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Biology Year 1 > 2.1.5-Biological Membranes > Flashcards

2.1.5-Biological Membranes Flashcards

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1
Q

what are the 3 roles of cell membranes?

A

1-as a bilayer (partially permeable membrane), so that small molecules can pass whereas large cannot.
2-Site of chemical reactions
3-Site of cell communication/signalling

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2
Q

what is the main role of membranes?

A

to control the movement of substances in and out of the cell.

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3
Q

what are some example of substances that can pass through membranes?

A

lipids

small water solubles

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4
Q

what are some examples of substances that cannot pass through membranes?

A

large water solubles

ions

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5
Q

what is the fluid mosaic model?

A

it describes the structure of the plasma membrane as mosaic of components
it is a sea of membrane-composed phospholipids with protein molecules between.

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6
Q

what are the 3 things that the fluid mosaic model can help to explain?

A
  • Passive and active movement between cells and their surroundings
  • Cell-to-cell interactions
  • Cell signalling
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7
Q

what are the four main components within the fluid mosaic model?

A
  • phospholipids
  • cholesterol
  • glycoproteins/glycolipids
  • transport proteins
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8
Q

what is the role of phospholipids?

A
  • form the basic structure of the membrane
  • the phospholipid bilayers act as a barrier to most water-soluble substances, so they cannot leak out of the cell/unwanted cannot enter the cell
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9
Q

what is the role of cholesterol?

A
  • it increases the fluidity of the membrane, preventing it from becoming too rigid at low temps.
  • it stops phospholipid tails from packing too closely together
  • it increases the mechanical strength and stability of the membrane.
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10
Q

what is the role of transport proteins?

A
  • create a hydrophillic channel to allow ions and polar molecules to travel through the membrane, controls what enters/leaves the cell
  • each specific to a molecule
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11
Q

what are carrier proteins?

A

transport proteins that change shape to transport substances

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12
Q

as well as carrier proteins, what is the other type of transport protein?

A

channel(pore) proteins

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13
Q

what do glycolipids/glycoproteins acts as?

A
  • receptor molecules, that bind with certain substances at cell’s surfaces
  • some act as cell markers/antigens for cell-to-cell recognition.
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14
Q

what are the 3 main receptor molecules?

A
  • Signalling receptors for hormones and neurotransmitters
  • Receptors involved in endocytosis
  • Receptors involved in cell adhesion and stabilisation
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15
Q

what is the plasma membrane?

A

=the cell surface membrane that separates the cell from it’s external environment

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16
Q

why do membranes exist as bilayers?

A
  • inside/outside of cell are aqueous so a single layer would repel on one side (tails)
  • bilayer=heads face the aqueous tissue/cytoplasm, while the tails face away/in the middle
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17
Q

what are the two main factors that affect membrane permeability and structure?

A
  • temperature

- solvents/alcohol

18
Q

how does temperature affect membrane structure/permeability?

A
  • increased temp, phospholipids gain more kinetic energy, so move more
  • therefore, the membrane becomes more fluid so loses it’s structure and can break
  • loss of structure means that the membrane has an increased permeability, so molecules can cross over it more easily
  • carrier/channel proteins become denatured
19
Q

how does solvents/alcohol have an affect on membrane structure/permeability?

A
  • less polar solvents/non-polar dissolve membrane
  • dissolvement disrupts cells between phospholipids
  • membrane becomes more fluid/permeable
  • this can affect the transmission of messages
20
Q

what are the two passive methods of the movement of molecules across membranes?

A
  • diffusion

- fascilitated diffusion

21
Q

what is diffusion?

A

the net movement of particles from a region of higher concentration to an area of lower concentration

22
Q

what is fascilitated diffusion?

A

the same as diffusion, but a channel protein is required to transport polar, charged and water soluble molecules across the partially permeable membrane

23
Q

what are the key differences/similarities between simple and fascilitated diffusion?

A
  • S=fat soluble through lipid bilayer, F=lipid soluble through protein channel
  • S=direction of down conc gradient, same with F
  • both are passive movements
  • S=solubles include oxygen, CO2, water and fats, F=insolubles include amino acids, sugars and ions
24
Q

what factors affect diffusion and how?

A
  • temp=increased temp, increased rate due to more ke

- conc difference=increased difference, increased rate as movement becomes larger

25
Q

what is osmosis?

A

the net movement of water molecules from a region of higher concentration to a region of lower concentration, through a partially permeable membrane

26
Q

what are the three types of solutions involved in osmosis?

A
  • isotonic
  • hypertonic
  • hypotonic
27
Q

what is a isotonic solution? +water movement

A

solutions have same concentration of water molecules as the cell, so movement into the cell=movement out of cell

28
Q

what is a hypertonic solution? + water movement

A

lower concentration of water molecules compared to inside the cell, so more water moves out of cell

29
Q

what is a hypotonic solution? + water movement

A

higher concentration of water molecules compared to inside the cell, so more water moves into the cell

30
Q

what is active transport?

A

the movement of molecules/ions into/out of a cell from a region of lower conc to a region of higher conc, involving the use of energy/ATP.

31
Q

what is exocytosis?

A

the contents of the vesicle are released outside of the cell

-the vesicle moves towards and fuses with cell membrane

32
Q

what is endocytosis?

A

the bulk transport of material into a cell

  • phagocytosis=solids
  • pinocytosis=liquids
33
Q

what is needed in active transport, exo/endocytosis?

A
  • energy in form of ATP
  • active transport= energy for particles being moved up conc gradient
  • metabolic energy supplied by ATP
34
Q

what is cell signalling?

A

the communication of cells, they work together to trigger a response
-signal molecule —> target cells

35
Q

how does cell signalling work?

A
  • signal molecule binds to receptor, complementary

- when it binds, it brings changed in the target cell, causing the cell to respond to the signal in some way

36
Q

what is compartmentalisation? and why is it vital?

A

=the formation of membrane-bound areas in a cell
-it is vital, as it contains reactions in separate parts of the cell, specific conditions for cellular reactions to be maintained and it protects vital cell components.

37
Q

what is the concentration and volume equation?

A

C1V1 = C2V2

38
Q

what happens to animal and plant cells when placed in hypertonic solution?

A
  • animal= cells shrivel

- plant= becomes plasmolysed

39
Q

what happens to animal and plant cells when placed in a hypotonic solution?

A
  • animal= cells swell, may lyse/burst

- plant= becomes turgid

40
Q

what happens to animal and plant cells when placed in isotonic solution?

A
  • animal= normal cells

- plant= remains the same

Biology Year 1 (12 decks)

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