6-Membrane Structure Functions Flashcards
Is a cell membrane just made of a phospholipid bilayer?
No, a membrane is a collage of different proteins embedded in the fluid matrix of the lipid bilayer
Are peripheral proteins embedded?
No, Peripheral proteins are not embedded
What integral proteins do?
Integral proteins penetrate the hydrophobic core and often span the membrane
What are transmembrane proteins
• Integral proteins that span the membrane are called transmembrane proteins
What are the hydrophobic regions of an integral protein consost of?
• The hydrophobic regions of an integral protein consists of one or more stretches of non polar amino acids, often coiled into alpha helices
What is te FLUID MOSSAIC MODEL?
Why FLUID?
Why MOSAIC?
Cell membranes also contain proteins within the bilayer.
This ‘model’ for the structure of the membrane is called the: FLUID MOSAIC MODEL
FLUID- because individual phospholipids and proteins can move around freely within a layer, it’s liquid.
MOSAIC- because of the pattern produced by the scattered protein molecules when the membrane is viewed from above.
Which are the types of membrane proteins?
1) Cell-cell recognition proteins Integrins 2) Intercellular junction proteins 3) Enzymes 4) Signal Transduction proteins-aka receptor proteins 5) Transport proteins Passive and active
What is the function of cell-cell recognition proteins?
What kind of proteins are they mostly?
Which other molecules play a role in cell recognition?
Carbohydrate chains vary between species, individuals, and even between cell types in a given individual. (INFO)
identify type of
cell and identify a cell as “self” versus foreign
Most are glycoproteins
Glycolipids also play a role in cell recognition
Are there any enzymes as membrane proteins?
yes, this is esoecially important on the membranes of organelles
What signal transduction (receptor)proteins do?
They bind hormones and other substances on the outside of the cell in order to trigger a change inside the cell and the process is called signal transduction
Hoe cells recognise each other?
by bindind to surface molecules, often carbohydrates, on the plasma membrane
During cell-cell recognition which type of molecules are binding together?
Carbohydrates covalently bonded to lipids (glycolipids) or more often to proteins (glycoproteins)
Which are the three transport processes and which of these require energy?
a. Simple Diffusion- directly through membrane
b. Facilitated diffusion-(passive transport)
c. Activate transport- requires energy
Which are the carrier proteins?
Uniport- one solute transported
Symport- two solutes in the same direction
Antiport- two solutes in opposite direction
Can caeeier proteins be active/passive transport procedure?
Yes, it can.
1.Passive Transport
Driving force concentration/ electrochemical gradient OR
2.Active Transport
Against gradient;unfavorable
Requires energy input
Where ions pumps are produced
In mitochondria
Where protons are found?
in the inner mitochondria membrane
What a nerce cell consist of?
1) Cell Body
2) Dendrites
3) The Axon
How is called the neuron that stimulates the muscle tissue?
It is called a motor neuron
Which is the dedrites’s function?
Dendrites receive impulses and conduct them toward the cell body.
Myelinated Axons
Which is their structure?
Which is their function?
From what is it surrounded?
Thin, long extension
Sends impulses to another neuron
Vary in length
Surrounded by a many-layered lipid and protein covering called the myelin sheath, produces by the schwann cells.
What about the potential in a resting neuron?
In a resting neuron (one that is not conducting an impulse),there is a difference in electrical charges on the outside and inside of the plasma membrane. The outside has a positive charge and the inside has a negative charge.
INFO:There are different numbers of potassium ions and sodium ions on either side of the membrane. Even when a nerve cell is not conducting an impulse, for each ATP molecule that’s hydrolysed, it is actively transporting 3 molecules of Na+ out of the cell and 2 molecules of K+ into the cell, at the same time by means of the sodium-potassium pump
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What happens whene there is an action potential( when the cell membrane is stimulated)
When the cell membranes are stimulated, there is a change in the permeability of the membrane to sodium ions (Na+)
The membrane become more permeable to Na+ and K+, therefore sodium ions diffuse into the cell down a concentration gradient. The entry of Na+ disturbs the resting potential and causes the inside of the cell to become more positive relative to the outside.
What needs to be done in order for the nervous cell to generate an impulse?
In order for the neuron to generate an action potential the membrane potential must reach the threshold of excitation
As the outside of the cell has become more positive than the inside of the cell, the membrane is now depolarised.
When enough sodium ions enter the cell to depolarise the membrane to a critical level (threshold level) an action potential arises which generates an impulse (see slide 34)
Is the precense of myelin sheath effective?
The presence of a myelin sheath greatly increases the velocity at which impulses are conducted along the axon of a neuron.
In unmyelinated fibres, the entire axon membrane is exposed and impulse conduction is slower
What is the purpose of patch clamp technique?
study of single or multiple ion channels in cells.
What does the respiratory system includes?
Trachea
- Bronchi
- Bronchioles
- Alveoli
What is the respiratory surface made of?
The respiratory surface is made of the alveoli and capillary walls
Can the walls of capillaries and alveoli share the same mebrane?
Yes
INFO: Air entering the lungs contains more oxygen and less carbon dioxide than the blood that flows in the pulmonary capillaries.
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What happens to the oxygen that enters the blooodstream?
Haemoglobin binds to it
What is the ending for carbon dioxide?
Carbon dioxide can dissolve in plasma, and about 70% forms bicarbonate ions
Some carbon dioxide can bind to haemoglobin for transport.
How many and which ones are the processes taht are essential for the transfer of oxygen from the outside air to the blood flowing through the lungs?
- Ventilation
Is the process by which air moves in and out of the lungs - Diffusion
Is the spontaneous movement of gases, without the use of any energy or effort by the body, between the gas in the alveoli and the blood in the capillaries in the lungs. - Perfusion
Is the process by which the cardiovascular system pumps blood throughout the lungs.
What does the inhaled smoke contain?
Inhaled smoke contains:
CO2, which affects the diffusion gradient
Carcinogenic chemicals that can trigger tumors
Toxic nicotine, which paralyses cilia which normally clean the lungs
What is emphysyma?
Besides cancer, smoking can also lead to emphysema. Alveoli become dry and brittle and eventually rupture.
(all types of smoke, not just tobacco, can cause emphysema)
What is Cystic Fibrosis(CF)?
Which is the average life-span?
Which is the cause?
What if a person is heterozygous?
Cystic Fibrosis (CF) is a chronic, progressive and frequently fatal genetic (inherited) disease of the body’s mucus glands. CF primarily affects the respiratory and digestive system in children and young adults.
CF is an autosomal recessive disorder caused by mutations in the CFTR (cystic fibrosis transmembrane conductance regulator) gene.
Heterozygous carriers( those who have inherited only one copy) are asymptomatic
Where dystrophin is located?
What happens if dystrophin is absent?
Dystrophin is a protein and is located between the sarcolemma and the outermost layer of myofilaments in the muscle fiber(myofiber)
In the absence of dystrophin, the cell membrane would be incapable of repairing itself, thus destroying it and bringing about the Duchenne Muscular Dystrophy.
