anatomy and physiology chapter 2

cytology

study of cell structure and function

what are some tenets of the cell theory?

• Cells are the basic structural and functional unit of all living things

• All cells have the same basic chemical composition (proteins, carbohydrates, lipids, DNA)

• Nearly all metabolism (biochemical change and energy flow) occurs within the cells
  

what are the universal characteristics of life?

• complex organization which requires energy to be expended

• metabolism for internal chemical change such as chemically changing molecules to make other structures, control physiology, or provide energy and eliminate waste

• response to stimuli

• homeostasis

• growth and development

• reproduction

example of a normal vital sign that indicates body can maintain homeostasis

T, P, R, BP

which cells in the body are responsible for responding to stimuli?

nerve and muscle cells

micrometers

One-thousandth of a millimeter, or 10^–6 meter; a convenient unit of length for expressing the sizes of cells.

examples of cells that can be seen without microscope

• egg cells

• some fat cells

light microscope

A microscope that produces images with visible light.

how are light microscopes like?

• cheap

• observe living cells and color

• limited magnification

resolution

the ability to distinguish fine details for microscopes

transmission electron microscope

A microscope that uses an electron beam in place of light to form high-resolution, two-dimensional images of ultrathin slices of cells or tissues from electrons passing through the specimen; capable of extremely high magnification.

How to view specimens under a TEM?

• slice it ultrathin

• stain with heavy metals that absorb electrons

magnification level of TEM

0.5 nm and biological material up to 600,000 times

what can be inspected with a TEM?

• proteins

• DNA

• other large molecules

scanning electron microscope

A microscope that uses an electron beam in place of light to dislodge secondary electrons from metal-coated specimens and form high-resolution, three-dimensional images of specimen surfaces from the secondary electrons. Capable of much higher resolution than the light microscope.

How do SEMs work?

• the electron beam strikes the specimen and discharges secondary electrons from the metal coating

• the electrons strike a detector and produce an image on a screen

what’s an advantage of an SEM?

it can make 3d images that are more informative than a TEM without getting cut into thin slices

what’s a disadvantage of an SEM

• it can’t see through an object only the surface

how can cell interiors be viewed for TEMs or SEMs?

a freeze fracture method in which a cell is frozen, cracked open, coated with gold vapor, then viewed by the microscope

vascular corrosion cast

a technique where a resin gets injected into a blood vessel while it dissolves away the actual tissue using a corrosive agent to leave the resin cast

How can a SEM be used for vascular corrosion cast?

the resin cast gets photographed by the SEM

why aren’t most human cells larger than 25 μm?

all cells have different purposes such as a sperm that needs mobility or a large fat cell that stores more energy while thinness in lung cells allows oxygen to pass more quickly

what’s another advantage about having a small cell size?

the death of a few small cells has less of an impact than having all large cells

what factors limit the size of cells?

• a cell can rupture if it swells too much

• the surface area of a cell is proportional to its diameter

• volume is proportional to the cube of a diameter

• for an increase in diameter, volume increases much faster than surface area

• A large internal volume needs metabolic support, but limited surface area through which those exchanges can occur

• Diffusion through a large internal volume would be too slow to support the cell’s metabolism

squamos

thin and flat, line the esophagus and alveoli, in the epidermis of skin

cuboidal

about equal in height and width, liver cells

columnar

taller than wide, inner lining of stomach & intestines

polygonal

irregularly angular shapes, secretory cells of glands

stellate

multiple pointed processes; starlike shape; cell bodies of nerve cells

spheroid to ovoid

round to oval. WBCs, egg cells

discoidal

disc-shaped. RBCs

fusiform

elongated with a thick middle and tapered ends. Smooth muscle cells.

fibrous

long, slender, and threadlike. skeletal muscle cells, axons of nerve cells

what’s the plasma membrane?

it forms the cell’s boundary

what are the surfaces of the plasma membrane?

basal lateral, and apical

basal surface

lower part of cell, anchored to deeper tissues

apical surface

upper part of cell, often faces interior cavity. Often faces the interior cavity & contents of an organ & serves such functions as absorption & secretion.

example of apical surface

intestinal lumen

lateral surface

side wall, adheres to neighboring cells

what parts enclose the cytoplasm

• cytosol

• cytoskeleton

• organelles

• inclusions

cytosol

clear fluid environment for the other cell contents

cytoskeleton

scaffold of filaments and tubule

inclusions

foreign matter or stored cell products

tissue (interstitial) fluid

the extracellular fluid between cells

examples of extracellular fluid

• blood plasma

• lymph

• cerebrospinal fluid

cytoplasm

The contents of a cell between the plasma membrane and the nuclear envelope, consisting of cytosol, organelles, inclusions, and the cytoskeleton

what are the major components of a cell?

• plasma membrane

• cytoplasm

• nucleus (usually the largest organelle)

what makes the plasma membrane selectively permeable?

it allows some substances to pass and prevents others

intracellular face

side of membrane facing the cytoplasm

extracellular face

side of membrane facing outward

what is a phospholipid’s hydrophilic head made of?

• nitrogen containing group (choline)

• phosphate group

• glycerol

what are the hydrophobic fatty acid tails made of in phospholipids?

carbon and hydrogen

how much percent of the membrane lipids do phospholipids make up?

75%

phospholipid

a molecule with a glycerol backbone, two hydrophobic fatty acid tails, and a hydrophilic phosphate head.

how much percent of the membrane lipid are made up of cholesterol?

20%

what do higher concentrations of cholesterol do for membrane lipids?

increases fluidity by preventing the phospholipids from packing as closely together as normal

how much percent of the membrane do glycolipids make up?

5%

glycolipids

Phospholipids with short carbohydrate chains bound to them

where are glycolipids located?

extracellular face of membrane

what do glycolipids contribute to?

glycocalyx

glycocalyx

fuzzy surface coat of sugars belonging to glycolipids and glycoproteins

transmembrane proteins

pass completely through the
phospholipid bilayer

what are most transmembrane proteins classified as?

glycoproteins with carbohydrate chains attached

peripheral proteins

adhere to inner or outer face of the
membrane

unit membrane

A membrane bilayer with embedded proteins

true or false? some organelles have a two-unit membrane with a space in between

true

examples of proteins in the plasma membrane

• receptors

• enzymes

• channel proteins

• transport proteins (carriers)

• cell-identity markers

• cell-adhesion molecules

• gated channels

receptors

bind chemical signals that trigger an internal response by the cell

enzymes

carry out chemical reactions at cell surface

channel proteins

form channels that allow water and
hydrophilic solutes to pass through the membrane

gated channels

open or close when stimulated

transport proteins (carriers)

bind to a substance on one side of membrane and release it on the other side

cell identity markers

serve as identification tags

cell adhesion molecules

allow cells to adhere to each other and to extracellular material

example of receptor function

binding to chemical messengers such as hormones sent by other cells

example of enzyme function

breaking down a chemical messenger and terminating its effect

example of channel function in plasma membrane

being constantly open to allow solutes to pass in and out of the cell

example of gated channel function

a gate that closes and opens to allow solutes in at certain times

example of cell identity marker function

a glycoprotein distinguishing the body’s own cells from foreign cells

example of cell admission molecule function

a CAM that binds one cell to another

what’s the role of glycocalyx?

• Cushions membrane and protects it from physical and
chemical injury
• Functions in cell identity; allows body to distinguish its own
healthy cells from diseased or foreign cells
• Determines human blood types & compatibility of blood
transfusions, tissue grafts & organ transplant
• Contains cell-adhesion molecules-sperm-egg binding at
fertilization

membrane transport

movement of materials into and out of
the organelles and cell as a whole

what’s filtration in membrane transport?

physical pressure forces fluid through the membrane

example of filtration in membrane transport

blood pressure forces fluid through the walls of capillaries

simple diffusion

net movement of particles from a place of high concentration to a place of lower concentration, down a concentration gradient

example of simple diffusion

movement of oxygen and steroid hormones into a cell and potassium ions leaving

how does osmosis work?

• Requires a nonpermeating solute that cannot pass through the membrane by itself (proteins, sugars)
• Water moves from the side of lesser solute concentration to the side of greater solute concentration
• Water can directly pass through cell membranes, but many cells have aquaporins

aquaporins

channels that allow rapid flow of water through the membrane

what’s osmosis critical for?

water balance in the body

facilitated diffusion

movement of a solute through a
membrane, down its concentration gradient, with the help of a carrier protein

examples of facilitated diffusion

• • Solutes that cannot pass through the membrane unaided
  (examples: sugars, amino acids)
  • Carrier binds to particle on one side and releases it on the other

what’s a key detail about facilitated diffusion?

No expenditure of energy

active transport

carrier-mediated transport of a solute up its concentration gradient

what does active transport require?

the expenditure of energy provided by ATP

example of active transport

Na K+ + pump ejects (3) sodium ions from the cell and transports (2) potassium ions into it

what does sodium potassium pump do for body?

• controlling cell volume

• generating body heat

• maintaining electrical excitability for nerves, muscles, and heart

• provide energy for other transport pumps to draw upon in moving solutes like glucose through plasma membrane

how many cycles is the process of the sodium potassium pump?

10 or 100 in some circumstances

steps of the sodium potassium pump

• Na+ is extracellular ion/K+ is an intracellular ion

• Na+ leaks into the cell (down its concentration gradient-diffusion)

• K+ leaks out of the cells (also down its concentration gradient-diffusion)

• Membrane is more permeable to K+ than Na+, so K+ is the primary influence on RMP. This causes it to be more negative on the inside of the cell at RMP.

• As K+ & Na+ move down their concentration gradients. It becomes more positive/less negative on the inside of the cell. Now the Na+/K+ pump works to bring the inside of the cell back to RMP (more negative on the inside)

• Na+-K+ pump works as an antiporter that pumps (three) Na+ out of cell and (two) K+ back into cell against their concentration gradients to bring them membrane
  back to RMP

vesicular transport

large particles or droplets of fluid are passed through the membrane in bubblelike vesicles

endocytosis

brings matter into the cell