Chapter 3-Sesay Lecture

Will be on test

Cell theory

1- All organisms are composed of cells and cell products

2-Cell is the simplest structural and functional unity of life

3- organisms structure and function are due to activities of its cells.

4- cells only come from existing cells.

what is a tissue?

a group of similar cells that work together to perform a similar function.

There are apx 200 cell types in the body. 9 common shapes are:

To know for test: Shape and thinness/thickness:

Squamous: flat tissue (like a floor tile), scaly- lungs

Cuboidal: cube/cuboidal- in kidney(absorbs and secretes)

Columnar: taller than wide- has large surface area- in stomach, small intestines

fusiform

fibrous

cuboidal-

columnar

discoidal

polygonal

stellate

spheroidal

Squamous-

squamous cell- function and where?

thin flat and scaly, often with bulge where nucleus is.

Diffusion and protection

outer layer of skin, esophogus.

cuboidal cells

secretion and absorbtion

liver, secretory portion of many glands

columnar cells- function and where?

high volume absorption and secretion

inner lining of stomach and intestines

Polygonal cells

irregular angular shapes

structural packing. allow cells to pack tightly

widespread, and many glands

stellate cells

communication

nerve cells

spheroidal cells

mobility and storage

white blood cells and egg cells

discoidal cells

gas exchange

red blood cells

fusiform cells:

sustained contraction

smooth muscle

fibrous cells

directional force and reach, long slender, and thread like

skeletal muscle cells and the axons of nerve cells

Microscope moments for the cell

Light vs. Electron (better mag and resolution)

light microscope revealed: plasma membrane, nucleus, and cytoplasm

Transmission electron microscope revealed : better resolution

Scanning electron microscope: dramatic 3d images at high mag and res but only on the surface.

Cell is surrounded by?

Plasma membrane:

Function: 1-protects/ defines cell boundary 2- controls exchange/what comes in and out of cell 3- communication-

components: made of proteins and lipids and defines cell boundaries.phospholipds, cholesterol, glycolipids

Cytoplasm

within the cell: contains organelles, cytoskeleton, inclusions (stored or foreign particles), and clear gel called cytosol or ICF (intracellular fluid).

cytosol

Intracellular fluid

Extracellular Fluid (ECF)

any fluid outside of cells including tissue (interstitial) fluid, blood plasma, lymph, cerebrospinal fluid

Membrane Lipids

98% of the cell membrane is composed of lipids, and mostly phospholipids (75%).

20% is cholesterol

5% glycolipids

Phospholipids

Primary (75%) lipid on plasma membrane.

amphipathic molecules arranged in a bilayer

Drifts lateral to keep membrane fluid

Phosphate head (hyrdophilic) with fatty acid tails (hydrophobic)

cholesterol

20% of the membrane lipids

Holds phospholipids still and can stiffen membrane, but at higher concentrations can increase membrane fluidity.

considered “parent” steroid from which other steroids are synthesized.

Glycolipids

5% of the membrane lipids

• Phospholipids with short carbohydrate chains on extracellular face

• Contribute to glycocalyx— comes in as glycolipid and comes at as glycoprotein. carbohydrate coating on cell surface

like a tag, helps to ID the cell.

Glycocalyx

carbohydrate moietie of glycoprotein and glycolipid, external to plasma membrane.

works as an ID tag.

Allows us to see foreign cells.

-protection

-immunity to infection

-cancer defense

membrane proteins % of membrane

not on test:

5% of membrane

larger than lipids, and account for 50% of weight

two classes are transmembrane and peripheral proteins.

The Plasma Membrane image

depict image

Transmembrane proteins

pass completely through

membrane

most are Glycoproteins bound to oligosaccharides on the extracellular side

• Hydrophilic regions contact the watery cytoplasm, extracellular fluid

• Hydrophobic regions pass through lipid of the membrane

Transmembrane Proteins Image

pass completely through

membrane

• Hydrophilic regions contact the watery cytoplasm, extracellular fluid

• Hydrophobic regions pass through lipid of the membrane

receptor (membrane proteins)

-bind chemical signals to trigger internal

changes

• May cause production of a second messenger within cell receiving

chemical message

Channel proteins—

allow hydrophilic solutes and water to

pass through membrane

• Some are always open, called leak channels, and some are gates

(gated channels) that open only when triggered

• Ligand-gated channels—respond to chemical messengers

• Voltage-gated channels—respond to charge changes

• Mechanically gated channels—respond to physical stress on cell

Leaky membrane channel

always open.

Ligand-gated channel

responds to chemical messengers

Voltage-gated channels—

respond to charge changes (ions)

Mechanically gated channels—respond to physical stress on cell

respond to physical stress on cell

Carriers—membrane proteins

bind solutes and transfer them across

membrane

Pump proteins—

carriers membrane proteins that consume ATP

Cell-identity markers—

glycoproteins acting as

identification tags

Functions of membrane proteins:

Receptor

enzyme

channel

gated channel

cell identity marker

cell adhesion molecule (CAM)

receptor protein

surface protein that receives chemical signal

enzymes in the plasma membrane

carry out final stages of starch and protein digestion in small intestine

produce secondary messengers

break down hormones and other signaling molecules

channel protein

allow water and hydrophilic molecules to pass through membrane.

Cell adhesion molecule (CAM)

how cells adhere to each other and extracellular material.

with few exceptions (such as blood cells and metastasizing cancer cells) cells need to be attached to EC material to grow properly.

Functions of Membrane Proteins image “abc”

receptor, enzyme, channel

functions of membrane proteins “cdf”

gated channel, cell identity marker, CAM cell adhesion molecule

secondary messengers

example how epinephrine works:

1- epinephrine (the first messenger) binds to receptor

2-receptor is linked, on the intracellular side to a g protein (get energy from GTP)

3- G protein relays signal to another membrane molecule adenylate cyclase

4- adenylate cyclase removes two phosphate groups from ATP and converts it into cyclic AMP (cAMP)- the second messenger

5- cyclic AMP activates cytoplasmic enzymes like kinases which add phosphate groups to other cellular enzymes.

this activates some enzymes, deactivates others, and triggers a lot of physiological change in the cell.

Glycocalyx— (3.2b)

“A fuzzy coat” carbohydrate moieties of glycoproteins and

glycolipids external to plasma membrane

• Unique in everyone but identical twins. acts like ID tag, enables body to distinguish healthy cells from bad.

• Functions-

• Protection-

• Immunity to infection

• Defense against cancer

• Transplant compatibility

• Cell adhesion

• Fertilization

• Embryonic development

Microvilli- Extensions of the cell surface (3.2c)

Found in the small intestine and allows more nutrients to absorb into blood stream.

destroying microvilli will inhibit food nutrition from getting into blood stream.

extensions (1 to 2 μm) of the membrane that

serve to increase surface area

• Provide 15 to 40 times more surface area to cells that

have them

• Best developed in cells specialized in absorption (epithelial cells of kidney and intestine)

• On some absorptive cells they are very dense and appear

as a fringe called the brush border

• Some microvilli contain actin filaments that are tugged

toward center of cell to milk absorbed contents into cell

Cilia—

Motile cilia- found in the lungs, respiratory tract. lungs are a big structure. located at the top of the lungs.

cilia repels unwanted things! thats why cilia is at the top.

hair-like processes 7 to 10 μm long

•

Single, nonmotile primary cilium found on nearly every

cell; serves as “antenna” for monitoring nearby conditions

• Helps with balance in inner ear; light detection in retina

non motile cilia- helps with balance in inner ear, light detection in retina.

Brush border

Microvilli densely packed at apical cell surface

Made of actin

motile verse nonmotile cilia

Multiple nonmotile cilia found on sensory cells of nose

• Motile cilia less widespread

• Found in respiratory tract, uterine tubes, ventricles of brain, ducts of

testes

• 50 to 200 on each cell

• Beat in waves sweeping material across a surface in one direction

• Power stroke followed by recovery stroke

image of Cilia

How Cilia Moves

Cilia move within saline layer at cell surface; mucus

“floats” atop this layer. this happens at the top of the lungs.

• Structure cilium:

• Dyenin arms “crawl” up adjacent microtubule, bending the cilium;

uses energy from ATP

Power stroke and recovery stroke

Kartagener syndrome

disease caused by destruction of dyenin arm

symptoms- difficulty breathing at birth, chronic cough/runny nose, frequent lung and sinus infection.

Cystic Fibrosis

problem with cilia! more respiratory issues.

hereditary disease in which cells make

chloride pumps, but fail to install them in the plasma

membrane

• Chloride pumps fail to create adequate saline layer on cell

surface

• Thick mucus plugs pancreatic ducts and respiratory tract

• Inadequate digestion of nutrients and absorption of

oxygen

• Chronic respiratory infections

• Mean life expectancy of 44

Flagellum—

whiplike structure

• Tail of a sperm is only functional flagellum in humans. sperm must travel all the way to the ovaries- flagellum helps.

Ciliary movement

1-axoneme is an array of thin protein cylinders called microtubules

2- 2 central microtubules are surrounded by a ring of nine microtubule pairs called the 9 plus 2 structure.

3- central microtubules stop at the cell surface.

4- peripheral microtubules continue a short distance into the cell as part of a basal body that anchors the cilium.

5- in each peripheral microtubules one tubule has two Dynenin arms. Dynenin is a motor protein, uses energy from ATP to crawl up the adjacent pair of microtubules.

6- on one side of the cilium, dynenin reaches out and grabs a microtubule of the adjacent pair, then pull towards them. collective movment makes the ciilium bend in one direction.

7- activation and inhibition alternate so that the back and forth of power and recovery strokes happens

Pseudopods

cytoplasm filled exensions of the cell varying in shape from fine filamentous processes to blunt fingerlike.

Filtration 3.3a

a physical pressure forces fluid through a selectively permeable membrane.

how kidneys filter waste from blood. how water, salts, nutrients, and other solutes are transferred from the blood stream to the tissue fluid.

simple diffusion 3.3b

net movement of particles from high to low concentration

affected by:

Temperature

Molecular weight

steepness of gradient

membrane surface area

membrane permeability

selectively permeable—

Plasma membrane and organelle membranes are

selectively permeable—allowing some things through, but

preventing others from passing

Passive mechanisms

require no ATP

• Random molecular motion of particles provides necessary energy

• Filtration, diffusion, osmosis

Active mechanisms

consume ATP

Active transport and vesicular transport

• Carrier-mediated mechanisms use a membrane protein to

transport substances across membrane

Osmosis

net flow of water through a selectively permeable

membrane

• Water moves from an area of higher water (lower solute)

concentration to an area of lower water (higher solute)

concentration

aquaporins

Water can diffuse through phospholipid bilayers, but osmosis is

enhanced by.————-—channel proteins in membrane

specialized for water passage

• Cells can speed osmosis by installing more ———————

• Crucial consideration for IV fluids

• Osmotic imbalances underlie diarrhea, constipation,

edema

Tonicity

1-Tonicity is describing extracellular…salt (NaCl) and glucose are major solutes..

2- water will go towards where we have more solutes

3- intracellular and extracellular fluid

Hypotonic solution—causes cell to absorb water, swell,

and possibly burst (lyse). less solute outside of cell.

• Cell Has a lower concentration of nonpermeating solutes than

intracellular fluid (ICF)

• Distilled water is an extreme example

• Hypertonic solution—causes cell to lose water and

shrivel (crenate). more solute outside of the cell.

• Has a higher concentration of nonpermeating solutes than ICF

• Isotonic solution—causes no change in cell volume

• Concentrations of nonpermeating solutes in ECF and ICF are the

same

• Normal saline (0.9% NaCl) is an example

Hypotonic solution—

causes cell to absorb water, swell,

and possibly burst (lyse). less solute outside of cell.

• Cell Has a lower concentration of nonpermeating solutes than

intracellular fluid (ICF)

• Distilled water is an extreme example

Hypertonic solution—

• causes cell to lose water and

shrivel (crenate). more solute outside of the cell.

• Has a higher concentration of nonpermeating solutes than ICF

Isotonic solution—

causes no change in cell volume

• Concentrations of nonpermeating solutes in ECF and ICF are the

same

• Normal saline (0.9% NaCl) is an example- must know!!!

There are three kinds of carrier proteins:

Uniport—carrier that moves one type of solute

• Example: calcium pump

• Symport—carrier that moves two or more solutes

simultaneously in same direction (cotransport)

• Example: sodium–glucose transporters

• Antiport—carrier that moves two or more solutes in

opposite directions (countertransport)

• Example: Sodium–potassium pump removes

+ Na

, brings in k

Three mechanisms of carrier-mediated transport

1-Facilitated diffusion,2- primary active transport,3- secondary

active transport

facilitated diffusion

carrier mediated transport of a solute through a membrane down its concentration gradient. require no metabolic energy (ATP) expenditure.

Primary active transport

carrier moves a substance through a cell membrane UP its concentration gradient, using ATP to do so. ATP supplies energy by transfering a phosphate group to the transport protein.

sodium potassium pump is a good example- half a day’s calories fuel this purpose!- maintains steep NA+ concetration across membrane.

regulates cell volume, maintains membrane potentials, heat production

secondary active transport

carrier moves solute

through membrane, but only uses ATP indirectly

• Example: sodium–glucose transporter (SGLT)

• Moves glucose into cell, up its concentration gradient, while

simultaneously carrying sodium down its gradient

• Depends on the primary transport performed by sodium-

potassium pump

• Does not itself use ATP

• SGLTs work in kidney cells that have sodium-potassium pump at

other end of cell; prevents loss of glucose to urine

-

Vesicular transport

moves large particles, fluid droplets, or numerous

molecules at once through the membrane in vesicles

Vesicles—

bubblelike enclosures of membrane

Endocytosis and exocytosis

brings material into cell;releases material

from cell

Three forms of endocytosis:

Phagocytosis—

• Pinocytosis—

• Receptor-mediated endocytosis—

Phagocytosis—

engulfing and destroying large particles; “cell eating”

• Pseudopods surround object, fuse to form internal phagosome, which merges

with lysosome to form phagolysosome within which object is digested

macrophages also phagocytize

Pinocytosis—

taking in droplets of ECF containing molecules useful in the

cell; pinocytic vesicles in cytoplasm; “cell drinking”

Receptor-mediated endocytosis—

particles bind to specific receptors on

plasma membrane

• Pit forms in membrane, cytosolic side covered in clathrin protein; forms clathrin-coated vesicle

coated vesicle that is directed to destination within cell by its “address label” (the clathrin coat)

Classic example is ldl (low density lipprotein) - liver has ldl receptor- that does receptor mediated endocytosis.

Receptor helps dump ldl into liver

Phagocytosis, Intracellular Digestion, and Exocytosis Image:

receptor mediated endocytosis image

Exocytosis—

discharge material from cell

• Examples:

• Release of insulin by endocrine cells

• Sperm cells release enzymes for penetrating egg

• Mammary gland cells release milk sugar

• Also functions to replace any plasma membrane lost by

endocytosis

Organelles

are the internal structures of a cell that carry out

specialized metabolic tasks

• Membranous organelles are surrounded by membranes

• Nucleus, mitochondria, lysosomes, peroxisomes, endoplasmic

reticulum, and Golgi complex

• Other organelles are without membranes

• free Ribosomes only one to know on test, centrosomes, centrioles, basal bodies

cytosol

clear vicous, watery colloid that bathes cytskelton and organelles. contains enzymes, proteins, amino acids, ATP, electrolytes, diverse ions, oxygen, CO2, and metabolic waste.

cytoskeleton

network of protein filaments and cylinders that structurally support a cell, determine its shape, organize contents, direct movement of material within cell. dense supportive scaffold within cytoplasm.

connects to transmembrane proteins, which is inturn connected to protein fibers external to the cell

cytoskeleton elements even connect to chromosomes in the nucleus!- could stimulate genetic function, timing of cell division

Made of microfilaments, intermediate filaments, and microtubules

microfilament

6nm thick and made of actin protein.

concentrated into fibrous mat called terminal web (membrane skeleton) on the cytoplasmic side of membrane.

phospholipds spread on the terminal web like butter on bread.

actin filaments form supportive core of the microvilli

intermediate filament

thicker and stiffer than microfilaments

make up strength of hair and fingernails

give cell its shape, resist stress, and form junction that attach cell to cell

microtubules

cylinders made of 13 parallel strands called protofilaments. each protofilamanet is a long chain of globular proteins called Tubulin.

these radiate from the centromeres,

hold organelles in place, maintain cell shape,

act like monorails for motor proteins to carry organelles/macromolecules around the cell.

microtubules form the axonemes of cilia and flagella

form mitotic spindle

nucleus—

usually largest organelle (5 μm in diameter);

contains cell’s genetic material

• Material within nucleus is called nucleoplasm

• Includes threadlike chromatin (DNA and proteins) and one or more

nucleoli (singular: nucleolus) where ribosomes are produced

mature red blood cells are anuclear.

some liver, urinary bladder, and heart cells have two nuclei.

nuclear envelope

double membrane encloses nucleus, peforated with nuclear pores.

raw material for DNA/RNA come into nucleus via the pores.

nucleoplasm

material in the nucleus”

chromatin..

nucleoplasm

Material within nucleus is called —————-

• Includes threadlike chromatin (DNA and proteins) and one or more

nucleoli (singular: nucleolus) where ribosomes are produced

structure of the nucleus

Endoplasmic reticulum (ER)—

network of interconnected parralel

membranous channels called cisterns

rough ER- covered in ribosomes.

continuous with outer membrane of nuclear envelope.

Rough endoplasmic reticulum—

parallel, flattened sacs

covered with ribosomes

• Continuous with outer membrane of nuclear envelope

• Produces phospholipids and proteins of nearly all cell membranes

• Synthesizes proteins that are packaged in other organelles or

secreted from cell

Smooth endoplasmic reticulum—

tubular ER lacking

ribosomes

• Synthesizes steroids and other lipids

• Detoxifies alcohol and other drugs

• Calcium storage

ribosomes

small granules of protein and RNA found in the nucleoli cytosol, mitochondira, rough ER< and nuclear envelope.

REads coded genetic messages (mRNA) and assemble into proteins.

free ribosomes make proteins that stay in the cell

what is this?

Golgi Complex

a system of membranous cisterns that

synthesizes carbohydrates and modifies newly synthesized

proteins

• Receives newly synthesized proteins from rough ER

• Sorts proteins, splices some, adds carbohydrate moieties

to some, and packages them into membrane-bound Golgi

vesicles

• Some vesicles become lysosomes

• Some vesicles migrate to plasma membrane and fuse to it

• Some become secretory vesicles that store a protein product for

later release

Lysosomes—

package of enzymes bound by a membrane

• Functions: autophagy and auto lysis

• Intracellular hydrolytic digestion of proteins, nucleic acids, complex

carbohydrates, phospholipids, and other substances

•

Autophagy—

digestion of cell’s surplus organelles