Cell

• There are 100 trillion cells in our body
• Most of the cell size ranges from 10 to 15 micrometers
• Important functions of the cell:

  • Cell metabolism and energy use involve different chemical processes that provide energy for muscle contraction and heat production
  • Synthesis of molecules includes proteins, nucleic acids, and lipids
  • Communication involves producing and receiving chemical and electrical signals for cell-cell communication
  • Reproduction and inheritance where each cell contains genetic information and specialized cells transmit this information to the next generation
• Plasma membrane or cell membrane acts as a boundary with gate-like properties
• Cytoplasm contains organelles and molecules
• Nucleus acts as the control center and contains the cell's genetic information
• Cell membranes are made of a lipid bilayer with hydrophilic phosphate-containing ends and hydrophobic fatty acid ends
• Cell membranes determine selective permeability and regulate the flow of substances in and out of the cell
• Proteins in the cell membrane function as membrane channels, carrier molecules, receptor molecules, enzymes, or structural supports
• Membrane channels and carrier molecules are involved in the movement of substances through the cell membrane
• Receptor molecules are part of an intercellular communication system for cell recognition and coordination of cell activities
• The nucleus carries genetic material, controls cell activities and structure, and produces ribosomes through nucleoli
• The nucleus consists of the nuclear envelope, nucleolus, and chromatin
• Nuclear pores in the nuclear envelope regulate the movement of substances into and out of the cell
• The nucleolus is responsible for making ribosomes and contains DNA, RNA, and proteins
• In a non-dividing cell, genetic material is spread out as chromatin, while in a dividing cell, it condenses into chromosomes
• There are 23 pairs of chromosomes, consisting of DNA and protein
• Cytoplasm is the gel-like substance between the plasma membrane and the nucleus, containing organelles that perform various tasks in cellular metabolism
• Intracellular fluid: fluids inside the cell
• Extracellular fluid: fluids outside the cell
• Interstitial fluids: fluids between cells within tissue
• Plasma: fluids within a blood vessel
• Lymph: fluids within a lymphatic vessel
• Cerebrospinal fluid: fluids that surround the brain and spinal cord
• Solute: a substance being dissolved in various fluids
• Solvent: a fluid or gas in which solute is being dissolved
• Concentration: the amount of solute dissolved in a given volume of solvent
• Concentration Gradient: the difference in concentration of a substance between two areas
• Cell membranes have the unique capability to only allow certain substances to pass through its selective permeability
• Passive transport: no cellular energy required during transport
• Active transport: a certain amount of cellular energy is needed for successful transport
• Diffusion: solutes move from an area of high concentration to areas of low concentration
• Osmosis: water moves from a region of lower concentration to higher concentration through a semipermeable membrane
• Osmotic pressure: the force required to prevent the movement of water across a selectively permeable membrane
• Isotonic: solute concentration outside the cell is the same as inside the cell, resulting in no net movement of water
• Hypotonic: solute concentration outside the cell is less than inside, causing water to flow into the cell
• Hypertonic: solute concentration outside the cell is greater than inside, causing water to flow out of the cell
• Three kinds of carrier-mediated transport: facilitated diffusion, active transport, and secondary active transport
• Facilitated diffusion: moves substances from high to low concentration through carrier proteins
• Active transport: uses ATP and transport proteins to pump particles from low to high concentration