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Biology of the Cell > Unit 1: Lipids and Membranes > Flashcards

Unit 1: Lipids and Membranes Flashcards

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1
Q

What are the main functions of cell membranes (5) ?

A
  • Form a barrier against pathogens
  • Be physically separated from external environment
  • Take in nutrients, minerals and ions
  • Excrete waste products from the cell
  • Receive and act on signals from outside and send signals to other cells
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2
Q

What are the components of the bilayer (3) ?

A
  • Lipids
  • Proteins
  • Carbohydrates
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3
Q

What is the job of lipids in the bilayer ?

A

They are responsible for forming the basic structure that seals each cell from its external environment

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4
Q

What are lipids made up from ?

A

Phospholipids and cholesterol

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5
Q

What is the job of proteins in the bilayer ?

A

They are responsible for communication with the external environment

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6
Q

How do proteins communicate with their environments ?

A

By compromising receptors, channels and pumps

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7
Q

What is the most abundant membrane lipid ?

A

Phospholipids

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8
Q

What is the main phospholipid ?

A

Phosphoglycerides

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9
Q

What are the components of a phospholipid ?

A

Head - Phosphate and glycerol
Tail- Two long chain fatty acid tails

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10
Q

What are the 4 main phospholipids present in the plasma membrane ?

A
  • Phosphatidylcholine
  • Phosphatidylethanolamine
  • Phosphatidylserine
  • Sphingomyelin
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11
Q

What phospholipids are present in the outer membrane ?

A

Phosphatidylcholine & Sphingomyelin

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12
Q

What phospholipids are present in the inner membrane ?

A

Phosphatidylethanolamine & Phosphatidylserine
& Phosphatidylinositol (an important cell signallng molecule)

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13
Q

What does fluidity of the plasma membrane depend on ?

A
  • Temperature
  • Composition of fatty acid tails
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14
Q

What is the job of cholesterol in lipid bilayers ?

A

To provide structure and rigidity

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15
Q

How can cholesterol influence membrane fluidity at cold temps ?

A

At cold temperatures cholesterol prevents phospholipids packing together and maintains fluidity

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16
Q

What is a lipid raft ?

A

Lipids that are restricted within specialised membrane micro domains

17
Q

What are the components of a lipid raft ?

A
  • Cholesterol
  • Sphingomylein
  • Glycolipids
18
Q

How do lipid rafts move within the membrane ?

A

Laterally (side to side)

19
Q

What are the functions of membrane proteins (5)?

A
  • Transport specific molecules
  • Provide channels for ion passage
  • Receptors for external cues (chemical, physical)
  • Structural links to other cells
  • Enzyme activity
20
Q

Are carbohydrates found on the interior or exterior side of the membrane ?

A

Exterior

21
Q

What are the 2 types of protein- carbohydrate molecules ?

A
  • Glycoproteins
  • Proteoglycans
22
Q

Carbohydrate chains that form a net around cells are known as what ?

A

The glycocalyx

23
Q

What is endocytosis ?

A

Mechanism by which cells internalise substances from the external environment

24
Q

Give 3 reasons why endocytosis is important

A
  • Nutrient uptake
  • Entry of pathogens
  • Phagocytosis
25
Q

What is Clathrin-mediated endocytosis ?

A

The major endocytic pathway in mammalian cells

26
Q

What are the 6 steps of Clathrin mediated endocytosis ?

A

1) Macromolecules bind to specific cell surface receptors e.g. Low-density lipoprotein binds to LDL receptor
2) Receptors cluster and recruit clathrin which builds a coat around the membrane forming a clathrin-coated pit
3)An actin network forms around clathrin and helps bend membrane inward
4) The neck of mature pits is cleaved from the membrane by dynamin to form small clathrin-coated vesicles containing receptors and bound cargo
5) Vesicles fuse with early endosomes for sorting of cargo
6) Clathrin is recycled back to membrane

27
Q

Give one type of lipid raft

A

Caveolae

28
Q

What are extracellular vesicles ?

A

Nano sized lipid bilayer decimated particles that are released from almost all cells

29
Q

Give 3 examples of extracellular vesicles

A
  • Exosomes
  • Microvesicles
  • Apoptotic bodies
30
Q

Where can extracellular vesicles be found ?

A

In plasma, urine, breast milk and saliva

31
Q

What is neurotransmission an example of ?

A

Exocytosis

32
Q

What is a SNARE complex ?

A

SNARE complexes mediate the docking of vesicles across a synapse

33
Q

Where is a V-SNARE located ?

A

Attached to the vesicle

34
Q

Where is a T-SNARE located ?

A

On the target membrane

34
Q

Neurotoxins cleave SNARE proteins, what does this mean ?

A

Prevents vesicles docking with the membrane

35
Q

What does PLA stand for ?

A

Phospholipases

36
Q

What does PLA do ?

A

Hydrolyses phospholipids- cleave (separate) fatty acid tails from glycerol backbone

Biology of the Cell (10 decks)

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