Membranes And Cystic Fibrosis Flashcards
What is the cause of cystic fibrosis?
The intrinsic (CTFR) channel proteins which transport salt across cell membranes aren’t functioning properly or are completely absent. This causes a thick mucus in the respiratory, digestive and reproductive system.
Symptoms of cystic fibrosis
-salty tasting skin
-Frequent infection
-Thick mucus
-Shortness/wheeziness of breath
-Issues with digestion
excess water in the mucus (normal)
- Na+ is actively pumped across the basal membrane
- Na+ diffuses through sodium channels in the apical membrane.
- Cl- diffuses down the electrical gradient (into the tissue fluid)
- Water is drawn out of the cell (into the tissue fluid) by osmosis due to the high salt concentration in the tissue fluid.
- Water is drawn out of the mucus by osmosis
(Refer to picture if confused)
Water deficit in membrane
- Cl- is actively pumped into the cell, across the basal membrane
- Cl- diffuses through the open CTFR channels in the apical membrane
- Na+ diffuses down the electrical gradient into the mucus.
- Elevated salt concentration in the mucus causes water to be drawn out of the cell by osmosis (into mucus)
- Water is them drawn into the cell by osmosis, at the tissue fluid.
Compare and contrast endocytosis and exocytosis
-both endocytosis and exocytosis are used in bulk transport.
-They are both forms of active transport and require ATP to work.
-They both involve the transportation of larger molecules and both use vesicles.
-Exocytosis releases molecules whereas endocytosis takes molecules in.
-In Exocytosis the vesicles fuse with the cell membrane to deposit molecules whereas endocytosis vesicles are made from the cell membrane.
Explain how the structure of a phospholipid molecule contributes to the partial permeability of a cell surface membrane
The phospholipid molecule contains a hydrophilic head and hydrophobic fatty acid chain tails. It allows non-polar molecules to pass through the membrane and polar molecules cannot pass through the phospholipid bilayer.
Effects of CF on digestive system
- difficulty maintaining body mass due to problems with digestion and absorption of nutrients, higher basal metabolic rate leading to them having to consume more high-energy food and a greater amount of daily calories, they also have to take food supplements to ensure they get the correct nutrients.
- can lead to a blocked pancreatic duct meaning many digestive enzymes cannot be transported to the pancreas, slowing the rate of digestion. Furthermore the blockage can lead to enzymes being trapped which leads to damage of the pancreas itself which can lead to cysts and reduction or stopping of production of the hormone insulin which can then lead to diabetes.
Effects of CF on gas exchange
Glycolipid and glycoprotein function
Receive signals
Cholesterol function in membrane
Fluidity
Phospholipid bilayer function in membranes
Barrier
Extrinsic proteins
Enzymes
Intrinsic proteins
Channels and carriers
Diffusion (movement profile)
Energy: no (passive)
Conc gradient: high to low
Through: phospholipid bilayer
Types: small, non polar molecules
Facilitated diffusion (movement profile)
Energy: no (passive)
Conc gradient: high to low
Through: intrinsic protein carrier/channel
Types: larger, polar
Active transport (movement profile)
Energy: yes
Conc gradient: low to high
Through: protein carrier
Types: larger
Osmosis (movement profile)
Energy:No (passive)
Conc gradient: high to low (water)
Through: phospholipid bilayer
Types: water only
Endocytosis
- used for bulk movement of substances in the cell.
- vesicles are created from the cell surface membrane, bringing their contents into the cell.
Exocytosis
- used for bulk transport of substances out of the cell.
- vesicles fuse with the cell surface membrane and release their contents
How is CF mucus formed?
CFTR protein channel does not work (usually transports Cl- ions into mucus) and so…
Na+ channel is permanently open allowing Na+ ions into cells lowering the water potential and so…. Water moves into the cell by osmosis making mucus even thicker
Similarities between globular and fibrous proteins
- Both made of amino acids joined by peptide bonds
- Both have other bonds between R groups holding protein in shape
How is the concentration gradient in mammalian lungs maintained?
Ventilation and blood flow
Cystic fibrosis
A genetic disorder that is present at birth, caused by a recessive allele that causes a faulty CTFR channel in the cell membranes. This gene that is faulty codes for the production of chloride ion channels (leads to them being non functional).
Goblet cells
Secrete mucus that traps particles
Ciliated epithelial cell function
to move substances along surface of tissue
