Cell biology (pt.2)

Question 1

define active transport

Answer 1

Active transport is a process where substances are transported across the cell membrane up their concentration gradient.

Question 2

what does it enable

Answer 2

This process enables cells to absorb substances that are already more concentrated in the cytoplasm than the extracellular
fluid.

Question 3

how does active transport work

Answer 3

Active transport usually involves pumps and carrier proteins, which combine specifically and reversibly with the
transported substances. Active transport requires the use of energy in the form of ATP.

Question 4

which three substances are transported via active transport

Answer 4

sugars (glucose)
amino acids

Question 5

what moves via carrier proteins

Answer 5

sugars (glucose)
amino acids

Question 6

define vesicular rransport

Answer 6

Vesicular transport is a process whereby large particles and macromolecules are transported through the cell membrane in
bubblelike vesicles. This process requires the use of energy in the form of ATP.

Question 7

derfine exocytosis

Answer 7

Exocytosis is the process of transporting particles from the cell interior into the extracellular space. Cells that secrete materials
in this manner include nerve cells, goblet cells, pancreatic cells and exocrine cells.

Question 8

define endocytosis

Answer 8

Endocytosis is the process of transporting particles into the cell’s interior from the extracellular space.
The electron micrograph below shows a cell undergoing exocytosis.

Question 9

what moves via exocytosis

Answer 9

macromolecules

Question 10

what are the types of endocytosis

Answer 10

There are three forms of endocytosis: phagocytosis, pinocytosis and receptor-mediated endocytosis.

Question 11

what is phagocytosis

Answer 11

Phagocytosis (cell eating) is the process where a cell engulfs large particles by surrounding the substance with footlike
extensions of the cell membrane (pseudopods) and trapping the substance into a vesicle (phagosome) in the cytoplasm
where it then merges with a lysosome (containing enzymes) forming a phagolysosome. Enzymes contained in the
phagolysosome then digest the substance.

Question 12

what is pinocytosis

Answer 12

Fluid phase pinocytosis (cell drinking) is the vesicular intake of droplets of extracellular fluid into the cell. The plasma
membrane sinks in at points forming pits which separate from the surface membrane forming membrane-bound pinocytotic
vesicles in the cytoplasm.

Question 13

what is receptor-mediated endocytosis

Answer 13

Receptor-mediated endocytosis enables a cell to selectively take in specific molecules from the extracellular fluid with a
minimum of associated fluid. Specific solute particles bind to receptors on the plasma membrane and are then taken into the
cell in clathrin-coated vesicles.

Question 14

membrainous organelles

Answer 14

These organelles include the nucleus, mitochondria, endoplasmic reticulum, Golgi complex (apparatus), Golgi vesicle and
lysosomes.

Question 15

what is diffusion

Answer 15

Diffusion is the net movement of molecules from an area of high concentration to an area of low concentration.

Question 16

what is passive diffusion

Answer 16

Passive
diffusion is a process that does not require the expenditure of energy.

Question 17

what factors affect diffusion rates

Answer 17

Diffusion rates through a membrane can depend upon
many factors including temperature, molecular weight, concentration gradient, membrane surface area and membrane
permeability.

Question 18

two substances that move through simple diffusion

Answer 18

Simple diffusion is a passive transport process which does not require a membrane transport protein.

Question 19

what is osmosis

Answer 19

Osmosis is a special case of passive diffusion involving movement of water molecules across a semi-permeable membrane
from an area of high water concentration to an area of low water concentration.

Question 20

what is osmotic pressure

Answer 20

Osmotic pressure is a measure of the driving force for diffusion of water molecules across a semi-permeable membrane. In the animation, the membrane was permeable to the solvent, H»O, but not to the solute, urea.

Question 21

what is osmotic pressure proportional to

Answer 21

Osmotic pressure is proportional to the concentration of the non-permeating
÷
solute
÷
I particles.

Question 22

what is tonicity

Answer 22

membranes. The ability of a solution to change the water content of a cell is called tonicity. Solutions which do not change the cell water content are called isotonic solutions.

Question 23

what is channel diffusion

Answer 23

CHANNEL DIFFUSION - SMALL POLAR OR IONISED SUBSTANCES. Proteins in the membrane form channels or pores

• water
• ions

Question 24

what is facilitated diffusion

Answer 24

Facilitated diffusion is the carrier-mediated transport of a solute (that would otherwise be unable to pass through the membrane unaided through a membrane down its concentration gradient.

Question 25

how much energy does facilitated diffusion require

Answer 25

Facilitated diffusion does not require the expenditure of energy. The solute attaches to a binding site on the carrier protein, the carrier protein then changes shape to release the
solute on the other side of the membrane.

Question 26

what are peripheral proteins

Answer 26

Peripheral proteins adhere to one face of the membrane and do not protrude into the phospholipid bilayer. Peripheral proteins
are usually associated with a transmembrane protein.

Question 27

what are transmembrane proteins

Answer 27

Transmembrane proteins (integral proteins) pass through the cell membrane. Some transmembrane proteins are anchored
to the cytoskeleton while others drift freely in the phospholipid layer.

Question 28

what are glycoproteins

Answer 28

Glycoproteins are transmembrane proteins joined with oligosaccharides (carbohydrate chains) on the extracellular side of the
membrane. Glycoproteins act as cell identity markers which enable our bodies to identify cells as self or non-self.

Question 29

what are channel proteins

Answer 29

Channel proteins are transmembrane proteins or protein clusters with pores that allow the movement of water and ions
through the membrane.

Question 30

what are carrier

Answer 30

Carrier proteins are transmembrane proteins which change shape when a solute binds to the protein, transferring the bound
solute across the membrane to the other side.

Question 31

what are intermediate filaments

Answer 31

Intermediate filaments are 8 - 10nm in diameter. Intermediate filaments line the inside of the nuclear envelope forming the
nuclear lamina enclosing the DNA.
Intermediate filaments may also extend throughout the cytoplasm and are found at cell-to-cell junctions.

Question 32

what is the cytoskeleton comprised of

Answer 32

The cytoskeleton is composed of microfilaments, intermediate filaments and microtubules.

Question 33

what are microfilaments

Answer 33

Microfilaments are approximately 6nm in diameter and are made of the protein actin. Microfilaments form a network on the
cytoplasmic side of the plasma membrane forming a membrane skeleton called the terminal web.

Question 34

what are actin microfilaments

Answer 34

Actin microfilaments are sometimes found in microvilli attaching to the inside of the plasma membrane at the tip of the
microvillus and extending down through the base of the microvillus into the terminal web.