Cell Biology and Homeostasis Notes

Cells

• Homeostasis:
  • Definition: The ability of an organism to maintain a stable internal balanced environment.
  • Failure to maintain homeostasis can result in sickness or death.
• Metabolism:
  • Definition: The sum of all the chemical reactions that occur within the cells of an organism.
• Organic Molecules:
  • Contain skeleton structures of carbon with hydrogen and oxygen.
  • Examples:
    • Carbohydrates (starch)
      • Basic Unit: Glucose (Simple Sugars)
      • Foods found: Grains, vegetables, fruit
    • Proteins
      • Basic Unit: Amino Acid (20 kinds)
      • Foods found: Meat, egg whites, beans
    • Lipids
      • Basic Unit: Fatty Acid & Glycerin
      • Foods found: Animal fats, nuts, oils
    • Nucleic Acid
      • Basic Unit: Nucleotide
      • Foods found: Small amounts in all foods
• Organization of Living Things:
  • [smallest] Cells → Tissues → Organs → Organ Systems → Organism [biggest]
• Organelles:
  • Small parts that make up a cell; each has at least one specific function.
  • Examples:
    • Vacuoles:
      • Function: Store waste and water.
      • Size: Large in plant cells, small in animal cells.
    • Ribosome:
      • Appearance: Very small and is often represented by a dot.
      • Location: Located on the ER or in cytoplasm.
      • Function: Where proteins are made (protein synthesis).
    • Mitochondria:
      • Function: The powerhouse of the cell where energy is made.
      • Site of cellular respiration in both plant and animal cells.
      • Formula for cellular respiration: $Glucose + oxygen \rightarrow carbon dioxide + water + ENERGY (ATP)$
    • Chloroplasts:
      • Location: Only in plant cells.
      • Function: Where the process of photosynthesis occurs.
      • Formula for photosynthesis: $Sun's energy + carbon dioxide + water \rightarrow glucose + water + oxygen$
    • Nucleus:
      • Function: The control center of the cell and contains DNA (the program or code of life).
    • Cytoplasm:
      • Function: The liquid media that fills the cell.
    • Cell Membrane:
      • Function:
        • Separates the contents of the cell from the outside environment.
        • Controls the transport of materials into and out of the cell (selective permeability).
      • Cellular communication: Recognizes and responds to chemical signals by using receptor molecules.

Transport

• Passive Transport or Diffusion:
  • Definition: The movement of molecules from areas of high concentration to areas of low concentration.
  • Energy Requirement: No energy used.
• Active Transport:
  • Definition: Moving a molecule from LOW concentration to a HIGH concentration.
  • Energy Requirement: USES ENERGY in the form of ATP.

Human Body Systems

• Digestive System:
  • Function: Breaks down food into nutrients & puts them in the blood stream
  • Parts: mouth, esophagus, stomach, small intestine, large intestine, rectum
  • Organelles with the same function: Vacuole and Lysosome
• Circulatory System:
  • Function: Carries gasses and nutrients throughout the body
  • Parts: heart, arteries, veins, capillaries
  • Organelles with the same function: Cytoplasm, ER or Golgi
• Respiratory System:
  • Function: Exchanges carbon dioxide and oxygen
  • Parts: lungs, alveoli, diaphragm
  • Organelles with the same function: Cell Membrane
• Excretory System:
  • Function: Removes wastes from the blood and then from the body
  • Parts: kidneys, bladder, urethra
  • Organelles with the same function: Cell Membrane or vacuole
• Nervous System:
  • Function: Fast control of the functioning of all body systems.
  • Parts: brain, spinal cord, nerve cells
  • Organelles with the same function: Nucleus
• Endocrine System:
  • Function: Slow control of the functioning of all body systems.
  • Parts: Pituitary, Thyroid, Adrenal, Pancreas, Gonads
  • Organelles with the same function: Nucleus

Life Functions and Homeostasis

• Control Chemicals:
  • Hormones produced in the endocrine glands and chemicals produced by nerve cells are primarily responsible for communication between cells.
• Receptor Sites:
  • Cells have receptor sites that receive signals.
• Respiration:
  • Definition: The process used by ALL organisms to produce energy by using oxygen to burn sugar in order to release energy in the form of (ATP).
  • Organelle used in this process: Mitochondria.
• Digestion:
  • Definition: Breaking large molecules down into smaller molecules.
    • Proteins are broken down into Amino Acids.
    • Carbohydrates and Starches are broken down into Simple Sugars.
    • Fats (Lipids) are broken down to Fatty Acids & Glycerol
• Transport:
  • Involves the movement of materials inside the cell as well as the movement between parts of a multicellular organism.
• Excretion:
  • The removal of all waste produced by the cells of the body.
• Synthesis:
  • The making or building of large molecules from smaller ones.
• Photosynthesis:
  • Definition: The process of storing the energy from the sun in the chemical bonds of glucose (sugar).
  • Organelle used in this process: Chloroplast.
  • Formula for Photosynthesis: $Sun + Carbon Dioxide + Water \xrightarrow{enzymes} Glucose + Oxygen + Water$
  • Location: Chloroplasts of Producers (plants)
• Cellular Respiration:
  • Occurs in the Mitochondria of All Organisms both plants and animals
  • Formula for Cellular Respiration:
    $Glucose + Oxygen \xrightarrow{enzymes} Carbon Dioxide + Water + Energy (ATP)$

Enzymes

• Enzymes:
  • Definition: Special proteins that affect the rate of chemical reactions.
  • Function: Catalysts used in digestion and synthesis.
  • Enzyme reaction rates are affected by:
    • Shape-"Lock and Key Model" if it is the wrong shape it will not work.
    • Temperature - each enzyme works best at a specific temperature
    • pH - each enzyme works best at a specific pH

Homeostasis

• Dynamic Equilibrium:
  • A steady state-balance-: HOMEOSTASIS
• Negative Feedback:
  • Controls hormone levels to maintain homeostasis.
  • Analogy: Thermostat; as the temperature in your house goes up, the thermostat turns your heat off; as the temperature goes down, the thermostat turns on. This maintains a balance or a comfortable home.
  • Example: How our body regulates the amount of sugar in our blood:
    • When glucose (sugar) levels are above normal the pancreas secretes INSULIN.
    • This hormone prompts glucose to move from the blood into body cells, resulting in a lower glucose level in the blood.
    • Another hormone secreted by the pancreas (glucagon) works in the opposite way.
    • When the glucose level in the blood is too low, this hormone prompts the release of glucose stored in the liver which raises BLOOD SUGAR LEVEL.

Immunity

• Defense:
  • Our Skin and Circulation Systems are the body's primary defense against disease-causing pathogens via White blood cells
• Surface Receptor Protein:
  • Definition: A molecule found on the cell membrane that the immune system recognizes as either part of the body or an outside invader.
  • Antigens are the receptor proteins on the membrane of pathogens (germs).
• Antibodies:
  • Definition: Special proteins produced by the white blood cells that can be thought of as your body's army to fight diseases.
    • Antibodies have specific shapes that fit over specific antigens
    • When an antibody fits into the antigen (receptor on the pathogen) it blocks communication preventing the germ from reproducing and making you sick.
• Immunity:
  • Definition: Our body's ability to fight disease.
  • Once you have been exposed to a specific virus white blood cells remember the antigens and produce antibodies that prevent you from getting sick from the same virus for the second time.
• Vaccination:
  • Definition: Composed of a weakened or dead virus that triggers our white blood cells to produce antibodies to fight a specific pathogen.
• Diseases:
  • Caused by pathogens (virus, bacterium, and fungus)