Cells And Organelles > Plasma Membrane > Flashcards

Plasma Membrane Flashcards

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1
Q

Cytoskeleton

A

Provides mechanical strength
Controls shape and regulates movement

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2
Q

Internal membranes

A

Encloses space in cell often involved in digestion and secretion like lysosomes endoplasmic reticulum and Golgi

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3
Q

Different types of cells in the body

A

Nerve cells
Gut cells
Skin cells
Red blood cells etc

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4
Q

Amphipathic

A

Molecules forming membrane
One part hydrophobic and one part hydrophilic
Basically plasma membrane

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5
Q

What leaves a substance through plasma membrane

A

Nitrogenous waste
Secretion
Oxygen
Carbon Dioxide

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6
Q

What substances enter a cell through plasma membrane

A

Nutrients
Ionic salts
Oxygen
Carbon dioxide

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7
Q

What can pass through freely in plasma membrane

A

Small molecules
Carbon dioxide oxygen (polar) passes fast
Water and ethanol (non polar) passes slowly
Large non polar molecules like benzene but passed slowly

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8
Q

What can’t pass through freely in plasma membrane

A

Macromolecules like glucose and ions like potassium sodium

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9
Q

What molecules requires membrane proteins to pass through freely

A

Large polar molecules like glucose and charges molecules like amino acid and ions like sodium chlorine

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10
Q

Components of plasma membrane

A

Lipids proteins and carbohydrates

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11
Q

Three major membrane lipids in plasma membrane are…

A

Phospholipids sterols like cholesterol and glycol ions

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12
Q

Micelle

A

Hydrophobic chains of the fatty acids are sequestered at the core of the sphere. No water inside like a sphere shape

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13
Q

Bilayer

A

All a yo side chains except those at the edges of the sheet are protected from interaction with water.

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14
Q

Liposomes

A

Filed two dimensional bilayer forms a three dimensional hollow vesicles enclosing an aqueous cavity

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15
Q

Membrane fluidity is infuenced by

A

Temperature
Phospholipid composition

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16
Q

Phospholipid composition is influenced by

A

Length of hydrocarbon chains
The number of double bonds - unsaturated hydrocarbons tails with kinks means fluid bc loose packing of tails but saturated hydrocarbons tails means viscous bc close packed tails
have a look at the slides

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17
Q
A
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18
Q

In animals membrane fluidity is also influenced by…

A

Short and rigid cholesterol molecules

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19
Q

Increase in fluidity means

A

Short tails
More double bonds (unsaturated)
Less cholesterol
Less packed together
High temperature

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20
Q

Decrease fluidity means

A

Long tails
Few double bonds (saturated)
More cholesterols (usually in high temps)
More packed together
Lower temp

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21
Q

Glycolipids

A

Found in non Cytosolic layer
Partition preferentially in lipid rafts
Sugar group added in the Golgi apparatus
Has 5% of lipid molecules in outer layer

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22
Q

Role of glycolipids

A

Markers for cellular recognition
Provided energy
Attaching cells to each other to form tissues
Maintain stability

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23
Q

Lipid rafts

A

Micro domain with specific lipid components
Sphingolipids concentrated here (longer tails therefore membrane thicker
Accommodate certain member and proteins which also accumulate there
Held together by van der Waals forces
About 70nm in diameter
Also rich in cholesterol

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24
Q

Tole of lipid rafts

A

Role in signal transduction, membrane trafficking and organisation pf the cytoskeleton pathogen entry

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25
26
Lipid bilayer is asymmetrical true or false
True
27
Role of plasma emebrane
Receive info Import and export small molecules Capacity for movement and expansion
28
Plasma membrane consists of
50% protein 50% lipid
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Na+ pump
Transporter Actively pumps Na out of cells and K+ in
30
K+ leak channel
Ion channels Allows k+ ions to leave cells having major influence on cell excitability
31
Integrins
Anchors Link intracellulae actin filaments to extrecellular matrix proteins
32
Platelet derived growth factor (PDGF) receptor
Receptors Bindsextrcellular PDGF and as a consequence generates intracellular signals that cause the cell to grow and divide
33
Adenylyl cyclase
Enzymes Catalyses the production of the small intracellular signalling molecule cyclic AMP in response to extra cellular signals
34
Carbohydrates
Can be attached to both glycolipids and glycoproteins in cell membrane they form glycocalyx
35
Glycocalyx functions?
Provide cushioning and protection for the plasma membrane Important for cell recognition Carbs interact with surface molecules for other cells facilitating cell cell recognition Carbs
36
Cell recognition
Cell hair litt to distinguish one type of neighbouring cell from another
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Tight junction
Seals neighbouring cells together in an epithelial sheet to prevent leakage of molecules between them Acts as a barrier
39
Adherens junction
Joins an actin bundle in one cell to a similar bundle in a neighbouring cell
40
Desmosome
Joins the inter mediate filaments on one cell to those in a neighbour
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Gap junction
Forms channels that allow small water soluble molecules inc ions to pass from cell to cell Communication channel
42
Hemidesmosome
Anchors intermediate filaments (usually keratin to provide strength) in a cell to the basal lamina (so the cell doesn’t peel away) Connects cell to the basement membrane instead of another cell
43
Tight junction main function
1. They limit the passage of molecules and ions through the space between cells. This pathway provides tighter control. 2. They block the movement of integral membrane proteins between the apical and basolateral surfaces of the cell. 3. Seal adjacent epithelial cells in a narrow band just beneath their apical surface. They consist of a network of claudins, occludins and other proteins
44
Adherens junctions
The provide strong mechanical attachments between adjacent cells.
45
Desmosomes
1. Localized patches that hold two cells tightly together. They are common in epithelia (e.g., the skin). Also called Anchoring junctions! 2. Desmosomes are attached to intermediate filaments of keratin in the cytoplasm. 3. The adhesion protein bridges the space between the cells. 4. Fasten cells together into strong sheets. (for example it attached muscle cells to each other in a muscle). Connects two cells together
46
Hemidesmosomes
Similar to desmosomes but attach epithelial cells to the basal lamina (basement membrane) instead of to each other.
47
Gap junctions
1. Intercellular channels (1.5-2nm in diameter). Also called Communication junctions!! 2. They permit the free passage between the cells of ions and small molecules (up to a molecular weight of about 1000 daltons). 3. They are cylinders constructed from 6 copies of transmembrane proteins called connexins. 4. Because ions can flow through them, gap junctions permit changes in membrane potential to pass from cell to cell.
48
Major kinds of membrane lipids are
Phospholipid Glycolipid Cholesterol
49
How many different types of cell in body
25
50
Bacteria’s plasma members lacks in what?
Carbohydrates
51
What does received information mean
Receiving signal from another cell or same cell
52
Why is cell division important in plasma membrane
Bc major rearrangement in membrane associated structures occurs as cells proceed from interphase through prophase etc Plasma membrane undergoes major shape changes during mitosis
53
Difference in micelle and liposomes
Micelle Mono layer water insoluble inside Liposomes Bilayer water soluble inside
54
movement of bilayer
Lateral diffusion so moving side ways Flip flop the phospholipid moves outside the bilayer sometimes with the help of proteins Rotation Flexion
55
Write size range of cell from small to big
Atom 0.1nm Lipids 1nm -10nm Protein 1nm -10nm Virus 10nm- 100nm mitochondria Bacteria 1 bequem Animal cell plant cell 10- 100 bequem Blastocyst (zygote) 100 bequem -1mm Frog egg 1mm Chicken egg 10-100mm Human 1m
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Phospolipid composition made of 4 major phospolipid which is
Phosphatidylcholine (PC) and sphingomyelin (SM) mainly in the outer leaflet Phosphatidylethanolamine (PE) and phosphatidylserine (PS) in the inner leaflet 50% of PM lipid
58
One minor phospholipid
Phosphatidylinositol (PI) minor component in the cytosolic leaflet but important for signaling
59
PS and PI are what charged
Negatively Giving net negative charge to cytosolic face
60
Glycolipids are located where
Mostly in outer leaflet 2% of PM lipid
61
Cytosolic
Is located in the inner leaflet The side where the cytoskeleton is
62
Examples of adherents junction
1. They hold cardiac muscle cells tightly togethere as the heart expands and contracts. 2. They hold epithelial cells together. 3. They seem to be responsible for contact inhibition.
63
What is adherens junction made of
They are made up from Cadherins and Catenins
64
Endoplasm
Central area with organelles
65
Ectoplasm
Outer gel like part
66
Golgi apparatus modifies proteins mainly by
Adding carbohydrates chains (glycosylation)
67
The acidic pH of lysosomes is maintained by
Proton pumps powered by ATP
68
After endocytosis the vesicles typically
Fuses with the lysosome for digestion
69
What is the main genetic difference between eukaryotes and prokaryotes? A. Prokaryotes have multiple linear chromosomes B. Eukaryotes store DNA in plasmids C. Eukaryotic DNA is enclosed in a nuclear envelope D. Prokaryotic DNA is double-stranded while eukaryotic DNA is single-stranded
c Eukaryotic DNA is enclosed in a nuclear envelope — that’s the key distinction. You’re right that it also sounded like D, but both eukaryotic and prokaryotic DNA are double-stranded.
70
Which statement about cell walls is correct? A. All eukaryotic cells have a cell wall B. Only animal cells have cell walls C. Prokaryotic cell walls are more complex than eukaryotic ones D. Eukaryotic cell walls contain peptidoglycan
c Only some eukaryotes (plants/fungi) have walls, but prokaryotic walls (e.g., in bacteria) are more complex and often made of peptidoglycan. So C is correct.
71
The term “semi-permeable” refers to the membrane’s ability to: A. Allow all molecules to pass through freely B. Allow only certain substances to pass through C. Prevent any molecules from entering or leaving D. Allow only ions to pass through
b
72
According to the fluid mosaic model, which statement is correct? A. Lipids and proteins are fixed in place B. Proteins and lipids can move laterally within the membrane C. Only lipids move while proteins stay fixed D. The membrane is rigid and static
b Proteins and lipids both move laterally — that’s why it’s called fluid. (C would be half-true; proteins can move too!)
73
The main function of membrane transport proteins is to: A. Store energy B. Synthesize lipids C. Regulate the movement of ions and molecules D. Strengthen the cytoskeleton
c
74
Glycolipids are found: A. In both leaflets equally B. Only in the inner leaflet C. Only in the outer (non-cytosolic) leaflet D. Only in prokaryotic cells
c
75
Which of the following would increase membrane fluidity? A. Long saturated fatty acid tails B. More cholesterol at high temperature C. More unsaturated fatty acids D. Lower temperature
c more unsaturated fatty acids (double bonds) make the membrane more fluid. Low temperature (D) actually reduces fluidity.
76
The inner leaflet of the plasma membrane contains which of the following? A. Phosphatidylcholine and sphingomyelin B. Phosphatidylserine and phosphatidylinositol C. Glycolipids and sphingomyelin D. Only cholesterol
b
77
The negative charge on the inner leaflet is mainly due to: A. Phosphatidylcholine B. Phosphatidylserine and phosphatidylinositol C. Cholesterol D. Glycolipids
b
78
what is cell adhesion
Cell adhesion = cells attaching to each other or the extracellular matrix via specialized membrane proteins (CAMs). It’s essential for tissue structure, communication, and stability. 💡 Why it’s important Tissue formation — keeps cells organized into layers (like epithelium, muscle). Cell signaling — adhesion triggers signals inside the cell to control growth, shape, or movement. Wound healing & immunity — cells must adhere temporarily, then detach to move or repair. Cancer — loss of normal adhesion lets cells detach and spread (metastasis).
79
Which of the following correctly describes the overall role of the plasma membrane? A. Passive barrier only B. Dynamic structure involved in signaling, transport, and movement C. Static outer wall for protection D. Site of DNA synthesis
b the plasma membrane is dynamic, meaning it’s constantly changing, moving, and interacting, not rigid.
80
Which of the following is NOT a function of lipid rafts? A. Signal transduction B. Membrane trafficking C. Cytoskeleton organization D. DNA transcription
d Lipid rafts work in signaling, trafficking, cytoskeleton organization — not gene expression (DNA transcription happens in the nucleus).
81
A membrane protein that spans across the lipid bilayer is called: A. Peripheral protein B. Integral protein C. Cytosolic protein D. Glycoprotein
b Integral proteins span the bilayer; glycoproteins have sugars but may not fully span it.
82
The loss of adhesion between cells is most associated with: A. Cell differentiation B. Metastasis in cancer C. Apoptosis D. Muscle contraction
b Loss of adhesion (e.g. cadherin dysfunction) = metastasis — cells detach and spread. Normally, cadherins keep cells anchored. When lost, cells detach → metastasis (cancer spread).
83
The primary function of integrins in epithelial cells is to: A. Form tight junctions between cells B. Mediate communication through gap junctions C. Anchor the cell to the basement membrane D. Allow ions to diffuse across the plasma membrane
c
84
What is glycocalyx?
both glycoproteins and glycolipids already have carbohydrate chains attached to them. The glycocalyx refers to the collective layer formed by all those carbohydrate components on the outer surface of the plasma membrane. In other words, the glycocalyx is not a separate molecule, but rather the sugar-rich “coat” that results from the combination of all the carbohydrates attached to membrane proteins and lipids. the glycocalyx includes the carbohydrate portions of glycoproteins and glycolipids (and sometimes proteoglycans) together, forming a protective and functional layer around the cell.
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