Chapter 3: Cellular Form and Function

Describe Plasma (cell) membrane?

Surrounds cell and defines its boundaries

Made up of proteins and lipids

What is Cytoplasm?

Gel-like matrix of the cell

Contains Organelles (perform the functions of the cell)

Cytoskeleton(provide structure and support)

Inclusions(stored or foreign particles)

Describe Cytosol (intercellular fluid, ICF)?

Fluid in the cell that houses the components of the cell

Describe Extracellular fluid (ECF)?

Body fluid not contained in cells

Describe Tissue (interstitial) fluid?

ECF located around cells

Describe Plasma membrane?

The barrier surrounding cells that houses cytoplasm and organelles

Strong but → flexible

The plasma membrane is a what?

Bilayer

Consists of layers of lipids

Has an amphipathic arrangement - bilayer contains both polar(charged) and non-polar(uncharged) parts

The plasma membrane is made of what?

Phospholipids

Polar phosphate heads are?

Hydrophilic

Able to interact with water found inside and outside the cell

Non-polar fatty acids are?

Hydrophobic

Able to interact with other non-polar molecules

Orient inward, away from water

The plasma membrane is fluid, allows parts of the membrane to what?

Move around

Fluidity depends on what?

The fatty acid tails of phospholipids

Unsaturated double bonds allow what?

Allow for a more fluid membrane

Fluidity maintains what?

Cell function and transport

What does cholesterol do in the membrane during temperature changes?

Regulates fluidity during temperature changes

Temp ↑ → increases rigidity

Temp ↓ → increases fluidity

Describe Integral proteins?

Go through or into the lipid bilayer

Describe Transmembrane proteins?

Pass completely through the membrane

Describe Peripheral proteins?

Attached to polar heads or to integral proteins on either side of the membrane

Describe Receptors?

Allow for the binding of chemical signals that cannot enter the cell

How cells communicate

Specific for one type of messenger

Some can bind messengers and then transport them into the cell

Describe Enzymes?

Speed up specific reactions inside or outside of the cell

Found in the small intestine and help in digestive break down

Describe Channel proteins?

Allow water or other hydrophilic substances to pass through the membrane

Selective to single types of ions (K+, Cl-)

Leak channels are always open for constant transport

Gates(gated channels)?

Open and close depending on certain conditions

Ligand-gated channels?

Chemical messngers

Voltage-gated channels?

Electrical potential (voltage)

Mechanically gated channels?

Physical stress on the cell (stretch or pressure)

Describe Carriers?

Transmembrane proteins that transport substances across the membrane

Describe Pumps?

Carriers that need ATP for transport

Describe Cell-identity markers?

Glycoproteins create an “ID” for the cell

Tells the body the difference between which cells belong and which foreign or corrupted

Describe Cell adhesion molecules(CAM)?

Allow cell to adhere to one another or to extracellular material

Allows most cells to grow and divide normally

Describe Glycocalyx?

A fuzzy material on the outside of animal cells

Chemically unique between individuals

Glycoproteins?

Carbohydrate chains attached to proteins

Glycolipids?

Carbohydrate chains attached to polar heads

What does the glycocalyx allow cells to tell the difference between?

Difference between health cells

Transplanted tissues

Microbes and pathogens

Diseased cells

Describe Microvilli?

Extensions of membrane (1-2 um)

Gives 15 to 40 times more → surface area

Best developed in cells specialized in absorption

On some absorptive cells they are very dense and appear as a fringe → “brush border”

Some microvilli contain what?

Actin filaments that are tugged toward center of cell to absorbed into the cell

Describe Cilia?

Hairlike processes

Single, nonmotile primary cilium found on nearly → every cell

Multiple nonmotile cilia

Found on sensory cells of the nose

Describe Motile cilia?

Respiratory tract, uterine tubes, ventricles of brain, ducts of testes

Beat in waves sweeping material across a surface in one direction

Describe Fagella?

Whip-like structure

Much longer than cilia

Tail of a sperm-only functional flagellum in humans

Stiffened by coarse fibers that support that trail

Movement is undulating, snake-like, corkscrew

Plasma membrane is what?

Selectively premeable

Allows substances to pass faster than others

Influenced by the non-polar, hydrophobic, middle layer

Non-polar molecules do what in the plasma membrane?

Move fast

Ions and large molecules do what in the plasma membrane?

They are blocked

How do ions and larger molecules make it though the middle layer?

Proteins

Channel and carrier proteins

Selective and specific

Passive transport?

A substance follows its concentration gradient, requires no energy input

Active transport?

A substance moves against its concentration gradient, requires energy input

Describe Simple diffusion?

Molecules diffuse from a high to low concentration, until equal on both sides of the membrane

In simple diffusion, how do substances move through the bilayer?

Moves freely through the bilayer without membrane proteins

What type of substances undergo simple diffusion?

Non-polar, hydrophobic molecules

Substances with no charge

Ex. O2, CO2, fatty acids, steroids

Describe Osmosis?

Process of diffusion where a net movement of solvent occurs through a selectively permeable membrane

Solvent in living systems is water

Water follow a high to low concentration gradient across membranes

Describe Aquaporins?

Integral proteins that channel water through the membrane

Water can also cross the membrane by moving between phosphates(very slow)

During osmosis, how does water move when the solute cannot pass through the selectively permeable membrane?

The left side has a higher water concentration, right has a higher solute concentration

Selectively permeable membrane does not allow the solute to pass

Water net movement is from left to right

In a living system, osmotic pressure of the cytosol in cells is what?

Equal to the fluid outside of cells(interstitial fluid)

The strength of a solution is referred to as its?

Tonicity

Certain tonicities can alter a cell’s shape and function

What is Isotonic solution?

Is a solution with a solute concentration that is equal on both sides of the membrane

Ex. Intravenous (IV) solutions

0.9% NaCl is isotonic to → RBCs

Red blood cells maintain their normal shape and function

What is Hypotonic solution?

A solution with a solute concentration that is lower than the cytosol of the RBCs (high water)

This causes water to rapidly enter the cells to reach an equilibrium (high to low)

Causes RBCs swell to the point of bursting, called hemolysis - RBCs rupture (lyse) because they are placed in a hypotonic solution

What is Hypertonic solution?

Solution with a solute concentration that is higher than the cytosol of RBCs (low water)

This causes water to rapidly leave cells to reach an equilibrium (high to low)

Causes RBCs to shrink/shrivel

Called crenation - RBCs shrink/shrivel when in a hypertonic solution