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.