ZL

Cell Biology and Energy Balance Notes

Acids, Bases, and pH

  • The pH scale measures the concentration of hydrogen ions [H^+]. A tenfold difference in hydrogen ion concentration exists between each number on the pH scale.
    • Example: A substance with a pH of 5 has 10 times more hydrogen ions than a substance with a pH of 6.

Antibiotics

  • Antibiotics are beneficial because they kill bacterial cells while being relatively safe for human cells.
  • They destroy bacteria without harming the human or animal host.

Types of Cells: Prokaryotic vs. Eukaryotic

  • Prokaryotic Cells:
    • Pro means "before," and karyo means "nucleus."
    • Classified as prokaryotic cells.
  • Eukaryotic Cells:
    • Eu means "true."
    • Larger cells with a membrane-bound nucleus and organelles.
    • Can be single-celled or multicellular.
    • All animal cells are eukaryotic.
  • Both Types:
    • Contain a cell membrane, a barrier between the inside and outside of the cell, composed of a phospholipid bilayer.

Penicillin and Cell Differences

  • Penicillin selectively kills bacterial cells because there's an important difference between prokaryotic and eukaryotic cells.

Osmosis and Solutions

  • Solute concentration affects osmosis, the movement of water from an area of high concentration to low concentration.
  • Hypotonic:
    • Less solute outside than inside the cell
  • Hypertonic:
    • More solute outside than inside the cell
  • Isotonic:
    • The same amount of solute in the solution as in the cell
  • In hypotonic environments, water enters bacterial cells, causing them to swell.

Penicillin Mass Production

  • During World War II, mass production of penicillin started using a strain of fungus that produced 200 times more penicillin than the original strain.

Cell Membrane and Transport

  • To understand how substances move across the cell membrane, it's important to discuss its structure.

Diffusion

  • Diffusion is the movement of a substance from an area of high concentration to an area of low concentration.

Simple Diffusion

  • Simple diffusion is the diffusion of a substance across the membrane without help or assistance.
    • Oxygen and carbon dioxide cross the membrane via simple diffusion.

Facilitated Diffusion

  • Facilitated diffusion is the diffusion of a substance across the membrane with the assistance of a transport protein.
  • Different antibiotics use different types of diffusion.

Active Transport

  • Active transport requires the cell to expend energy in the form of ATP.
  • Large or hydrophilic molecules are actively transported.
  • Eukaryotic cells use active transport.

Endocytosis

  • Endocytosis involves bringing things into the cell using a membrane-bound vesicle.

Nucleus

  • The nucleus is the defining structure of eukaryotic cells, where DNA is found.
  • It is the control center of the cell.

Lysosomes

  • Contain enzymes that break down materials.
  • Garbage disposal of the cell.

Endosymbiotic Theory

  • The theory proposes that eukaryotic organelles were once free-living prokaryotic cells engulfed by other prokaryotic cells.
  • Evidence supporting this theory includes:
    • Mitochondria and chloroplasts being similar in size and shape to bacteria (prokaryotic cells).

Antibiotic Resistance

  • A major issue with antibiotics is antibiotic resistance.
  • Patients sometimes stop taking antibiotics too early, leading to surviving bacteria becoming resistant.
  • Example: Strains of Staphylococcus aureus, once sensitive to penicillin, are now over 90% resistant.
  • Drug companies are constantly working to develop new antibiotics.

Obesity and Energy Balance

  • Obesity is defined as having an unhealthy amount of body fat.
  • Body Mass Index (BMI) is used as a tool.
  • Energy expenditure is influenced by activities like sitting or standing.
  • Energy is defined as the capacity or ability to do work.

Energy Sources

  • Our bodies get energy from fats, proteins, and carbohydrates.
  • Fats (lipids) are the most energy-dense, storing nine calories per gram.
    • 1 \text{ gram of fat} = 9 \text{ calories}
  • Proteins and carbohydrates provide four calories per gram.
    • 1 \text{ gram of protein or carbs} = 4 \text{ calories}

Energy Expenditure

  • Three main ways our bodies use energy:
    • Basal Metabolism or Basal Metabolic Rate (BMR)

Excess Energy

  • If we consume more food energy than we use, the excess is stored as fat.
  • Excess carbohydrates and sugars are converted into fat.

Citric Acid Cycle (Krebs Cycle)

  • The citric acid cycle occurs in the mitochondria.
  • It involves stripping high-energy electrons from the bonds between carbon and hydrogen in pyruvate.
  • The cycle produces four ATP molecules.
  • Energy is stored in electrons released from broken bonds.

Aerobic Respiration

  • Electrons are picked up by carrier molecules and passed to the electron transport chain.
  • Oxygen is the final electron acceptor, forming water (H_2O).

Anaerobic Respiration

  • Occurs when oxygen delivery is lower than oxygen consumption, such as during exercise.
  • Without oxygen, the electron transport chain stops, and aerobic respiration ceases.
  • Anaerobic means without oxygen.
  • Pyruvate molecules do not go through the citric acid cycle or electron transport chain.

Weight Management

  • Physical activity has decreased by about 1,500 calories per day over the past 50-70 years.
  • When you eat more calories than you expend, the extra energy is stored as fat.
  • To lose weight, you must use more energy than you consume.
  • Increase Non-exercise activity thermogenesis (NEAT).
    • Fidgeting, gardening, shopping, doing dishes, etc.

Exam Information

  • The exam questions are based on the notes.
  • A study guide is posted for each unit with objectives for each chapter.