Cell Membrane

Question 1

What is a symport?

Answer 1

Secundary transport that lets two molecules at the same time in the same direction

Question 2

What are the levels of organisation of life?

Answer 2

Atom-molecule-macromolecule-organelle-cell-tissue-organ-organsystem-organism

Question 3

What are the bodyfluid contents of a body?

Answer 3

60% of body weight, 2/3 intracellular fluid (ICF), 1/3 extracellular fluid (ECF)

Question 4

What are the reasons for water output?

Answer 4

Insensible loss= lungs/breathing, evaporation from skin

Sensible loss= sweating, feces, urine

Question 5

What are reasons for water input?

Answer 5

Drinking
Food
Metabolically produced water

Question 6

What is membrane proteins?

Answer 6

Peripheral proteins- loosely bound to surface, cell surface identity markers (antigens)
Integral proteins- goes through the membrane (transmembrane), transport proteins (channels, pumps)

Question 7

What is the main solute in ECF and thereby responsible for ECF osmolarity?

Answer 7

Na+

Question 8

What is an antiport?

Answer 8

Secundary transport of molecules in different directions (one in-one out)

Question 9

What are the major differences between ICF and ECF?

Answer 9

ICF-more protein, more K+ ions, less Na+ ions, more PO3-

ECF-no protein (except in plasma), less K+ ions, more Na+ ions, more Cl- ions

Question 10

What are the concequence of isotonic ECF?

Answer 10

None

Question 11

What is secondary active transport?

Answer 11

Uses the gradient of one ion to let another one through at the same time. No ATP needed

Question 12

What is osmolarity?

Answer 12

The concentration of solute particles dissolved in the fluid

Question 13

What makes the cell membrane semi-permiable?

Answer 13

Protein channels

Specific channels allow soecific material across

Question 14

How does large molecules move through the cell membrane?

Answer 14

Through vesicles and vacuoles

Question 15

What is the use of membrane carbohydrates?

Answer 15

Cell-cell recognition (ability to distinguish one cell from another)
Antigens
Immune system (basis for rejection of foreign cells)

Question 16

What does diffusion mean?

Answer 16

Since the universe strives for entropy (disorder) diffusion is movement from high concentration to low concentration

Question 17

What is the main solute in ICF, and thereby responsible for ICF osmolarity?

Answer 17

K+

Question 18

What different kinds of endocytosis are there?

Answer 18

Phagocytosis-“cell eating”
Pinocytosis-“cell drinking”
Receptor medlares endocytosis-triggered by molecular signal

Question 19

What is the Na+/K+ pump?

Answer 19

Active transport (requires ATP) and lets 3 Na+ into cell and 2 K+ out

Question 20

What are the functions of membrane proteins?

Answer 20

Transporters
Enzyme activity
Cell surface receptors
Cell surface identity markers
Cell adhesion
Attachment to cytoskeleton

Question 21

What can move freely through a phospholipid bilayer?

Answer 21

Hydrophobic molecules (O2, CO2, N2, benzene) can move freely
Small uncharged polar molecules (H2O, urea, glycerol) can move in some extent
Large uncharged molecules (glucose, sucrose) can hardly move in

Question 22

What is endocytosis?

Answer 22

The movement of large molecules into the cell via vesicles (phagocytosis or pinocytosis)

Question 23

What is the meaning of the Fluid Mosaic Model?

Answer 23

It is not rigid, it is asymmetrical, comprised of different molecules
Consists of phospholipid bilayer, proteins and carbohydrates

Question 24

What is facilitated diffusion?

Answer 24

Diffusion through protein channels, do not need ATP

Question 25

Where can you find polar amino acids?

Answer 25

On outersurface of membranes since hydrophilic

Question 26

How is fluid balance regulated?

Answer 26

ECF volume | ECF osmolarity

Question 27

What are the concequence of hypertonic ECF?

Answer 27

Cells shrink due to water leaving the cell

Question 28

What are the main composition of ions in ICF and ECF?

Answer 28

ICF mainly K+ and PO4--- | ECF mainly Na+ and Cl-

Question 29

What is active transport?

Answer 29

When molecules move AGAINST concentration gradient Through "pumps" that changes shape while moving solute from one side to the other Requires ATP

Question 30

What is physiology?

Answer 30

The study of functions in living systems

Question 31

What is needed to maintain stable water balance?

Answer 31

Water input must equal water output

Question 32

What are the concequence of Hypotonic ECF?

Answer 32

Cell swells due to water entering the cell

Question 33

What are the different transports through the cell membrane?

Answer 33

``` Passive transport (simple diffusion) needs no ATP Facilitated transport (through protein channel) needs no ATP Active transport (protein pump) against concentration gradient=needs ATP ```

Question 34

What classes of amino acids are there?

Answer 34

Nonpolar=hydrophobic | Polar=hydrophilic

Question 35

What is the osmolarity of ICF/ECF?

Answer 35

~300mOsm/L

Question 36

What is Hypertonic, isotonic and hypotonic?

Answer 36

Hypertonic=more solute, less water Isotonic-equal solute and water Hypotonic=less solute, more water

Question 37

Describe the phospholipid bilayer

Answer 37

Consists of two layers of phospholipids which each has a hydrophilic (polar) head and a hydrophobic tail (nonpolar) The heads turn outwards and the tails inwards creating a double layer in membranes

Question 38

Where can you find nonpolar amino acids?

Answer 38

Within membrane, since hydrophobic

Question 39

What is plasma membrane?

Answer 39

A thin bi-layered phospholipid layer surrounding each cell

Question 40

What is osmosis?

Answer 40

The diffusion of water from high concentration of water to low concentration of water (across semi-permiable membranes)

Question 41

What can NOT move through phospholipid bilayers?

Answer 41

Ions Polar molecules Large molecules (starch, proteins)

Question 42

What is exocytosis?

Answer 42

The movement of large molecules out through cell membrane via vesicles