Chap 4 pT 3 Flashcards
Tonicity
Relative concentration of solutes (compared to cell)
Isotonic
cytosol and solution have same solute concentration E.g., saline with a concentration of 0.9% NaCl is commonly in IV solutions
No net movement of water
Hypotonic
solution has a lower concentration of solutes (and higher concentration of water) than the cytosol
Water enters the cell
Lysis
rupturing of cells occurs if enough osmotic pressure
Hypertonic
Solution with a higher concentration of solutes (and lower concentration of water) than the cytosol
Water leaves the cell
Crenation
cell shrinks
Active Process: active transport (and vesicular transport)
Movement of a solute against its concentration gradient
Active Transport
Maintains gradient between cell and interstitial fluid
Active Transport
Source of energy determines whether movement is primary or secondary
Primary Active Transport (energy directly from breakdown of ATP)
Phosphorylation
Phosphate group added to protein
Changes protein’s shape
Ion Pumps
Protein pumps that move ions across cell membrane
Maintains internal concentrations of ions
E.g., proton pumps from Chapter 3—electron transport system
Ca2+ pumps in plasma membrane of erythrocytes
E.g., Sodium-Potassium Pumps
Secondary Active Transport 1
Moves substance against concentration gradient via energy from movement of second substance down its gradient
Secondary Active Transport 2
Kinetic energy providing “power” to pump other substance
Na+ moves down concentration gradient
Dependent on Na+/K+ pumps to generate gradient of Na+
2 types of Active Transport (1)
Symport
Same direction
2 types of Active Transport (2)
Antiport
Opposite direction
Vesicular Transport (“bulk transport”)
Involves energy input to transport large substances across the plasma membrane by a vesicle
Membrane-bounded sac filled with material
Exocytosis
substances secreted from cell in vesicles
Endocytosis
substances taken into cells in vesicles from external environment
Macromolecules
too large to be moved across membrane is packed in vesicles
Vesicle and plasma membrane fuse
Requires ATP
Contents released to outside of cell following fusion
-E.g., release of neurotransmitters from nerve cells
Endocytosis: Cellular uptake of large substances from external environment
Functions
Uptake of materials for digestion
Retrieval of membrane parts after exocytosis
Regulation of membrane protein composition
Steps of endocytosis (Reverse of exocytosis)
Substances packaged into a vesicle formed at cell surface
Invagination—small area of membrane folds inward, forming a pocket
Pocket deepens and pinches off when lipid bilayer fuses
Requires expenditure of energy
Steps of endocytosis (reverse of exocytosis) pT 2:
New intracellular vesicle with material that was formerly outside the cell
Phagocytosis “Cellular eating”
A cell engulfs a large particle external to cell
(only a few cells do this Immune )
Forms large extensions to surround particle, enclosing it in a membrane sac
Contents of sac digested after fusing with lysosome
Pinocytosis “cellular drinking”
Internalization of droplets of interstitial fluid with dissolved solutes
Multiple, small vesicles formed
Performed by most cells
Resting membrane potential
Cells establish and maintain electrochemical gradient
Essential for muscle and nerve cell function
Membrane Potential
potential energy of charge difference across membrane
Resting membrane potential (RMP)
membrane potential when a cell is at rest (as opposed to “excited”)
Unequal distribution of ions across cell membrane
Unequal relative amounts of positive and negative charges
More positive on outside than inside of cell—RMP is negative!
Na+ and K+
diffuse across membrane through leak channels
What does Na+ / K+ pump maintain
K+ and Na + gradients despite diffusion
–uses ATP energy to do so
Direct cellular contact important for immune system
Need to destroy unhealthy and foreign cells
Distinguishes normal cells from unwanted cells
Unhealthy and foreign cells express different glycocalyx pattern than normal cellsSubsequently destroyed
Sperm and oocyte
Egg with unique glycocalyx
Allows for recognition by sperm during fertilization
Cellular regrowth following injury
Damaged tissue replaced by cell division in epidermis
Cellular contact prevents overgrowth
Ligands
Molecules that bind with receptor molecules
Neurotransmitters and hormones Controls growth, reproduction, and other cellular processes
Channel Linked receptors
Permit passage of ions into or out of cells
Occurs in response to neurotransmitters
Help initiate electrical changes to RMP in muscle and nerve cells
Enzymatic Receptors
Activated to phosphorylate other enzymes within the cell
Provides mechanism for altering enzymatic activity (off or on)
