Chapter 4 Cytology (no photos)

cell theory

cell smallest functional living unit, life depends on individual & collective cell function, biochemical activities of cells are dictated by organelles

irregular shaped

Nerve cells are this shape:

biconcave disc

Blood red cells are this shape:

cube

Kidney tubule cells are ____ shaped

column

Intestinal lining cells are ______ shaped

spherical

Cartilage cells are ______ shaped

cylindrical

Skeletal muscle cells are ______ shaped

aquaporins

protein channels in the plasma membrane allowing the passage of water

membrane bound organelles

enclosed by a membrane similar to the plasma membrane

• Specific activities of the organelle can proceed w/o disruption

• Ex: ER, Golgi apparatus, lysosomes, peroxisomes, mitochondria

nonmembrane bound organelles

not enclosed within a membrane, generally composed of protein

• Ex: ribosomes, centrosome, proteasomes, & cytoskeleton

Glycocalyx

sugar coated layer that covers surface of cells, for identification; includes glycolipids & glycoproteins

integral protein

protein embedded within & extending completely across the phospholipid bilayer

• most are glycoproteins

peripheral protein

proteins that aren't embedded within the lipid bilayer, attached loosely to either external/ internal surfaces of the membrane & often "anchored" to the exposed parts of an integral protein

cholesterol

four-ring lipid molecules, scattered within the inner hydrophobic regions of the phospholipid bilayer, strengthens membrane & stabilizes it at extreme temps

anchoring site

proteins that secure the cytoskeleton to the plasma membrane

cell-adhesion protein

proteins for cell-to-cell attachments

• Proteins that form membrane junctions perform many functions

Transport proteins

This type of plasma membrane proteins provide a means of regulating the movement of substances across the plasma membrane

• includes channels, carrier proteins, & pumps

cell surface receptor

Type of membrane protein that binds ligands to initiate biochemical activities

enzyme

Type of membrane protein that may be attached to the internal or external surface of a cell for cataylyzing chemical reactions

identity markers

Membrane protein that communicate to other cells that they belong to the body

• immune system use these to distinguish normal, healthy cells

membrane junction

composed of integral & peripheral membrane proteins which function to connect & support cells

tight junction

composed of plasma membrane proteins that form strands or rows of proteins; positioned like spot welds at the apical surfaces around the circumference of each adjacent cells

• seal off intercellular space & prevent substances from passing unregulated b/w epithelial cells

• Ex: small intestine, prevents corrosive enzymes within the lumen from move b/w cells

desmosomes

type of intercellular junction that holds cells together at a single point (like a button), provides integrity to cells that are exposed to stress (external skin layer + cardiac muscles)

• protein plaque - thickened structure located on internal surface of plasma membrane of adjoining cells w/t many extending protein filaments

hemidesmosomes

half of a desmosome; anchor the basal surface of the cells of the epidermis to the underlying basement membrane

gap junction

composed of connexons that form a very small fluid filled tunnel/ pore that extends across a small gap b/w adjacent cells

• direct passageway for substances to move b/w neighboring cells

• ions, glucose, amino acids, small solutes can pas directly from cytosol of one cell into neighboring cell

• allows spread of electrical activity in cardiac cells

passive transport

Membrane transport that don’t req expenditure of cellular energy, simple depend upon kinetic energy of ions & molecules as each moves down its concentration gradient

• involves diffusion + osmosis

Active process

Membrane transport requiring expenditure of cellular energy where a solute is moved up its concentration gradient

• includes Active transport + vesicular transport

diffusion

the movement of either ions or molecules down their concentration gradient

• dependent on concentration gradient, spreading out of ions + molecules, if unopposed results in equilibrium

simple diffusion

passive transport process used when small & nonpolar molecules cross the plasma membrane unassisted

• respiratory gases, small fatty acids, ethanol, & urea

• not regulated by plasma membrane, dependent only on [] gradient

facilitated diffusion

passive transport process using carrier/ channel proteins to move a chemical across the plasma membrane, small solutes that are charged ions/ polar molecules

• 2 types: channel mediated & carrier mediated

channel mediated diffusion

 the movement of small ions across the plasma membrane through water-filled protein channels, each channel typically specific

• leak channel & gated channel

leak channel

protein channel allowing the movement of small ions across the plasma membrane; typically continuously open

• allows Na+ to leak out & K+ to leak out, helps resting membrane potential to remain at - 70mV

gated channel

protein channel allowing movement of small ions across the membrane, usually closed & opens in response to a stimulus

• stays open for fraction of a second

• important for normal function of muscle & nerve cells

carrier mediated diffusion

movement of polar molecules across the plasma membrane, large size of polar molecules req assistance by carrier proteins

3 Events:

• carrier protein membrane binds to polar molecule

• conformation change to carrier protein & polar molecules moves to the other side

• polar molecule released

uniporter

a carrier protein that only transports one substance

• Ex: glucose carriers, prevents glucose in urine

transport maximum

the maximum rate at which a substance can be transported

• Cells can alter transport rate by changing # of channels/ carrier proteins

osmotic pressure

the pressure exerted by the movement of water across a semipermeable membrane due to a difference in water concentration

• The steeper the gradient, the greater amount of water moved, the higher the ____ _____

hydrostatic pressure

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

primary active transport

a membrane transport that uses energy derived directly from the breakdown of ATP

ion pump

cellular protein pumps that move ions across the membrane

sodium potassium pump

an exchange pump in which 3 Na+ ions are pumped out of a cell for every 2 K+ ions that are pumped into a cell

secondary active transport

cotransport or coupled transport; transport process that req the movement of a substance down its concentration gradient to provide energy to move a different substance up its concentration gradient

• dependent on primary transport mechanism, Na+ gradient often energy source bc its gradient is steep (potential energy harnessed)

symport

two substances are moved in the same direction by a symporter protein

- Ex: Na+ & glucose

antiport

two substances are moved in the opposite direction by an antiporter

• Ex: H+ & Na+, Na+ moves into the cell & H+ moved out

vesicular transport

bulk transport; involves a vesicle which allows for the movement of large substances across the membrane

• Two types: exocytosis & endocytosis

exocytosis

process whereby contents within a vesicle are exported outside a cell

• release of neurotransmitter molecules from nerve cells

endocytosis

the cellular uptake of large substances or large amounts substances from the external environment into the cell

• uptake of nutrients & extracellular debris for digestion by lysosomes

• retrieval of membrane regions added to the plasma membrane during exocytosis

• regulation of the composition of membrane proteins to alter cellular processes

• 3 types: phagocytosis, pinocytosis, receptor-mediated

phagocytosis, pinocytosis, receptor-mediated endocytosis

What are the 3 types of endocytosis?

invagination

occurs when a small area of the plasma membrane folds inward into the cytosol to form a pocket

• occurs during endocytosis

phagocytosis

a form of endocytosis by which cells ingest & digest solid substances; "cell eating"; nonspecific

• pseudopodia (membrane extensions) used to capture large particles external to the cell

• only few types of cells can perform this

• Ex: WBCs engulfing & digesting a microbe

pinocytosis

a form of endocytosis by which cells ingest liquid; "cell drinking"; nonspecific

• multiple small regions of the membrane invaginate & multiple small vesicles are formed

• performed by most cells

receptor mediated endocytosis

uses receptors on the plasma membrane to bind specific molecules within the interstitial fluid & bring the molecules into the cell

• ligands bind to integral membrane protein receptors forming ligand receptor complex

• clathrin protein > clathrin coated pit > clathrin coated vesicle

• Ex: transport of cholesterol from the blood

resting membrane potential

voltage measured across the plasma membrane of an excitable cell at rest

• ranges from -50mV to -100mV

• established & maintained: unequal distribution of ions + charged molecules + relative number of positive & negative charges aren’t equally distributed

interstitial fluid; cytosol

Na+ concentration is greater in the _____ ____ while K+ is greater in concentration in the _____

cytoplasm

located b/w plasma membrane & nucleus

Cytosol

intracellular fluid, water with solutes (proteins, salts, sugars)

inclusions

a temporary store of molecules in the cytosol; substances continuously being added/ removed

• granules of glycogen or pigments, lipid droplets, vacuoles, & crystals

mitochondria, peroxisomes, lysosomes, endoplasmic reticulum, golgi apparatus

What are the membrane bound organelles? (5)

Cytoskeleton, centrioles, ribosomes

What are the nonmembranous organelles? (3)

Rough endoplasmic reticulum (Rough ER)

protein synthesis for membrane, modifies + stores proteins, helps form peroxisomes, forms transport vesicles for proteins to Golgi apparatus

Smooth endoplasmic reticulum (Smooth ER)

lipid synthesis+transport+storage, carbohydrate metabolism, detoxifies, vesicle formation

• Prominant in the liver, skeletal + cardiac muscles (stores & release calcium ions for contraction)

Golgi apparatus

mix + modify proteins, forms proteoglycans, synthesize digestive enzymes for lysosomes, vesicle formation delivering components for plasma membrane + releasing contents from cell by exocytosis

• prominent in glands

lysosomes

Suicide sack, contain digestive enzymes formed by the Golgi

• break down molecules within vesicle that enter cell by endocytosis

• autophagy + autolysis

autophagy

Removal of damaged organelles & cellular components

autolysis

break down of cellular components; apoptosis

peroxisomes

hydrolytic enzymes: chemical digestion, beta oxidation of fatty acids, lipid synthesis

• antiviral: vitamin D + zinc can aid _____ to fit viruses

• they’re pinched off vesicles from the Rough ER

• gets its name from H2O2 hydrogen peroxide < break down into H2 + O2

mitochondria

ATP synthesize

• have independent movement

• through exercise can increase ATP production by 25%

• Aerobic

Kinesin

Motor molecules that move organelles

ribosome

Protein production

• composed of protein + RNA

• arranged into large & small subunits

• made within nucleolus & assembled in cytoplasm

free floating ribosome

Protein production that stays in the cell

• includes microtubules, enzymes, & cytoskeletal filaments

• make enzymes that anaerobically produce lactic acid in the cytosol

membrane bound ribosomes

Produce proteins that get exported by the cell membrane, become part of the cell membrane, or are repackaged into enzymes for lysosomes

• proteins go toward other membrane bound organelles

microtubules

hollow cylinders of tubulin protein that are part of the cytoskeleton; able to lengthen & shorten; largest component of cytoskeleton (25 nanometers)

• constantly changing & moving (dynamic), arranged like railway tracks for directing movement of organelles & vesicles within a cell

• extend into core of cilia + flagella for movement

• found in centrioles

microfilament

smallest structural protein of the cytoskeleton; strand made of spherical protein actin subunits

• participate in muscle contraction

intermediate filament

intermediate in size relative to microfilaments & microtubules, less flexible proteins extend across the inside of the cell & function as rigid rods to support cell & stabilize junctions

• tough, insoluble protein fibers constructed like woven ropes composed of tetramer fibrils

cytoskeleton

framework of diverse proteins that extends both beneath the plasma membrane & through the interior of the cell; supports the cell & organizes organelles

• Microfilaments, microtubules, & intermediate filaments

• intracellular support, organization of organelles, cell division, movement of materials

proteasomes

degrade proteins that are damaged, incorrectly folded, or no longer needed

• control quality of exported cell proteins

microvilli

microscopic extensions of the plasma membrane supported by microfilaments that increase the surface area for secretion/ absorption

• Densely packed together, lack powered movement

• Provide more extensive plasma membrane for more efficient membrane transport

• Seen throughout small intestine

cilia

extensions of the plasma membrane supported by microtubules that move materials past the cell

• Usually found in large numbers on exposed surfaces of specific cells (lining respiratory passage)

• Movement moves mucus & substances along the cell

flagella

similar in structure to cilia but longer & wider; when present, there's usually only one; help propel an entire cell

• Humans, only ______ is sperm

histones

a cluster of special nuclear proteins that DNA winds around

nucleosome

a complex of histones & DNA

• beads on a string

chromatin

genetic material of the nucleus in a nondividing cell; finely filamented mass resembles unrolled spool of thread

• DNA typically present in our cells in this form

• looser arrangement allows cellular structures to access genes

chromosome

when chromatin becomes tightly coiled masses when the cell divides

• Tightly coiled mass needed to prevent DNA from becoming tangled during cell division

interphase

first phase of cell cycle during which the cell carries out normal activities & prepare for cell division

• G1, S, G2

helicase

enzyme that breaks the hydrogen bond, exposing the DNA

DNA polymerase

enzyme that assembles new DNA strands

G2 phase

A phase of interphase where centriole replication is completed & enzymes + other structures needed for mitotic phase are synthesized

9+2

The arrangement of microtubules in a cilium: microtubule doublets encircle two central microtubules & are held together by cross linking proteins & radial spokes

dynein arms

Doublets of the cilium have attached motor proteins call the _____ ____