Cellular Form and Functions

cell theory

1. All organisms are composed of cells and cell products.

2. The cell is the simplest structural and functional unit of life.

3. An organism's structure and all of its functions are ultimately due to the activities of cells.

4. Cells come only from preexisting cells, not from nonliving matter.

5. The cells of all species have many fundamental similarities in their chemical composition and metabolic mechanisms.

squamous

thin and flat with a bulge where the nucleus is

cuboidal

cells with equal height and width

columnar

cells with greater height than width

polygonal

irregularly angled shapes with four or more sides

stellate

star-like shape

spheroidal

round or oval

discoid

disc shaped

fusiform

spindle-shaped with a thick middle and tapered ends

fibrous

long, slender and threadlike

surface area

The ___________ ____________ of a cell is is proportional to the square of its diameter,

while its volume is proportional to the cube of its diameter

A cell that is too big cannot support itself

multiplication of cells

Tissue and organ growth is based on the _____________ ____ ________, not the enlargement of existing cells

Cytoplasm

material between the plasma membrane and the nucleus

Cytosol

Viscous fluid in which organelles are suspended; mostly water with dissolved proteins, salts, sugars, etc.

extracellular fluid

fluid outside of the cells (in cytoplasm)

Cytoskeleton

cellular support and intracellular transport (in cytoplasm)

organelles

("little organs") - Metabolic machinery

nonmembranous organelles

organelles without membranes (Cytoskeleton, Ribosomes, Centrioles)

membranous organelles

organelles with membranes; allows them to be part of the endomembrane system

Inclusions

chemical substances stored depending on cell type; lipid droplets in fat cells; glycogen deposits in Liver and Muscle cells

volume

the ____________ of a cell is proportional to the cube of its diameter

A cell that is too big cannot support itself

structure of microtubules

largest elements in cytoskeleton; composed of protein subunits called Tubulin; each cylinder is composed of 13 protofilaments

function of microtubules

they determine the shape of a cell; allow movement within a cell

centrioles

formed by nine microtubule triplets

cilia

propels substances in one direction across cell surfaces (i.e. respiratory cells)

flagella

propels the cell itself (i.e sperm)

intermediate filament structure

intermediate size; vary in protein composition (in cytoskeleton)

intermediate filament function

most stable and permanent of the cytoskeleton elements

keratin

in hair, nails, and epithelial cells of the skin (intermediate filament)

neurofilament

in the axon tails of neurons (intermediate filament)

nuclear lamin

give structure to the nucleus (intermediate filament)

microfilament structure

thinnest elements of the cytoskeleton; composed of protein actin; attach to cytoplasmic face of plasma membrane

microfilament function

strengthens and resists compression; allows for movement of cells (including cleavage)

actin

protein in microfilament; allow for muscle cell contraction

microvilli

finger like projections which are most often found on absorptive cells (i.e. intestine and kidney tubules)

cellular transport

involves the transport of water, nutrients, proteins, enzymes, debris, electrolytes and even whole cells between the cell and its environment

cellular interaction

can be made between neighboring cells for adhesion and communication

intracellular fluid

fluid contained within the cells

interstitial fluid

fluid located between the cells

body fluid

blood plasma, CSF, etc.

plasma membrane

cellular transport and interactions are regulated by ____________ _______________

plasma membrane function

defines the event of the cell; regulates transport of substances into and out of the cell; allows for various forms of cellular signaling

phospholipid bilayer

plasma membrane is a _______________ ___________, embedded with proteins, lipids, and carbohydrates

selectively permeable

phospholipid chemistry makes the plasma membrane ______________ __________________.

phosphate heads

polar and hydrophillic and face the ECF and the ICF

fatty acid tails

nonpolar and hydrophobic and face the center of the bilayer

membrane

____________ is very fluid due to the constant movement of phospholipids

glycocalyx

collection of glycoproteins and glcyolipids; contain sugar groups which are important for cell signaling and recognition; offer protection, immunity to infection, defend against cancer, transplant compatibility, cell adhesion, fertilization, and embryonic development (contribute to plasma membrane structure)

cholesterol

inserted between phospholipids; promote fluidity of the membrane in low temperatures; promote rigidity of the membrane in moderate to high temperatures (contribute to plasma membrane structure)

protein receptors

provide specific bonding sites for chemicals such as hormones and neurotransmitters, binding to a one can have a short term or long term effect depending on the receptor site

cell identity markers

glycoprotein, in the glcocalyx

cell adhesion markers

allows cells to adhere to extracellular material and one another

membrane enzymes

catalyze reactions along the surface of the plasma membrane

protein carriers

bind to and transport substances across the membrane; for facilitated diffusion and active transport

active transport

requires ATP because molecules are driven against their concentration gradient

pumps

carriers which consume ATP are called ________

tight junctions

hold cells so nothing can get through; like a ziploc bag... fusion of integral membrane proteins between adjacent cells form an impermeable junction and prevent substances from passing through extracellular space between cells EX: lining of stomach so acid can't get out

desmosomes

anchoring junctions which distribute tension through a cellular sheet to reduce tearing; junctions formed by extracellular cadherins (glycoproteins) EX: Cardiac muscles; when it moves it doesn't erupt

gap junctions

communication junction between cells in electrically excitable tissues; allows ions to be transported between neighboring cells rapidy EX: all types of muscle and neurons

protein chanels

a form of facilitated diffusion; formed by transmembrane protein, allow water and hydrophilic solutes to move across the membrane

voltage gated channel

a protein channel; a change in membrane charge triggers the gate to open and close (most cells use this)... initially closed, open when current runs through cell

ligand gated channel

binding of chemical triggers the gate to open or close... open when neurotransmitters and hormones bind to channel

mechanically gated channel

stresses such as stretch or pressure trigger the gate to open or close... when there is weight on channel

filtration

fluid and small solutes are forced by pressure to pass through a selectively permeable membrane... not all things can pass through (membrane transport)

simple diffusion

a movement of particles from a place of high concentration to a place of lower concentration (down concentration gradient until equilibrium is achieved)

facilitated transport

a substance requires a carrier or pump for transport across the plasma membrane

osmosis

the net flow of water from one side of a selectively permeable membrane to the other

vesicular transport

movement of large packages through the use of membrane vesicles

passive process

simple diffusion is a _________ __________ driven by spontaneous motion; molecules move down their concentration gradient; rate of diffusion is altered by temperature, membrane permeability and surface area, steepness of concentration gradients

aquaporin

the transport of large amounts of water will require a specific protein channel __________

water

small amounts of ___________ can also pass through the cell membrane even though its polar

small, non polar, hydrophobic

_________, ______________, __________________ lipid soluble substances easily diffuse through the plasma membrane.. includes oxygen, nitric oxide, alcohol, and steroid hormones

ions, large, hyrdophillic

_________ (electrolytes) and ________, ___________ polar solutes do not readily diffuse through the plasma membrane and require protein channels or carriers for transport

specificity

protein carriers exhibit __________ for ligands based on the chemistry of their active site

transport maximum

when all carriers for a particular substance become saturated (completely coated)

uniport transport

a carrier which can only transport one type of solute

cotransport

a carrier which can transport more than one type of solute at a time

symport

both solutes transported in the same direction (cotransport)

antiport

solutes are transported in opposite directions, cotransport EX: sodium potassium pump

facilitated diffusion

solute is transported down its concentration gradient, passive process, solute channels

primary active transport

solute is transported against its concentration gradient, requires ATP, sodium potassium pump ex

secondary active transport

a solute is transported against its concentration gradient and is indirectly fueled by ATP hydrolysis

body cells

_______ ________ are altered by the osmolality of your body fluids

osmolarity

the amount of dissolved solutes per liter of solution

endocytosis

vesicular transport which brings matter into a cell

phagocytosis

"cell eating" bacteria, dust and debris are enflamed and enter the cell

pinocytosis

"cell drinking" drops of ECF are brought into the cell

receptor mediated endocytosis

only substances which bind to a specific receptor are endocytosed

isotonic solutions

solutions which the same concentrations of non penetrating solutes as those found in cells

hypertonic solutions

solutions with a higher concentration of non penetrating solutes than cells (cause cells to crenate or shrink)

hypotonic solutions

solutions with a lower concentration of non entreating solutes than the cells (cause cells to lyse or burst)

exocytosis

cell passes material from inside to outside, golgi vesicles and secretory vesicles bind to plasma membrane, can release cellular secretions such as mucus, hormones, enzymes or milk... also serves to replace membrane regions lost in endocytosis

solutes with higher extracellular concentration

sodium, calcium, bicarbonate, chloride

solutes with higher intracellular concentration

proteins, potassium, magnesium, phosphates, sulfates

membrane potential

movement of a select few solutes can influence the charge of a cell membrane, the distribution of these charges is referred to as ______________ _______________

influx

movement of solutes into the cell

efflux

movement of solutes out of the cell

resting membrane potential

the difference in electrical charge between the external and internal surface of the cell membrane, prior to depolarization, established by constant efflux of K+

sodium potassium pump

maintains resting membrane potential, without the pump, k+ diffusion would reach equilibrium