Anatomy & Physiology (McGraw Hill) - Chapter 4

Cells

light microscope

passes light through specimen to produce 2D image

transmission electron microscope (TEM)

beam of electrons passes though specimen to produce magnified/high resolution 2D image

scanning electron microscope (SEM)

beam of electrons passes through and across surface of specimen to produce 3D image

integral proteins

proteins embedded within/extend across phospholipid bilayer of cell membrane

peripheral protein

proteins loosely attached to external or internal surface of membrane

diffusion

passive transport of solutes/ions across membrane down the concentration gradient

• simple - small, nonpolar solutes move unassisted

• facilitated - small, polar solutes require channels (leak or gated) and carrier proteins

osmosis

passive movement of water across semipermeable membrane based on concentration gradient, either directly through phospholipid bilayer or via aquaporins (protein water channels)

osmotic pressure

pressure exerted by movement of water across semipermeable membrane (caused by different solution concentrations)

hydrostatic pressure

pressure exerted by a fluid on the inside wall of its container

tonicity

ability of a solution to change the volume or pressure of a cell by osmosis

• isotonic

• hypertonic

• hypotonic

active membrane transport

substances move across membrane against concentration gradient (requires energy)

• primary - uses energy directly from ATP via phosphorylation

• secondary - uses energy from movement of additional substance down its gradient

ion pump

cellular protein pumps that move ions across membrane

• phosphorylation of ATP changes protein structure

• Ex: Ca²+ pumps prevent calcium accumulation, cell remains flexible

symport

(secondary active transport) two substances moved in the same direction

antiport

(secondary active transport) two substances moved in the opposite direction

vesicular transport

transporting large substances across plasma membrane by a vesicle (requires energy)

• exocytosis

• endocytosis

phagocytosis

“cellular eating”

cell engulfs a large particle (ex: white blood cell engulfs microbe)

pinocytosis

“cellular drinking”

cell internalizes droplets of interstitial fluid containing dissolved solutes

receptor-mediated endocytosis

cell uses receptors on plasma membrane to bind external molecules and trigger endocytosis

resting membrane potential

electrochemical gradient when a cell is at rest

• unequal distribution of ions across plasma membrane (more K+ in cytoplasm, more Na+ outside cell)

• unequal charge (more positive+ inside cell)

channel-linked receptors

permits ion passage in or out of cell in response to ligand binding to gated channel

enzymatic receptors

ligand binds to receptor to activate protein kinase enzyme, which then phosphorylates other enzymes within the cell

G protein-coupled receptors

indirectly activates protein kinase enzymes with use of g-protein and GTP

1. Ligand binds to receptor

2. G protein binds to activated receptor

3. GTP binds to G protein

4. GTP/G protein leave receptor, binds to/activates effector protein (i.e. enzyme, ion channel)

5. Activated effector protein generates secondary messenger

6. Secondary messenger activates protein kinase

7. Activated protein kinase phosphorylates other enzymes

rough endoplasmic reticulum

• Synthesis: synthesizes proteins for secretion, plasma membrane, and lysosome enzymes

• Processing molecules: modifies (i.e. add carbohydrates) and stores proteins

• Organelle formation: helps form peroxisomes

• Vesicle formation: forms transport vesicles for shipping proteins to Golgi apparatus

smooth endoplasmic reticulum

• Synthesis: site of lipid synthesis (i.e. steroids)

• Processing molecules: carbohydrate metabolism (i.e. glycogen synthesis)

• Detoxification: detoxifies drugs, alcohols, poisons

• Vesicle formation: forms transport vesicles for shipping to Golgi apparatus

Golgi apparatus

• Synthesis: forms proteoglycans

• Processing molecules: modifies and stores proteins from rough ER

• Organelle formation: synthesizes digestive enzymes for lysosomes

• Vesicle formation: forms secretory vesicles for delivering components to cell membrane and releasing contents from cell via exocytosis

lysosomes

small, membranous sac that contains digestive enzymes (formed by Golgi)

• break down molecules of endocytosed vesicles

• remove damaged organelles and cellular components (autophagy)

• break down cellular components following cellular death (autolysis)

peroxisomes

membrane-enclosed sacs that form from rough ER vesicles

• Digestion: break down molecules (fatty acids, amino acids, uric acid) via beta oxidation

• Synthesis: form specific lipids (i.e. bile salts)

mitochondria

“powerhouse” of the cell

digest organic molecules to produce ATP via aerobic respiration

ribosomes

Bound (attached to ER): synthesize proteins destined to be incorporated into plasma membrane, exported from cell, or housed within lysosomes

Free (suspended in cytosol): synthesize proteins for use inside cell

BOTH:

• contain protein and RNA

• arranged into small and large subunit (A, P, E sites)

• made within nucleolus and assembled in cytoplasm

centrosome

pair of perpendicularly oriented cylindrical centrioles, surrounded by amorphous protein

• Synthesis: organize microtubules (cytoskeleton proteins) and support their growth in nondividing cells

• Cell division: direct formation of spindle fibers in dividing cells

proteasomes

protein-digesting organelles located in cytosol and cell nucleus

• Protein digestion: degrade ubiquitin-tagged proteins that are damaged, incorrectly folded, or no longer needed

• Quality assurance: control quality of exported cell proteins

cytoskeleton

• Structural support and organization: maintains cell shape and organize organelles, provides internal support to plasma membrane and microvilli (microfilaments), stabilize desmosome cell junctions (intermediate filaments)

• Cell division: separate chromosomes during cell division (microtubules), splits cell into two daughter cells via cytokinesis (microfilaments)

• Movement: facilitate cytoplasmic streaming (microfilaments), serve as track for organelle/vesicle movement (microtubules), muscle contraction (microfilaments), control proteins of cilia and flagella (microtubules)

microfilaments

smallest component of cytoskeleton composed of two intertwined actin protein monomers

Functions - maintain cell shape, internal support, cell division

intermediate filaments

intermediate-sized, rigid filaments that provide structural support (i.e. cell junctions)

microtubules

largest component of cytoskeleton, composed of tubulin, may be elongated or shorted as needed

Function. - maintain shape, cell transport, cell division

cilia

hair-like projections that move substances along cell surfacef

flagella

long, whip-like cellular appendage that propels entire cell

microvilli

extensions of plasma membrane that increase surface area

tight junctions

strands or rows of transmembrane proteins linking cells, which prevent substances from passing between cells

• linked to actin microfilaments

• maintain polarity of epithelia

desmosomes

proteins that bind neighboring cells