2. Cell physiology Flashcards
Cell Structure:
3 major subdivisions
o Plasma memb. that encloses cell
o Nucleus which contains DNA
o Cytoplasm liquid environment of inner cell
Plasma Membrane
Lipid molecules and proteins which enclose cell and act as selective barrier between ICF and ECF
Nucleus
Largest organized cell component; contains DNA, which directs protein synthesis and serves as genetic blueprint during cell replication
RNA
Messenger (mRNA) copies code
Ribosomal (rRNA) makes up ribosomes, large and small subunit
Transfer (tRNA) delivers amino acids to peptide
Cytoplasm
Compartment between membrane and nucleus
Filled with cytosol (gel liquid), organelles, and cytoskeleton
Organelles
Membranous vs nonmembranous
ER
Site of protein synthesis
Rough ER- contains ribosomes
Smooth ER- lacks ribosomes, processes and packs protein, and stores calcium for release as second messenger
Golgi
Completes protein modifications and sorts, packs, and directs proteins to organelles or exocytosis
Exocytosis
o Protein called clathrin helps to form a vesicle; this protein is useful for moving proteins and vesicles in and out of cells, esp. within synapses
Endocytosis
o Pinocytosis: simple fluid uptake
o Receptor-mediated endocytosis: uses surface proteins to activate clathrin, which in turn enables pinching and vesicle formation
o Phagocytosis: large particle uptake (eating)
Metabolism
Lysosomes: Large, uses hydrolytic enzymes to break peptides, destroys things
Peroxisomes: Small, uses oxidative enzymes and produces H2O2, detoxifies things
Mitochondria
Converts food energy into ATP, which is cell’s energy currency
2 membranes- inner one is folded into cristae, inside of which is the matrix
Cytoskeleton
Cell support and structure
Plasma membrane–phospholipid bilayer
Describe phospholipid structure
Glyceral molecules form the backbone.
To each glyceral is bound 2 fatty acids and a phospholipid head group
Cholesterol
tucked between phospholipids, it contributes to membrane fluidity and stability
Membrane Proteins
Form channels across membrane, Carrier molecules, Docking-marker acceptors, Membrane-bound enzymes, Receptor sites, Cell adhesion molecules (CAMs), Cell recognition
Membrane Carbohydrates
glycolysis of Erythrocytic membrane groups plays large part in determining blood groups
ECM made up of
o Collagen - multiple forms of connective protein
o Elastin - thin, shimmery membrane
o Fibronectin
Desmosomes
Made of keratin intermediate filaments which are very flexible and stretchy in the extracellular state (over the intracellular state)
Anchors close, non-touching cells in stretchy tissues
Tight junctions
Used to separate compartments
Prevent movement of substances between cells by firmly bonding cells together
This forces substances through the cells, which is more selective
Esp. important in digestive tract
Gap junctions
small connecting tunnels made of connexon proteins
Allows free passage of very small ions and/or membrane potentials to pass between cells w/o an action potential
Each cell assembles half of a channel
Diffusion:
Uniform spreading out of molecules
Dependent on Brownian motion and conc. gradients
Critical for muscle contractions, nervous signaling, exchange of O2 and CO2, and movement of substances across kidney tubules
Fick’s Law of Diffusion
> conc. grad. inc. diff.
ECF is large, so conc. changes very slowly
Substances move freely between blood and ECF, but not ECF and ICF
> permeability inc. diff.
> S.A. inc. diff.
> Mol. Weight dec. diff.
> distance of diff. dec. diff.
Osmosis: Net diffusion of water down its conc. gradient
Hydrostatic pressure prevents infinite movement to side with higher conc. gradient
Tonicity: osmolarity of solution in comparison to the cell
Isotonic solution: Cell stays the same size
Hypotonic solution: cell will swell (> water conc.)
Hypertonic solution: cell will shrink (< water conc.)
This generally initiates apoptosis