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Bio 2 > Unit 3: Membranes > Flashcards

Unit 3: Membranes Flashcards

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Biology 101 flashcards
1
Q

What is the membrane structure composed of?

A
  1. Lipids (usually phospholipids)
  2. Sterol lipids
  3. Proteins
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2
Q

What are phospholipids like?

A

They have a hydrophobic tail and a hydrophilic head. The hydrophilic head is attracted to water and to other heads. The hydrophobic tail is made up of fatty acids.
Phospholipids form a bilayer (with the hydrophobic tails in the center) There is constant movement.

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3
Q

What are sterol lipids like?

A
  1. Fit between fatty acid chains
  2. keep membrane fluid
  3. stabilize the membrane
    Ex: cholesterol (animal cells) and phytosterols (plants)
    Most cholesterol we have is used to make bile
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4
Q

What are proteins like?

A
  1. Many different types
  2. Specific to cell type
    Ex: integral membrane proteins and transmembrane proteins; peripheral membrane proteins
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5
Q

What are the membrane functions?

A
  1. Define cell – contains and separates
  2. Selective transport
  3. Enzyme activity
  4. Signal transduction – protein receptors (transfer message from outside to inside the cell)
  5. Cell adhesion – cell-to-cell links (holds all together)
  6. Cell recognition
  7. Attachment to cytoskeleton

The functions 2-7 are due to membrane proteins

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6
Q

What are the types of traffic across membranes?

A

Passive transport and active transport

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7
Q

What are the different types of passive transport?

A
  1. Diffusion
  2. Osmosis
  3. Facilated diffusion
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8
Q

What is diffusion?

A

The movement of particles down concentration gradient (from high concentration to low concentration)

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9
Q

What are examples of molecules that can diffuse through the membrane?

A

H20, EtOH, O2, CO2, N2, hydrophobic molecules, lipid-soluble molecules

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10
Q

What is osmosis?

A
  • The passive transport of water through aquaporin (water/protein) channels and through the membrane.
  • From hypotonic concentration to hypertonic concentration until isotonic concentration – from less salt concentration to more salt concentration.
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11
Q

What are examples of osmosis?

A
  1. Turgor pressure (plants)
  2. Using salt or sugar as a preservative
  3. Water moving into stomach (after addition of H+ AND Cl-)
  4. Contractile vascuoles (in some protists)
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12
Q

What is facilitated diffusion?

A

Transport of solutes across the membrane down concentration gradient via specific transport proteins (through transmembrane proteins = channels)

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13
Q

What are examples of facilated diffusion?

A
  1. Glucose transporter

2. Gated ion CHANNELS in membranes of neurons

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14
Q

What are the different types of active transport?

A
  1. ion pumps
  2. co-transport
  3. exocytosis
  4. endocytosis
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15
Q

What is transportation through ion pumps?

A

Moves ions across membranes, against their concentration gradient

  1. Maintain membrane potential – maintain electrochemical gradient (difference in charge across the membrane)
  2. help maintain osmotic pressure
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16
Q

What is active transport?

A
  • Transport against concentration gradient (low concentration to high concentration)
  • requires energy as ATP
  • requires transmembrane proteins (“pumps”)
17
Q

What are examples of ion pumps?

A
  1. Na+/K+ ion pump, sodium potassium pump (Na+/K+ ATPase)
  2. Ca++ pump, calcium pump in sarcoplasmic reticulum (muscle cells)
  3. Proton pump
  4. H+/K+ ATPase
18
Q

How does the Ca++, calcium pump work?

A

– In sarcoplasmic reticulum (muscle cells)
Muscle contraction requires release of calcium ions for sarcoplasmic reticulum
-Ca++ stored in specialized organelles in muscle cells
-Ca++ low in cytosol
-Ca++ high in sarcoplasmic reticulum

19
Q

How does the proton pump work?

A
  • Maintains acidic environment inside lysosome

- transports H+ into, for examples, lysosome; mitochondria (ATP production)

20
Q

How does the H+/K+ ATPase (H+/K+ exchager) work?

A

Moves H+ into the lumen

21
Q

What is co-transport?

A
  • Movement of ion down its concentration gradient
  • is coupled to movement of “transported” molecule against its gradient
  • Both molecules move through the same transport protein
  • Transport of 2 molecules through the same transport protein (1 is down gradient and 1 is against gradient)
22
Q

What are examples of co-transport (aka secondary transport)?

A
  1. Symport

2. Antiport

23
Q

What is symport?

A

-both molecules (coupled molecules) move in the same direction

24
Q

What are examples of symport?

A

Plant cell uptake of sucrose coupled to H+ diffusion

-Sucrose transport – H+ down gradient, sucrose against gradient

25
Q

What is antiport?

A

-Coupled molecules move in opposite directions
-Transport of 2 molecules through same transport protein
1 moves into cell and 1 moves out of cell

26
Q

What are examples of antiport?

A

Na+/Ca++ exchanger

In cardiac muscle cells, Na+ diffusion into cell, coupled t Ca++ export out of cell

27
Q

What is exocytosis?

A

-Secretion of macromolecules (big molecules) outisde of the cell by fusion of vesicles with plasma membrane

  • molecules inside the vesicle
  • vesicle fuses with cell membrane
  • ATP used to move vesicles
28
Q

What are examples of exocytosis?

A
  1. Neuron secretion of neurotransmitters
  2. Secretion of hormones and enzymes and other proteins by glandular cells
  3. Insertion of plasma membrane
  4. Insertion of transmembrane proteins and external surface proteins
  5. antigen presentation – immune response
  6. make more cell membranes (makes cell surface larger)
29
Q

What is endocytosis?

A

The reverse of exocytosis (molecules are larger)
The uptake of macromolecules by formation of vesicles with plasma membrane from exterior of cell
The vehicle formed from cell membrane enters the cell

30
Q

What are the three types of endocytosis?

A

Phagocytosis
Pinocytosis
Receptor-mediated endocytosis

31
Q

What is phagocytosis

A

Creates food vacuole

Cell membrane changes shape to surround the food or whatever is being taken up

32
Q

What is am example of phagocytosis

A

White blood cells engulf invading bacterial cells

33
Q

What is pinocytosis

A

Bulk phase endocytosis
The nonspecific uptake of extracellular fluid and dissolved solutes (stuff in fluid)
Unspecific

34
Q

What is an example of pinocytosis

A

Kidney cells use pinocytosis to absorb proteins from urine

35
Q

What is receptor-mediated endocytosis

A

Requires receptor proteins within membrane and inner surface of membrane
Uses receptors to select specific molecules

36
Q

What is an example of receptor-mediated endocytosis

A

Used to take up cholesterol

37
Q

What creates the shape of the vesicle

A

Clathrin (the cell does not know how to do this)

Bio 2 (6 decks)

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