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Bio > Chapter 12 > Flashcards

Chapter 12 Flashcards

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Biology 101 flashcards
1
Q

Where is the plasma membrane found and what does it have ?

A

The plasma membrane is found at the boundary of the cell and it has selective permeability

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2
Q

What is the structure for all biological membranes

A

The structure is a phospholipid bilayer

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3
Q

Explain the structure of the phospholipid

A

The head is hydrophilic facing the outside
The tail is hydrophobic being able to reach the membrane

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4
Q

In the animal membrane what type of steroid is found?

A

The steroid cholesterol is found and is located in between the phospholipids in the bilayer

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5
Q

What does the plasma membrane consists of ?

A

proteins, carbs, cholesterol ,phospholipid

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6
Q

What are the two types of membrane proteins

A

Integral proteins and peripherical proteins

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7
Q

What are integral proteins ?

A

The proteins are embedded in the lipid bilayer by their hydrophobic regions

They may have a hydrophilic region extending on oner or both sides of the membrane -(Transmembrane proteins)

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8
Q

What are the peripheral proteins ?

A

Do not penetrate in the lipid bilayer

Associated loosely with the inner or outer side of the plasma membrane

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9
Q

How are the membrane proteins held in place?

A

The membrane may be held in place by attaching fibres to the ECM

OR

May be held in place by attaching to the cytoskeleton

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10
Q

What are the functions of the membrane proteins ?

A

Transport
Enzymatic activity
Signal transduction
Cell to cell recognition
Intercellular joining ( proteins involved in forming gap junctions)
Attachment to the cytoskeleton and the ECM( helps gives cells shape and structural support )

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11
Q

What are the membrane carbs ?

A

Most membranes contain small significant amounts of carbs
Usually branched chains that have less than 15 sugar units

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12
Q

What form are the membrane carbs found in ?

A

Most of them are found as Glycoproteins (proteins attached to a carb )
Some are found in the form of glycolipids(a lipid with a carb attached to it)

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13
Q

Where are carbs found in the membrane

A

They are found in the external side of the membrane and function in cell to cell recognition

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14
Q

What is an example of glycoproteins ?

A

Human blood types( different types of glycoproteins found on the surface)
They have an RH factor either positive or negative
Play a role in cell to cell recognition > need blood type to match for recognition

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15
Q

How do carbs found in the membrane differ?

A

They differs in terms of cell types , between species and differ in between members of the same species

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16
Q

What is the fluid mosaic model?

A

The most accepted current model that is sued to describe the structure of a membrane
Proposed by Jonathan singer and Garth nicolson in 1972

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17
Q

What does mosaic mean

A

Refers to the different types of proteins present within the phospholipid bilayer

Examples are RBC have around 50 different of proteins in it’s plasma membrane

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18
Q

What does fluid mean

A

The membrane is fluid
The phospholipids and proteins can move freely around the membrane

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19
Q

Why is maintaining fluidity important?

A

Allows membrane proteins to move freely in order to carry out the functions

Allows cells to change shape which is important during cell division and movement

Allows materials like lipids and proteins to diffuse

Allows membrane to self heal

Is Able to adjust to temp which is vital for cellular functions

20
Q

What is membrane fluidity affected by ?

A

Affected by temp and the types of lipids that make up the membrane

21
Q

How does temp affect fluidity ?

A

Fluidity increases with increasing temp
Decreases with decreases temp

22
Q

How does lipid composition affect the membrane fluidity ?

A

Dependant on the type of lipid that makes up the membrane

23
Q

How does fatty acid composition affect the fluidity of a membrane ?

A

The length of the fatty acid side chain- membrane that have longer fatty acids chains are less fluid with those with shorter chains

Membranes that contain unsaturated fatty acids are more fluid - this is because the unsaturated fatty acids contain one or more double bonds which Create kinks preventing the molecules from packing tightly together

Presence of sterols= found in between the phospholipids in either layers

24
Q

How does cholesterol influence fluidity ?

A

Cholesterol acts as a temp buffer - experts different effects at different temperatures

At high temps makes the membrane less fluid (restrains the movement of phospholipids )

At low temps makes the membrne more fluid
(Interacts with the hydrocarbon chains so that they don’t fit as tight together when the temperature is low )

25
Q

What is the role of cholesterol

A

Helps keep the membrane fluid with the temperature changes

26
Q

How can organisms regulate membrane fluidity ?

A

By changing the lipid composition of the membrane
Called homeoviscous adaption takes place in bacteria , yeasts , plants and ectotherms

27
Q

Examples of homeviscous adaptions

A

Fish in an outdoor pond in the cold will increase unsaturated fatty acids

And archea in hot springs will have more unsaturated fatty acids

28
Q

What is membrane asymmetry

A

Membranes contain diff kinds of lipids and proteins which are randomly disturbuted in between the two monolayers
Each membrane has a distinct side that has a unique composition of proteins and lipids

29
Q

What side of the membrane will the glycoprotein be found ?

A

On the extra cellular side , carb chains facing outward interacting with the external environment

30
Q

How are materials transported across a membrane ?

A

Solutes are carried across through three different mechanisms
1) simple diffusion
2)facilitated diffusion
3) active transport

31
Q

What are the difference in between active and passive ?

A

Passive = simple , no energy , movement is with the concentration gradient, transport proteins are used for facilitated diffusion

Active transport = energy is required , movement id against the concentration gradient and transport proteins are always involved

32
Q

What is the function of active transport

A

Allows cells to uptake essential nutrients from the environment when they are lower outside the cell then inside the cell

Allows secretory or waste products to be removed from the cell when the concentration is higher outside the cell

Allows a constant , non equilibrium concentration of certain ions inside the celll

33
Q

What is the sodium potassium pump?

A

Sodium is pumped out of the cell and potassium is pumped into the cell
Both are pumped against their concentration gradient
A transport protien called the sodium potassium pump located in the plasma membrane move here ion

34
Q

How many Na + are pumped for every K+ ions?

A

Every 3 for every 2
Results in difference in charge between the outside and the inside of the cell
Cytoplasm is negative in charge compared to the extracellular fluid

35
Q

What is membrane potential?

A

Voltage across the plasma membrane

36
Q

What is an electrogenic pump?

A

Pumps that generate voltage
Sodium potassium is major electrogenic pump in animal cells

37
Q

What is the electrogenic pump in plants , bacteria and fungi

A

Proton pump
Helps the store energy that can be used for future cellular work
Transport materials across the membrane( transport sucrose into sieve tube cells)

38
Q

What is co transport

A

Occurs when a pump transporting a specific solute across the membrane is responsible for indirectly pumping another solute across the membrane against the concentration gradient

39
Q

How can water and small molecules move across the membrane

A

They can move via diffusion
other transport processes that move molecules include facilitated diffusion and active transport

40
Q

How do large molecules enter and exit the cell

A

Large proteins and polysaccharides
Generally cross the membrane by a mechanism involving vesicles

41
Q

What is exocytosis?

A

Large molecules exit via exocytosis
I)A vesicle that contains proteins buds from the golgi
II) the vesicle travels along a microtubule to the plasma membrane
III) the outside of the vesicle binds to the inside of the plasma membrane
IV) the two membranes fuse , releasing (secreting) the proteins outside of the cell
Example = pancreatic cell secreting insulin

42
Q

What is endocytosis ?

A

The cells take in the molecules by forming new vesicles from the plasma membrane

43
Q

What are is phagocytosis

A

1)phagocytosis (cellular eating)= folds the plasma membrane called pseudopods surround a particle
Basically a phagocytic vacuole is formed and the vacuole fuses with a lysosome and the material is digested (defences by certain white blood cells)

44
Q

What is pinocytosis ?

A

pinocytosis (cellular drinking )= results from the inward folding of the plasma membrane to form a pocket. Fuses to make a vesicle and then fuses with lysosome to breakdown internalized materials

45
Q

What is receptor mediated endocytosis ?

A

On the plasma membrane are receptors for certain substances
When the receptor binds to its Ligand, the complex moves to a special region on the plasma membrane called a coated pit
It forms a vesicle and then the vesicle fuses with a lysosome

Bio (17 decks)

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