functional structure of the cell membrane Flashcards
what does the cell membrane contain?
it contain lipid bilayer, protiens, cholesterol, and carbohydrates
which of the following is true about cell membrane?
A. the cell membrane attached to cytokeleton in the inner surface and extracellular matrix in the outer side.
B. the thickness of the lipid bilayer is :10-11 nm, not even
C. the membrane is permeable
D. the phospholipid bilayer consist of hydrophobic heads and hydrophilic tails
A
what is the total thickness of the membrane with proteins?
up to 20 nm
what are the functions of cell membrane? list 3
•Forms and preserves a cell’s integrity.
•Control water and material transport into and out of the
cell
•Facilitated diffusion, Carrier proteins, Channels, Endo / exocytosis
•Gives a cell its identity: receptors, ID molecules etc.
•Cell movements (ameboid / flagellar / cilliar movements). •Signal transduction
•Determines electrical status of a cell : Excitation of the cell, propagation of an excitation.
•Attachment to extracellular environment.
•Intercellular interactions: junctions, receptor-ligand binding
which of the following is false about the permeability of the cell membrane?
A. gases like CO2, N2, O2 can cross the cell membrane easily without a channel
B. the cell membrane is a selectively permeable membrane
C. ions like K+ can pass without channel
D. charged polar molecules cannot pass the membrane without channels
C
true or false
the cholesterol makes up 27% of the cell membrane
true
which one is false statement about phospholipids?
A. Phospholipids are a class of lipids that are a major component of all cell membranes.
B. The structure of the phospholipid molecule generally consists of two hydrophobic fatty acid “tails” and a hydrophilic “head” consisting of a phosphate group.
C. The two components are joined together by a hydrogen bonding.
D. The phosphate groups can be modified with simple organic molecules such as choline, ethanolamine or serine.
C
true or false..
glycolipids are sugar molecules bonded to phosphate backbone..
false
they are sugar molecules bonded to sphingosine backbone
what is the difference between cerebroside and ganglioside?
the cerebroside is a single sugar such as glucose and galactose, while ganglioside is multiple sugar which means oligosaccharide
Pathological accumulation of gangliosides in genetical disorders called …………………………….
gangliosidosis
what is the advantage of having cholesterol in the plasma membrane?
it increases membrane flexibility and stability
and it generally decreases membrane fluidity
which of the following is false about sphingolipids:
A. Sphingolipids are commonly believed to protect the cell surface against harmful environmental factors by forming a mechanically stable and chemically resistant outer leaflet of the plasma membrane lipid bilayer.
B. Metabolites of sphingolipids like ceramide and sphingosine-1 phosphate act like inhibitors for important cellular processes like apoptosis, cell proliferation, inflammation, autophagy, aging and differentiation.
C. They are abundant in lipid rafts.
B
what are lipid rafts?
Lipid rafts are submicroscopic membrane microdomains rich in sphingomyelin and cholesterol.
all of these are lipid raft’s function except:
A. membrane fluidity
B. protein trafficking
C. inhibits receptor trafficking
D. regulate host - pathogen interaction
C
which one of the following about asymmetric distribution of membrane lipids is false?
A. Outer and inner leaflet of bilayer are different in type. This asymmetry is help in the function of the cell membrane.
B. Membranes lose asymmetry in dying cells.
C. Many cytosolic proteins bind to specific lipid head groups found in the cytoplasmic monolayer. They take part in converting extracellular signals into intracellular ones.
D. similar shapes and sizes of membrane lipids creates stability in the thickness and causes curvatures on the membrane.
D
- the glycolipids are ……………….. bonded to ……………………….
- while the glycoproteins are ………………………… bonded to ……………………….
- carbohydrates / phospholipids
2. carbohydrates/ proteins
membrane proteins are divided into 2 types, mention them and explain each type.
- Integral proteins: A protein molecule (or assembly of proteins) that is permanently attached to the biological membrane. Such proteins can be separated from the biological membranes only using detergents, nonpolar solvents, or sometimes denaturing agents.
- Peripheral proteins: enzymes, intracellular signal mediators, usually attached to other proteins, but not permanently. They can be extracted without disrupting the membrane.
transmembrane proteins are: A. mostly channels B. signaling proteins C. anchoring proteins D. enzymes
A
what are the functional classes of membrane proteins?
- intercellular joining
- enzymatic activity
- transport (active/ passive)
- cell- cell recognition
- anchorage/ attachment
- signal transduction
Glycosylation of Membrane Components
Lipids + oligosaccharides :
Proteins + oligosaccharides :
Proteins + polysaccharides :
Glycolipids
Glycoproteins
Proteoglycans
which of the following is false about the function of the membrane carbohydrates:
A. Many of them have a negative electrical charge, giving most cells a surface charge that repels other negative things.
B. Endothelial glycocalyx forms a smooth surface for blood flow and attracts the blood cells preventing unnecessary inflammation etc.
C. The glycocalyx of some cells attaches to the glycocalyx of other cells, thus attaching cells to one another.
D. Many of the carbohydrates act as receptor substances for binding hormones, such as insulin; when bound, this combination activates attached internal proteins that, in turn, activate a cascade of intracellular enzymes.
B
Membrane carbohydrates function as cell …………
IDs
lectins are mostly abundant in?
- Red kidney beans
- Soybeans
- Wheat
- Peanuts
- Potatoes
- Tomatoes
- Corn
list 2 from the function of lectins..
- They interfere with the absorbtion of food and minerals, help microorganisms attach to the target cells.
- They act like antioxidants, support cell growth.
