Prokaryotic and Eukaryotic cells -...
Transcript of Prokaryotic and Eukaryotic cells -...
Prokaryotic cellsA prokaryotic cell is a cell which has no
nucleus or other organelles with a membrane around them. An example of a
prokaryotic cell is a bacteria.
pro = before
karyon = nucleus
Prokaryotic cells DO NOT HAVE
• Nuclei
• Mitochondria
• Endoplasmic reticulum
Prokaryotic cells DO HAVE
• Naked, circular DNA, loose in cell
• Small ribosomes
• Possibly plasmids
• Cell wall (murein) CCEA SPEC
Electron micrograph of a E. coli bacterium
Structure of Prokaryotic
cells
Eukaryotic cells
Animal and plant cells have a nucleus and are termed eukaryotic cells.
eu = true
karyon = nucleus
Eukaryotic cells have• Membrane bound nucleus• Chromosomes (helical DNA with
histone protein coat)• Can develop a mitotic spindle• Microtubules• Large Ribosomes• Membrane bound organelles:
– Mitochondria– Endoplasmic reticulum– Golgi apparatus– Vesicles– Lysosomes
CCEA SPEC
Structure prokaryotic cell eukaryotic cell
Capsule
Cell wall
Plasma membrane
Ribosomes
Mesosomes
Mitochondria
Chloroplasts
Golgi apparatus
RER and SER
Nucleus
DNA
made of murein made of cellulose
small large
DNA loose in cell
coil, no histones chromosomes, histones
ANIMAL CELL
Structure of animal cells
A Plant Eukaryotic cell
PLANT CELL
Nuclear pore
Chloroplast
Cell wall
vacuole
nucleus
nucleolus
mitochondrion
Starch
grain
Tim & Moby
Mitochondrion
Chloroplast
Rough endoplasmic reticulum
Ribosomes
Golgi apparatus
Lysosomes
Microtubules
Plasmodesmata
Nucleus
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• Outer membrane separated from a folded inner membrane by an inter-membrane space
• A fluid matrix is found in the inner cavity.. • Folds of the inner membrane, called
cristae, are covered in stalked particles.• These enzyme complexes release energy
during aerobic respiration to form energy rich ATP (adenosine triphosphate).
• Cells that are metabolically active contain many mitochondria e.g. cells involved in active transport.
• Inside an outer membrane is a network of flattened sacs called thylakoids.
• Thylakoids are stacked to form grana that have a large surface area for the space they take up.
• Photosynthetic pigments and enzymes are found on and in the thylakoid membranes.
• Between the outer membrane and the thylakoids is the stroma.
• Large starch grains and small lipid droplets are found in the stroma; products of photosynthesis.
• Most abundant in palisade mesophyll cells of leaves
• System of membranous tubes, studded with ribosomes, running through the cytoplasm
• Distributes/transports substances (especially proteins) throughout the cell.
• Found in cells that manufacture lots of protein e.g. pancreatic cells that make digestive enzymes
• Non-membrane bound organelles • Composed of 2 sections that are
made in the nucleolus of the nucleus. • Found attached to RER or free in the
cytoplasm. • Site of protein synthesis.• Found in huge numbers in all cells.
smooth Endoplasmic Reticulum (sER)
• System of membranous tubes running through the cytoplasm.
• Site of lipid and steroid synthesis.
• Curved stack of flattened membrane bound sacs.
• Small vesicles join the cis surface from the RER and others bud off the trans surface.
• Stores and chemically modifies substances produced in the cell, ready for secretion
• e.g. carbohydrates are added to proteins here to form glycoproteins such as mucin.
Nucleus side
nucleus
rough ER
Vesicle containing
protein buds off RER
vesicles join cis face
of golgi body
vesicles containing
modified protein
bud off trans face
Exocytosis through
plasma membrane
• Small vacuoles pinched off the golgi apparatus that contain hydrolytic enzymes (lysozymes).
• These enzymes are used to digest protein in old organelles, substances taken up by the cell and even complete cells.
• Draw diagram page 35 Froggy
membrane
Digestive enzymes
• Rigid hollow rods found in the cytoplasm.• The centriole is a pair of short
microtubules positioned at right angles to each other.
• Found in a clear area called the centrosome just outside the nucleus.
• Each centriole is composed of 9 triplets of microtubules arranged at an angle.
• At cell division the centrioles move to opposite poles of the cell and produce the spindle that organises and separates the chromosomes.
• NOT FOUND IN PLANT CELLS
Spindle fibres
• Strands of cytoplasm that connect plant cells through the cell wall.
• The plasma membrane of one plant cell is continuous with the next.
• Allows substances to pass easily between cells.
Electron micrograph of a liver (eukaryotic cell) nucleus
• Surrounded by the nuclear envelope, a double membrane containing nuclear pores.
• The outer membrane is covered with ribosomes; this is where RER originates.
• Inside the nucleus is a large dense area called the nucleolus. This is where ribosomes are made.
• They are made in 2 parts, leaving the nucleus through the nuclear pores and assembling in the cytoplasm.
Nuclear envelope
Nuclear pore
Nucleolus
Nucleoplasm
Euchromatin
Heterochromatin
• Inside the nuclear membrane the nucleoplasm contains chromatin, made up of DNA attached to proteins called histones.
• At cell division chromatin condenses, wrapping into tight structures called chromosomes.
• The chromatin of non-dividing cells is spread out throughout the nucleus. Areas of chromatin that are actively being transcribed (copied) appear light under the microscope and are called euchromatin.
• Areas that are not being expressed are more tightly wrapped, appear dark and are called heterochromatin.
DNA
HISTONE‘BEADS’
Plant cell walls are composed of cellulose.
The cell wall is freely permeable to water and dissolved substances.
Cell walls of adjacent cells are glued together by a sticky substance composed of calcium pectate called
the middle lamella.
As a cell matures it adds layers of cellulose and lignin below the cell wall. This adds strength to the cell and is called the secondary cell wall. The original cell wall
is then called the primary cell wall.
Middle lamella
Animal Plant Fungus
•Lacks chloroplasts
•Has no cell wall
•Has centrioles
•May have glycogen granules (carbohydrate storage)
•Possesses chloroplasts
•Has a cell wall composed of cellulose
•Has vacuole
•Have starch grains (carbohydrate storage)
•Have plasmodesmata
•Often have many nuclei
•Has a cell wall composed of chitin
•Have glycogen granules (carbohydrate storage)
Identifying tem photographs
Levels of organisation
Page 40 Froggy
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