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bio-membrane transport Flashcards

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0
Q

“fluid mosaic” model

A

Lumpy, constantly changing / shifting mosaic of “tiles” (proteins)

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1
Q

Functions of the plasma membranes

A

Isolates cells contents from environment
Regulates exchange of essential substances
Communicate with other cells
Creates attachments within and between other cells
Regulates biochemical reactions

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2
Q

Structure of cell membranes

A

Phospholipid bilayer with proteins scattered throughout

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3
Q

Describe phospholipid bilayer

A

2 rows of phospholipids, hydrophilic heads facing outwards on both sides, hydrophobic tails facing inwards in between

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4
Q

What drives the phospholipids to form a bilayer

A

The exterior and interior of the membrane face watery environments (extracellular fluid, cytosol), hydrophilic heads must face outwards in both sides with tails between

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5
Q

Purpose of cholesterol in membranes on animal cells

A

Keeps it flexible

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6
Q

What holds the phospholipids together

A

Weak interactions between phospholipids NOT BONDED TOGETHER

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7
Q

What happens if the fatty acid tails of the phospholipids are unsaturated? Saturated?

A

If it’s unsaturated there are kinks in their tails, if Saturated they are more straight

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8
Q

What makes the membrane fluid?

A

Individual phospholipids aren’t bound together,

Unsaturated fatty acids make membrane more fluid than if they were saturated

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9
Q

Where are proteins found in the membrane

A

Embedded within phospholipid bilayer (either floating or anchored in)

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10
Q

Glycoproteins

A

Proteins with attached carbohydrates

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11
Q

Categories of membrane proteins

A 
Receptor proteins 
Recognition proteins
Enzymatic proteins
Attachment proteins 
Transport proteins
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12
Q

Receptor proteins

A

Trigger cellular responses upon binding specific molecules (look at pics in ppt)

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13
Q

Recognition proteins

A

Serve as identification tags on the surface of the cell

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14
Q

Enzymes

A

Promote chemical reactions that either make or break up biomolecules

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15
Q

Attachment proteins

A

Anchor the cell membrane to the inner cytoskeleton, to proteins outside the cell, and to other cells

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16
Q

Transport proteins

A

Regulate import/export of hydrophilic molecules

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17
Q

Types of transport proteins

A

Channel and carrier proteins

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18
Q

Homeostasis

A

Maintain a stable internal state

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19
Q

Biggest contributor in maintaining homeostasis in a cell

A

Cell membrane

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20
Q

What does it mean to reach equilibrium

A

All molecules are equally spread out

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21
Q

Opposite of equilibrium

A

Gradient

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22
Q

Fluid

A

A substance that can move or change shape in response to external forces

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23
Q

Solute

A

A substance that can be dissolved (dispersed as ions or molecules)in a solvent

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24
Solution
A mixture in which one substance is dissolved evenly in another
25
Solvent
Fluid capable of dissolving a solute
26
Concentration
How much solute in a given amount of solvent
27
Gradient
A physical difference in temperature, pressure, charge, or concentration in 2 adjacent regions
28
Why do molecules move from one place to another
In response to a concentration gradient
29
Concentration gradient
A difference between concentrations in a space
30
Diffusion
When molecules spread from an area of high concentration to an area of low concentration until equilibrium is reached
31
The greater the concentration gradient...
...the faster the rate of diffusion
32
Diffusion cannot...
...move molecules rapidly over long distances
33
Supersaturated solution
Dissolves as much as it can, excess comes out | Ex: coffee with too much sugar, sugar settles at bottom
34
2 types of transport across plasma membrane
Passive transport | Active transport
35
Passive transport : Which direction do molecules move (in terms of concentration gradient)? Is energy is expended?
Molecules move down concentration gradient **membrane proteins and phospholipids may limit what can cross, but not direction of movement No energy expended
36
Active transport : Which direction do molecules move (in terms of concentration gradient)? Is energy is expended?
Molecules move against concentration gradient | Energy is expended
37
Selectively permeable
Membranes that allows some things through but not all, like the cell membrane
38
Types of passive transport
Simple diffusion Facilitated diffusion Osmosis
39
Simple diffusion
Lipid soluble molecules and very small molecules directly diffuse across the phospholipid bilayer
40
Facilitated diffusion
Water soluble molecules diffuse across the bilayer with the aid of channel and carrier (carrier changes shape) transport proteins (look at pics in ppt)
41
Osmosis
Diffusion of water
42
Types of solutions
Isotonic Hypotonic Hypertonic
43
What makes water less pure
More dissolved substances because -> Less free water molecules
44
Isotonic solutions
No net flow of water (equal amount flowing in and out) | When both sides of the membrane have an equal amount of water and dissolved substances
45
Hypertonic solution
Low water concentration/high dissolved particle concentration More Water moves TOWARDS hypertonic solution (than the amount that's going opposite direction)
46
Hypotonic solution
Higher concentration of water/lower concentration of dissolved particles More Water moves AWAY from hypotonic solution (than going in opposite direction)
47
Red blood cell in isotonic solution
Equal water going in and out of cell
48
Red blood cell in hypertonic solution (ex: ocean water)
Red flood cell will shrivel up | net water movement is out of cell
49
Red blood cell in hypotonic solution
Cell will fill up and eventually burst | Net water movement is into the cell
50
Explain the contractile vacuole in freshwater Protists
Cytosol in protist is hypertonic to freshwater so water flows into protist, but contractile vacuole is pumped with salt, and becomes hypertonic to the cytosol, so water flows into the contractile vacuole where it is contracted out Freshwater--> cytosol--> vacuole--> out to freshwater
51
Types of energy-requiring transport
Active transport Endocytosis Exocytosis
52
Why is active transport necessary
To stockpile things -- must move against concentration gradient
53
Active transport
Uses Membrane proteins called pumps that have a molecule binding site and an ATP binding site Molecule and ATP bind--> energy from ATP changes shape of transport protein --> molecule is moved across membrane (against concentration gradient)--> protein closes / goes back to original shape and used ATP is released as ADP and P
54
Purpose of endocytosis
To import large molecules or substances
55
Types of endocytosis
Pinocytosis Receptor-mediated endocytosis Phagocytosis
56
Pinocytosis ("cell drinking")
A dimple forms in plasma membrane --> it deepens and fills with extracellular fluid--> membrane closes off the dimple, forming a vesicles filled with extracellular fluid
57
Receptor-mediated endocytosis
Only moves specific molecules into the cell Receptor proteins for specific particles on coated pit sites--> receptors bind the particles and membrane dimples inward--> coated pit región encloses the receptors forming a "coated vesicle" that is released into cytosol
58
Phagocytosis ("cell eating")
Moves large particles or even whole organisms into cell Cell membrane extends pseudopods toward the particle--> ends of pseudopods fuse together, encircling the particle, and forming a vesicles called a "food vacuole"
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Exocytosis
Vesicle fuses with the cell membrane and dumps its contents out
60
Problem with large cells
The organelles get further away from plasma membrane | There isn't enough surface are of cell membrane to satisfy the needs of the large cell
61
Types of specialized junctions
Desmosomes Tight junctions Gap junctions/plasmodesmata
62
Desmosomes
Has protein strands that Attach cells together | Found where cells need to adhere tightly together under stresses of movement (ex: skin)
63
Tight junctions
Formed by strands of proteins Make cell leakproof Found where tubes and sacs must hold contents without leaking (ex: urinary bladder)
64
Gap junctions
Allow for communication cell-to-cell channels allowing for passage of hormones, nutrients, and ions Only in animals
65
Plasmodesmata
Allows for communication Cytoplasmic connections with same function as gap junctions Only in plants
66
How are plasma membranes adapted for caribous (who live in cold temperatures)?
Cell membranes near their hooves are made of more phospholipids with unsaturated fatty acid tails because unsaturated fats can stay liquid at cold temperatures, allowing the membrane to stay fluid
67
What does the plasma membrane have to do with snake and spider venoms?
The venoms have an enzyme that breaks down phospholipids, so the venoms attack cell membranes and destroy them, causing the cells and tissue to die

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