anatomy and physiology ch. 3 cells

Cytology

• the scientific study of cells

• Born in 1663 by Robert Hooke when observing empty cell walls of cork

Cell theory

• especially credited by Theodore Schwann and Matthias Schleiden

Most essential points of the cell theory

• all living organisms are made of one or more.

• Basic structural and functional units of all living organisms.

• All activities of an organism stem from the activities of its cells.

• All cells arise from preexisting cells and pass hereditary information

Squamous

Thin, flat cell, often have a bulge where the nucleus is (like a fried egg, "sunny side up")

Cubodial

Squarish cells and approx. as tall as they are wide (liver cells)

Columnar

Cells taller than they are wide (intestine lining)

Polygonal

• cells with irregularly angular shapes and with four, five, or more sides.

• Like wax cells of a honeycomb

• Densely packed cells in many glands

Stellate

• Starlike cell shape (nerve cells)

• Cell bodies of many nerves are stellate.

Spheroid to ovoid

• Spherically shaped cells

• In egg cells and white blood cells

Discoid

• disc shaped cells

• (red blood cells)

Fusiform

• Spindle shaped, elongated

• thick in the middle and tapered toward the end

• In smooth muscle cells

Fibrous

• Long, slender

• threadlike cells

• In skeletal muscle cells an the axons of nerve cells

Why do some cell shapes look different?

Does not capture the 3-D shape of the cell

Some cell shapes can look like others if viewed from its upper surface.

Micrometer (µm)

• The most useful unit of measure for designating cell sizes

• The smallest objects most people can see with the naked eye are about 100 µm

How big (in micrometers) are most human cells

10 to 15 micrometers wide

How long are the longest human cells

Nerve cells are sometimes over a meter long

Muscle cells are up to 30 cm long

Both are too slender to be seen with the naked eye.

Why can't cells grow to unlimited size

• if cells swelled to an excessive size, it could rupture like an overfilled water balloon.

• Limited between its volume and surface area.

• A cell that is too big cannot support itself.

• Molecules could not diffused from place to place fast enough to support its metabolism.

• The death of one or a few cells has less effect on structure and function of the whole organ.

Cytoplasm

the gel like fluid between the nucleus and surface membrane, contains cytoskeleton, organelles, inclusions

The clear structureless gel in a cell is its

Cytosol

The Na+-K+ pump is

A transmembrane protein

What process can only occur in the plasma membrane

Active transport

Membrane carriers resemble enzymes except the fact that carriers

Do not chemically change their ligands

Most cellular membranes are made by

The ER

When a hormone cannot enter a cell it activates a

Second messenger

The force exerted on a membrane by water is called

Hydrostatic pressure

Two granular organelles that synthesize and degrade proteins

Ribosomes, proteasomes

Liver cells detoxify alcohol w the two organelles

Smooth ER and peroxisomes

The space enclosed by the membranes of the Golgi and ER is called the

Cistern

TEM: Transmission Electron Microscope

• reveals more detail than the light microscope. (LM)

• uses a beam of electrons in place of light. Assisted in seeing the cells ultrastructure.

SEM: Scanning electron microscope

3-D images at high magnification and resolution can only view surface features

Vascular corrosion cast technique

• The vessels are drained and flushed with saline, then carefully filled with a resin.

• After resin solidifies the actual tissue is dissolved w corrosive agent

• This leaves only a resin cast of the vessels

Plasma (cell) membrane

• made up of proteins and lipids

• Composition and functions differ significantly from one region of a cell to another, especially the basal, lateral and apical surfaces of cells

Cytoskeleton

a supportive framework of protein filaments and tubules, an abundance of organelles, and inclusions.

Cytosol or intracellular fluid (ICF)

a clear fluid that the organelles and cytoskeleton are embedded in

Extracellular Fluid

• all body fluids not contained in the cells

• fluid outside of the cell

• located amid cells is also called tissue (interstitial) fluid.

• Some fluids include blood plasma, lymph, or cerebrospinal fluid.

The plasma membrane

• Defines boundaries of the cell

• Governs its interactions with other cells

• Controls the passage of materials into and out of the cell.

Intracellular face

The side that faces the cytoplasm (inside)

Extracellular face

The side that faces outward the cytoplasm (outside)

What percentage of membrane molecules are lipids and how many of those are phospholipids?

98%, 75%

What percentage of cholesterol molecules constitute the membrane lipids

20%

What membrane lipids make up the last 5% of the membrane lipids

Glycolipids

Glycolipids

• phospholipids with short carbohydrate chains on the Extracellular face of the molecule.

• carbohydrates help form the glycocalyx (a carb coating with multiple functions)

Transmembrane Proteins

• pass completely though the phospholipid bilayer protruding on both sides.

• Have hydrophilic regions in contact with the water

• Have hydrophobic regions that pass back and forth through the lipid.

• Most of these are glycoproteins

Peripheral proteins

• do not protrude into the phospholipid layer but rather adhere to one face of the membrane

• often times anchored to a transmembrane protein and tethered to the cytoskeleton

Function of membrane proteins: Receptors

Surface proteins usually specific for a particular messenger that allows for said messenger to communicate with the cell

Functions of membrane proteins: enzymes

• carry out the final stages of starch and protein digestion

• Help produce second messengers

• Break down hormones and other molecules whose job it done.

Functions of membrane proteins: channel proteins

• passages that allow water and hydrophilic solutes to move through membrane.

• Leak channels are always open and allow materials to pass continually.

Gates (gated channels)

• open and close under different circumstances and allow solute thru sometimes but not others

Three types of stimuli that would open gates

1) Ligand respond to chemical messengers

2) Voltage respond to changes in voltage of plasma membrane

3) mechanically respond to physical stress on a cell such as stress and pressure.

These channels play an important role in the timing of nerve signals and muscle contractions.

Functions of membrane protiens: carriers

• Are transmembrane proteins that bind to glucose, electrolyte and other solutes and transfer them to the other side of the membrane.

• Pumps consume ATP in the process.

Functions of membrane proteins: cell-identity markers

• acts like an “identification tag” that enables the immune system to tell which cells belong to the body and which are foreign invaders.

Functions of membrane proteins: cell-adhesion molecules (CAMs)

• cells adhere to one another and extracellular materials through membrane proteins

Calcium Channel Blockers

• a class of drugs

• Changes of the gated membrane channels strongly influence blood pressure.

• This type of drug prevents channels from opening and relax the arteries, increase blood flow, relieve angina and lower BP.

G protein

• named from the ATP-like chemical GTP

• Relays the signal to another membrane protein adenylate cyclase

• Triggers physiological changes within the cell

• Up to 60% of drugs work by altering the activity of these proteins

Adenylate cyclase (enzyme in membrane)

When the G protein is activated by the receptor it relays it to ____ _____ which removes two phosphate groups from ATP and converts it to cyclic AMP (cAMP)

Cyclic AMP

a second messenger, activates enzymes called Kinases in the cytosol

Kinase

activated by cAMP, add phosphate groups to other cellular enzymes

Glycocalyx: definition/composition

A fuzzy coating of the cell that acts as an ID tag.

• enables the body to distinguish its own healthy tissues from transplanted tissues, invading organisms and diseased cells.

- gives us our blood type.

Glycocalyx: Functions

1) Protection- cushions and protects membrane from chemical and physical injury

2.) immunity to infection- enables the immune system to recognize and selectively attack foreign organisms

3.) Defense against Cancer - recognize and destroy

4. ) transplant compatibility- forms the basis for compatibility of blood transfusions, tissue grafts, organ transplants

5) cell adhesion- binds cells together so tissue don’t fall apart

6. Fertilization - sperm recognize & bind to eggs

7. Embryonic development - guides embryonic cells to destinations

Microvilli

• extensions of the plasma membrane that serve primarily to increase a cell's surface area

• best developed in cells specialized in absorption.

• Give cells 15 to 40 times as much absorptive surface area

Cells like taste buds and inside ear serve more for sensory (tiny bumps)

Actin

Protein that attach to the inside of the plasma membrane at the tip of the microvillus, anchor the microvillus to the terminal web.

Cilia (nonmotile)

• hairlike processes about 7 to 10 micrometers long

• Nearly every human cell has a single nonmotile primary cilium

• Serve as the cells antenna for monitoring nearby conditions.

• Ex: in the ear, they play a role in the sense of balance

• Defects in the development, structure or functions of this are sometimes responsible for birth defects and hereditary diseases

Motile cilia

• less widespread but more numerous on cells that have them

• Occur in the respiratory tract, uterine fallopian tubes, internal cavities of the brain and short ducts

• Propel materials such as mucus, an egg cell or cerebrospinal fluid.

Cystic Fibrosis

lack of cilia in apical membranes, so respiratory tract lots of sticky mucus, clogs it up, in pancreas it clogs up ducts so nutrition so digestion nutrition and respiration are compromised. life expectancy 44 yrs.

Axoneme

structural basis from for ciliary movement, consisting of microtubules, two central tubules and nine microtubule pairs (9+2 structure)

Basal Body

anchors the cilium

Dynein Arms

resides in each pair of peripheral microtubules, makes the cilia move, using ATP to crawl up adjacent microtubles, bending cilia forward.

Flagella

Only one functioning one in human body: Sperm. they are longer than cilium and has a identical axoneme. movement is whiplike

Pseudopods

-cytoplasm filled extensions of the cell

• change continually

Selectively Permeable

• Allows some things to cross such as nutrients and wastes

• prevents others like proteins and phosphates from entering or leaving.

Carrier-Mediated Transport

a method of transportation where ATP is needed, active transport, facilitated diffusion, and vesicular are types of this

Passive diffusion

passive mechanisms no ATP is required; filtration, simple diffusion, and osmosis are types of this

Filtration

• a process in which physical pressure that forces fluid through a selectively permeable membrane.

• An example is a coffee filter, where it holds back larger particles

• Blood capillaries are the most important case of filtration bc of blood pressure forces fluid through gaps, it is how water, salts, nutrients and other solutes are transferred from the bloodstream to the tissue fluid and how the kidney filters wastes from blood.

Simple Diffusion

• is the net movement of particles from a place of higher concentration to a place of lower concentration

• as the result of their constant spontaneous motion.

Concentration gradient

when the concentration of a substance differs from one point to another- up=against gradient, down=with gradient

Why are diffusion rates important for cell survival

They determine how quickly a cell can acquire nutrients or rid itself of wastes.

Factors that affect the rate of diffusion

Temperature (the hotter the faster)

Molecular weight (the heavier the slower)

Steepness of concentration gradient (the greater the concentration the more rapid the diffusion)

Surface Area (the more surface area the faster the diffusion)

Membrane permeability (the more permeable the easier the diffusion)

Osmosis

• the net flow of water from one side of permeable membrane to the other.

• Crucial for the body’s water distribution

• Imbalances underlie problems such as diarrhea, constipation, hypertension and tissue swelling.

The rate and direction of osmosis depend on the

Relative concentration of non-permeating solutes on the two sides of the membrane

Aquaporins

• channels of transmembrane proteins through which water diffuses easily.

• the more aquaporins the more water can be transported.

• In red blood cell amount of water passing through a membrane every 1 sec=100times the volume of the cell.

Osmotic Pressure

The amount of pressure that would have to be applied to one side of a selectively permeable membrane to stop osmosis

Reverse Osmosis

• process where mechanical pressure applied to one side of the system can override osmotic pressure and drive water through a membrane against its concentration gradient.

Osmolality

the number of osmoles of a solute per kilogram of water

osmolarity

number of osmoles per liter of solution

1 osmole= 1 mole of dissolved articles

Tonicity

the ability of a solution to affect the fluid volume and pressure in a cell

Osmolarity does not = tonicity

cell placed in solution of

300 miliosm/L of urea (urea penetrates cell easily)

Hypotonic

• solution has a lower concentration of nonpermeating solutes than the intracellular fluid.

• Causes cells to lose water and shrivel

• inside cell

Isotonic

Iso=equal. A solution where the total concentration of a nonpermeating solutes is the same as in the ICF

Hypertonic

a solution with a higher concentration of nonpermeating solutes than the ICF.

Outside cell

Carrier mediated transport

• a solute binds to a carrier in the plasma membrane which then changes shape and releases the solute to the other side.

• The process is rapid, one carrier can transport 1000 glucose molecules per second

Transport maximum

When the carriers are saturated and no more are available to handle the increased demand.

Uniport Carrier

carries one type of solute at a time maintains a low intracellular concentration.

Cotransport

Process moves two or more solutes through a membrane simultaneously in the same direction.

Symport Carrier

Carrier protein that performs cotransport

Ex: the cells in the small intestines and kidneys have a symptom that takes up sodium and glucose simultaneously.

Countertransport

process carrying solutes in opposite directions (the carrier is antiport)

Antiport

Performs countertransport. carries two or more solutes in oppposite directions.

Facilitated Diffusion

Carrier mediated transport of a solute through a membrane down its concentration gradient.

• requires no expenditure of ATP

Primary Active Transport

• process in which a carrier moves a substance through a cell up its concentration gradient

• Uses energy provided by ATP

Secondary Active Transport

• requires energy output but depends only indirectly on ATP

Sodium-Potassium Pump (4 functions)

Basal part of cell, constantly removes Na from cell

3 Na out of cell, 2 K in the cell keeps potential (-70mv) across membrane.

1. Regulation of cell volume- anion (proteins and phosphates) attract and retain cations retntion of these would cause swelling. so cellular swelling increase Na Ka ATP pump, feedback loop reduces intracellular ion concentration, controls osmolarity, and prevents cellular swelling.

2. Secondary Active Transport maintains steep Na concentration gradient across the membrane

3. Heat Production-Thyroid stimulates synthesis of Na K Pumps consuming ATP releases heat.

4. Maintenance of a membrane potential- resting membrane potential, inside negative outside positive.