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Tour of the Cell 1
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Prokaryote bacteria cells Eukaryote animal cells
Types of cells - no organelles - organelles Eukaryote animal cells Eukaryote plant cells
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Why organelles? mitochondria chloroplast Golgi ER
Specialized structures specialized functions cilia or flagella for locomotion Containers partition cell into compartments create different local environments separate pH, or concentration of materials distinct & incompatible functions lysosome & its digestive enzymes Membranes as sites for chemical reactions unique combinations of lipids & proteins embedded enzymes & reaction centers chloroplasts & mitochondria chloroplast Golgi Why organelles? There are several reasons why cells evolved organelles. First, organelles can perform specialized functions. Second, membrane bound organelles can act as containers, separating parts of the cell from other parts of the cell. Third, the membranes of organelles can act as sites for chemical reactions. Organelles as specialized structures An example of the first type of organelle is cilia, these short filaments act as "paddles" to help some cells move. Organelles as Containers Nothing ever invented by man is as complex as a living cell. At any one time hundreds of incompatible chemical reactions may be occurring in a cell. If the cell contained a uniform mixture of all the chemicals it would not be able to survive. Organelles surrounded by membranes act as individual compartments for these chemical reactions. An example of the second type of organelle is the lysosome. This structure contains digestive enzymes, these enzymes if allowed to float free in the cell would kill it. Organelle membranes as sites for chemical reactions An example of the third type of organelle is the chloroplast. The molecules that conduct the light reactions of photosynthesis are found embedded in the membranes of the chloroplast. ER
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Cells gotta work to live!
What jobs do cells have to do? make proteins proteins control every cell function make energy for daily life for growth make more cells growth repair renewal
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Building Proteins
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Proteins do all the work!
cells DNA Repeat after me… Proteins do all the work! organism
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Cells functions Building proteins read DNA instructions build proteins
process proteins folding modifying removing amino acids adding other molecules e.g, making glycoproteins for cell membrane address & transport proteins
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Building Proteins Organelles involved nucleus ribosomes
endoplasmic reticulum (ER) Golgi apparatus vesicles The Protein Assembly Line Golgi apparatus nucleus ribosome ER vesicles
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What kind of molecules need to pass through?
histone protein chromosome DNA Nucleus Function protects DNA Structure nuclear envelope double membrane membrane fused in spots to create pores allows large macromolecules to pass through nuclear pores pore nuclear envelope nucleolus What kind of molecules need to pass through?
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production of mRNA from DNA in nucleus
nuclear membrane 1 production of mRNA from DNA in nucleus small ribosomal subunit large cytoplasm mRNA nuclear pore 2 mRNA travels from nucleus to ribosome in cytoplasm through nuclear pore
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Nucleolus Function ribosome production
build ribosome subunits from rRNA & proteins exit through nuclear pores to cytoplasm & combine to form functional ribosomes small subunit large subunit ribosome rRNA & proteins nucleolus
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Ribosomes Function Structure protein production rRNA & protein
small subunit large Ribosomes Function protein production Structure rRNA & protein 2 subunits combine 0.08mm Ribosomes Rough ER Smooth The genes for rRNA have the greatest commonality among all living things. There is very little difference in the DNA sequence of the rRNA genes in a humans vs. a bacteria. Means that this function (building of a ribosome) is so integral to life that every cell does it almost exactly the same way. Change a base and this changes the structure of the RNA which causes it to not function.
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Types of Ribosomes Free ribosomes Bound ribosomes suspended in cytosol
synthesize proteins that function in cytosol Bound ribosomes attached to endoplasmic reticulum synthesize proteins for export or for membranes membrane proteins
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Endoplasmic Reticulum
Function processes proteins manufactures membranes synthesis & hydrolysis of many compounds Structure membrane connected to nuclear envelope & extends throughout cell accounts for 50% membranes in eukaryotic cell
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Types of ER rough smooth
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Smooth ER function Membrane production Many metabolic processes
synthesis synthesize lipids oils, phospholipids, steroids & sex hormones hydrolysis hydrolyze glycogen into glucose in liver detoxify drugs & poisons ex. alcohol & barbiturates
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Membrane Factory Build new membrane synthesize phospholipids
builds membranes ER membrane expands bud off & transfer to other parts of cell that need membranes
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Which cells have lot of rough ER?
Rough ER function Produce proteins for export out of cell protein secreting cells packaged into transport vesicles for export Which cells have lot of rough ER? Which cells have a lot of ER? protein production cells like pancreas = production of digestive enzymes (rough endoplasmic reticulum from a cell of exocrine pancreas (88000X))
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Synthesizing proteins
cytoplasm cisternal space mRNA ribosome membrane of endoplasmic reticulum polypeptide signal sequence ribosome
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Which cells have lots of Golgi?
Golgi Apparatus Function finishes, sorts, tags & ships cell products like “UPS shipping department” ships products in vesicles membrane sacs “UPS trucks” transport vesicles secretory vesicles Which cells have lots of Golgi? Cells specialized for secretion? endocrine glands: produce hormones pituitary, pancreas, adrenal, testes, ovaries exocrine glands: produce digestive enzymes & other products pancreas, mammary glands, sweat glands
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Golgi Apparatus
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Vesicle transport vesicle budding from rough ER fusion of vesicle
with Golgi apparatus migrating transport protein ribosome
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endoplasmic reticulum
nucleus protein on its way! DNA TO: RNA vesicle TO: TO: vesicle ribosomes TO: protein finished protein Golgi apparatus Making Proteins
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Making proteins Putting it together… cytoplasm nucleus cell membrane
transport vesicle Golgi apparatus smooth ER rough ER nuclear pore nucleus ribosome cell membrane protein secreted cytoplasm
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Any Questions!!
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Tour of the Cell 2
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Cells gotta work to live!
What jobs do cells have to do? make proteins proteins control every cell function make energy for daily life for growth make more cells growth repair renewal
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Making Energy ATP
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ATP Cells need power! Making energy take in food & digest it
take in oxygen (O2) make ATP remove waste ATP
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Where old organelles go to die!
Lysosomes Function little “stomach” of the cell digests macromolecules “clean up crew” of the cell cleans up broken down organelles Structure vesicles of digestive enzymes synthesized by rER, transferred to Golgi only in animal cells
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white blood cells attack & destroy invaders = digest them in lysosomes
1960 | 1974 Lysosomes white blood cells attack & destroy invaders = digest them in lysosomes 1974 Nobel prize: Christian de Duve Lysosomes discovery in 1960s
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Cellular digestion Lysosomes fuse with food vacuoles
polymers digested into monomers pass to cytosol to become nutrients of cell vacuole lyso– = breaking things apart –some = body
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Lysosomal enzymes Lysosomal enzymes work best at pH 5
organelle creates custom pH how? proteins in lysosomal membrane pump H+ ions from the cytosol into lysosome why? enzymes are very sensitive to pH enzymes are proteins — pH affects structure why evolve digestive enzymes which function at pH different from cytosol? digestive enzymes won’t function well if some leak into cytosol = don’t want to digest yourself! lysosomes create a space where cell can digest macromolecules safely rupturing a few lysosomes has little impact on a cell (pH of cytosol affects functionality of the lysosomal enzymes), but massive leakage from lysosomes can destroy cell why evolve digestive enzymes which function at pH so different from cytosol? digestive enzymes won’t function well if leak into cytosol = most times don’t want to digest yourself! low pH = acid environment cause oxidation (removing electrons) & promotes hydrolysis
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When things go bad… Diseases of lysosomes are often fatal
digestive enzyme not working in lysosome picks up biomolecules, but can’t digest one lysosomes fill up with undigested material grow larger & larger until disrupts cell & organ function lysosomal storage diseases more than 40 known diseases example: Tay-Sachs disease build up undigested fat in brain cells
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Lysosomal storage diseases
Lipids Gaucher’s disease Niemann-Pick disease Tay Sachs Glycogen & other poylsaccharides Farber disease Krabbe disease Proteins Schindler’s disease
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But sometimes cells need to die…
Lysosomes can be used to kill cells when they are supposed to be destroyed some cells have to die for proper development in an organism apoptosis “auto-destruct” process lysosomes break open & kill cell ex: tadpole tail gets re-absorbed when it turns into a frog ex: loss of webbing between your fingers during fetal development Feedback mechanism There are sensors in the cell that monitor growth. They trigger self-destruct when they sense processes. Brown spots on leaves too. Virus infected plant cell auto-destructs and even cells around it to wall off virus.
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syndactyly Fetal development 6 weeks 15 weeks
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Apoptosis programmed destruction of cells in multi-cellular organisms
programmed development control of cell growth example: if cell grows uncontrollably this self-destruct mechanism is triggered to remove damaged cell cancer must over-ride this to enable tumor growth Feedback mechanism There are sensors in the cell that monitor growth. They trigger self-destruct when they sense processes gone awry. Brown spots on leaves too. Virus infected plant cell auto-destructs and even kills cells around it to wall off virus.
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Making Energy Cells must convert incoming energy to forms that they can use for work mitochondria: from glucose to ATP chloroplasts: from sunlight to ATP & carbohydrates ATP = active energy carbohydrates = stored energy ATP ATP +
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Mitochondria & Chloroplasts
Important to see the similarities transform energy generate ATP double membranes = 2 membranes semi-autonomous organelles move, change shape, divide internal ribosomes, DNA & enzymes
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Mitochondria Function cellular respiration generate ATP
from breakdown of sugars, fats & other fuels in the presence of oxygen break down larger molecules into smaller to generate energy = catabolism generate energy in presence of O2 = aerobic respiration
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Mitochondria Structure 2 membranes
smooth outer membrane highly folded inner membrane cristae fluid-filled space between 2 membranes internal fluid-filled space mitochondrial matrix DNA, ribosomes & enzymes Why 2 membranes? increase surface area for membrane-bound enzymes that synthesize ATP
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Mitochondria
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Membrane-bound Enzymes
glucose + oxygen carbon + water + energy dioxide C6H12O6 6O2 6CO2 6H2O ATP +
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Dividing Mitochondria
Who else divides like that? What does this tell us about the evolution of eukaryotes?
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Mitochondria Almost all eukaryotic cells have mitochondria
there may be 1 very large mitochondrion or 100s to 1000s of individual mitochondria number of mitochondria is correlated with aerobic metabolic activity more activity = more energy needed = more mitochondria What cells would have a lot of mitochondria? active cells: • muscle cells • nerve cells
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Mitochondria are everywhere!!
animal cells plant cells
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Chloroplasts Chloroplasts are plant organelles
class of plant structures = plastids amyloplasts store starch in roots & tubers chromoplasts store pigments for fruits & flowers chloroplasts store chlorophyll & function in photosynthesis in leaves, other green structures of plants & in eukaryotic algae
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Chloroplasts Structure 2 membranes
stroma = internal fluid-filled space DNA, ribosomes & enzymes thylakoids = membranous sacs where ATP is made grana = stacks of thylakoids Why internal sac membranes? increase surface area for membrane-bound enzymes that synthesize ATP
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Membrane-bound Enzymes
+ water + energy glucose + oxygen carbon dioxide 6CO2 6H2O C6H12O6 6O2 light energy +
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Who else divides like that?
Chloroplasts Function photosynthesis generate ATP & synthesize sugars transform solar energy into chemical energy produce sugars from CO2 & H2O Semi-autonomous moving, changing shape & dividing can reproduce by pinching in two Who else divides like that? bacteria!
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Chloroplasts Why are chloroplasts green?
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Mitochondria & chloroplasts are different
Organelles not part of endomembrane system Grow & reproduce semi-autonomous organelles Proteins primarily from free ribosomes in cytosol & a few from their own ribosomes Own circular chromosome directs synthesis of proteins produced by own internal ribosomes ribosomes like bacterial ribosomes Who else has a circular chromosome not bound within a nucleus? bacteria
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Endosymbiosis theory 1981 | ??
Mitochondria & chloroplasts were once free living bacteria engulfed by ancestral eukaryote Endosymbiont cell that lives within another cell (host) as a partnership evolutionary advantage for both one supplies energy the other supplies raw materials & protection Lynn Margulis From hypothesis to theory! Paradigm shifting ideas in evolutionary biology. Lynn Margulis U of M, Amherst
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Evolution of eukaryotes
Endosymbiosis theory Evolution of eukaryotes
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Compare the equations Photosynthesis
+ water + energy glucose + oxygen carbon dioxide 6CO2 6H2O C6H12O6 6O2 light energy + Respiration glucose + oxygen carbon + water + energy dioxide C6H12O6 6O2 6CO2 6H2O ATP +
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The Great ENERGY Circle of Life
sun Photosynthesis ATP plants glucose sugar CO2 + H2O + O2 Respiration animals & plants ATP
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Food & water storage plant cells animal cells food vacuoles
central vacuole animal cells contractile vacuole
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Vacuoles & vesicles Function little “transfer ships” Food vacuoles
phagocytosis, fuse with lysosomes Contractile vacuoles in freshwater protists, pump excess H2O out of cell Central vacuoles in many mature plant cells
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Vacuoles in plants Functions storage
stockpiling proteins or inorganic ions depositing metabolic byproducts storing pigments storing defensive compounds against herbivores selective membrane control what comes in or goes out
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Peroxisomes Other digestive enzyme sacs in both animals & plants
breakdown fatty acids to sugars easier to transport & use as energy source detoxify cell detoxifies alcohol & other poisons produce peroxide (H2O2) must breakdown H2O2 H2O
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Putting it all together
animal cells plant cells
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Any Questions??
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Tour of the Cell 3
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Cells gotta work to live!
What jobs do cells have to do? make proteins proteins control every cell function make energy for daily life for growth make more cells growth repair renewal
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Making New Cells
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Cytoskeleton Function structural support motility regulation
maintains shape of cell provides anchorage for organelles protein fibers microfilaments, intermediate filaments, microtubules motility cell locomotion cilia, flagella, etc. regulation organizes structures & activities of cell
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Cytoskeleton actin microtubule nuclei
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Centrioles Cell division
in animal cells, pair of centrioles organize microtubules spindle fibers guide chromosomes in mitosis
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Any Questions??
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