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biological membranes > roles of membranes and their structure > Flashcards

roles of membranes and their structure Flashcards

1
Q

is it true that biological membranes have different roles depending on whether they are on the outer surface of the cell-plasma membrane or within the cell

A

yes it is true

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2
Q

what are the two main types of biological membranes

A

-plasma membrane-(the cell-surface membrane that surrounds the cell
-intracellular membranes

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3
Q

what is the name for membranes contained within the cell

A

intracellular membranes

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4
Q

are all membranes partially permeable

A

yes

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5
Q

What is the role of membranes on the surface of cells-the plasma membrane

A

-acts as partially permeable barrier, controlling the substances that enter an leave the cell/controls enxhange of materials between the internal cell environment an the external environment

-acts as a site of cell signalling/cell communication

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6
Q

explain how the plasma membrane is a site of cell signalling

A

The cell-surface membrane has receptors which bind to hormones or other chemicals like drugs which triggering a response in the cell

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7
Q

what is the role of membranes within cells

A

-form concentration gradients in the cell

-they compartmentalize the cell

-they form organelles like vesicles, which they use to transport substances within the cell

-also form lysosomes, which they use to break down worn-out organelles and to engulf and kill pathogens

-site of chemical reactions

-provide attachment sites for enzymes-meaning they separate organelles from the cytoplasm

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8
Q

what is compartmentalisation

A

it is the separation of organelles and their contents from the cytoplasm via the formation of membrane-bound compartments known as organelles

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9
Q

How can substances cross the partially permeable membranes,both on the surface of the cell and within the cell

A

-via diffusion
-facilitated diffusion
-active transport
-osmosis

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10
Q

what is the name of the model that describes how biological molecules are arranged to form cell membranes

A

Fluid Mosaic model

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11
Q

why are cell membranes described as fluid

A

The phospholipids are free to move within the phospholipid bilayer in relation to each other,giving the membrane flexibility

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12
Q

Why are cell membranes described as a mosaic

A

desribed as mosaic because the protein molecules are scattered throughout the phospholipid like tiles in a mosaic

-also they have different sizes,positions and shape like tiles in a mosaic

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13
Q

what biological molecules make up the phospholipids bilayer

A

-phospholipids
-cholesterol
-glycoproteins
-glycolipids
-carrier proteins
-channel proteins

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14
Q

how do phospholipids arrange in water

A

they form a bilayer

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15
Q

what is the structure of phospholipids

A

consists of hydrophilic phosphate head and hydrophobic fatty acid tails

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16
Q

explain how phospholipids arrange to form a bilayer

A

the hydrophilic phosphate heads are attracted to water so face outward and towards it to form hydrogen bond switch surrounding water molecules, allowing membranes to play a role in compartmentalization

the hydrophobic fatty acid tails are repelled by water so face outwards and towards each other creating the hydrophobic core of the phospholipid bilayer

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17
Q

whats the role of the hydrophobic core

A

it acts as a barrier to water-soluble substances,
it means that water-soluble substances like glucose cannot leak out the cell and unwanted water-soluble substances cannot get in

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18
Q

can phospholipids be chemically modified to act as signalling molecules

A

yes,they move within the bilayer activating molecules like enzymes

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19
Q

what type of biological molecules does cholesterol fall into

A

lipids

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20
Q

what is the role of cholesterol.Explain it

A

it regulates the stability and fluidity of cell membranes.At low temperatures, cholesterol prevents phospholipids’ hydrophobic fatty acid tails from packing too closely together.This increases the fluidity of cell membranes

At high temperatures, cholesterol binds to the hydrophobic fatty acid tails,this stabilises the phospholipids and causes them to pack closely together, reducing the fluidity of cell membranes and increasing their stability.

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21
Q

where is cholesterol present in the phospholipid bilayer

A

between the hydrophobic fatty acid tails of phospholipids

21
Q

is cholesterol only hydrophilic

A

no

cholesterol has one hydrophilic end which interacts with the hydrophilic phosphate heads of phospholipids and they have a hydrphobic end which interacts with the hydrophobic fatty acid tails of phospholipids

22
Q

does high concentrations of cholesterol in the membrane make it fluid or rigid

A

rigid

22
Q

what else does cholesterol control

A

the impermeability of mebranes to ions and polar molecules,as the membranes become more fluid they become less impermeable to ions and polar molecules as the hydrophobic fatty acid tails of phospholipids are further apart

23
Q

what are the two types of protein present in the phospholipid bilayer

A

-intrinsic proteins
-extrinsic proteins

24
Q

are lipid-soluble molecules able to pass through the membrane

A

yes,they diffuse by simple diffusion

25
Q

state two differences between intrinsic and extrinsic proteins

A

-intrinsic proteins are embedded in both sides of the bilayer, whereas extrinsic proteins are embedded in one

-intrinsic proteins have hydrophobic R groups on their surface, whereas extrinsic proteins have hydrophilic R groups on their surface

26
Q

what is the role of intrinsic proteins

A

they are channel and carrrier proteins and transport water soluble substances across the membrane

27
Q

how do channel proteins also known as pore protein transport charged/polar molecules through the membrane

A

-they form a hydrophilic channel in the cell membrane
It allows the passive movement, down the concentration gradient of charged/polar molecules only through

28
Q

how do carrier proteins transport charged/polar molecules through the membranes

A

they change shape to transport polar/charged particles across the membrane by both passive and active movement of charged/polar molecules across the membrane

29
Q

do channel protein move molecules through active or passive movemnt

A

passive meant down concentration gradient so no energy is required

30
Q

do carrier proteins move molecules by active or passive movement

A

both active and passive

31
Q

whats meant by passive movement

A

movement down the concentration gradient so no energy is required

32
Q

are they specific to a particular ions/molecule

A

yes

32
Q

What is meant by active movement

A

movement across the concentration gradient so energy is required

33
Q

whats the role of glycoproteins

A

-act as antigens thus they play a role in the recognition of cells as self or non-self

-play a role in cell signalling/communication between cells

-acts as receptors, binding sites for hormones

  • play a role in cell adhesion, binding to other cells to hold them together in a tissue

-attach to water molecules to stabilise membranes

33
Q

what are glycoproteins

A

proteins with a carbohydrate chain attached to them

34
Q

whats type of chain is attatched to the glycoprotein

A

carbohydrate chain/sugar chain

35
Q

are glycoprotein intrinsic or extrinsic proteins

A

intrinsic

36
Q

where are extrinsic proteins located

A

embedded in one side of the bilayer

37
Q

what r groups do extrinsic proteins have on their surface

A

hydrophilic ,interact with the polar phosphate heads of phospholipids and with intrinsic proteins

38
Q

what is the role of extrinsic proteins

A

they function as enzymes and catalyse reaction inside cells

39
Q

what are glycolipids

A

a lipid with a carbohydrate chain attached to it

40
Q

what chain do glycolipids have attached to them

A

carbohydrate chain

41
Q

what is the role of glycolipids

A

-act as receptors ,binding sites for specific hormones
-act as antigen thus play a role in the recognition of cells as self and non-self

42
Q

role of protein in membranes

A

-allow polar ,charged particles to pass through the membrane

43
Q

role of phosospholipids

A

acts as barrier to water soluble substances

44
Q

how do hormones cause a reaction on cells

A

cell-surface receptors are specific ,hormones bind to complementary receptors which triggers a reaction

45
Q

explain structure of a membrane bilayer

A

-contain phospholipids, hydrophilic phosphate heads facing outwards and hydrophobic fatty acids tails facing inwards and towards each other

-it contains intrinsic and extrinsic proteins

-glycolipids and glycoproteins stick out the surface of the membrane/bilayer

-cholesterol between fatty acid tails of phospholipids

46
Q

describe whats meant by communication between cells

A

molecules released by one cell .That molecule then attaches to receptors of another cells, causing a change in that cell

47
Q

describe how a molecule is released from one cell and then makes a difference in another

A

-the signal molecule is released by one cell via exocytosis

-the glycoproteins and glycolipids in the membrane of the target cell act as receptors

-the receptors on the target cell are specific and are complementary to the shape of the signal molecule

-the attachment of the signal molecule to the receptors causes a change inside the cell

48
Q

is it true that each transport protein is specific to an ion/molecule

A

yes

biological membranes (4 decks)

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