58 Questions
Which type of molecules can easily diffuse across a lipid bilayer?
Nonpolar molecules
What type of proteins are present in biological membranes to facilitate the transport of substances into and out of the cell?
Transport proteins
What characterizes a transport protein in biological membranes?
It undergoes a change in conformation to move solutes across the membrane
What is a role of membranes in a cell?
To define the boundaries of the cell and internal compartments
Which organelles are specifically mentioned as having membranes in Eukaryotic cells?
Nucleus, mitochondria, and chloroplasts
What characterizes the presence of organelles in Eukaryotic cells?
Presence of membranes defining internal compartments
Which type of proteins allow cells to recognize, transmit, and respond to specific signals in nearly all cell types?
Receptors
What is the function of gap junctions in animal cells?
Allowing exchange of cellular components between cells
What is the main function of plasmodesmata in plant cells?
Allowing exchange of cellular components between cells
Who first proposed the fluid mosaic model of the membrane?
S. Jonathan Singer and Garth Nicolson
What is a key characteristic of the membrane according to the Singer-Nicolson model?
Fluid nature
In the Singer-Nicolson model, what is a significant feature of the lipid components of a membrane?
In constant motion with lateral mobility
Who proposed the concept of the lipid bilayer in 1925?
Evert Gorter and François Grendel
What are the main classes of membrane lipids?
Phospholipids, glycolipids, and sterols
What components make up a phospholipid molecule?
Two fatty acids, a negatively charged phosphate group, and a charged or polar head group
Which lipid is the most abundant in cell membranes?
Phospholipids
What gives phospholipids their amphipathic character critical for membrane structure?
Highly polar head and two nonpolar tails
Which molecule forms a hydrophobic barrier in phospholipids?
Glycerol
What is the common head group found in phosphoglycerides like phosphatidylcholine?
Choline
What is the main sterol found in animal cell membranes?
Cholesterol
What type of fatty acids have higher transition temperatures and are considered less fluid in membranes?
Long-chain saturated fatty acids
How do membrane lipids with saturated fatty acids differ from those with unsaturated fatty acids in terms of packing?
They pack together tightly
What effect do sterols like cholesterol have on the permeability of a lipid bilayer to ions and small polar molecules?
Decrease permeability
What is the primary mechanism by which organisms regulate membrane fluidity?
Changing lipid composition
What do amphibians and reptiles do to adapt to lower temperatures in terms of their membrane lipid composition?
Increase unsaturated lipids
What technique involves freezing a membrane quickly and then subjecting it to a sharp blow from a diamond knife?
Freeze fracturing
Where are integral membrane proteins located within the lipid bilayer?
Embedded within the lipid bilayer
What characterizes lipid-anchored proteins in membranes?
They are hydrophilic proteins located on membrane surfaces
What is the main characteristic of transmembrane proteins?
They span both sides of the lipid bilayer
What is the function of GPI-anchored membrane proteins?
Released from the membrane by the enzyme phospholipase C
What is a common feature of glycoproteins in membranes?
Covalently linked to amino acid side chains
Where does glycosylation, the addition of a carbohydrate side chain to a molecule, occur for proteins?
Endoplasmic Reticulum and Golgi compartments
In terms of diffusion, how do membrane proteins typically compare to lipids?
Membrane proteins are much more variable in their diffusion rates than lipids
Why are some membrane proteins constrained in their movement within the lipid bilayer?
Due to being anchored to protein complexes adjacent to the membrane
What role do glycoproteins, which have undergone glycosylation, play in plasma membranes?
Cell-cell recognition
What structures do animal cells use for joining cells in long-term associations to form tissues and organs?
Adhesive junctions
Which type of junctions in plants carry out functions similar to cell-cell junctions in animal cells?
Plasmodesmata
What is the main function of adhesive junctions in multicellular organisms?
Maintain tissue integrity
What type of interactions occur when cells interact with identical molecules on the surface of the cell to which they adhere?
Homophilic interactions
What type of proteins are predominantly involved in forming adherens junctions between cells?
Cadherins
Which feature is common between desmosomes and adherens junctions in terms of the type of proteins they rely on for adhesion?
Cadherins
What is the key function of tight junctions in epithelial tissue?
Blocking lateral movement of lipids and proteins
What is the main role of lectins in cell adhesion?
Secreting carbohydrate-binding proteins
How do gap junctions facilitate communication between adjacent cells?
By allowing the passage of ions and small molecules
What is the primary constituent of stretchable elastic fibres providing elasticity?
Elastins
Which family of proteins primarily binds proteoglycans and collagen molecules to receptors on the plasma membrane surface?
Fibronectins
What is the main function of laminins in the basal lamina beneath epithelial cells?
Maintain tissue organization
Which component is the most abundant in the extracellular matrix of animal cells?
Collagens
What is a defining characteristic shared by all collagens in animal tissues?
Rigid triple helix structure
Where are fibronectins primarily located in relation to the lamina?
On either side of the lamina
How do integrins link the cytoskeleton with the extracellular matrix?
By interacting with proteins in the cytosol
Where do epithelial cells attach to laminin in the basal lamina?
Through hemidesmosomes
What family of transmembrane proteins do integrins belong to?
Integrin family
Which plant cell wall component is most abundant in tissues providing mechanical support?
Extensins
What is the primary constituent of the secondary cell wall that makes it significantly stronger and more rigid than the primary wall?
Lignin
Which structure is synthesized first in the plant cell wall and holds adjacent cells together?
Middle lamella
In some plant cells, which type of wall creates a relatively thin and flexible structure?
Primary cell wall
What do plasmodesmata provide in plant cells through their channels between adjacent cells?
Plasma membrane continuity
Test your knowledge on the cellular membrane, which acts as a hydrophobic permeability barrier with phospholipids, glycolipids, membrane proteins, and sterols. Learn about the essential role of water as a solvent system in cell function.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
