Cell Biology and Biochemistry/ cell strucutre

Question 1

prokaryotic cell

Answer 1

cell that does not have a nucleus or other membrane-bound organelles e.g. bacteria

Question 2

eukaryotic cells

Answer 2

contain a nucleus and other organelles that are bound by membranes.

Question 3

plasma membrane

Answer 3

selectively permeable phospholipid bilayer

Question 4

what is the purpose of cholesterol in the cell membrane?

Answer 4

to provide, structure, stability and fluidity to the cell membrane

Question 5

structure of lipids in the cell membrane

Answer 5

amphipatic: polar head groups and hydrophobic tails

Question 6

types of proteins found on the cell membrane

Answer 6

integral and peripheral proteins

Question 7

integral proteins

Answer 7

embedded with hydrophobic regions in the membrane and hydrophilic regions on either side

Question 8

what are the functions of integral proteins?

Answer 8

channels, transporters, receptors for hormones or NTs

Question 9

peripheral proteins

Answer 9

loosely bound to the surface/edge of the lipid bilayer (or to the integral proteins)

Question 10

electrochemical gradient

Answer 10

has 2 components: concentration gradient and charge on the membrane (inside of cell is more -ve therefore +ve ions are likely to diffuse through, concentration gradient only matters for uncharged molecules)

Question 11

modes of transport across the cell membrane

Answer 11

passive transport (e.g. diffusion, facilitated diffusion) and active transport (e.g. via carrier protein, endocytosis)

Question 12

facilitated diffusion

Answer 12

transport from an area of high to low concentration; the molecule must bind to its transporter but it is passive and not requiring energy; can be supported (faster) if concentration outside cell is already high and transporters are occupied

Question 13

active transport

Answer 13

energy is required to transport substances against their electrochemical gradient, and occurs with the sodium-potassium pump (the maintenance of higher Na+ outside the cell can be used to drive secondary active transport or to allow membrane depolarization in AP)

Question 14

secondary active transport

Answer 14

movement of material that is due to the electrochemical gradient established by primary active transport

Question 15

secondary active transport in intestinal cells

Answer 15

a mechanism moving sodium and glucose from the digestive tract into the body: sodium is pumped out of intestinal cells so that it is low within the cell (can bind to a transporter that will then bind glucose - higher in cell than in lumen); glucose enters ECF where its [ ] is lower by passive transport

Question 16

lysosomes

Answer 16

membrane bound organelle containing digestive enzymes that break down substances in the cell; maintain a pH of 5.5 for enzymatic function (enzymes use energy to pump H+ into lysosome)

Question 17

mitochondria

Answer 17

site of most energy generation and consisting of an inner and outer membrane

Question 18

inner membrane of the mitochondria

Answer 18

site of the enzymes involved in cellular respiration

Question 19

matrix of the mitochondria

Answer 19

TCA cycle and other oxidative pathways

Question 20

nucleus

Answer 20

largest organelle where most of cell’s DNA is located; where DNA replication and transcription occurs (once mRNA is transcribed it leaves nucleus to be translated in cytosol)

Question 21

nuclear transport

Answer 21

proteins involved in DNA replication and transcription are targeted to re-enter the nucleus and these proteins have a nuclear localization signal (NLS) that allows them to enter through nuclear pores

Question 22

endoplasmic reticulum

Answer 22

an internal membrane system in which components of cell membrane and some proteins are constructed; made up of smooth and rough areas

Question 23

smooth ER

Answer 23

contains enzymes for lipid synthesis and cytochrome P450 oxidative enzymes of drug metabolism

Question 24

rough ER

Answer 24

site of proteins bound for outside the cell or within the membrane or organelles (where posttranslational modifications occur)

Question 25

cell signaling

Answer 25

the process of cell-to-cell communication mediated by signaling molecules and membrane receptors

Question 26

where do endocrine hormones/messengers act?

Answer 26

secreted into the blood and travel to act on target cells

Question 27

where do paracrine messengers act?

Answer 27

on cells that are close by

Question 28

where do autocrine messengers act?

Answer 28

bind on the same cell from which they are released

Question 29

cell surface receptors

Answer 29

receptors found in the plasma membrane that bind hydrophilic ligands; deliver a chemical signal (transduction) to the nucleus

Question 30

intracellular receptors

Answer 30

receptors located inside the cell; hydrophobic signal molecules are able enter and bind inside the cell nucleus