1.3 Biomembranes, Substance Transport, and Intercellular Communication, Receptors

If peripheral proteins:
a) carry a negative charge, they attach directly to the membrane
b) carry a negative charge, they attach to the membrane via Ca²⁺ ions
c) carry a positive charge, they attach directly to the membrane
d) carry a positive charge, they attach to the membrane via Ca²⁺ ions

F - a) carry a negative charge, they attach directly to the membrane
T - b) carry a negative charge, they attach to the membrane via Ca²⁺ ions
T - c) carry a positive charge, they attach directly to the membrane
F - d) carry a positive charge, they attach to the membrane via Ca²⁺ ions

What is the main role of receptors in cells?
a) to transmit signals from the external environment into the cell
b) to regulate ATP levels in the cell
c) to control cell motility
d) to enable protein synthesis

T - a) to transmit signals from the external environment into the cell
F - b) to regulate ATP levels in the cell
F - c) to control cell motility
F - d) to enable protein synthesis

Which substances/molecules are transported by vesicular transport?
a) large particles - e.g., fragments of organelles
b) macromolecules
c) fluids
d) all of the above

T - a) large particles - e.g., fragments of organelles
T - b) macromolecules
T - c) fluids
T - d) all of the above

Which substances/molecules are transported by vesicular transport?
a) large particles - e.g., fragments of organelles
b) macromolecules
c) fluids
d) all of the above

T - a) large particles - e.g., fragments of organelles
T - b) macromolecules
T - c) fluids
T - d) all of the above

What is the name of the phenomenon of red blood cell rupture?
a) hemoptysis, occurs in a hypertonic environment
b) hemolysis, occurs in an isoosmotic environment
c) hemolysis, occurs in a hypotonic environment
d) plasmolysis, occurs in a hypertonic environment

F - a) hemoptysis, occurs in a hypertonic environment
F - b) hemolysis, occurs in an isoosmotic environment
T - c) hemolysis, occurs in a hypotonic environment
F - d) plasmolysis, occurs in a hypertonic environment

What is the environment called when the osmotic value of the medium is lower than that of the cell?
a) hypertonic
b) hypotonic
c) isoosmotic
d) isotonic

F - a) hypertonic
T - b) hypotonic
F - c) isoosmotic
F - d) isotonic

What is the environment called when the osmotic value of the medium is higher than that of the cell?
a) hypertonic
b) hyperosmotic
c) isotonic
d) hypotonic

T - a) hypertonic
T - b) hyperosmotic
F - c) isotonic
F - d) hypotonic

What is the environment called when the osmotic value of the medium equals that of the cell?
a) isotonic
b) isoosmotic
c) hypertonic
d) hypotonic

T - a) isotonic
T - b) isoosmotic
F - c) hypertonic
F - d) hypotonic

What is the ability of a cell to engulf microorganisms called?
a) diffusion
b) phagocytosis
c) osmosis
d) pinocytosis

F - a) diffusion
T - b) phagocytosis
F - c) osmosis
F - d) pinocytosis

What is the general mechanism for releasing substances from cells?
a) pinocytosis
b) diffusion
c) osmosis
d) exocytosis

F - a) pinocytosis
F - b) diffusion
F - c) osmosis
T - d) exocytosis

Active transport is:
a) diffusion and osmosis
b) movement of substances against their concentration gradient
c) movement of substances requiring energy
d) plasmolysis and cytolysis

F - a) diffusion and osmosis
T - b) movement of substances against their concentration gradient
T - c) movement of substances requiring energy
F - d) plasmolysis and cytolysis

A biological membrane is:
a) composed of phospholipids and proteins
b) the basis of membrane-bound organelles such as mitochondria and chloroplasts
c) part of the cell wall
d) the basis of membrane-bound organelles such as ribosomes

T - a) composed of phospholipids and proteins
T - b) the basis of membrane-bound organelles such as mitochondria and chloroplasts
F - c) part of the cell wall
F - d) the basis of membrane-bound organelles such as ribosomes

A biological membrane:
a) is found only in eukaryotic cells
b) is composed of a phospholipid bilayer and proteins
c) in animal cells, it does not contain cholesterol
d) performs various functions such as uptake of substances, cell-cell interactions, signal recognition, etc.

F - a) is found only in eukaryotic cells
T - b) is composed of a phospholipid bilayer and proteins
F - c) in animal cells, it does not contain cholesterol
T - d) performs various functions such as uptake of substances, cell-cell interactions, signal recognition, etc.

Biological membranes contain:
a) phospholipids
b) cholesterol
c) peripheral and integral proteins
d) polar lipids

T - a) phospholipids
T - b) cholesterol
T - c) peripheral and integral proteins
T - d) polar lipids

Cell junctions include:
a) macula occludens
b) desmosome
c) G proteins
d) zonula adhaerens

F - a) macula occludens
T - b) desmosome
F - c) G proteins
T - d) zonula adhaerens

Cell junctions are:
a) cornea occludens
b) desmatozome
c) G proteins
d) zonula adhaerens and desmosome

F - a) cornea occludens
F - b) desmatozome
F - c) G proteins
T - d) zonula adhaerens and desmosome

What are the proteins called that are embedded in the phospholipid bilayer or span across it?
a) peripheral proteins
b) integral proteins
c) glycoproteins
d) lipid rafts

F - a) peripheral proteins
T - b) integral proteins
F - c) glycoproteins
F - d) lipid rafts

What is osmotic lysis of a cell?
a) the phenomenon when a cell takes up water, increases in volume, and bursts
b) the phenomenon occurring when an animal cell is placed in a hypotonic environment
c) the phenomenon when a cell shrinks upon water uptake
d) the phenomenon when a cell does not change volume upon water uptake

T - a) the phenomenon when a cell takes up water, increases in volume, and bursts
T - b) the phenomenon occurring when an animal cell is placed in a hypotonic environment
F - c) the phenomenon when a cell shrinks upon water uptake
F - d) the phenomenon when a cell does not change volume upon water uptake

Facilitated diffusion:
a) is transport mediated by lipid droplets
b) is the most common form of transport into the nucleolus
c) occurs without energy expenditure along the concentration gradient
d) consumes energy in the form of ATP

F - a) is transport mediated by lipid droplets
F - b) is the most common form of transport into the nucleolus
T - c) occurs without energy expenditure along the concentration gradient
F - d) consumes energy in the form of ATP

Facilitated diffusion:
a) is transport mediated by plasma membrane proteins
b) occurs without energy expenditure
c) occurs along the concentration gradient
d) occurs by binding of a substance to a transport protein at the cell surface, followed by conformational change and release into the cytoplasm

T - a) is transport mediated by plasma membrane proteins
T - b) occurs without energy expenditure
T - c) occurs along the concentration gradient
T - d) occurs by binding of a substance to a transport protein at the cell surface, followed by conformational change and release into the cytoplasm

Types of chemical communication include:
a) endocrine
b) paracrine
c) motocrine
d) autocrine

T - a) endocrine
T - b) paracrine
F - c) motocrine
T - d) autocrine

Which processes belong to endocytosis?
a) diffusion
b) pinocytosis
c) phagocytosis
d) osmosis

F - a) diffusion
T - b) pinocytosis
T - c) phagocytosis
F - d) osmosis

Which substances can enter cells by free diffusion?
a) gases
b) urea
c) ethanol
d) oxygen

T - a) gases
T - b) urea
T - c) ethanol
T - d) oxygen

Which type of receptor mediates the effects of insulin?
a) tyrosine kinase receptor
b) nuclear receptor
c) ion channel
d) G protein-coupled receptor

T - a) tyrosine kinase receptor
F - b) nuclear receptor
F - c) ion channel
F - d) G protein-coupled receptor

Which mechanism is most typical for tyrosine kinase-associated receptors?
a) change in ion permeability across the membrane
b) receptor dimerization
c) activation of cyclic AMP (cAMP)
d) activation of cAMP kinase

F - a) change in ion permeability across the membrane
T - b) receptor dimerization
F - c) activation of cyclic AMP (cAMP)
F - d) activation of cAMP kinase

Membrane receptors are classified into:
a) receptors that are part of ion channels
b) mechanoreceptors
c) G protein-coupled receptors
d) enzyme-linked receptors

T - a) receptors that are part of ion channels
F - b) mechanoreceptors
T - c) G protein-coupled receptors
T - d) enzyme-linked receptors

For what purpose does the cell use osmotic energy?
a) for transport of substances across membranes
b) for the transport of substances during protein synthesis
c) for the transport of substances during photosynthesis
d) for transport of osmotically active substances

T - a) for transport of substances across membranes
F - b) for the transport of substances during protein synthesis
F - c) for the transport of substances during photosynthesis
T - d) for transport of osmotically active substances

Which statements about the polarity of the biological membrane surface are correct?
a) the biological membrane is nonpolar
b) the biological membrane is polar
c) the membrane surface carries a negative charge
d) the membrane surface carries a positive charge

F - a) the biological membrane is nonpolar
T - b) the biological membrane is polar
T - c) the membrane surface carries a negative charge
F - d) the membrane surface carries a positive charge

Osmosis is the process by which water passes through the cytoplasmic membrane from an environment:
a) of lower concentration into one of higher concentration
b) of higher concentration into one of lower concentration
c) from a hypotonic to a hypertonic environment
d) from a hypertonic to a hypotonic environment

T - a) of lower concentration into one of higher concentration
F - b) of higher concentration into one of lower concentration
T - c) from a hypotonic to a hypertonic environment
F - d) from a hypertonic to a hypotonic environment

The movement of molecules against a concentration gradient:
a) requires energy, e.g., in the form of ATP
b) is active transport
c) continues until the concentrations on both sides of the membrane equalize
d) is passive transport

T - a) requires energy, e.g., in the form of ATP
T - b) is active transport
F - c) continues until the concentrations on both sides of the membrane equalize
F - d) is passive transport

G protein-coupled receptors:
a) are not found in the plasma membrane of eukaryotic cells
b) consist of polynucleotide chains spanning the membrane
c) do not have an extracellular domain
d) represent the most numerous group of membrane receptors

F - a) are not found in the plasma membrane of eukaryotic cells
F - b) consist of polynucleotide chains spanning the membrane
F - c) do not have an extracellular domain
T - d) represent the most numerous group of membrane receptors

What is the role of cholesterol in the biological membrane?
a) it is a major receptor
b) it increases its flexibility
c) it strengthens it
d) it imparts a positive charge

F - a) it is a major receptor
F - b) it increases its flexibility
T - c) it strengthens it
F - d) it imparts a positive charge

What are biomembranes composed of?
a) two layers of phospholipid molecules and protein molecules
b) two layers of phospholipid molecules and RNA
c) a phospholipid bilayer
d) a single layer of phospholipids

T - a) two layers of phospholipid molecules and protein molecules
F - b) two layers of phospholipid molecules and RNA
T - c) a phospholipid bilayer
F - d) a single layer of phospholipids

What are the basic components of the plasma membrane?
a) phospholipids, cholesterol, proteins, glycolipids
b) calcium, cholesterol, cerebrosides, gangliosides
c) hormones, proteins, ATP, phospholipids
d) peptidoglycans, chitin, cellulose, glycoproteins

T - a) phospholipids, cholesterol, proteins, glycolipids
F - b) calcium, cholesterol, cerebrosides, gangliosides
F - c) hormones, proteins, ATP, phospholipids
F - d) peptidoglycans, chitin, cellulose, glycoproteins

Which part of a membrane receptor mediates the cellular response?
a) extracellular domain
b) intracellular domain
c) transmembrane segment
d) lipid bilayer

F - a) extracellular domain
T - b) intracellular domain
F - c) transmembrane segment
F - d) lipid bilayer

What is the typical function of ion channel-forming receptors?
a) phosphorylation of proteins
b) changing ion permeability across the membrane
c) activation of G proteins
d) initiation of apoptosis

F - a) phosphorylation of proteins
T - b) changing ion permeability across the membrane
F - c) activation of G proteins
F - d) initiation of apoptosis

Which statement about enzyme-linked receptors is correct?
a) they contain seven transmembrane helices
b) they most often catalyze phosphorylation
c) they are activated by GTP binding
d) they are typical receptors for the neurotransmitters GABA and glycine

F - a) they contain seven transmembrane helices
T - b) they most often catalyze phosphorylation
F - c) they are activated by GTP binding
F - d) they are typical receptors for the neurotransmitters GABA and glycine

Which of the following is an example of an ion channel receptor?
a) insulin receptor
b) nicotinic acetylcholine receptor
c) β-adrenergic receptor
d) epidermal growth factor receptor (EGFR)

F - a) insulin receptor
T - b) nicotinic acetylcholine receptor
F - c) β-adrenergic receptor
F - d) epidermal growth factor receptor (EGFR)

What is the main role of second messengers in cell signaling?
a) they transmit the signal from the extracellular space directly to the DNA
b) they amplify and relay the signal between the receptor and intracellular effectors
c) they serve as receptors for neurotransmitters
d) they form the primary ligand-binding domain of membrane receptors

F - a) they transmit the signal from the extracellular space directly to the DNA
T - b) they amplify and relay the signal between the receptor and intracellular effectors
F - c) they serve as receptors for neurotransmitters
F - d) they form the primary ligand-binding domain of membrane receptors

What is the significance of lipid rafts in cell signaling and immune processes?
a) they serve as storage for cholesterol and fatty acids
b) they ensure degradation of damaged proteins in the membrane
c) they concentrate receptors and signaling molecules, enabling more efficient activation of pathways (e.g., during immune responses)
d) they reduce membrane fluidity and thereby block signaling

F - a) they serve as storage for cholesterol and fatty acids
F - b) they ensure degradation of damaged proteins in the membrane
T - c) they concentrate receptors and signaling molecules, enabling more efficient activation of pathways (e.g., during immune responses)
F - d) they reduce membrane fluidity and thereby block signaling

Where are glycolipids located in the biomembrane, and what is their main function?
a) cytoplasmic side; catalysis of biochemical reactions
b) nuclear membrane; regulation of transcription
c) extracellular side; cell recognition and antigenic determinants
d) mitochondria; electron transport

F - a) cytoplasmic side; catalysis of biochemical reactions
F - b) nuclear membrane; regulation of transcription
T - c) extracellular side; cell recognition and antigenic determinants
F - d) mitochondria; electron transport

What applies to the type and number of membrane proteins?
a) they are always the same in all cells
b) they change only during apoptosis
c) they are variable and depend on differentiation and the cell cycle phase
d) they depend only on the amount of cholesterol in the membrane

F - a) they are always the same in all cells
F - b) they change only during apoptosis
T - c) they are variable and depend on differentiation and the cell cycle phase
F - d) they depend only on the amount of cholesterol in the membrane

What is the significance of communication through intercellular junctions (gap junctions or plasmodesmata)?
a) transmission of hormones over long distances
b) activation of gene expression in the nucleus
c) direct transfer of ions and small molecules between neighboring cells
d) prevention of any exchange between cells

F - a) transmission of hormones over long distances
F - b) activation of gene expression in the nucleus
T - c) direct transfer of ions and small molecules between neighboring cells
F - d) prevention of any exchange between cells

What is the principal mechanism by which receptors mediate a cellular response?
a) oxidation of fatty acids
b) activation or inactivation of proteins via phosphorylation
c) synthesis of DNA in the nucleus
d) passive diffusion of water

F - a) oxidation of fatty acids
T - b) activation or inactivation of proteins via phosphorylation
F - c) synthesis of DNA in the nucleus
F - d) passive diffusion of water

Which enzyme catalyzes the transfer of a phosphate group from ATP to a protein?
a) phosphatase
b) protein kinase
c) DNA polymerase
d) telomerase

F - a) phosphatase
T - b) protein kinase
F - c) DNA polymerase
F - d) telomerase

Which cell junctions provide the strongest mechanical anchoring between cells?
a) gap junctions
b) desmosomes (macula adhaerens)
c) zonula occludens
d) zonula adhaerens

F - a) gap junctions
T - b) desmosomes (macula adhaerens)
F - c) zonula occludens
F - d) zonula adhaerens

Which types of signaling are classified as humoral (chemical) communication?
a) endocrine
b) paracrine
c) synaptic
d) autocrine

T - a) endocrine
T - b) paracrine
F - c) synaptic
T - d) autocrine

Which receptor type has 7 transmembrane helices and uses second messengers?
a) enzyme-linked receptors
b) ion channel receptors
c) G protein-coupled receptors
d) antigen receptors

F - a) enzyme-linked receptors
F - b) ion channel receptors
T - c) G protein-coupled receptors
F - d) antigen receptors

What is a typical function of enzyme-linked receptors?
a) catalyzing phosphorylation reactions
b) opening ion channels
c) binding antibodies
d) transporting glucose

T - a) catalyzing phosphorylation reactions
F - b) opening ion channels
F - c) binding antibodies
F - d) transporting glucose

Which example belongs to ion channel receptors?
a) nicotinic acetylcholine receptor
b) insulin receptor
c) EGF receptor
d) G protein-coupled receptor

T - a) nicotinic acetylcholine receptor
F - b) insulin receptor
F - c) EGF receptor
F - d) G protein-coupled receptor

Which cell junction allows direct transfer of small molecules between neighboring cells?
a) desmosomes
b) zonula occludens
c) gap junctions
d) zonula adhaerens

F - a) desmosomes
F - b) zonula occludens
T - c) gap junctions
F - d) zonula adhaerens

Which three parts does a typical membrane receptor contain?
a) extracellular domain, transmembrane segment, intracellular domain
b) ribosomal subunit, cytoskeleton, phospholipid
c) nuclear DNA, nucleosome, histone
d) cytoplasm, nucleus, mitochondrion

T - a) extracellular domain, transmembrane segment, intracellular domain
F - b) ribosomal subunit, cytoskeleton, phospholipid
F - c) nuclear DNA, nucleosome, histone
F - d) cytoplasm, nucleus, mitochondrion

What happens after a ligand binds to its receptor?
a) the receptor is degraded immediately
b) a conformational change occurs and a signaling cascade is initiated
c) DNA replicates immediately
d) the receptor is transported into the nucleus

F - a) the receptor is degraded immediately
T - b) a conformational change occurs and a signaling cascade is initiated
F - c) DNA replicates immediately
F - d) the receptor is transported into the nucleus

What is the function of the extracellular domain of a receptor?
a) to bind the ligand
b) to mediate phosphorylation
c) to anchor the receptor in the lipid bilayer
d) to transmit the signal into the nucleus

T - a) to bind the ligand
F - b) to mediate phosphorylation
F - c) to anchor the receptor in the lipid bilayer
F - d) to transmit the signal into the nucleus

What is the function of the intracellular domain of a receptor?
a) to bind the ligand
b) to anchor the receptor in the membrane
c) to mediate the cellular response
d) to produce ATP

F - a) to bind the ligand
F - b) to anchor the receptor in the membrane
T - c) to mediate the cellular response
F - d) to produce ATP