Last time •The components of cells
•Membranes •Cell wall /extracellular matrix •Nucleus and ribosomes
Today •The components of cells (continued)
•The endomembrane system •Mitochondria and chloroplasts (structure and origin) •Cytoskeleton, cilia and flagella
•Visualization of organelles
The Endomembrane System: Manufacturing and Distributing Cellular Products
Many of the membranous organelles in the cell belong to the endomembrane system.
•Endoplasmic reticulum (ER)
•Golgi apparatus
•Lysosomes
•Vacuoles
•Peroxisomes – not mentioned in the book
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The Endoplasmic Reticulum
The endoplasmic reticulum (ER) •Produces an enormous variety of molecules.
•Is composed of smooth ER (no ribosomes) and rough ER (covered with ribosomes).
Transmission electron
microphotography
Smooth ER Functions: •Produces lipids, including steroids (the cells in ovaries or testes that produce sex hormones, which are steroids, are enriched with smooth ER)
•Detoxification of alcohol and other drugs (e.g., sedatives (진정제) such as barbiturates, stimulants (각성제) such as amphetamins, and some antibiotics)
•As the liver cells are exposed to a drug, the amounts of smooth ER and its detoxifying enzymes increase drug tolerance increases more drug needed to achieve same effect.
•Role in storage of calcium in muscle cells
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Rough ER Functions: •Production of secretory proteins
•Cells that secrete a lot of protein (such as the cells of salivary glands) are especially rich in rough ER
•Production of membrane proteins •Newly produced proteins are transported to their destinations in transport vesicles
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The Golgi Apparatus
•The Golgi apparatus –Works in partnership with the ER. –Refines, stores, and distributes the chemical products (proteins) of cells.
• Products (proteins) made in the ER reach the Golgi in transport vesicles
• One side of a Golgi stack serves as a receiving dock (= cis side) for these vesicles
• Enzymes of the Golgi modify many of these products during their stay in Golgi
(Golgi tag protein products to mark their final destination within the cell)
• The shipping side (trans side) of a Golgi stack serves as a depot from which the finished molecules can be dispatched in transport vesicles to other organelles or to the plasma membrane
• Vesicles that bind with the plasma membrane secrete finished chemical products to the outside of the cell
Secretion of a protein
Cis
-sid
e
Tra
ns-s
ide
Synthesis Tagging, sorting Transport to surface
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Lysosomes A lysosome is a membrane-enclosed sac. –It contains digestive enzymes The enzymes break down macromolecules.
•They break down damaged organelles. •They fuse with food vacuoles to digest the food.
• Lysosomes have several types of digestive functions.
Lysosome’s protective function
White blood cell Bacteria
• Destruction of bacteria:
a, our white blood cells (5) ingest bacteria (1) into vacuoles (2) (“phagosomes”), b, lysosomes (3) fuse with the phagosomes c, the resulting vesicle containing digested bacteria (4) releases the digest into the
environment
In tuberculosis, this mechanism is blocked: Mycobacterium tuberculosis secretes a protein that blocks this fusion these bacteria can now survive within the host cells tuberculosis
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Vacuoles Vacuoles are membranous sacs
•Central vacuoles of plant cells Store nutrients, poisons and pigments Enlarge cells plant growth
Chloroplasts and Mitochondria: Energy Conversion
• Cells require a constant energy supply to do all the work of life.
• All cells have a primitive energy producing system that “generates” a modest amount of energy from food molecules in the absence of oxygen (this is called “fermentation”)
• In addition, most cells have one or two types of organelles that are specialized in providing large amounts of energy:
– Chloroplasts capture the energy from light
– Mitochondria burn down food molecules and capture the released energy
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Chloroplasts Chloroplasts are the sites of photosynthesis
• Three-membrane system • Grana (granum): the chloroplast's solar power packs • Stroma: the thick fluid
Mitochondria •Mitochondria are the sites of cellular respiration, which involves the production of ATP (an energy-rich molecule) from food molecules.
•Cells have 100 - 10,000 mitochondria
Structure of mitochondria
•This organelle is formed by two membranes that encase a semi-fluid matrix •Matrix contains enzymes that break down sugar, fatty acid, and amino acid molecules •Inner membranes contain the enzymes that harvest the energy released by the breakdown •Surface of inner membrane is increased by folds (“cristae”)
•Mitochondria and chloroplasts contain their own DNA and can multiply in the cell. •Mitochondrial and chloroplast DNA show sequence homology with present bacteria •Mitochondria and chloroplasts show many molecular similarities with bacteria (ribosomes, membranes, details of protein synthesis) Do mitochondria and chloroplasts derive from bacteria?
The origin of mitochondria and chloroplasts
•The endosymbiont theory
Symbiosis = The living together of different species Endosymbiosis = One species lives within the other
Photosynthetic bacterium
Mitochondrion
Chloroplast
Proto-eukaryote
Aerobic bacterium
Origin of the endomembrane system
Origin of oxidative energy extraction
Origin of light energy extraction
Mitochondrion
Event (2): Endosymbiosis
Event (1): Origin of endomembrane system (not yet understood)
Endosymbiosis is one of at least 2 key events leading to the three domains of life
Lynn Margulis (U.S. American)
Boris Kozo-Polyansky (Russian)
Discovered endosymbiosis in 1924 - Ridiculed and forgotten
Re-discovered endosymbiosis in the 1960s - Ridiculed but then recognized
Endosymbiosis is still happening today One of many examples:
A protist (Paramecium) with endosymbiontic algae (Chlorella)
Also, recall tuberculosis bacteria
The Cytoskeleton: Cell Shape and Movement
•The cytoskeleton is an infrastructure of the cell consisting of a network of fibers.
Copyright © 2007 Pearson Education, Inc. publishing as Pearson Benjamin Cummings
•Three major functions of the cytoskeleton
•Mechanical support to maintain cell shape.
•Change cell shape (e.g., amoeboid movement).
•Provides the intracellular roads for movements of organelles
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
CYTOSKELETON There are several kinds of cytoskeleton •Microfilament (actin filament): predominant form of cytoskeleton muscle-like function •Intermediate filament: various types shape, rigidity •Microtubule (tubulin filaments): hollow tubes roadways for movements of vesicles and organelles
Animation (22 sec): http://www.youtube.com/watch?v=y-uuk4Pr2i8
• The microtubules are the “roads “on which the membrane vesicles move along.
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
• Microtubules also form cilia and flagella (hair-like structures on the cell)
Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings
Cilia and flagella are motile appendages.
•Flagella propel sperm cell cells. •Cilia move protozoa. •Cilia clean the respiratory tract
How organelles are visualized
•Traditional methods mostly kill the cells •These methods are usually antibody-based
• What is an antibody? A protein that can specifically bind another protein
• Antibodies occur naturally in the blood
• For each protein in the world an antibody can be produced
• Principle of antibody-based detection: A labeled antibody binds to the target protein
Antibodies are highly specific: Anti-A recognizes the protein A but not the protein B or any other protein.
Typical example of antibody-based detection •Green: Mitochondria •Blue: Filaments •Red: Nucleus (not an antibody but DNA stain)
These cells are dead
• Newer methods allow to study organelle dynamics in living cells
•Genetic tags (by genetic engineering, add a fluorescent domain to a protein of interest) •Organic dyes that are tropic for an organelle
How organelles are visualized
Mitochondria stained genetically with autofluorescent protein domain: Mito-GFP
This cell is alive
Endoplasmic reticulum stained with autofluorescent protein: ER-OFP
These cells are alive
Golgi apparatus stained with autofluorescent protein: Golgi-GFP
These cells are alive
~5 seconds
http://www.plantmitochondria.net/Plant_Mitochondria/Movies.html
Movie One Epidermis of an Arabidopsis plant expressing Green Fluorescent Protein (GFP)-targeted to mitochondria (Logan and
Leaver, 2000). False coloured green. One frame per second. Six-times real-time. Captured from an epifluorescent microscope.
40 seconds
http://www.youtube.com/watch?v=Pf1kIs7gQVk&feature=related
Mitochondria moving inside of a fibroblast
• By staining organelles in living cells we can observe movements of organelles
Mitochondria and lysosomes stained with organic dyes: Lysotracker (bluewhite) and mitotracker (red)
This cell is alive
Mitochondria and lysosomes stained with organic dyes Mitotracker red, lysotracker green
This cell is alive
Mitochondria stained with organic dye: Mitotracker green
This cell is alive
Endoplasmic reticulum and mitochondria stained with organic dyes: ER tracker (green), mitotracker (red)
These cells are alive
Mitochondria and Golgi apparatus stained with organic dyes: Mito-tracker (red), BODIPY Ceramide Golgi (Green), Hoechst nuclei (blue)
These cells are alive
Staining of actin filaments with organic dye (Alexa Fluor Phalloidin)
These cells are alive
Summary – The components of cells
•Membranes. •Membranes are two-dimensional liquids consisting of a lipid bilayer with embedded proteins. •They define, delineate, and connect the cell and its internal compartments (organelles).
•Cell walls / extracellular matrix. •Plant cells form thick cell walls, many animal cells form an extracellular matrix.
• Nucleus. •The nucleus contains the chromosomes (carriers of genetic information). •The nuclear membrane contains pores and is continuous with the endoplasmic reticulum..
•Ribosomes. •Nanomachines (not organelles) that synthesize proteins according to instructions from the nucleus.
•The endomembrane system. •Consists of endoplasmic reticulum (ER), Golgi apparatus, and diverse vesicles (e.g., lysosomes) •Rough ER: secreted/membrane protein synthesis; Golgi: tagging/distribution of secreted/membrane proteins; smooth ER: lipid synthesis/detoxification; lysosomes: breakdown/clearance.
•Mitochondria and chloroplasts. •Organelles extracting energy from organic molecules (mitochondria) or light (chloroplasts). •Chloroplasts use that energy mainly for biosynthesis of glucose. •Both organelles contain DNA and originate from endosymbiontic bacteria.
•Cytoskeleton, cilia and flagella. •Different types of cytoskeletal fibers enable movement of cells, organelles, provide shapes. •Cilia and flagella are hair-like structures that propel cells or agitate nearby fluid.
•Visualization of organelles. •Traditionally through lethal methods (often using antibodies), now vital stains have become available.
• 세포막. • 세포막은 단백질이 박혀있는 지질 이중 층으로 이루어진 이차원적의 유동막이다. • 세포와 그것의 내부 구조물들 (소기관들)을 정의하고, 설명하며, 연결한다.
• 세포벽 / 세포 외 기질. • 식물 세포들은 두꺼운 세포벽을 형성하며, 많은 동물 세포들은 세포 외 기질을 형성한다.
• 핵 • 핵은 염색체를 포함한다 (유전 정보의 전달자). • 핵 막은 핵공 (구멍)을 가지고 있으며, 이것은 소포체와 연결된다.
• 리보좀 • 핵으로부터 나온 지시에 딸 단백질을 합성하는 나노머신 (소기관 아님)이다.
• 세포내막계 • 소포체 (ER), 골지체, 그리고 다양한 소포들을 구성 (e.g., 리소좀). • 조면 소포체: 분비/세포막 단백질을 합성; 골지체: 분비 될 또는 막 단백질을 표지/분배; 활면 소포체: 지질 합성/해독; 리소좀: 분해/청소.
• 미토콘드리아와 엽록체 • 유기분자 (미토콘드리아)나 빛 (엽록체)로부터 에너지를 추출하는 소기관. • 엽록체는 주로 포도당의 생합성을 위해 에너지를 사용한다. • 두 소기관 모두 DNA를 가지고 있으며, 세포내 공생세균으로부터 유래되었다.
• 세포골격, 섬모 그리고 편모 • 여러 종류의 세포골격 섬유는 세포, 소기관의 이동을 가능하게 하고, 형태를 잡는다. • 섬모와 편모는 머리카락 같은 구조이며, 세포를 앞으로 나아가게 하거나, 가까운 유체를 흔든다.
• 소기관의 가시화 • 전통적으로 세포를 죽인 후 실험하나 (종종 항체를 이용), 지금은 생체 염색 (살아있는 채로)이 가능해졌다.
요약- 세포 구성요소들
