chapter 3 - Cells

Question 1

Name the two general classes of cells in the human body

Answer 1

Sex cells

Somatic cells

Question 2

Define somatic cell

Answer 2

any cell of a living organism other than the reproductive cells.

Question 3

Define Sex cells

Answer 3

Sperm of males or oocytes of females

Also called germ cells or reproductive cells

Question 4

Name the three major parts of a cell

Answer 4

Cell membrane
Nucleus
Cytoplasm

Question 5

Cell membrane is also called?

Answer 5

Plasma membrane

Question 6

Functions of cell membrane

Answer 6

The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. The basic function of the cell membrane is to protect the cell from its surroundings.
Allows selective communication between intracellular and extracellular compartments.
Gives form to the cell.

Question 7

Define semipermeable

Answer 7

allowing certain substances to pass through it but not others, especially allowing the passage of a solvent but not of certain solutes.

Question 8

Two types of selective permeability

Answer 8

Differentially permeable

Semipermeable

Question 9

Cell membranes are made of?

Answer 9

Lipids and proteins. Usually a double layer of phospholipid molecules. (Phospholipid bilayer)
Phosphate outer surface
Fatty acid inner surface

Question 10

Passive cell mechanisms

Answer 10

Diffusion
Osmosis
Filtration

Question 11

Explain the passive cell mechanism: diffusion

Answer 11

Spontaneous movement of substances from regions of higher concentration to regions of lower concentration (concentration gradient). Until evenly distributed throughout a substance, achieving equilibrium.
Two types: simple and facilitated diffusion

Question 12

Explain the passive cell mechanism: simple diffusion

Answer 12

Diffusion of very small or lipid soluble particles.
Non polar and lipid-soluble substances are diffused through the lipid bilayer. Including carbon dioxide, fat soluble vitamins and oxygen.

Question 13

Explain the passive cell mechanism: facilitated diffusion (assisted diffusion)

Answer 13

Its a passive transport process.
Some substances cannot pass through the lipid bilayer, requiring proteins in the cell membrane to assist them. E.g. Certain amino acids, ions and glucose.
Two types: channel mediated and carrier mediated
Facilitated diffusion rate is controllable: membrane permeability may be regulated by altering the number or activity of individual channels (or carriers).

Question 14

The two types of facilitated diffusion are called?

Answer 14

Carrier mediated

Channel mediated

Question 15

Carrier mediated facilitated diffusion

Answer 15

Is when a peripheral protein (transmembrane integral) envelopes a polar molecule, sugar or amino acid. protecting it from the non polar lipid bilayer and transports it to the other side of the cell membrane. Always moves down the concentration gradient like in simple diffusion.

Question 16

Channel mediated facilitated diffusion

Answer 16

Transmembrane proteins that move ions, water and other substances through aqueous channels from one side of the cell membrane to another.
Because of pore size and amino acid charges in the lining of the channel they act selectively.
Gated channels - opened and closed by electrical or chemical signals
Leakage channels - open constantly
Allows water or ions movement through based on concentration gradients.
facilitated diffusion rate is controllable because membrane permeability may be altered by regulating the number or activity of individual channels (or carriers)

Question 17

define: Osmosis

Answer 17

Osmosis is a special type of diffusion where water molecules diffuse from an area of higher water concentration to an area of lower water concentration. This requires a selectively permeable membrane like a cell membrane.

Question 18

Define: Osmosis

Answer 18

Osmosis is a special type of diffusion that occurs when water molecules diffuse form an area of higher concentration to an area of lower water concentration.
This requires a selectively permeable membrane, such as a cell membrane.
Solutions containing higher concentrations of solutes have a lower concentration of water and vica versa.
Osmosis continues until Osmotic and Hydrostatic pressures acting upon the cell membrane are equal.

Question 19

define: Osmotic Pressure

Answer 19

The ability of osmosis to create enough pressure to raise a volume of water is called osmotic pressure.
Water always diffuses towards solutions of greater osmotic pressure.
the higher the amount of non-penetrating (non-diffusible) solutes in a cell, the higher the Osmotic pressure.

Question 20

where does Osmosis take place

Answer 20

Through the lipid bilayer of the cell.
Via osmosis water equilibrates throughout the body so the concentration of water and solutes in both intracellular and extracellular fluids is nearly the same.
Distributes water in the cells, blood and fluid containing body compartments.

Question 21

define: Aquaporins

Answer 21

Aquaporins are transmembrane proteins that construct water-specific channels that allow water to move freely and reversibly and water molecules to be diffused in a single file manner.
Believed to exist in all cell types they are most prevalent in red blood cells and cells involved in water balance (kidney tubule cells and others).

Question 22

Define: Osmolarity

Answer 22

The total concentration of all solute particles in a solution.
Net diffusion of both solute and water occurs, moving down their concentration gradients, when the same volumes of aqueous solutions of different osmolarity are separated by a membrane that is permeable to all molecules in the system. When the water and solute concentration on both sides of the membrane is the same, equilibrium is reached.
Osmolarity is based only on a solutions total solute concentration. It is expressed as osmoles per litre (osmol/L). One osmol is equal to one mole of nonionizing molecules.

Question 23

Define: Hydrostatic pressure

Answer 23

Hydrostatic pressure pushes water out, Osmotic pressure pulls water in.

Question 24

Define: Isotonic

Answer 24

Any solution with the same osmotic pressure as body fluids. When a cell is exposed to an isotonic solution, it retains normal shape, with no net gain or loss of water.
The body’s extracellular fluids and most intravenous solutions are isotonic.

Question 25

define: Hypertonic

Answer 25

Any solution with a higher osmotic pressure than body fluids.
Has a higher concentration of non-penetrating solutes than in the cells. Cells that receive hypertonic solutions loose water and crenate (shrink).

Question 26

define: Hypotonic

Answer 26

Any solution with a lower osmotic pressure than body fluids.
Hypotonic solutions are more dilute with a lower concentration of non-penetrating solutes, than cells.
Cells receiving hypotonic solutions swell quickly and eventually lyse (burst).

Question 27

define: Active cell mechanisms

Answer 27

Particle movement from a region of lower concentration to a region of higher concentration. When this occurs, energy is required. This energy comes from the cellular metabolism, specifically from the molecule known as ATP, which is created in the mitochondria of cells.

Question 28

Types of active cell mechanism’s

Answer 28

Active transport
Endocytosis
Exocytosis

Question 29

define: Active transport

Answer 29

the movement of particles through membranes from regions of lower concentrations to regions of higher concentrations (moves solutes, mostly ions, against the concentration gradient, requiring energy).
Requires carrier proteins similar to facilitated diffusion, but active transport also requires ATP.
In primary active transport hydrolyzed ATP causes phosphorylation of the transport protein, changing its shape so it pumps the bound solute accross the membrane.

Question 30

the two types of active transport

Answer 30

primary active transport

secondary active transport

Question 31

the two subforms of secondary active transport

Answer 31

secondary active transport is a coupled system that moves more then one substance at a time.

Symport system; moves the two substances in the same direction

Antiport system; the two substances cross the membrane in opposite directions

Question 32

where does the energy for primary and secondary active transport come from

Answer 32

In primary active transport, required energy comes directly from the hydrolysis of ATP. In secondary active transport the process indirectly uses energy that is stored in ionic gradients. These are created by primary active transport pumps.

Question 33

three forms of Endocytosis

Answer 33

Phagocytosis
Pinocytosis
Receptor mediated endocytosis

Question 34

What is endocytosis

Answer 34

When a secretion from the cell membrane forms a vesicle that transports molecules in to the cell that are too large to enter via other processes.

Question 35

Describe phagocytosis

Answer 35

Cell eating

Involves cells taking in solids

Question 36

Describe pinocytosis

Answer 36

Aka: fluid phase endocytosis
Cell drinking
Involves cells taking in liquids from extracellular space with a small indentation of the cell membrane
Infolding plasma membrane surrounds extracellular fluid that contains dissolved molecules.

Question 37

Receptor mediated endocytosis

Answer 37

Involves the movement of specific types of particles into the cell. with protein molecules extending through the membrane to the outer surface of the cell.
Triggered when a particle binds to receptors on the cells surface.

Question 38

Define: exocytosis

Answer 38

A secretory vesicle forms, enclosing the substance to be removed from the cell. It then migrates to and fuses with the plasma membrane. It then ruptures, and its contents are spilled outside of the cell.