Plasma Membranes Flashcards

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1
Q

Define: plasma membrane

A

a selectively (semi/differentially) permeable membrane that surrounds cells and most organelles that separates their contents from the external environment. It containing a phospholipid bilayer and associated proteins.

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2
Q

Define: external environment

A

blood plasma and extracellular fluid

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3
Q

Does the plasma membrane surround organelles?

A

most

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4
Q

How big is the plasma memrbane? how can they be seen?

A

8 nanometres, with transmission electron microscope.

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5
Q

2 components of the plasma membrane?

A

Phospholipids and proteins

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6
Q

Describe the phospholipid bilayer (4 parts!)

A

Phospholipids, WHICH CAN INTERACT WITH WATER, containing:
-> Hydrophilic heads, containing a phosphate group
-> Hydrophilic tails which INTERACT POORLY WITH WATER, containing 2 fatty acid chains that are liquid at HBT
Arranged into a phospholipid bilayer, with hydrophilic heads facing aqueous solutions as they are ok to sit near the water, and hydrophobic tails facing inwards as they don’t mix with water

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7
Q

Define: integral proteins

A

FUNDAmental components of the plasma membrane that are embedded into the plb

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8
Q

Define: transmembrane proteins

A

when oart of a protein is exposed on both sides of a membrane.

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9
Q

What are glycoproteins/lipids?

A

Carbohydrate group attached to a protein/lipid

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10
Q

Define: peripheral protein

A

proteins anchored to the exterior of the plasma membrane through bonding with lipids or are indirectly associated with the plasma membrane through interaction with integral proteins

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11
Q

Are peripheral or integral proteins easier to separate from the plb?

A

peripheral

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12
Q

What does the fluid mosaic model propose?

A
  • Plasma membranes surround all cells and many organelles
  • Plasma membranes are very flexible and can change shape, because the fatty acid chains are liquid at human body temperature (fluid)
  • Plasma membranes are studded with proteins (mosaic)
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13
Q

4 purposes of the plasma membrane?

A
  1. active and selective boundary
  2. denotes cell identity
  3. some proteins are receptor molecules, receiving signals from outside the cell
  4. enables transport
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14
Q

How is the plasma membrane an active and selective boundary?

A

Controls when, what and how much of a substance passes through it; enables cells (and organelles) to maintain conditions that are unique from outside of the memrane

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15
Q

How does the plasma membrane denote cell identity?

A

Glycoproteins act as cell surface markers (including antigens etc); each cell type has a different combination of surface markers.

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16
Q

Define: receptors

A

trans-membrane proteins that receive signals from outside of the cell

17
Q

How do receptor proteins work?

A

THe signal binds to the receptor protein and this changes its shape; starting a specific response in the cell

18
Q

Describe transport due to the cell memrbane.

A

Some substances can pass directly through the cell membrane but sometimes transport proteins are required to enable this.