Physio prelims

• Structural organization of cells:

  • Chemical level
  • Cellular level
  • Tissue level
  • Organ level
  • System level
  • Organism level
• Cytology is the study of cells
• Main parts of the cell:

  • Plasma Membrane: the cell's flexible outer surface that separates the internal environment from the external environment and regulates the flow of materials
  • Fluid mosaic model: the arrangement of molecules within the membrane resembles a sea of lipids containing many types of proteins
  • Cytoplasm: consists of all the cellular contents between the plasma membrane and the nucleus, including cytosol and organelles
  • Nucleus: a large organelle that contains DNA, chromosomes, genes
• Structure of membrane proteins:

  • Ion channel: forms a pore for specific ions to flow through
  • Carrier: transports specific substances by changing shape
  • Receptor: recognizes specific ligands and alters cell function
  • Enzyme: catalyzes reactions inside or outside the cell
  • Linker: anchors filaments inside and outside the plasma membrane, providing structural stability and shape
• Centrosome:

  • Located near the nucleus and consists of centrioles and the pericentriolar matrix
  • Functions in organizing the growth of the mitotic spindle for cell division and microtubule formation
• Cilia and Flagella:

  • Motile projections of the cell surface
  • Cilia: short, hairlike projections that cause fluid movement along the cell's surface
  • Flagella: longer projections that generate forward motion, e.g., sperm cell's tail
• Ribosomes:

  • Sites of protein synthesis
  • Attached ribosomes synthesize proteins for insertion in the plasma membrane or secretion
  • Unattached/free ribosomes synthesize proteins used in the cytosol
• 
  

  • Smooth ER: lacks ribosomes, synthesizes fatty acids and steroids, detoxifies substances
  • Rough ER: studded with ribosomes, synthesizes proteins like glycoproteins and phospholipids
  • Golgi complex: modifies, sorts, and packs proteins for transport
• Lysosomes:

  • Membrane-enclosed vesicles that work best at an acidic pH
  • Contain enzymes for recycling worn-out cell structures and digesting organelles
  • Autophagy: process of digesting entire worn-out organelles
  • Autolysis: destroys the entire cell
• Peroxisomes:

  • Similar to lysosomes but smaller, contain oxidase enzymes and catalase
  • Detoxify substances, abundant in the liver
• Proteasomes:

  • Barrel-shaped structures that destroy unneeded proteins
  • Found in liver, kidney, and intestinal cells
• Mitochondria:

  • Generate most ATP through aerobic respiration
  • Play a role in apoptosis and contain genes inherited only from the mother
  • Mitochondrial matrix: area for chemical reactions producing ATP
• Nucleus:

  • Contains chromatin and the genome
  • Chromatin carries the genetic information in a cell or organism
• Transport across the plasma membrane:

  • Passive processes: substances move down their concentration or electrical gradient using kinetic energy
  • Simple diffusion: substances move freely through the lipid bilayer
  • Facilitated diffusion: integral membrane proteins assist specific substances across the membrane through channel or carrier mediation
• Passive transport moves a solute down its concentration gradient across the plasma membrane
• Stereospecificity: D-glucose is transported, but the L-isomer is not
• Saturation: The number of carriers available in a plasma membrane places an upper limit, called the transport maximum
• Competition: Structurally related solutes compete for transport sites on carrier molecules
• Osmosis involves net movement of a solvent through a selectively permeable membrane
• Two methods of movement in osmosis:

  • Simple diffusion
  • Aquaporins (water channels)
• Hydrostatic pressure is the pressure exerted on a membrane by a liquid, forcing water molecules to move back
• Nuclear envelope separates the nucleus from the cytoplasm and is a double membrane similar to the plasma membrane
• Nuclear pores are openings found in the nuclear envelope that control the movement of substances between the nucleus and cytoplasm
• Nucleoli are contained inside the nucleus for the production of ribosomes and the synthesis and assembly of rRNA and proteins into ribosomal subunits
• Chromatin is a complex of DNA, proteins, and some RNA with a beads-on-a-string structure
• Osmotic pressure is proportional to the concentration of solute particles that cannot cross the membrane
• Tonicity measures a solution's impact on cell volume by modifying water content
• Active processes use cellular energy to drive substances "uphill" against their concentration or electrical gradient
• Cellular energy used is usually in the form of adenosine triphosphate (ATP)
• Vesicle-mediated active transport includes endocytosis, exocytosis, and transcytosis
• Homeostasis is a dynamic condition in maintaining the internal environment
• Control systems of the body include receptors, control centers, and effectors
• Receptors monitor changes in a controlled condition and send input to the control center
• Control center evaluates input from receptors and generates output commands
• Effectors produce a response that changes the controlled condition
• Negative feedback reverses a change in the controlled condition, while positive feedback strengthens or reinforces it
• Feedback loops include the hypothalamic-pituitary axis
• Nervous system functions include sensory, integrative, and motor functions
• The brain consists of the brainstem, cerebellum, diencephalon, and cerebrum
• Protective coverings of the brain include the cranium and cranial meninges