Biology - F214 - 4 - Structure and function of mitochondria

How does the inner membrane of the mitochondria enable it to carry out its function?

- different lipid composition from the outer membrane and is impermeable to most small ions, including hydrogen ions. - folded into many cristae to give large surface area - has many electron carriers and ATP synthase enzymes embedded in it.

Why do synaptic knobs contain many mitochondria?

Mitochondria provides adenosine triphosphate (ATP) which in turn supplies the energy for synthesizing new neurotransmitter or transmitter substance. Since the nervous system is always active throughout your life and sending nerves impulses every fraction of a second, relatively it needs alot of energy (ATP) to do this and therefore mitochondria are found in abundance there.

Why do the mitochondria of more metabolically active cells have a longer and more densely packed cristae?

To house more electron transport chains and more ATP synthase enzymes.

What is an oxidoreductase enzyme?

an enzyme that catalyses a reduction reaction that is coupled with an oxidation reaction

What is an electron carrier?

an enzymes associated with a cofactor. they are harm groups with an iron atom.

What is chemiosmosis?

the flow of hydrogen ions through channels of ATP synthase enzymes down the proton gradient, from inter membrane space to mitochondrial matrix

What is proton motive force?

the force generated by the flow of protons. it changes the configuration of parts of the ATP synthase enzymes and causes ADP and Pi to join and make ATP

What is the function of cofactors?

they can accept and donate electrons because the iron atoms can become reduced to Fe²⁺ by accepting an electron and oxidised to Fe³⁺ by donating an electron to the next electron carrier.

How were mitochondria first identified and when?

using light microscopy in 1840

How are mitochondria moved around the cell?

using the cytoskeleton (microtubules)

What is FAD made up of?

Flavine adenine dinucleotide - vitamin B₂ (riboflavin), adenine, ribose and 2 phosphate groups

What is the range in length of mitochondria?

2-5 micrometers

Why is it useful that the inner membrane is impermeable to small ions?

protons accumulate in the inter membrane space, building up a proton gradient - a source of potential energy

Describe the mitochondrial ultrastructure

- inner and outer phospholipid membrane that make up the envelope. - outer membrane is smooth and inner membrane is folded into cristae that give the inner membrane a large surface area. - The two membranes enclose and separate the two compartments within the mitochondrion. Between the inner and outer membranes this is the intermembrane space. The matrix is enclosed by the inner membrane. It is semi-rigid and gel-like, consisting of a mixture of proteins and lipids. It also contains looped mitochondrial DNA, mitochondrial ribosomes and enzymes.

How does the outer membrane of the mitochondria enable it to carry out its function?

- phospholipid composition of outer membrane is similar to membranes around other organelles. It contains proteins some of which form channels or carriers that allow the passage of molecules such as pyruvate. Other proteins in this membrane are enzymes.

What is the range in diameter of mitochondria?

0.5-1.0 micrometers

What is a cofactor?

Non-protein group (haem groups that contain an iron atom)

What is the definition of mitchondria?

Organelles found in eukaryote cells. They are sites of the link reaction, krebs cycle and oxidative phosphorylation.

What does the inner membrane being impermeable to small ions cause?

protons accumulare in the intermembrane space, building up a proton gradient which is the source of potential energy.

Describe ATP synthase enzymes

They are large and protrude from the inner membrane into the matrix. they allow protons to pass through them. Also known as stalked particles.

How does the matrix of the mitochondria enable it to carry out its function?

Where the link reaction and krebs cycle takes place, it contains: - enzymes that catalyse the stages of these reactions - molecules of coenzyme NAD - oxaloacetate (4C compound that accepts acetate from the link reaction) - mitochondrial DNA some of which codes for the mitochondrial enzymes and other proteins. - mitochondrial ribosomes where these proteins are assembled

How would the structure of a mitochondrion from a skin cell differ to one from a heart muscle tissue?

Would have a longer more densely packed cristae to house more electron transport chains and ATP synthase enzymes.

What is the function of the coenzyme FAD?

it is reduced during the Krebs cycle and is tightly bound to the dehydrogenase enzyme that is embedded in the inner membrane. the hydrogen atoms accepted by FAD pass back into the matrix