Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochem Ca1 Cram > Transport Across Cell Membrane > Flashcards

Transport Across Cell Membrane Flashcards

1
Q

4 modes of passive transport ?

A

a). Simple diffusion
b). Facilitated diffusion
c). Osmosis
d). Filtration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

2 types of active transport

A

a). The “pumps”
b). Endocytosis/ Exocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is simple diffusion

A

“ Movement of solute from an area of high concentration to an area of low concentration in solution i.e. down a concentration gradient”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

6 things that affect rate of diffusion

A

-Magnitude of the concentration gradient
-Viscosity of the fluid
-Temperature - ­increased temperature increased rate
of diffusion
-Solubility of solvent
-Gases diffuse rapidly; liquids more slowly
-Molecular size
e.g Glycerol diffuses faster than larger fatty acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

2 places where diffusion occur and example

A
  • Lipid bilayer
  • Membrane channels
    ( Integral channel proteins )
    +example = Some nutrients enter the cell / some waste products leave the cell by diffusion.
    E.g. - Oxygen from blood stream diffuse into the body cells
  • Carbon dioxide diffuses out of the cell into the blood stream
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is facilitated diffusion

A

-Carrier mediated process
-Moves substances into or out of cells from a
high to a low concentration ( i.e. Down a
concentration gradient )
-It DOES NOT require Energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

2 things affecting rate of facilitated diffusion with examples

A
  • cocentration gradient
    -Saturation of the carrier molecule
    E.g. Glucose carrier of RBC
    Glucose carrier of skeletal muscle &
    adipose tissue( Insulin dependent)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is osmosis ?

A

-Diffusion of water through a semipermeable membrane.
-Water can move freely across cell membrane of
cells, either through protein channels or by
slipping between the lipid tails of membrane.
-However, it is the concentration of solutes within the water that determine whether or not water will be moving into the cell, out of the cell, or both
- Osmosis occurs when there is an imbalance of solutes outside of a cell versus
inside the cell.
-More solute a solution contains, the greater the osmotic pressure that solution will have

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is hypotonicity

A

-A solution with a lower concentration of solutes than another solution is hypotonic

  • Cells in a hypotonic solution will take on too
    much water and swell, with the risk of eventually bursting.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is hypertonicity

A

Ø A solution with a higher concentration of solutes than another solution is said to be hypertonic.
Ø Water molecules tend to diffuse into a hypertonic solution because the higher osmotic pressure pulls water in.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is isotonicity

A

A solution with same concentration of solute as other solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is filtration and example

A

Filtration through a porous membrane refers to bulk flow of a solvent along with
substances dissolved in it ( except for molecules that are larger than the pores)
Ex. Glomerular membrane of Kidney

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is active transport

A

Carrier mediated process that moves substances across cell membranes against a concentration gradient at the expense of Energy ( ATP)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What affects rate of active transport

A

Ø Number of carrier molecules
Ø Availability of adequate energy i.e. ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

3 examples of active transport

A
  • Na+/K+ ATPase
  • Calcium pump
  • Proton pump (ATP dependent H pump)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Function of Na+ / K+ transporting ATPase system

A

Most mammalian cells maintain a higher concentration of K+ inside the cell while the Na+ concentration is higher outside the cell

                                      Na+.          K+.       Cl-  Plasma                              142.           4.         103 Intra cellular fluid             10.           152

If no mechanism is there to maintain this difference, Na+ & Cl- will enter the cell down its conc. gradient
Creation of an osmotic gradient
Water will move into the cell
Cells will swell while pressure inside them balanced the influx

But this does not occur. Because Na+/K+ pump maintains the
normal solute levels of these two ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What can inhibit Na+/K+ pump

A

ØCardiac glycosides Digitalis/Oubain inhibit this pump by acting on the extra cellular surface of the membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What does endocytosis and exocytosis do

A

Transport macromolecules thru membrane

19
Q

What is endocytosis

A

small region of plasma membrane folds inwards / invaginates until it has formed a new intracellular vesicle with the macromolecule inside.
This is drawn into cytoplasm

20
Q

3 types of endocytosis ?

A

a. Pinocytosis
b. Receptor Mediated Endocytosis
c. Phagocytosis

21
Q

What is pinocytosis

A

Non specific uptake of small droplets of extracellular fluid
( Along with any material dissolved in it e.g. amino acids, Glc, Vitamins, low molecular weight nutrients )
e.g. Kidney cells

22
Q

2 types of pinocytosis ?

A

Absorptive pinocytosis / receptor mediated endocytosis
Fluid phase pinocytosis

23
Q

What is Receptor Mediated Endocytosis

A

Involves a specific receptor on plasma membrane that recognizes the extracellular macromolecule and binds it. Substance bound to receptor ( Referred to as ligand )
Region of plasma memebrane that contains the receptor-ligand complex undergoes endocytosis

24
Q

4 examples of receptor mediated endocytosis

A

Hepatitis virus ( affecting liver cells )
Poliomyelitis virus (Affecting motor neurons )
AIDS virus ( Affecting T-Cells )
LDL( ligand ) and its receptor

25
Q

What is phagocytosis

A

Active movement that allows large molecules and other cells to pass through the plasma membrane into the cytoplasm
Phagocytosis ( Cell eating Gr.)
When large molecules make contact with membrane of a phagocyte
The membrane begins to form a pocket around the particle by sending out PSEUDOPODIA (False feet )
Pocket closes to form a Phagosome Phagosome with particle enter the cytoplasm.

26
Q

Example of phagosome

A

WBC engulfing a harmful bacteria

27
Q

What is exocytosis ?

A

In some cells secretions accumulate within vesicles.
The secretary vesicle then moves to the plasma membrane

The contents of the vesicle are expelled from the cell.

28
Q

3 examples of exocytosis

A

Secretion of digestive enzymes
Secretion of mucous by salivary glands
Secretion of milk by mammary glands

29
Q

What are ionophores

A

Ionophores are chemicals that facilitate the transport of monovalent and divalent cations across membranes.

30
Q

2 examples of ionophores

A

Antibiotics -Valinomycin
Thermogenin

31
Q

What are 2 types of ionophores

A
  1. Ion carriers
  2. Ion channels ( depending on their mechanism of action )
32
Q

Describe structure of ion carrier

A

cyclic structure or has the ability to form a cyclic structure.
-Inside of the ring contains several oxygens that can chelate a cation.
-Outside of the ring is hydrophobic

33
Q

Function of ion carrier

A

complex made up of a cation and the ionophore is capable of diffusing across the membrane.

34
Q

Example of ion carrier

A

Ex. Valinomycin
(carries K+ across membranes.)

35
Q

Function of ion channel

A

Ion channel ionophores insert themselves into
the membrane in such a way as to create a pore or channel through which ions can flow

36
Q

Example of ion channel

A

Ex. 1. Antibiotic Gramicidin A

37
Q

Describe structure of ion channel

A

forms a helical structure in the membrane
ØHas a central hydrophilic pore large enough
to accommodate ions.
ØThe ions diffuse through the membrane via
the hydrophilic pore.

38
Q

4 types of transport systems based on functional sense according to no. Molecules moved and direction of movement . With example

A
  1. Uniport - Moves one type of molecule bi- directionally
  2. Cotransport - Here the transfer of one solute depends on the simultaneous / sequential transfer of another solute

3.Symport - The two solutes moves in the same direction
e.g.- Na+ - amino acid transport
- Na+ - sugar transporters
( Glc, Mannose, Galactose etc.)

4.Antiport - Moves the two molecules in opposite directions
e.g. Na+ / K+ ATPase etc.

39
Q

What is jeevanee ?

A

Oral rehydration solution
Used to rehydrate persons who are dehydrated.

40
Q

Composition of jeevanee . With total osmolarity

A

Composition:
grams/ litre
Sodium chloride
2.6
Glucose anhydrous
13.5
Potassium chloride
1.5
Trisodium citrate, dihydrate
2.9

mmol/litre
Sodium
75
Chloride
65
Glucose anhydrous
75
Potassium
20
Citrate, dihydrate
10
Total osmolarity
245

41
Q

3 things required for endocytosis

A
  1. Energy usually from hydrolysis of ATP
  2. Ca2+
  3. Contractile elements in cell
42
Q

How does jeevanee work

A

In dehydration giving a saline solution (water plus Na+) by mouth has no beneficial effect (as normal mechanism by which Na+ is absorbed by the healthy intestinal wall is impaired in the diarrhoea).
Ø Thus as Na+ is not absorbed water is not absorbed as well.

Ø Furthermore, excess Na+ in the lumen of the intestine causes increased secretion of water and diarrhoea may even worsen.

Ø If glucose is given along with Na+ and water sodium glucose co-transporter comes into play.
Ø Glucose is absorbed through the intestinal wall and in conjunction Na+ is carried through by the co-transport coupling mechanism (in a glucose : Na+ ratio of 1:1)

Glucose does not co-transport water. It is the now increased relative concentration of Na+ across the intestinal wall which pulls water inside.

43
Q

What is fluid phase pinocytosis

A

Non selective process
Uptake of solute by formation of small vesicle is simply proprotionate to conc. in surrounding extracellular fluid. Formation of vesicles is an extremely active process.

process occurs more rapidly than membranes are made. The surface area and volume of a cell do not change much, so membranes must be replaced by exocytosis or by being recycled as fast as they are removed by endocytosis.

44
Q

Example of fluid phase pinocytosis

A

Fibroblasts, for example, internalize their plasma membrane at about one-third the rate of macrophages

Biochem Ca1 Cram (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions