Chapter 3 - The Cell Flashcards
3 Major Parts of a Cell
- Plasma membrane - separates inside of cell from outside of cell
- Cytoplasm - everything between the plasma membrane & the nucleus
- Nucleus - control center; contains the cell’s DNA
3 Functions of Plasma Membrane
- Cell barrier - movement in & out of cell: movement determined by the cell
- Selectively Permeable - some things are allowed through
- Cellular Communication
Structure of Plasma Membrane
Fluid Mosaic Model–model to describe plasma membrane
fluid - refers to liquid & moves around;
mosaic - refers to proteins which give structure & function to plasma membrane; so many shapes & functions; diversity
Fluid Mosaic Model Structure contains:
3 Lipids:
- Phospholipids bilayer - make up bulk of membrane
- Cholesterol
- Glycolipids - part lipid part carb; carb attached to lipid
3 Proteins:
- Periphereal proteins - loosely attached; on side
- Integral proteins - imbedded or inside
- Glycoproteins - carbs attached to proteins (stick outside of cell)
“Glyco” part of glycolipids & glycoproteins
Glycocalyx - carbs on outer surface of plasma membrane;
Function: cellular recognition
Transport Processes - how things cross the plasma membrane (lipid barrier); selectively permeable
- Passive Processes - does not require chemical energy; moves from high to low concentration
- Active Processes - needs ATP (requires chemical energy)
3 Types of Passive Processes - driving force is concentration gradient
1. Simple Diffusion - very few things can cross bc lipids (nonpolar); must be nonpolar & small; ex. O2 & CO2
- Facilitated Diffusion - polar molecules (ions-charged particles) cannot cross by simple diffusion but may cross by facilitated diff w/help of a protein; Needed for facilitated diff - protein channel - places where ions can cross & protein carriers - amino acids, glucose; needs a helping protein to cross;
- Osmosis - diffustion of water across a selectively permeable membrane; 3 kinds of solutions: Isotonic, Hypotonic solution & Hypertonic solution
Diffusion
passive process; depends on concentration gradience; things move from high to low concentration
3 Different Kinds of Solutions for Osmosis:
- Isotonic - same solute concentration; mixture is matched to cell; H2O concentration is same inside cell & outside cell; no net movement of water: osmosis does not occur; cell maintains its shape
- Hypotonic solution - lower solute concentration; solution w/very few solutes (like distilled water); very few salts; lower H2O in cell & highest water in solution; H2O moves into cell & cell swells up & could burst (lyse)
- Hypertonic solution - higher solute concentration; put into very salty solution; less H2O surrounding cell & higher amount in cell; H2O goes out of cell & cell shrinks
Water follows
salts; wherever there is more salts , water will be sucked into it
Active Processes;
we want things to move from low concentration to high concentration; usually low to high concentration–which is not favorable
3 Types of Active Processes:
- Primary Active Transport
- Secondary Active Transport
- Vesicular Transport–a. exocytosis & b. endocytosis –1. phagocytosis, 2. pinocytosis, 3. receptor-mediated endocytosis
Primary Active Transport (Active Process) - uses ATP; from low - high
ex. Na+ K+ pump -moves 2 substances in diff directions from low to high; found in every single cell in body; protein
Na+ - pumped OUT of cell (from low -high);
K+ - pumped INTO cell (from low -high);
very little Na+ in cells & very little K+ outside cells & lots of salt outside cells;
ATP - ase - enzyme that hydrolizes ATP
Secondary Active Transport (Active Process)
only works when primary is working; uses concentration gradient that was already established; Na+ tends to want to go back in cell bc it goes from high - low; will go in through Secondary Active transport & will pump out Ca2+ or can move Na+ into cell & H+ out; can move glucose or amino acids in as Na+ moves in; indirectly uses ATP; links movement of one ion w/movement of 2nd particle by concentration gradient that has already been established; relies on concentration gradient; does not directly use ATP but does not work unless Primary Active Transport setup concentration gradient
Vesicular Transport (Active Process)
refers to vesicles; how we bring fairly bulky materials across membrane w/assistance of vesicles; uses vesicles (membrane sacs); uses ATP
- exocytosis - uses vesicles to transport substances out of cell; the way proteins, hormones leave the cell
- endocytosis - uses vesicles to transport substances into cell
3 different mechanisms of endocytosis- phagocytosis, pinocytosis, receptor mediated endocytosis
