Levels of Organization in Multicellular Organisms

• Multicellular organisms exhibit levels of organization.
• The levels of organization from smallest to largest are: cells, tissues, organs, organ systems, and organism.
• The cell is the smallest unit of life.
• A tissue consists of a group of similar cells performing a specific function.

Human Body Systems

• Three human body systems include the digestive, respiratory, and circulatory systems, all containing organs.
• Digestive: stomach, intestines.
• Respiratory: lungs, trachea.
• Circulatory: heart, blood vessels.

Structure and Function

• Structure and function are related.
• This relationship applies to all levels of biological organization.

Homeostasis

• Homeostasis is maintaining a stable internal environment.
• A feedback loop is a biological mechanism that regulates a process.
• Negative feedback reduces the original stimulus, whereas positive feedback enhances it.
• Negative feedback is directly related to homeostasis.
• Examples of negative feedback loops include body temperature and blood sugar regulation.
• Examples of positive feedback loops include blood clotting and childbirth.

Atoms and Molecules

• An atom is the basic unit of matter.
• A molecule is a group of atoms bonded together.
• A covalent bond involves sharing of electrons between atoms.
• Hydrogen bonds hold water molecules together.
• Inorganic molecules do not contain carbon-hydrogen bonds, while organic molecules do.
• Water and salt are inorganic molecules.
• Carbohydrates and proteins are organic molecules.

Monomers and Polymers

• A monomer is a small building block molecule.
• A polymer is a large molecule made of repeating monomer subunits.
• Monomers join to form polymers.
• Monomers connect through dehydration reactions.
• Polymers break apart through hydrolysis.

Biomolecules

• The four main categories of biomolecules are carbohydrates, lipids, proteins, and nucleic acids.
  • Carbohydrates:
    • Monomer is monosaccharide
    • Polymer is polysaccharide
    • Structure is a ring shape.
  • Lipids:
    • Monomer is fatty acids
    • Polymer is triglycerides
    • Structure is chains of carbon atoms.
  • Proteins:
    • Monomer is amino acids
    • Polymer is polypeptide
    • Structure is complex 3D shape.
  • Nucleic Acids:
    • Monomer is nucleotide
    • Polymer is DNA/RNA
    • Structure is a double helix or single strand.
• Carbohydrates mostly function as energy sources.
• Proteins have the most diverse functions.
• Nucleic acids function as genetic material.
• Carb-loading is increasing carbohydrate intake to increase energy stores, this is done before endurance events, and involves eating foods like pasta and bread.
• Saturated lipids have single bonds, while unsaturated lipids have double bonds.
• DNA is double-stranded and contains deoxyribose sugar, while RNA is single-stranded and contains ribose sugar.
• Not all proteins are enzymes.
• Substrate-specific means an enzyme acts on a particular substrate.
  • Example: lactase acts on lactose.
• Enzymes are important because they speed up reactions necessary for life.
• Enzymes work by lowering the activation energy of chemical reactions.
• Enzymes decrease activation energy.

Cell Types

• Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have them.
• Bacteria and Archaea are made of prokaryotic cells.
• Eukaryotic cells compose protists, fungi, plants, and animals.
• Prokaryotic cells lack a nucleus, mitochondria, and endoplasmic reticulum.
• Ribosomes are present in all cells, but freely scattered in a prokaryotic cell's cytoplasm, and their job is protein synthesis.
• A microscope is needed to view a cell.
• The unit of measurement for cells is the micrometer (µm).
• Cells range in size from 1-100 µm.
• Cells are small to maintain a high surface area-to-volume ratio.
• Differences include: nucleus, membrane-bound organelles and cell wall (plants only).
• The nucleus stores DNA, and ribosomes synthesize proteins based on the instructions from the nucleus.
• Three parts the same among ALL eukaryotic cells: cell membrane, cytoplasm, ribosomes.
• The job of the cell membrane is protection and controls what enters and exists the cell.
• The job of the cytoplasm is as the location of cellular processes.
• The jog of the ribosome is to synthesize proteins.
• Differences between plant & animal cells: chloroplasts, cell wall, and large central vacuole are in plant cells only.

Cell Membranes and Walls

• The cell membrane regulates what enters and exits the cell.
• Compare and contrast eukaryotic cell membranes to cell walls.
• Plant and fungi eukaryotic cells have a cell wall surrounding the cell membrane.
• Animal eukaryotic cells have a cell membrane as the outer most layer.
• ATP stands for adenosine triphosphate.
• ATP supplies energy for cellular processes.
• Humans make ATP through cellular respiration.
• ATP production in eukaryotic cells occurs in the mitochondria.
• During the ATP-ADP cycle, ATP loses a phosphate to release energy, becoming ADP, then ADP gains a phosphate to become ATP, recharging the energy supply.
• Cellular energy is vital for maintaining homeostasis through various processes.

Photosynthesis and Cellular Respiration

• Photosynthesis chemical equation: 6CO2 + 6H2O -> C6H12O6 + 6O2
• Cellular respiration (aerobic) chemical reaction: C6H12O6 + 6O2 -> 6CO2 + 6H2O + ATP
• Photosynthesis produces glucose and oxygen, which cellular respiration uses to produce carbon dioxide, water, and ATP.
• Organisms that perform both in their cells: plants.
• Photosynthesis converts light energy to chemical energy, while cellular respiration releases chemical energy.
• Aerobic cellular respiration is more efficient, producing about 36 ATP per glucose, while photosynthesis converts light into stored energy.
• Photosynthesis occurs in the chloroplasts, and aerobic cellular respiration occurs in the mitochondria. for Eukaryotic cells
• Aerobic requires oxygen, while anaerobic does not.
• The two types of fermentation are lactic acid and alcoholic, producing lactic acid or alcohol and CO2, respectively.
• Fermentation occurs in bacteria, yeast, and muscle cells, and yields less ATP than aerobic.

Phospholipids and Diffusion

• Phospholipids form a bilayer because they have a hydrophilic head and hydrophobic tails.
• The cell membrane is also called the plasma membrane.
• Small, nonpolar molecules can move through the phospholipids.
• Large, polar molecules need a transport protein.
• Passive transport does not require energy.
• Example of cells doing passive transport: osmosis moves water across a membrane.
• Active transport requires energy.
• Example of cells doing active transport: protein pumps moving ions against their concentration gradient.
• Diffusion is the movement of molecules from high to low concentration.
• Facilitated diffusion (passive) uses a protein channel, while a protein pump (active) uses energy to move molecules against the concentration gradient.
• Concentration is the amount of a substance in a defined space.
• Hypotonic means a lower solute concentration, isotonic means equal solute concentration, and hypertonic means a higher solute concentration.
• A cell with 13% solute in a solution of 45% solute will experience osmosis out of the cell.

Explore the hierarchical organization of multicellular life, from cells to organ systems. Learn about tissues, organs, and the major human body systems: digestive, respiratory, and circulatory. Understand the relationship between structure and function and the importance of homeostasis.