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Chapter 4
Functional Anatomy Eukaryotic
Cells
part B
Prokaryotic and eukaryotic cells are more alike than
different
• All cells, whether they are prokaryotic or eukaryotic, have some common
features.
– DNA
– Plasma membrane
– Cytoplasm
– Ribosomes
All the current scientific evidence strongly indicates that all
cells are related through evolution.
Functions of the prokaryotic plasma membrane
•
•
Osmotic or permeability barrier.
Location of transport systems for specific solutes
(nutrients and ions).
• Energy generating functions
– Involving respiratory and photosynthetic electron transport systems
• establishment of proton motive force, and ATP-synthesizing ATPase
• Synthesis of membrane lipids
• including lipopolysaccharide in Gram-negative cells
• Synthesis of murein (cell wall peptidoglycan)
• Coordination of DNA replication and segregation with
septum formation and cell division
• Location of specialized enzyme systems
– CO2 fixation, nitrogen fixation
Eukaryotic cells
• Eukaryotic cells 10-100 m
– ( prokaryotic cells - 0.2 -1.0 µm  2 - 8 µm)
Eukaryotic cells
• Surface:volume ration
– 0.3:1 in eukaryotic cells
– (3:1 in prokaryotes)
– Eukarya
• Protista
– Protozoa
– Algae
• Fungi
Figure 4.22a
Flagella and Cilia
• Eukaryotic cells may have flagella or cilia.
• Flagella and cilia are organelles involved in locomotion.
Euglena (Algae)
Tetrahymena (Protozoa)
• In eukaryotic cells they consist of a distinct arrangement of
sliding microtubules surrounded by a membrane.
– Microtubules are made of protein tubulin
– The microtubule arrangement is referred to as a 2X9+2 arrangement
Cell Wall
• The cell walls of:
– Many algae contain cellulose.
– Fungal cell walls is chitin, polymer of NAG.
– Yeast cell walls consist of polysaccharides glucan and
mannan.
• Animal cells – lacking cell wall - are surrounded by a glycocalyx
– Structure
• Carbohydrates extending from animal plasma membrane
• Bonded to proteins and lipids in membrane
– Function
• Strengthens the cell
• Provides a means of attachment to other cells.
Plasma Membrane - structure
•
Like the prokaryotic plasma membrane, the eukaryotic
plasma membrane is a phospholipid bilayer containing
proteins.
– Peripheral,
– Integral,
– Transmembrane proteins.
• In addition eukaryotic plasma membranes contain:
– Carbohydrates attached to the proteins
– Sterols
• not found in prokaryotic cells
(except Mycoplasma bacteria).
Plasma Membrane – function
•
•
•
•
Selective permeability allows passage of some molecules
Simple diffusion, Facilitative diffusion, Osmosis
Active transport
Endocytosis
– Phagocytosis: Pseudopods extend and engulf particles
– Pinocytosis: Membrane folds inward bringing in fluid and
dissolved substances
Prokaryotic - The membrane is incapable of
endocytosis and exocytosis
Cytoplasm
• The cytoplasm of eukaryotic cells includes everything inside the
plasma membrane and external to the nucleus
• Cytosol and organelles
• Cytosol - Fluid portion of cytoplasm
– The cytosol contains thousands of enzymes that are responsible for
glycolysis and for the biosynthesis of sugars, fatty acids, and amino acids.
– Cytoskeleton - Microfilaments, intermediate filaments, microtubules
– Cytoplasmic streaming - Movement of cytoplasm throughout cells
Prokaryotic - They may contains only actin-like proteins that,
along with the cell wall, contribute to cell shape.
Organelles
• Membrane-bound:
– Nucleus
– ER
– Golgi complex
– Lysosome
– Vacuole
– Peroxisome
– Mitochondrion
– Chloroplast
Contains chromosomes
Transport network
Membrane formation and
secretion
Digestive enzymes
Brings food into cells and
provides support
Oxidation of fatty acids;
destroys H2O2
Cellular respiration
Photosynthesis
Organelles
• Not membrane-bound:
– Ribosome
Protein synthesis
– Centrosome
Consists of protein fibers and
centrioles
Mitotic spindle formation
– Centriole
Nucleus
• The nucleus, is the most characteristic eukaryotic organelle.
• Nuclear envelope – double membrane
• Nuclear pores
•
•
Chromatin ( threadlike mass) – DNA and histones
Nucleolus – rRNA synthesis
Nucleus -chromosomes
• Contains DNA in the form of chromosomes, ( rod-like bodies)- DNA,
histones and nonhistones proteins
Endoplasmic Reticulum
• The ER is continuous with the outer
membrane of nuclear envelope
• Extensive network of flattened
membranous sacs or tubules called
cisterns
– The internal space of the cisterns is called
the ER lumen
• Rough ER – contain ribosomes
– factory for synthesizing proteins and
membrane molecules
• Smoot ER - extend from rough ERnetwork of membrane tubules
– synthesis of fats, steroids
– secretory function
Figure 4.25
Golgi Complex
• The Golgi apparatus is a membrane-bound structure with a
single membrane.
• The stack of larger vesicles is surrounded by numerous
smaller vesicles containing those packaged
macromolecules.
• It is important in packaging macromolecules for
transport elsewhere in the cell.
Figure 4.26
Lysosomes
• Lysosomes are formed from Golgi complexes.
• Store hydrolytic enzymes necessary for intracellular
digestion.
• Common in animal cells, but rare in plant cells.
– Hydrolytic enzymes of plant cells are more often found in the
vacuole.
Figure 4.22b
Vacuoles
• Vacuoles are membrane-enclosed cavities derived from the
Golgi complex or endocytosis.
• They are usually found in plant cells
– Store various substances
– Help bring food into the cell
– Increase cell size, and provide rigidity to leaves and stems.
Figure 4.22b
Ribosomes
• Eukaryotic ribosomes - 80S (large unit– 60S, small unit 40S)
– Attached to ER formed rough ER
– Free in cytoplasm
• Ribosomes 70S
– In chloroplasts and mitochondria
Prokaryotic - The ribosomes
are composed of a 50S and
a 30S subunits forming an
70S ribosome
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Centrosomes
• Centrosome: consists of protein fibers and centrioles
• They are involved in formation of the mitotic spindle and
microtubules.
Duplicated centrosomes with centriole pairs
Spindle microtubules
Mitochondrion
• Mitochondria provide the energy a cell needs - they are the power
centers of the cell.
• They are about the size of bacteria
• They are membrane-bound organelles
• Have a double membrane
– The outer membrane is fairly smooth,
– The inner membrane is highly convoluted, forming folds (cristae)
• The cristae increase the inner membrane's surface area.
• It is on these cristae that food (sugar) is combined with oxygen to produce ATP the primary energy source for the cell.
• They have their own DNA and 70S ribosomes
• They are self replicated
Chloroplast
• Algae and green plants have chloroplasts
– this organelle is responsible for photosynthesis
• Chloroplasts have a double outer membrane.
• Within the stroma are other membrane structures - the thylakoids.
– Thylakoids appear in stacks called "grana" (singular = granum).
• The chloroplast has its own DNA, which codes for redox proteins
involved in electron transport in photosynthesis.
– 70S ribosomes
• Prokaryotic - There are no chloroplasts.
• Photosynthesis usually takes place
in infoldings or extensions derived from
the cytoplasmic membrane.
Figure 4.15
Figure 4.28
Endosymbiotic Theory
• The endosymbiotic theory concerns
the origins of mitochondria and
chloroplasts
• Lynn Margulis - According to the
endosymbiotic theory, eukaryotic
cells evolved from symbiotic
prokaryotes living inside other
prokaryotic cells.
1. Large bacteria lost their cell wall
2. Plasma membrane folded around
the chromosome- nucleus
3. Ingested aerobic bacteria
4. Endosymbiosis
Figure 10.2
Mitosis and meiosis
Learning objectives
• Differentiate between prokaryotic and eukaryotic flagella.
• Compare and contrast prokaryotic and eukaryotic cell
walls and glycocalyx.
• Compare and contrast prokaryotic and eukaryotic plasma
membranes.
• Compare and contrast prokaryotic and eukaryotic
cytoplasm.
• Define organelle.
• Describe the functions of the nucleus, endoplasmic
reticulum, ribosomes, Golgi complex, lysosomes,
vacuoles, mitochondria, chloroplasts, peroxisomes, and
centrosomes.
• Discuss evidence that supports the endosymbiotic theory
of eukaryotic evolution.
• Compare and contrast Mitosis and Meiosis