Cystic Fibrosis Mutation Quiz

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Questions and Answers

What is the primary consequence of the ΔF508 mutation in cystic fibrosis?

Enhanced function of the CFTR channel

Blockage of sodium transport

Increased chloride excertion

Improper folding and degradation of the CFTR protein (correct)

Which of the following describes cystic fibrosis?

A respiratory condition leading to increased lung capacity

A disease characterized by low salt levels in sweat

An autosomal recessive disease with thick mucus production (correct)

A dominant genetic disorder

In which tissues is the CFTR chloride channel notably located?

Nervous tissue and brain

Sweat and pancreatic ducts, conducting airways (correct)

Digestive tract and skin

Heart and skeletal muscles

What is the prevalence of cystic fibrosis mutations in the Caucasian population?

1 in 2,500 Signup and view all the answers

What does CFTR stand for in the context of cystic fibrosis?

Cystic Fibrosis Transmembrane Conductance Regulator Signup and view all the answers

What is the primary structure of the cell membrane?

Phospholipid bilayer Signup and view all the answers

What role does cholesterol play in the cell membrane?

It decreases the movement of fatty acids Signup and view all the answers

What are glycolipids primarily involved in?

Cell-to-cell interactions Signup and view all the answers

Which of the following best describes the behavior of phospholipids in the membrane?

They undergo lateral movement and flexion Signup and view all the answers

What is a characteristic function of membrane proteins?

They facilitate cell adhesion Signup and view all the answers

How do fatty acid double bonds affect membrane structure?

They induce a kink that reduces some types of motion Signup and view all the answers

What defines the inner and outer leaflets of the phospholipid bilayer?

Their proximity to the cytosol and exterior Signup and view all the answers

Which type of membrane protein is embedded within the lipid bilayer?

Transmembrane proteins Signup and view all the answers

What is the primary function of the drug Kalydeco approved in 2012?

To enhance the opening capability of a specific mutant protein Signup and view all the answers

Which condition is suggested to cause increased exposure of phosphatidylserine (PS) on red blood cells?

Lead intoxication and uremia Signup and view all the answers

In assessing fetal lung maturity, what L/S ratio indicates a typical term birth?

2.0 Signup and view all the answers

What is the risk associated with an L/S ratio of 1.5 to 1.9 in amniotic fluid?

40% risk of developing respiratory distress syndrome Signup and view all the answers

What characteristic do macrophages exhibit in relation to phosphatidylserine (PS)?

They bind and internalize PS from dead cells Signup and view all the answers

Which statement correctly describes the arrangement of glycolipids in cell membranes?

Glycolipids always reside on the outer leaflet with their attached carbohydrates projecting away from the cell. Signup and view all the answers

What is the primary function of lipid rafts in cellular membranes?

To enable cholesterol transport and signal transduction. Signup and view all the answers

Which type of transport requires the use of ATP?

Active transport of ions against a concentration gradient. Signup and view all the answers

Which of the following is NOT a type of transport protein mentioned?

Caveolae Signup and view all the answers

What distinguishes facilitated diffusion from passive diffusion?

Facilitated diffusion is assisted by transporter proteins. Signup and view all the answers

Which characteristic is true about peripheral proteins in cell membranes?

They are only located on the inner leaflet of the membrane. Signup and view all the answers

What type of conformational change occurs in glucose transporters?

They change shape to facilitate the transport of glucose. Signup and view all the answers

Which of the following statements about cholesterol's role in membranes is true?

Cholesterol helps to stabilize membrane fluidity. Signup and view all the answers

Study Notes

Membranes and Membrane Transport

Membranes are a stable yet dynamic barrier maintaining the cell's internal environment.
They facilitate cellular functions.
They act as attachment points for intracellular and extracellular structures.
Membranes maintain a selectively permeable environment.

Basic Structure

Membranes consist of a phospholipid bilayer.
The bilayer is composed of two antiparallel phospholipid sheets.
The layer closest to the cytosol is the inner leaflet.
The layer closest to the exterior environment is the outer leaflet.
Cholesterol is interspersed between the phospholipid layers.
Proteins are associated with the membrane.

Membrane Lipids

Phospholipids are the most abundant membrane lipids.
They are amphipathic, meaning they have both polar heads and hydrophobic tails.
Polar heads point outwards, and hydrophobic tails point inwards.
The length of the fatty acid chains and their degree of saturation affect membrane structure.
Fatty acid chains undergo flexion, rotation, and lateral movement.
Double bonds in fatty acids create kinks, reducing tight packing.
Phospholipids in healthy cells rarely flip-flop between leaflets.
Cholesterol is an amphipathic molecule.
It fits into spaces created by unsaturated fatty acid tails, decreasing their movement and stiffening/strengthening the membrane.

Glycolipids

Glycolipids are lipids with attached carbohydrate chains.
The carbohydrate portion points outwards.
They help form the carbohydrate coat on cells.
They participate in cell-to-cell interactions.
They can be a source of blood group antigens.
They can act as receptors for toxins (e.g., cholera and tetanus).

Membrane Proteins

Membrane proteins are diverse and have various functions.
Transmembrane proteins are embedded within the membrane.
Lipid-anchored proteins are attached to the membrane through lipids.
Peripheral membrane proteins are associated with the membrane surface.
These proteins play roles in cell adhesion, ion transport, ligand binding, G protein activation, and cell signaling.

Functions of Membrane Proteins

Cell adhesion molecules enable cell-cell contact.
Ion channels regulate ion passage.
Transport proteins facilitate molecule movement.
Ligand receptors bind to specific molecules.
G proteins mediate signaling cascades.
Peripheral proteins function as cytoskeletal components.
Cell signaling proteins transmit signals throughout the cell.

Characteristics of Membrane

Bilayer arrangement: Phospholipids arrange with their hydrophilic heads facing the exterior and interior environments, and their hydrophobic tails forming the interior of the membrane. Head groups are on the outsides, and fatty acid tails are within the hydrophobic core.
Asymmetric distribution: Different phospholipids and glycolipids are concentrated on either side of the bilayer.

Fluid Mosaic Model

The fluid mosaic model describes the membrane as a dynamic structure where components (lipids and proteins) move laterally within the bilayer.

Lipid Rafts

Lipid rafts are specialized cholesterol-rich microdomains within the membrane.
They play a role in cholesterol transport, endocytosis, and signal transduction.
Three types: Glycosphingolipid-enriched membranes (GEMs), polyphosphoinositide-rich rafts, and caveolae.
Caveolae are flask-shaped invaginations of the cell membrane, containing caveolin, which causes a change in membrane morphology.

Transport Across Membranes

Membranes import materials for biosynthesis.
Membranes export waste products.
Membranes move ions.
Membranes secrete proteins.
The barrier function of the lipid bilayer prevents the free transport of large polar molecules and ions.

Different Kinds of Transport

Passive transport: Thermodynamically favorable, occurs without energy input. Diffusion and facilitated diffusion.
Diffusion: Movement of small, non-polar molecules across the membrane.
Facilitated diffusion: Movement of molecules with the help of transport proteins.
Active transport: Thermodynamically unfavourable, requires energy (ATP).

Types of Transporters

Channels: Pores (always open). Gated channels (open or close in response to a signal).
Transporters: Conformational changes. Enzymatic activity.

Glucose Transporter

Glucose binds to a transporter site on the outside of the cell.
This binding triggers a conformational change.
The binding site moves glucose further into the cell.
The glucose is released to the inside of the cell upon dissociation of glucose from the transporter.
The transporter reverts to its original form.

Cystic Fibrosis

Cystic fibrosis is an autosomal recessive disease.
It is characterized by thick mucus in the lungs and other tissues.
It involves lung infections, malnutrition, and excessive salt in sweat.
A mutation in the CFTR gene, coding for a chloride channel, is the direct cause.
Common causes of CF: deletion, missense, and others.
Chloride channels are critical in normal lung function and electrolyte transport.
Mutations in CFTR can cause abnormally thick mucus.
Inadequate fluid production in the lungs reduces the ability of cilia to remove mucus.

CFTR Channel

The CFTR protein is a chloride channel.
It opens in response to phosphorylation.
CFTR is present in sweat and pancreatic ducts, gut, seminiferous tubules, conducting airways, and other tissues.

Clinical Correlations

Phospholipids in the cell membrane are found asymmetrically, in particular, in RBCs.
Macrophages recognize PS and recycle this cell component.
Normal RBC aging exposes PS as part of the normal aging process.
Lead poisoning and uremia are examples of conditions affecting RBCs and causing renal failure.
Respiratory Distress Syndrome (RDS): A major cause of neonatal mortality.
It's caused by the immaturity of lung development and surfactant deficiency in premature babies.
The maturity of lung development is assessed by analyzing the ratio of lecithin (lung surfactant) to sphingomyelin in amniotic fluid.
Ratios below 2.0 indicate an increased risk of RDS.

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Description

Test your knowledge on cystic fibrosis, particularly focusing on the ΔF508 mutation and its primary consequences. This quiz will help you understand the genetic basis of this condition and how it affects individuals.