2009 Lecture 7

1 Cell Energy Production - Mitochondria
2 Introduction
- 2.1 Lecture Audio
- 2.2 Archive
3 Objectives
4 Double Membrane Organelles
5 History Mitochodria
6 Evolution Mitochondria
7 Chloroplasts
- 7.1 Function
- 7.2 Structure
8 Mitochondria
9 Mitochondrial Division and Fusion
- 9.1 Mitochondria Fission
- 9.2 Mitochondrial Fusion
10 Energy Production
11 Apoptosis
12 Abnormalities
13 References
14 Mitochondrion Images
15 2009 Course Content
- 15.1 Lectures
- 15.2 Laboratories

Cell Energy Production - Mitochondria

Welcome to the Matrix!

Introduction

This lecture introduces the cytoplasmic organelles that produce the energy required for cellular processes to occur. In recent years mitochondria have also been shown to have important roles in other cellular functions, in particular, cell death by apoptosis. This second role will be covered in detail in later lectures in this current series.

Dr Mark Hill (2009)

Lecture Audio

The University has a system for automated recording of lectures called Lectopia. Lectopia requires login using your student number and unipass. I will be adding the link to each iLecture Audio following the Lecture. Due to the automated recording method, most lectures begin 4-5 minutes into MP3 recordings and occasionally stop before the lecture does. 2009 All Audio Files

Lecture 7: Cell Energy Production - Mitochondria Lecture Date: 31-03-2009 Lecture Time: 13:00 Venue: BioMed F Speaker: Mark Hill

Objectives

Broad understanding of processes requiring energy within the cell
Brief understanding structure and function of plant chloroplast
Understand the structure and function of plant and animal mitochondria
Brief understanding of mitochondria evolution
Brief understanding of mitochondrial abnormalities

Double Membrane Organelles

Mitochondrion structure cartoon

Nucleus - all eukaryotes
Chloroplasts - plants
Mitochondria - plants and animals

History Mitochodria

1857 Kölliker discovers mitochondria in muscle

1929 Karl Lohmann discovered ATP

1940s and 1950s ATP is formed in cell respiration in mitochondria and photosynthesis in chloroplasts of plants

1960 Efraim Racker and co-workers isolated, from mitochondria, the enzyme "F o F 1 ATPase" now call ATP synthase

1963 There’s DNA in those organelles DNA is directly visualized in first chloroplasts and then mitochondria, from the JCB Archive.

1992 Wallace identified degenerative disease caused by mtDNA mutations

1997 Nobel Prize in Chemistry - The three laureates have performed pioneering work on enzymes that participate in the conversion of the "high-energy" compound adenosine triphosphate (ATP).

Paul D. Boyer and John E. Walker "for their elucidation of the enzymatic mechanism underlying the synthesis of adenosine triphosphate (ATP)"
Jens C. Skou "for the first discovery of an ion-transporting enzyme, Na+, K+ -ATPase

Evolution Mitochondria

primitive Eubacterium
symbiotic relationship with eukaryotic cell
- circular DNA
- see antibiotic-induced deafness due to similarity of mitochondrial and bacterial ribosomes
genes transferred to nucleus
mitochondrial genome bp
- 366,924 Arabidopsis
- 16,569 Human
- 5966 Plasmodium

Chloroplasts

Plant cell structure
Plant Chloroplast organelles

Double membrane cytoplasmic organelle
present in photosynthetic Eubacteria, algae and plants
- thought to originate as an endosymbiotic cyanobacteria (blue-green algae)

Function

photosynthesis
chlorophyll captures light energy
chloroplasts interact with peroxisomes

Structure

flat discs usually 2 to 10 micrometer in diameter and 1 micrometer thick. In
plants 5 μm in diameter and 2.3 μm thick
inner and an outer phospholipid membrane
intermembranous space
stroma
- stacks of thylakoids (site of photosynthesis)
- contains copies of small circular DNA
- ribosomes
- proteins transported to the chloroplast

(MH - will not cover this cell organelle in any depth in current course)

Mitochondria

Greek, mito = thread; chondrion = granule
Located throughout cytoplasmic compartment
- has itself several membrane enclosed compartments
- each compartment has different function
Ancient aerobic organisms in symbiosis (endosymbiosis)

present in all cells

Mitochondria Function

Energy production
Respiratory Chain
Apoptosis role
- Programmed cell death

Mitochondria Structure

Mitochondrial membraneous compartments

Mitochondrion rat liver

Double membrane
outer membrane
intermembrane space
inner membrane
crista (plural, cristae)
- originally considered specialized folds of the inner membrane
- variable invaginations with narrow tubular connections to each other and by crista junctions to the peripheral region of inner membrane
matrix

Mitochondria Shape

Come in different shapes & sizes
Can rapidly change shape (minutes)

EM: Mitochondria EM: Mitochondria EM: Mitochondria Mitochondrial Morphology

Mitochodrial Movie

Mitochondria Location

cells with high energy requirements: Muscle, sperm tail, flagella
generally located where energy consumption is highest in the cell
Mitochondria (fibroblasts)
Mitochondria (sperm)
- Packed around initial segment
- Energy for sperm motility, microtubules (9+2)

Mitochondria Components

Outer Membrane

porin - membrane channel, allows ions amd metabolites into the mitochondria

Intermembrane Space

enzymes that use ATP

Inner Membrane

cardiolipin - phospholipid

Cristae

Adenosine triphosphate (ATP) synthase
respiratory electron transfer chain proteins
transport proteins

Matrix

metabolic enzymes of citric acid cycle (=Krebs) (100s of enzymes) (MH- do not need to know biochemical details of this cycle)
genetic material DNA, tRNA, ribosomes

Mitochondria DNA

Eukaryotic mitochondrial genomes

double stranded circular DNA (mitoDNA. mtDNA)
1981 complete human sequence (16,569 nucleotides)
37 genes
- encodes 13 polypeptides involved in oxidative phosphorylation
- remaining genes transfer RNA (tRNA) and ribosomal RNA (rRNA)
multiple copies within the matrix
maternally inherited
remainder encoded by nuclear DNA
proteins made in cytosol and imported into mitochondria

Links: Home Reference - Mitochondrial DNA

Mitochondria Protein Synthesis

yeast - Petite mutants
- all mitochondrion-encoded gene products missing
- forms small anaerobic colonies
- organelle is constructed entirely from nucleus-encoded proteins

Many mitochondrial proteins are encoded by nuclear DNA

synthesis begins in the cell cytoplasm
imported into the mitochondria
- targeting similar to signal sequence for RER
once in matrix signal sequence is cleaved (by Hsp70)
- protein then folds (by Hsp60)
proteins for mitochondrial membrane or intermembranous space
- have additional signal following matrix localization

Links: Replication and preferential inheritance of hypersuppressive petite mitochondrial DNA | Home Reference - Mitochondrial DNA

Mitochondrial Division and Fusion

Mitochondria Fission

Mitochondrial Division
Divide independently of the whole cell cycle
Generated by existing mitochondria
inward furrowing like bacterial division
- mitochondria lack FtsZ ring (seen in bacteria)
- rely on dynamin on the cytosolic face for fission

Mitochondrial inheritance

Mitochondrial Fusion

when two separate mitochondria join as one
fission and fusion considered to be balanced
disruption causes normal tubular network of mitochondria to fragment into short rods or spheres
Requires large GTPases
- Mitofusins 1 and 2 (Mfn1, Mfn2) and OPA1

Energy Production

Respiration

Raw Materials
- Oxygen
- Pyruvate & Fatty Acids
Products
- Carbon Dioxide
- Adenosine Triphosphate (ATP)

Apoptosis

Mitochondria in addition to energy production, have a second major function related to programmed cell death by apoptosis.

cytochrome C release activates caspases
other changes include
- electron transport, loss of mitochondrial transmembrane potential
- altered cellular oxidation-reduction
- Bcl-2 family proteins (pro- and antiapoptotic)
Vesicular Mitochondria
- begin to appear during the release of cytochrome C which initiates mitochondrial mediated apoptosis
- transformation from normal morphology
- with an inner boundary membrane connected to lamellar cristae via crista junctions
- multiple vesicular matrix compartments
- facilitates membrane fission or fragmentation as the matrix is fragmented at this stage
- fragmentation of the mitochondrion requires only outer membrane fission

(MH- this topic will be covered again in the Cell Death Lecture)

Links: Lecture - Cell Death 1 | Lecture - Cell Death 2 | Movie - Vesicular Mitochondria | Role of mitochondria in apoptosis

Abnormalities

Mitochondrial Myopathies

A group of several diseases
- Kearns-Sayre syndrome (KSS) Genes and Disease - Kearns-Sayre syndrome
- Leigh's syndrome Genes and Disease - Leigh's syndrome
- mitochondrial DNA depletion syndrome (MDS)
- mitochondrial encephalomyopathy, lactic acidosis and strokelike episodes (MELAS) Genes and Disease - MELAS
- myoclonus epilepsy with ragged red fibers (MERRF)
- mitochondrial neurogastrointestinal encephalomyopathy (MNGIE)
- neuropathy, ataxia and retinitis pigmentosa (NARP) Genes and Disease - NARP
- Pearson syndrome Genes and Disease - Pearson syndrome
- Progressive external ophthalmoplegia (PEO) Genes and Disease - Progressive External Ophthalmoplegia

Friedreich's ataxia (FRDA)

mutation in gene for frataxin (a mitochondrial iron (Fe) chaperone)
mechanism may be a mitochondrial iron (Fe) loading and reactive oxygen species
animal models show H2O2 is an important pathogenic substrate underlying the phenotypes arising from frataxin deficiency
Genes and Diseases - Friedreich's ataxia

Charcot–Marie–Tooth type 2A

inherited neuropathy
caused by mutations in mitofusin 2
- proper regulation of mitochondrial dynamics required in neurons

Leber Hereditary Optic Neuropathy

Leber hereditary optic neuropathy

maternally inherited cause of blindness Genes and Diseases - LHOM
mutation of mitochondrial DNA (mtDNA)
- three common mtDNA mutations: G11778A, T14484C, G3460A

Aminoglycoside-induced deafness

due to aminoglycoside antibiotic treatment Genes and Diseases - Aminoglycoside-induced deafness
- gentamycin, streptomycin, and tobramcyin
similarity of mitochondrial ribosomes to bacterial ribosomes

Other

Cyclic vomiting syndrome?

Links: Genes and Diseases -Mitochondria and Disease | GeneReviews - Mitochondrial Disorders Overview | Genes and Diseases - Friedreich's ataxia | Muscular Dystrophy Association - Mitochondrial Myopathies | The Cleveland Clinic - Mitochondrial Myopathies | Genes and Diseases | OMIM - Online Mendelian Inheritance in Man

References

Textbooks

Essential Cell Biology

Chapter 13 Energy Generation in Mitochondria and Chloroplasts
Chapter 14 Intracellular Compartments and Transport

Molecular Biology of the Cell

Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter New York and London: Garland Science; c2002

The Mitochondrion

Molecular Cell Biology

Lodish, Harvey; Berk, Arnold; Zipursky, S. Lawrence; Matsudaira, Paul; Baltimore, David; Darnell, James E. New York: W. H. Freeman & Co.; c1999

The Cell- A Molecular Approach

Cooper, Geoffrey M. Sunderland (MA): Sinauer Associates, Inc.; c2000

The Cell - A Molecular Approach - III. Cell Structure and Function 10. Bioenergetics and Metabolism - Mitochondria, Chloroplasts, and Peroxisomes
Mitochondria

Search Online Textbooks

"mitochondria" Molecular Biology of the Cell | Molecular Cell Biology | The Cell- A molecular Approach | Bookshelf

"chloroplast" Molecular Biology of the Cell | Molecular Cell Biology | The Cell- A molecular Approach | Bookshelf

Books

PubMed

PubMed is a service of the U.S. National Library of Medicine that includes over 18 million citations from MEDLINE and other life science journals for biomedical articles back to 1948. PubMed includes links to full text articles and other related resources. PubMed

PubMed Central (PMC) is a free digital archive of biomedical and life sciences journal literature at the U.S. National Institutes of Health (NIH) in the National Library of Medicine (NLM) allowing all users free access to the material in PubMed Central. PMC

Online Mendelian Inheritance in Man (OMIM) is a comprehensive compendium of human genes and genetic phenotypes. The full-text, referenced overviews in OMIM contain information on all known mendelian disorders and over 12,000 genes. OMIM

Entrez is the integrated, text-based search and retrieval system used at NCBI for the major databases, including PubMed, Nucleotide and Protein Sequences, Protein Structures, Complete Genomes, Taxonomy, and others Entrez

Search Pubmed

"mitochondria" PubMed reviews | PubMed all articles | PMC reviews | PMC all articles | OMIM | Entrez all databases

Reviews

Mitochondrial fragmentation in neurodegeneration. Knott AB, Perkins G, Schwarzenbacher R, Bossy-Wetzel E. Nat Rev Neurosci. 2008 Jul;9(7):505-18. Review. PMID: 18568013
Emerging functions of mammalian mitochondrial fusion and fission. Chen H, Chan DC. Hum Mol Genet. 2005 Oct 15;14 Spec No. 2:R283-9. Review. PMID: 16244327

Articles

Bcl-x L increases mitochondrial fission, fusion, and biomass in neurons. Berman SB, Chen YB, Qi B, McCaffery JM, Rucker EB 3rd, Goebbels S, Nave KA, Arnold BA, Jonas EA, Pineda FJ, Hardwick JM. J Cell Biol. 2009 Mar 9;184(5):707-19. Epub 2009 Mar 2. PMID: 19255249