STRUCTURES AND
FUNCTIONS OF
EUKARYOTIC CELLS
STRUCTURES AND FUNCTIONS OF
EUKARYOTIC CELLS
Recall: The kingdoms fungi, protista, plantae and animalia are
all composed of eukaryotic cells
Similarities:
-
Membrane bound nucleus with DNA
-
Cell membrane composed of a phospholipid bilayer
-
Cytoplasm filled interior (everything outside the nucleus
but within the cell membrane – cytosol, organelles,
molecules, ions)
ANIMAL CELL
PLANT CELL
NUCLEUS
Contains DNA
CHROMATIN: uncondensed DNA mixed with proteins
CHROMOSOME: condensed DNA molecule with an
equal mass of protein
-
Quantity varies between species (Ex: Humans have 46)
-
Only visible during cell division
NUCLEUS
NUCLEUS
NUCLEOPLASM: thick fluid filling the nucleus
NUCLEAR MATRIX: network of protein fibres
providing internal structure and support
NUCLEUS
NUCLEOLUS: non-membrane bound, denser region in
the nucleus filled with RNA and proteins
NUCLEAR ENVELOPE: double membrane composed
of a phospholipid bilayer which surrounds the nucleus
LUMEN: space between the bilayer
NUCLEAR PORE COMPLEXES: groups of proteins
that form openings in the nuclear envelope; allow small
particles and ions to travel freely
NUCLEUS
ENDOPLASMIC
RETICULUM
(ER)
Complex membrane-bound tubules and sacs attached to the
nuclear envelope
SMOOTH ENDOPLASMIC RETICULUM (SER):
endoplasmic reticulum without ribosomes
-
Site of synthesis for lipids and lipid containing molecules
-
Site specific functions (Ex: liver SER detoxifies drugs and
alcohol, gonad SER produces testesterone and estrogen)
ROUGH ENDOPLASMIC RETICULUM (RER): ER surface
studded with ribosomes
- Site of protein synthesis
ENDOPLASMIC
RETICULUM (ER)
ENDOPLASMIC
RETICULUM (ER)
RIBOSOMES
Structure composed of RNA and proteins
Structure is different in eukaryotic and prokaryotic cells
Responsible for protein synthesis
a) Ribosomes attached to RER: proteins for cell
membrane and cell export
b) Free floating ribosomes: proteins carrying out
functions in the cytosol
RIBOSOMES
RIBOSOMES
GOLGI APPARATUS
Stack of curved membrane sacs
Packages, processes, sorts and distributes proteins, lipids
and other substances within a cell
Produce lysosomes (animal cells only)
LYSOSOMES
Membrane-enclosed sacs containing over 40 digestive
enzymes (pH ~5)
-
Catalyze hydrolysis reactions, break down
macromolecules for parts to be reused in cell
-
Break down old or no longer needed parts in cell
-
Break down bacteria and other foreign particles
PEROXISOMES
Membrane enclosed sacs containing enzymes that catalyze
redox redox reactions
-
Break down biological molecules and toxic molecules
-
Found in large numbers in the liver to oxidize and break
down alcohol
-
Commonly produce hydrogen peroxide (H2O2) and so
contain catalase to break it down into water and oxygen gas
-
Can sometimes synthesize molecules (Ex: liver
peroxisomes produce cholesterol and bile)
PEROXISOMES
VESICLES AND
VACUOLES
VESICLE: membrane bound sacs used for the transport
and storage of substances in the cell
-
Formed by pinching off from cell membranes and
organelle membranes
-
Can fuse with cell membranes and organelle
membranes to release their contents
•
Animal Cell: Many small vesicles
•
Plant cell: Single large central vesicle (Vacuole)
VESICLES AND
VACUOLES
VACUOLE
Found in plant cells
Stores water, ions, sugars, amino acids, and
macromolecules
Contains enzymes that break down macromolecules and
wastes
Determines turgor pressure in plants
ENDOMEMBRANE SYSTEM:
PROTEIN MODIFICATION AND
TRANSPORT
Consists of:
-
Nuclear envelope
-
Endoplasmic Reticulum
-
Golgi Apparatus
-
Vesicles
Function: synthesizing, product-processing and
transportation section of cell; compartmentalizes cell
ENDOMEMBRANE SYSTEM:
PROTEIN MODIFICATION AND
TRANSPORT
ENDOMEMBRANE SYSTEM:
PROTEIN MODIFICATION AND
TRANSPORT
-
Ribosomes on RER synthesizes polypeptides which are released
into the lumen of RER
-
Polypeptides travel through SER where they are stored and
processed
-
When ready for transport, pieces of SER pinch off into vesicles
containing the protein
-
Vesicles transport from SER to cis face of golgi apparatus
-
Vesicle contents are released into the golgi apparatus where some
proteins are stored and others are further modified
-
Pieces of golgi apparatus pinch off from the trans face of the
golgi apparatus and travel to the cell membrane or other
destinations in the cell
ENDOMEMBRANE SYSTEM:
PROTEIN MODIFICATION AND
TRANSPORT
- Also used in transport of lipids and lipid containing
molecules from SER
CHLOROPLASTS
Organelles containing the photosynthetic pigment chlorophyll, which
absorbs light energy (plant cells only)
- Double membrane, own DNA
STROMA: thick liquid in the inner membrane
THYLAKOIDS: flattened disks containing chlorophyll
GRANUM: stack of thylakoids
MITOCHONDRIA
Break down high-energy organic molecules to convert
stored energy into usable energy
-
Double membrane, own DNA
CRISTAE: folds of inner membrane
MATRIX: fluid filled space in inner membrane
CELL WALL
Rigid layer surrounding plant, fungi, and many types of
protists
-
Provides protection and support
-
Composed of polysaccharides and/or glycoproteins
CYTOSKELETON
Internal network of protein fibres that extend through the
cytoplasm
-
Provides structure and anchors cell membrane and
organelles in place
-
Act as tracks for vesicles and other organelles to move
along
-
For some cells, provides appendages that enable the
cell to propel itself
CYTOSKELETON
CILIA AND
FLAGELLA
Appendages on the outside of of some eukaryotic cells
Composed of an internal shaft made of microtubules
covered with an outer membrane that is a continuation of
the cell membrane
Used for movement
FLAGELLA: One or two longer appendages
CILIA: many shorter appendages
CILIA AND
FLAGELLA