Ultrastructure of cells Flashcards
What are the characteristics of prokaryotes?
- The DNA is freely floating in the cytoplasm
- Unicellular (simple cell structure)
- Have does not have a membrane-enclosed nucleus, no compartmentalization, no membrane-bound organelles
- The organisms in this kingdom differ in cell wall composition and RNA
- Have no mitochondria
What are the 8 cellular structures and their functions of a prokaryote?
- Cell wall (protects and maintains its shape, prevents the cell from bursting)
- Plasma membrane (controls entry and exit of substances)
- Cytoplasm (site of metabolic reactions)
- Pili (protein filaments on the cell wall) and glycoproteins help in cell adhesion and transfer DNA between cells)
- Flagella (responsible for movement)
- 70s ribosomes (site of protein synthesis)
- Nucleoid region (naked DNA, controls activities of the cell)
- Plasmids (parts of DNA containing genes that give the cell antibiotic resistance)
Remember the ultrastructure
What is and what are the steps of binary fission?
Form of reproduction of prokaryotic cells by splitting in half to produce two genetically identical cells. (Asexual reproduction)
- The chromosome is replicated from the point of origin
- The two copies of DNA move to opposite ends of the cells
- The cell elongates (grows longer)
- The plasma membrane grows inwards and pinched off, producing 2 genetically identical cells
What are the characteristics of eukaryotes?
- Eukaryotes are included in the 4 kingdoms: protoctist, fungi, Plantae and Animalia
- The cells vary in size and have a compartmentalized cell structure
- Have a membrane-enclosed nucleus, complex system of membrane-bound organelles
What is compartmentalization and what are its advantages?
The formation of compartments within the cell by membrane-bound organelles. The membranes are used to isolate certain parts of the cell.
- More efficient metabolism as the enzymes are enclosed and hence more concentrated
- Internal conditions can be altered to maintain the optimal conditions for enzymes
- Toxic or damaging substances can be isolated from the cytoplasm
- It is possible to change the position of organelles within the cell, based on its needs
What are the 15 cellular structures and their functions of a eukaryote?
Plasma membrane (controls the entry and exit of substances)
Cytoplasm (contains enzymes that catalyze various reactions)
Mitochondria (site of cellular respiration, ATP energy generated)
80s ribosomes (site of protein synthesis, the proteins used inside the cell itself)
Nucleus (controls all activities of the cell)
Nucleolus (part of the nucleus involved in ribosome production)
Smooth endoplasmic reticulum (produces and stores lipids)
Rough endoplasmic reticulum (transports the proteins produced by ribosomes on its surface to the Golgi apparatus, these proteins are used outside the cell)
Golgi apparatus (processes and packages proteins that are released by Golgi vesicles)
Vesicles (transports and releases substances by fusing with the cell membrane)
Lysosomes (contains hydrolytic enzymes and helps destroy microbes engulfed by w.b.c) animal only
Centrioles (helps in nuclear division)
Vacuole (helps in osmotic balance and stores substances)
Cell wall (protects and maintains its shape, prevents the cell from bursting)
Chloroplast (contain chlorophyll in which photosynthesis takes place) plant only
Remember the ultrastructure
What are the structures and functions of organelles within the exocrine gland cells of the pancreas?
The gland cells secrete digestive enzymes into the pancreatic duct and then into the small intestine. The cells have a good ER system to for protein synthesis (enzymes).
After passing through the Golgi apparatus, the vesicles (containing the enzymes) release their content through exocytosis into the small intestine.
What are the structures and functions of the organelles of the palisade mesophyll cells in plants?
Contain chlorophyll where photosynthesis takes place. The palisade mesophyll cells are placed under the upper epidermis where they are exposed to as much light as possible.
What is microscope resolution?
The shortest distance between two separate points in a microscopic field of view which can still be distinguished as distant objects.
Why are electron microscopes better?
Electron microscopes have a much higher resolution than light microscopes. (can determine detail better). The higher the value, the lower the resolution.
They can observe non-living specimens and magnify them up to 500,000 times to study small cellular structures.
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