Brainscape's Knowledge GenomeTM

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


See full index

Biochemistry Intro lectures 1-6 > L5 - Membranes > Flashcards

L5 - Membranes Flashcards

1
Q

Diffusion

A

Net movement of particles from an area of higher to lower solute concentration

NB: molecules will diffusé both ways but net Movement will be from H-L

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

Passive process means no…. is needed?

A

Energy , ATP etc.

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

Gas exchange surfaces are adapted for efficient diffusion. In what way?

A
  • Thin surface- only one layer of epithelium thick = short diffusion pathway
  • give gas exchange organs LARGE SA TO VOLUME
  • increases rate of diffusion and temp!! ( bcos molecules have more Ek – move faster )
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Another name for cell membrane

A

Plasma membrane

Surface membrane??

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

What do cell membranes contain?

A
  • LIPIDS ( usually phospholipid as they are membrane lipids remember!) its amphipathic also !
  • PROTEINS
  • CARBOHYDRATES (usually attached to lipids or proteins)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Model of cell membrane : Fluid Mosaic model

EXPLAIN

A
  1. phospholipid bilayer forms :
    Fatty acids x2 = tails = Hphobic
    Phosphate group = heads = Philic

Protein molecules scattered like a mosaic
Nb this layer is LIQUID

  1. GlycoPROTEINS - some proteins attached to polysaccharide i.e. Type of carbohydrate
  2. GlycoLIPIDS - some lipids = attached to polysaccharide chain (carbohydrate )

Glycol is referring to carbs I think! CORRECT

  1. Membrane is partially permeable to small molecules
    - larger molecules or ions must go through special membrane proteins i.e. Channels and carriers
  2. Cholesterol = membrane lipid
    - Flows through phospholipids
    - Forms BONDS
    - Decreases fluidity of membrane
    - Makes it more RIGID
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Osmosis

A

Net movement of water through a selectively permeable membrane, as it passes from an area of high water concentration to an area of low water concentration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How to molecules go past or through or transport material through CELL MEMBRANE

A
  • small molecules diffusé or pass through easily
  • larger molecules need more help - special membrane proteins called
    CARRIERS & CHANNEL PROTEINS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How CARRIER proteins work

A
  • Molécule that wants to get through etc attaches to carrier protein
  • Causes a CHANGE OF SHAPE ( In what tho? ) IN CARRIER PROTEIN
  • molecule released other side of membrane
  • Down CG
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How CHANNELS work ?

A
  • Create PORES in the membrane to allow molecule to pass through
  • Down CG
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Active transport :

A
  • ATP needed
  • only works with CARRIER proteins
  • forces molecules to move AGAINST their CG - think is to do with ECF & ICF?? YES
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Some molecules are too big a carrier proteins can’t help them.
Alternatives?

A
  1. ENDOCYTOSIS
    - cell membrane of cell surrounds a molecule
    - CM piches off to form a vesicle inside the cell contains the ingested substance

ATP NEEDED

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

EXOCYTOSIS

What happens?

A

How cells secrete or get rid of substances
How it occurs :
- vesicles containing unwanted substances move away from Golgi and towards the cell membrane
- fuse with CM & release their substances outside of the cell
- note: some membrane proteins won’t go OUTSIDE the cell but will go back into the cell membrane

ATP NEEDED

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

Cholesterol controversy !! Which is it ???

A

Lecture says moderated fluidity of molecule but CPG’s say decrease fluidity of membrane
????

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

Membrane proteins

  • What are they?
    • function (4)
A
  • Proteins part of or inserted into the membrane
  • most form ALPHA HÉLICES crossing the membrane
  • membrane inserted but is HPHOBIC
  • functions :
  • TRANSPORTERS & CARRIERS
  • Anchors?
  • Receptors -
  • ENZYMES - bio catalysts
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Fluid mosaic model - function of FLIPPASE enzymes

A

Causes the flipping of phospolipds in fluid mosaic model of CM
- v unfavourable & thus delta G must be pos!!

17
Q

Transporters splits into

A

Active - ATP needed
Passive - no ATP needed

Slow process for both

  • AT - aka : PUMP since ATP must be pumped

AT : vs CG
PT : with CG

18
Q

Are transporters the same as carriers??

A

Think So

19
Q 
Channels i.e. Ion channels 
- what type of process is allowed
- fast or slow 
- types of ion channels 
-
A
  • ONLY ALLOW FACILITATED DIFFUSION ( passive diffusion)
  • fast
  • 2 types : voltage gated - open/close due to membrane potenitial changing - AP’s etc
    &
  • ligand gated ion channels - open/close due to ligands binding to them
20
Q

At: active transport can be further subdivided into :

Check this re lecture notes

A

Primary - driven by ATP

Secondary - driven by a transport of ATP

PRIMARY :

  • Na+/ K+ ATPase pump
  • 3 Na out & 2 K in
  • Vs CG

But DIGOXIN inhibits this process
- Meaning Na CG is reduced
- Meaning concentration of Ca inside the cell increase
(NB; Ca needed for muscle contraction)
- used to treat heart failure ; heart can contract faster

SECONDARY :

  • Energy produced in same way ( Na / K pump etc)
  • but this energy is used to drive other transport reactions in same : SYMPORT or opposite: ANTIPORT direction

Eg symporters glucose & AA uptake in gut
Antiporters : Na + & Ca 2+ antiport In heart!

21
Q

Primary active transport
How does it occur
YouTube video animation v good!!

A

Picture the diagram,
- ECSurface of cell where Na + conc is higher than K+
- Na / K ATPase pump
-ICS of cell where K = higher conc than Na
Process :
- 3 Na & 1 ATP attach to pump

NOTE ; 3 Na join on side where there is less Na and more K ; NB

  • ATP — ADP & Pi
  • 3 Na join pump
  • ADP is released
  • this causes pump where Na ions are to change shape and thus Na moves towards outside of cell against its conc grad
  • then 2 K ions attach to pump
  • Pi is released
  • causes pump To change shape & K is released into cell vs gradient
  • continuous process
22
Q

How does secondary AT occur?

A

Picture the image: same as PAT but there’s GLUCOSE &; another pump/ transporter aswell as normal pump.

( think it’s just a carrier protein as it changes shape when Na & glucose go in)

  • Glucose is pumped into the cell along with Na ion
  • energy is needed for this to occur (AS we are moving glucose VS its CG)
  • the energy is provided by the sodium gradient ( which occurs due to ATP - IN primary active transport)
  • thus it’s not directly from ATP that glucose is pumped vs it’s conc grad
  • Na is then pumped back out of cell by PAT
  • etc.
  • since Glucose & Na go In same direction SYMPORTER protein
    Opposite? ANTIPORTER protein
23
Q

Receptors

A
  • Special proteins that attach to ligands (signalling molecules ) &; produce a cellular response
  • function of receptor will usually have changed
24
Q

Eg of ligands

A

ligands; signalling molecules that bind to receptors

  • Hormones
  • Cytokines
  • Neurotransmitters - Ach ?
25
Q

Types of receptors and ex.

A 
Cell surface receptors
- Ligand gated ion channels 
( NB : IC only support facilitated diffusion )
- enzyme coupled receptors 
- G protein coupled receptors

Intracellular Receptors

  • bind Hydrophobic ligands
  • eg. Steroid hormones like testosterone & oestrogen
  • Thyroid hormone
  • Vitamin D
26
Q

Ligand gated ion channels that are receptors aka?

A
  • Inotropic Receptors

- IC Coupled Receptors

27
Q

GPCR - how do they work ?

A

Picture this:

  • Receptor with an indent made for a ligand to bind easily
  • alpha beta &; gama subunits attached to the receptor
  • ADP is attached to the alpha subunit ; NB NB NB NB
  • Once ligand binds all subunits move away
  • GDP—- GTP
  • alpha subunit moves away with GTP = ACTIVATED
  • once ligand is removed alpha uses its own phosphorylation activity - GTP—–GDP & Pi
  • subunits return to to the receptor
28
Q

What activated G proteins can do:

A
  • Can stimulate enzymes that produce second messengers
  • they can AMPLIFY signals
  • eg cAMP stimulates protein kinases (enzymes) &; thus they can phosphorylate various substances
  • this can cause change in gene expression or metabolic regulation
29
Q

Enzyme coupled receptors

How it occurs in receptor tyrosine kinase for eg

nb video - YOUTUBE

A
  • Switched on by ligands binding
  • often leads to DIMERISATION
    ( 2 polypeptides bond )

Receptor tyrosine kinase

  • receptor that has tyrosine attached (AA) along polypeptide chain
  • has kinase activity – can cause phosphorylation

Process:

  • ligand binds to the receptor (2)
  • causes a changé In shape
  • 2 polypeptides aggregate
  • ATP —-ADP & Pi
  • Pi is added to each tyrosine
  • relay inactive protein binds to tyr & Pi - cause A cellular response

Biochemistry Intro lectures 1-6 (6 decks)

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