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Bio test 2 > Lecture 8a > Flashcards

Lecture 8a Flashcards

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Biology 101 flashcards
1
Q

what do membranes do?

A

provide the structural basis for metabolic order

  • they keep groups of embedded enzymes of one metabolic pathway together and separate from other enzyme systems
  • form most of the eukaryotic cell’s organelles and therefore partition the cell into compartments
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2
Q

what happens when there are no membranes?

A

no homeostasis
no metabolism

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3
Q

what is an example of a cellular membrane?

A

the plasma membrane

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4
Q
A
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5
Q

what are the functions of the plasma membrane?

A
  • separates living cells from their surroundings
  • maintains a constantly controlled intracellular environment
  • selectively permeable: takes up substances required + helps dispose of unwanted wastes
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6
Q

what is the plasma membrane composed of?

A

-composed of phospholipid bilayer with proteins and certain steroid lipids embedded in it

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7
Q

what does amphipathic mean?

A

a molecule containing both polar and nonpolar portions in its structure

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8
Q

what are hydrophilic heads composed of?

A

a phosphate group attached to a glycerol

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9
Q

what are hydrophobic tails?

A

contain a saturtated or unsaturated fatty acid

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10
Q

do phospholipids and proteins move laterally or vertically?

A

laterally and rarely vertically

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11
Q

what did the protein movement experiement with human and mouse cells demonstrate?

A

the mouse and human cells were labelled and fused together.
The results demonstrated a hybrid cell with blended mouse and human proteins. This demonstrates that at least some plasma membrane proteins must be able to move around the phospholipid bilayer.

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12
Q

how to organisms maintain optimal membrane fluidity?

A

they alter the fatty acid content of their membrane lipids

they do this to comensate for temperature changes

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13
Q

what is a homeoviscous adaptation?

A

when the temperature goes down, the proportion of unsaturated fatty acids goes up and the membrane stays fluid.

homeoviscous=you want to maintain fluidity

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14
Q

what do longer fatty acid chains mean in terms of fluidity?

A

the longer the fatty acid chains, the less fluid the membrane is likely to be.
= this is a result of the increased number of potential van der waals association between chains.

fatty acid chain lengths can vary

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15
Q

what will happen to membrane fluidity if the number of double bonds in fatty acids is increased?

A

double bonds decrease fluidity

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16
Q

what will happen to membrane fluidity if the length of fatty acid chains is increased?

A

the fluidity will decrease

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17
Q

what does cholesterol act as in terms of the plasma membranes fluidity?

A

cholesterol affects the plasma membrane differently as it acts as a fluidity buffer

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18
Q

what happens with cholesterol at high temperatures?

A

Cholesterol stabilizes the membrane(fluidity buffer)
The polar hydroxyl group on cholesterol will bind to the hydrophilic head of an adjacent phospholipid restricting motion and preventing unstability.

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19
Q

what happens with cholesterol at low temperatures?

A

Cholesterol acts as a spacer between fatty acid chains preventing Van der Waals interactions thus increasing fluidity.

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20
Q

what are the two types of proteins associated with the plasma membrane?

A

1) intergral (inside)
2) peripheral (outside)

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21
Q

what is the classification of membrane proteins based on?

A

based on how the proteins are positioned in relation to the phospholipid bilayer.

22
Q

Describe integral proteins

A
  • firmly bound to the membrane, penetrating the core of the lipid bilayer
  • amphipathic: - hydrophilic region extends out of the cell and/or into the cytoplasm
    - hydrophobic regions interact with the fatty acid tails.
23
Q

what are transmembrane integral proteins?

A

extend all the way through the membrane, sometimes spans the membrane just once or many times (up to 24 times)

24
Q

what type of shape structure does the transmembrane have?

A

alpha-helix

25
Q

name two types of integral proteins

A

1) aquaporins - transport water in and out of the cell down its concentration gradient (osmosis)
2) Glycoproteins- proteins that are embedded in the plasma membrane and the oligosaccharide faces the extracellular matrix

26
Q

describe peripheral proteins

A
  • not embedded in the lipid bilayer
  • located on the inner or outer surface of the membrane
  • may be receptors on the surface of the cell or enzymes associated with the inner membrane
27
Q

identify the transmembrane proteins, peripheral membrane protein, and intergral membrane proteins

A
28
Q

Comparing both sides to the membrane, are both sides the same?

A

no, they are asymmetrically orientated because of the highly specific way each protein is inserted into the bilayer.
- one side more proteins are firmly attached than the other

29
Q

what makes peripheral proteins on the inner surface?

A

made by free ribosomes in the cytoplasm

remember that these are on the inner surface of the plasma membrane

30
Q

what makes integral proteins or peripheral proteins on the outer surface of the plasma membrane?

A

made by ribosomes embedded in the rough ER

31
Q

what are the six major functions of membrane proteins?

A

1) transport
2) enzymatic activity
3) signal transduction
4) cell-cell recognition
5) intercellular joining
6) attachment to cytoskeleton and extracellular matric (ECM)

32
Q

how do cell-cell recognition distinguish among different cells?

A

they provide identification tags to cells
- the outer portion of the plasma membrane contains glycoproteins and glycolipids
- allows the immune system to recognize and reject foreign cells
- enables cells to sort themselves into tissues and organs during embryogenesis

33
Q

how do autoimmune diseases get created?

A

occurs when antibodies that the immune system produces fail to distinguish what is ‘self’ and what is ‘foreign’.

most common autoimmune disease= rheumatoid arthritis = attacls the synovial membrane of joints

34
Q

what is the difference in binding in intercellular joining compared to cell-cell recognition?

A

membrane proteins of adjacent cells may hook together in various kinds of juctions. this binding is more longlasting than the binding found in cell-cell recognition

35
Q

Name a plant cell junction

A
  • plasmodesmata ( for communication)
36
Q

Name animal call junctions

A
  • desmosomes( for anchoring)
  • tight junctions( prevents leakage)
  • gap junctions (for communication)
37
Q

what is the plasmosdesmata?

A

channels that provide rapid chemical communication between plant cells
- water, small molecules and ions can pass through these channels so that plant cells share water, nutrients and chemical messages.

plant cells can dilate these channels

these channels not only bridge the plasma membranes of adjacent cells but also their cell walls

38
Q

what is the role of desmosomes?

A

they anchor animal cells to eachother or to the ECM without stopping the passage of materials between cells.
- very strong junctions

39
Q

why don’t plant cells have desmosomes?

A

because they have a cell wall for strength

40
Q

what do desmosomes consist of?

A

-consists of a pair of buttom-like discs associated with the cytosolic side of the plasma membrane of adjacent cells and the intercellular protein filaments that connect them.
- intermediate filaments in the cells are attached to the discs and are connected to other desmosomes

the intermediate filaments are connected where mechanical stresses can be distributed throughout the tissue.

41
Q

what is the role of tight junctions?

A

sheet of tissue between animal cells that are so tight that substances cannot leak between them
- hold the cells together in actual physical contact
- forms a sheet of tissue
- **purpose: prevents movements of solutions or solvents **

42
Q

where can you find tight junctions?

A

bladder: tight junctions that prevent urine from leaking to the rest of the body
stomachs: contain acids that tight junctions keep in place
capillaries of the brain: the tight junctions in the capillaries of the brain form the brain-blood barrier which prevents many substances in the blood from passing into the brain.

43
Q

what is the role of gap junctions?

A

purpose: allows for rapid chemical and electrical communcation between animal cells
- bridge the space between animal cells like desmosomes for communcation however the space they span is narrower.

they also contain channels that connect the cytoplasm of adjacent cells thus allowing for communcation

44
Q

where can you find gap junctions?

A

cells in the pancreas = if one group of cells received a signal to secrete insulin, the signal is passed on to other pancreatic cells, ensuring a coordinated response.
heart muscle cells= linked by gap junctions that permit the flow of ions to synchronize contractions

45
Q

what do proteins attached to the cytoskeleton and ECM do?

A

they are fixed proteins that help keep the membrane in place
- noncovalently linked to the cytoskeleton and to fibers of the adjacent ECM

46
Q

what does the ECM consist of ?

A
  • consists of gel-like substances made of carbohydrates and fibrous proteins
  • collagen ( forms tough fibers )
  • fibronectins (glycoproteins that help organize the matrix and also aid cells in attaching to the matrix by binding to proteins that extend from the plasma membrane.
47
Q

what do fibronectins bind to?

A

they bind to proteins called integrins

48
Q

what are integrins?

A

integral transmembrane proteins that:
- serve as membrane receptors for the ecm, they activate signaling pathways that communicate information to the cell from the ecm
- they play a role in cell movement and in organizing the cytoskeleton so that cells assume a definite shape
- anchor the ecm to the microfilaments of the internal cytoskeleton

49
Q

what is an example of ecm?

A

cancer cells can metastasize(spread through the body) because they have lost the requirement to be anchored to the ecm.

50
Q
A

Bio test 2 (9 decks)

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