Question

In: Chemistry

When the protein gramicidin is integrated into a membrane, an H+ channel forms and the membrane becomes very permeable to protons (H+ ions).

When the protein gramicidin is integrated into a membrane, an H+ channel forms and the membrane becomes very permeable to protons (H+ ions). If gramicidin is added to an actively respiring muscle cell, how would it affect the rates of electron transport, proton pumping, and ATP synthesis in oxidative phosphorylation? (Assume that gramicidin does not affect the production of NADH and FADH2 during the early stages of cellular respiration.)

Sort the labels into the correct bin according to the effect that gramicidin would have on each process.

[The following are some hints to help you approach the problem.]

You know that membranes treated with gramicidin become very leaky to protons. Consider these four questions (in this order) to help you evaluate how gramicidin alters oxidative phosphorylation

1. Is a proton gradient across the inner mitochondrial membrane required for ATP synthesis during oxidative phosphorylation?

2. What effect does a membrane that is very leaky to protons have on the ability of the mitochondrion to maintain a proton gradient across that membrane?

3. What effect does the ability of the mitochondrion to maintain a proton gradient have on the rate of proton pumping?

4. How is the rate of electron transport related to the rate of proton pumping, and are these rates affected by the membrane being leaky to protons? 

Solutions

Expert Solution

1) Yes. The proton gradient across the inner mitochondria is essential for the enzyme ATP synthetase for producing ATP.

2) In order to maintain the proton gradient (despite leaky membrane), there will be continuous pumping of the proton into the mitochondria membrane.

3) The proton pumping rate remains the same.

4) When an electron is transferred from one molecule to another in ETC, there is a need for a proton to further drive the process, which is provided by the proton pumping system. In the case of the leaky membrane, there will the same rate of electron transport and proton pumping rate but there will be a decrease in the proton gradient and the synthesis of ATP is inhibited.

Electron transport Rate - Remains the same (the defect is with the leaky membrane and not with the electron transport).

Proton Pumping Rate - Remains the same (Proton is pumped with regard to electron transport and it remains the same)

The rate of ATP synthesis - Decreases (failing to have a proton gradient due to leaky membrane)

The rate of Oxygen uptake - Remains the same

Size of Proton Gradient - Decreases (Due to leaky membrane)

Related Solutions

Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism? Select all that apply.
Some solutes are able to pass directly through the lipid bilayer of a plasma membrane, whereas other solutes require a transport protein or other mechanism to cross between the inside and the outside of a cell. The fact that the plasma membrane is permeable to some solutes but not others is what is referred to as selective permeability. Which of the following molecules can cross the lipid bilayer of a membrane directly, without a transport protein or other mechanism? Select...
which of these illustrates the secondary structure of a protein?
Which of these illustrates the secondary structure of a protein?  
Which of the following factors does not affect membrane permeability?
Which of the following factors does not affect membrane permeability? Temperature The saturation of hydrocarbon tails in membrane phospholipids The amount of cholesterol in the membrane The polarity of membrane phospholipids  
Which molecules do not normally cross the nuclear membrane?
Which molecules do not normally cross the nuclear memebrane? Nucleotide Triphosphates proteins mRNA DNA  
A cell membrane has a resistance and a capacitance and thus a characteristic time constant.
What is the time constant of a 9.0-nm-thick membrane surrounding a 0.040-mm-diameter spherical cell? Assume the resistivity of the cell membrane as 3.6×107 ??m and the dielectric constant is approximately 9.0.  
Cells require a constant exchange of solutes (ions and small molecules) with the outside of the cell.
Cells require a constant exchange of solutes (ions and small molecules) with the outside of the cell. Many of these solutes undergo passive transport across the membrane. Passive transport occurs without the input of cellular energy. Some solutes are transported into the cell while others are transported out of the cell. Part A - Diffusion All molecules have energy that causes thermal motion. One result of thermal motion is diffusion: the tendency of substances to spread out evenly in the...
Draw the organic product for the following reaction. Omit any inorganic byproducts or ions.
Draw the organic product for the following reaction. Omit any inorganic byproducts or ions.
Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?
Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene? a base substitution at the beginning of the gene a base substitution at the end of the gene a frameshift deletion at the beginning of the gene a frameshift deletion at the end of the gene
what name is given to the process by which water crosses a selectively permeable membrane?
 What name is given to the process by which water crosses a selectively permeable membrane? diffusion pinocytosis phagocytosis passive transport osmosis 
Y varies directly as the square of X. If Y = 144 when X = 6, what is the value of y when x = 3
Y varies directly as the square of x. If y = 144 when x = 6, what is the value of ywhen x = 3