Bio 225 Exam 1 - Epithelial Cells and Basic Biochemistry - Lloyd

Epithelial Cells and Basic Biochemistry

Epithelial cells are important for

controlling transport

Epithelial cells general features

1) have asymmetrically distributed transporters (apical side and basolateral side)

2) are interconnected by protein linkages (tight junctions, leaky junctions, leaky tight junctions)

3) high lvl of cell type diversity — even w/in same tissue

4) abundant mitochondria

How are epithelium classified? (main classifications)

simple epithelium and stratified epithelium

simple epithelium

single layer of cells, indirect contact w/ basement membrane

stratified epithelium

multilayered, usually found where body linings are under mechanical pressure.

cells generally flatten as they are farther away from the basement membrane (more apical)

Classification of stratified epithelium

keratinized, parakeratinzed, transitional

keratinized stratified epithelium

mostly dead, lack nuclei and cytoplasm, contain tough resistant protein called keratin — found mostly in outer layers of skin

parakeratinized stratified epithelium

contains keratin, retain nuclei but it is reduced (pyknotic) — found in the esophagus and oral mucosa

transitional stratified epithelium

stretchy , appears to be stratified cuboidal — mostly in bladder, ureters, and urethra

All classifications of epithelium?

simple squamous epithelium, simple cuboidal epithelium, simple columnar epithelium, pseudostratified columnar epithelium, stratified squamous epithelium, stratified cuboidal epithelium, stratified columnar epithelium, transitional epithelium

Simple squamous epithelium location and function

air sacs of lungs and the lining of the heart, blood vessels, and lymphatic vessels

allows materials to pass thru by diffusion and filtration and secretes lubricating substance

Simple cuboidal epithelium

in ducts and secretory portions of small glands and in kidney tubules

secretes and absorbs

simple columnar epithelium

ciliated tissues are in bronchi, uterine tubes, and uterus; smooth (nonciliated tissues) are in the digestive tract, bladder

absorbs; also secretes mucous and enzymes

pseudostratified columnar epithelium

ciliated tissue lines trachea and much of upper respiratory tract

secretes mucus; ciliated tissue moves mucus

Stratfied squamous epithelium

lines esophagus, mouth, and vagina

protects against abrasion

stratified cuboidal epithelium

sweat glands, salivary glands, and mammary glands

protective tissue

stratifed columnar epithelium

male urethra and the ducts of some glands

secrets and protects

Transitional epithelium

lines bladder, urethra, and ureters

allows the urinary organs to expand and stretch

Transit around or thru cells

transcellular transport and paracellular transport

Transcellular transport

tight epithelia can transfer solutes across cell using transporters on the apical and basolateral plasma membrane

paracellular transport

in leaky epithelia, small solutes can move b/w cells, passing thru tight junctions that interconnect cells

energy units

4184 J = 1 cal

1 kCal = 1000 calories

1 kCal = 4.184 J

Types of energy

radiant energu, mechanical energy (potential energy, kinetic energy), electrical energy, thermal energy, chemical energy

1 J is

the amount of energy used when 1 watt of power (W) is expended for 1 sec

1 W = 1 J/s

Most biological processes involve the

transfer of energy from one form to another

(touch) mechanical E —> chemical E —> electrical E

Energy can be stored in/as

electrochemical gradients

chemical energy

How energy is stored in electrochemical gradients

biological systems can use energy to move molecules out of random distribution (molecules w/in a system tend to diffuse randomly w/in open space) —> this leads to diffusion gradients (a form of energy storage) which are either chemical, electrical, or electrochemical

movement of what controls relative charges

ions

Hyperpolarization and depolarization example of elctrochemical gradient

gradients of Na+ and K+ across cell membrane largely determine resting membrane potential. when specific ion channels open, movement of ions changes the membrane potential. depolarization and hyperpolarization

hyperpolarization

If K+ moves out of cell, magnitude of membrane potential inc.s

depolarization

If Na+ moves into cell, magnitude of membrane potential dec.s

Every chemical has

a characteristic energy associated with it; this energy is associated with the bonds b/w atoms

Most chemical rxns involve

changes in chemical energy

transition of substrate to product requires

certain lvl of activation energy

enzyme catalysts function

reduce activation energy of a reaction (make S—>P more likely to occur) increasing the rate of the reaction

S+E ←→ES←→ES*←→EP*←→EP←→E+P

Enzyme catalysts important info

they aren’t consumed during this process (they are recycled: broken down and then translated again when needed)

don’t change the nature of the substrate or product

energy carrying molecules often involve

a phosphate bond (not always)

common energy carrying molecules

ATP, ADP, GTP, PCr (phosphocreatine)

ACetyl-CoA uses ___ instead of _____

CoA, phsophate

Protein structure

primary, secondary, tertiary, quaternary

proteins are made up of

20 different amino acids

LAMPVIG, WFY, STCNQ, DEKHR

Primary structure main features

peptide bonds (covalent bonds) —> polypeptide chains

Secondary structure main features

polypeptide backbone exists as alpha-helices or beta-pleated sheets

hydrogen bonding is the main form of stabilization for this structure

Tertiary structure

secondary structures are folded into globular protein structures

disulfide bonds (disulfide bridges) and noncovalent bonds (hydrogen bonds, ionic bonding, LDFs/Van Der Waals) with some salt bridges (combination of hydrogen bond and ionic bond) and hydrophobic interactions are the primary bonds involved in tertiary structure

Quaternary structure

proteins that contain more than one polypeptide chain

Bonding: Van der Waals, H-bonds, ionic bonds, hydrophobic interactions, occasional disulfide bonds (covalent bonds)

What can denature proteins

heat/pH changes

Denaturation refers to

the loss of any aspect of 3D quaternary, tertiary, or even secondary structure sufficient to cause protein loss of function

What are chaperones

molecules that hep to fold proteins correctly

Hsp

Heat shock proteins

Help to maintain or refold proteins

Not all chaperones are _____ __ ____, but all are referred to as ____

responsive to heat; Hsp

Carbohydrates are

polymers made of monosaccharides which are joined by glycosidic bonds

monosaccharides—>disaccharides—>polysaccharides

polysaccharides

polymers of monosaccharides combined in linear or branched fashion (amylose, amylopectin, glycogen)

may contain amino sugars

polysaccharides may

may contain additional amino sugars (chitin)