6-Membrane Structure Functions

Question 1

Is a cell membrane just made of a phospholipid bilayer?

Answer 1

No, a membrane is a collage of different proteins embedded in the fluid matrix of the lipid bilayer

Question 2

Are peripheral proteins embedded?

Answer 2

No, Peripheral proteins are not embedded

Question 3

What integral proteins do?

Answer 3

Integral proteins penetrate the hydrophobic core and often span the membrane

Question 4

What are transmembrane proteins

Answer 4

• Integral proteins that span the membrane are called transmembrane proteins

Question 5

What are the hydrophobic regions of an integral protein consost of?

Answer 5

• The hydrophobic regions of an integral protein consists of one or more stretches of non polar amino acids, often coiled into alpha helices

Question 6

What is te FLUID MOSSAIC MODEL?
Why FLUID?
Why MOSAIC?

Answer 6

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.

Question 7

Which are the types of membrane proteins?

Answer 7

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

Question 8

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)

Answer 8

identify type of
cell and identify a cell as “self” versus foreign

Most are glycoproteins

Glycolipids also play a role in cell recognition

Question 9

Are there any enzymes as membrane proteins?

Answer 9

yes, this is esoecially important on the membranes of organelles

Question 10

What signal transduction (receptor)proteins do?

Answer 10

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

Question 11

Hoe cells recognise each other?

Answer 11

by bindind to surface molecules, often carbohydrates, on the plasma membrane

Question 12

During cell-cell recognition which type of molecules are binding together?

Answer 12

Carbohydrates covalently bonded to lipids (glycolipids) or more often to proteins (glycoproteins)

Question 13

Which are the three transport processes and which of these require energy?

Answer 13

a. Simple Diffusion- directly through membrane
b. Facilitated diffusion-(passive transport)
c. Activate transport- requires energy

Question 14

Which are the carrier proteins?

Answer 14

Uniport- one solute transported

Symport- two solutes in the same direction

Antiport- two solutes in opposite direction

Question 15

Can caeeier proteins be active/passive transport procedure?

Answer 15

Yes, it can.

1.Passive Transport
Driving force concentration/ electrochemical gradient OR

2.Active Transport
Against gradient;unfavorable
Requires energy input

Question 16

Where ions pumps are produced

Answer 16

In mitochondria

Question 17

Where protons are found?

Answer 17

in the inner mitochondria membrane

Question 18

What a nerce cell consist of?

Answer 18

1) Cell Body
2) Dendrites
3) The Axon

Question 19

How is called the neuron that stimulates the muscle tissue?

Answer 19

It is called a motor neuron

Question 20

Which is the dedrites’s function?

Answer 20

Dendrites receive impulses and conduct them toward the cell body.

Question 21

Myelinated Axons
Which is their structure?
Which is their function?
From what is it surrounded?

Answer 21

 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.

Question 22

What about the potential in a resting neuron?

Answer 22

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.

Question 23

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

Answer 23

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Question 24

What happens whene there is an action potential( when the cell membrane is stimulated)

Answer 24

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.

Question 25

What needs to be done in order for the nervous cell to generate an impulse?

Answer 25

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)

Question 26

Is the precense of myelin sheath effective?

Answer 26

 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

Question 27

What is the purpose of patch clamp technique?

Answer 27

study of single or multiple ion channels in cells.

Question 28

What does the respiratory system includes?

Answer 28

Trachea

• Bronchi
• Bronchioles
• Alveoli

Question 29

What is the respiratory surface made of?

Answer 29

 The respiratory surface is made of the alveoli and capillary walls

Question 30

Can the walls of capillaries and alveoli share the same mebrane?

Answer 30

Yes

Question 31

INFO:  Air entering the lungs contains more oxygen and less carbon dioxide than the blood that flows in the pulmonary capillaries.

Answer 31

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Question 32

What happens to the oxygen that enters the blooodstream?

Answer 32

 Haemoglobin binds to it

Question 33

What is the ending for carbon dioxide?

Answer 33

 Carbon dioxide can dissolve in plasma, and about 70% forms bicarbonate ions
Some carbon dioxide can bind to haemoglobin for transport.

Question 34

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?

Answer 34

1. Ventilation
   Is the process by which air moves in and out of the lungs
2. 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.
3. Perfusion
   Is the process by which the cardiovascular system pumps blood throughout the lungs.

Question 35

What does the inhaled smoke contain?

Answer 35

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

Question 36

What is emphysyma?

Answer 36

 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)

Question 37

What is Cystic Fibrosis(CF)?
Which is the average life-span?
Which is the cause?
What if a person is heterozygous?

Answer 37

 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

Question 38

Where dystrophin is located?

What happens if dystrophin is absent?

Answer 38

 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.