transport:
  • Simple Diffusion: Movement from high concentration to low concentration without energy.
  • Osmosis: Specialized diffusion of water across a selectively permeable membrane.
  • Facilitated Diffusion: Utilizes proteins (channel or transport proteins) to assist movement from high to low concentration.
  • Active Transport:
  • Movement from low concentration to high concentration against the gradient requires energy (ATP).
  • Examples:
    • Endocytosis: Bulk transport into the cell.
    • Exocytosis: Bulk transport out of the cell.
  • Types of Endocytosis:
    • Phagocytosis: Uptake of solids.
    • Pinocytosis: Uptake of liquids.
    • Receptor-Mediated Endocytosis: Specific uptake triggered by receptor binding.
• Tonicity Effects on Cells:
  • Isotonic Solution: Equal concentrations of solids and fluids, water moves equally in and out through aquaporins.
  • Hypertonic Solution: Higher concentration of solids outside the cell causes the cell to shrink and undergo crenation.
  • Hypotonic Solution: Higher concentration of fluids outside the cell causes water to enter, leading to potential cell lysis (bursting).

Metabolism and Reactions

• Anabolic Reactions:
  • Involve the creation of bonds, requiring energy (endergonic reaction).
• Glycolysis:
  • Occurs in the cytoplasm of eukaryotes. Yields a net gain of 2 ATP after investing 2 ATP and producing 4 ATP.
  • If no oxygen is available, pyruvate can be converted into lactic acid in animal cells.
• Krebs Cycle:
  • Takes place in the mitochondrial matrix of eukaryotic cells. Producers 2 ATP per cycle, along with carbon dioxide and water.
• Electron Transport Chain:
  • Occurs along the inner mitochondrial membrane; can produce up to 34 ATP depending on the efficiency of the process. In total, aerobic respiration can yield about 38 ATP.

Virus Structure and Lifecycle

• Virus Shapes:
  • Icosahedral: 20-sided structure.
  • Helical: Spiral corkscrew shape.
  • Complex: Any other irregular shapes.
• Virus Envelopes:
  • Envelopes are derived from host cell membranes, primarily composed of phospholipids.
• Nucleic Acids in Viruses:
  • Viruses can contain either DNA or RNA, but not both; can be single-stranded or double-stranded.
• Lifecycle of Viruses: Consists of six stages:
  1. Adhesion: Virus attaches to host cell.
  2. Penetration: Virus enters the host cell.
  3. Uncoating: Viral nucleic acid is released into the host cell.
  4. Synthesis: Replication of viral components occurs.
  5. Assembly: New viral particles are assembled.
  6. Exit: New viruses leave the cell, often destroying the host.
• Lysogenic Cycle: Viral DNA can integrate into the host cell's DNA, remaining dormant until triggered to re-enter the lytic cycle, producing massive quantities of viruses simultaneously.

Cellular Respiration Breakdown

• In prokaryotes, glycolysis takes place in the cytoplasm, as they lack mitochondria.
• Electron Transport Chain in Prokaryotes: Usually embedded in the plasma membrane.
• Cellular respiration results in a higher yield of ATP when oxygen is present: maximum potential of 38 ATP during efficient aerobic processes.

Enzymes and Regulation

• Enzymes: Biological catalysts that lower activation energy, facilitating metabolic processes (anabolism and catabolism).
  • Specificity: Enzymes are not one-size-fits-all; each enzyme is specific to its substrate.
  • Inhibitors:
  • Competitive Inhibitors: Bind to the active site, preventing substrate binding.
  • Noncompetitive Inhibitors: Bind elsewhere on the enzyme, causing a change in shape and making the enzyme ineffective.
• Co-factors and Co-enzymes: Essential for the functionality of enzymes, forming a holoenzyme when combined with the active protein component (apoenzyme).

Additional Topics

• Halophiles: Bacteria adapted to high salt conditions.
• Endospores: Formed by bacteria as a survival mechanism under adverse conditions.
• Prions: Misfolded proteins causing neurodegenerative diseases (e.g., Creutzfeldt-Jakob disease, mad cow disease).
• Bacteriophages: Viruses specifically infecting bacteria.
• Virions: Complete virus particles not currently inside a host cell but capable of infecting a host.