Ultrastructure of Cells Flashcards
What are Prokaryotes? and what are the two domains of prokaryotes?
‘Pro’ means before & ‘karyon’ means nucleus
(Thus, prokaryotic cells lack a nucleus)
Prokaryotes are organisms that lack a nucleus and membrane-bound organelles.
Two Domains of Prokaryotes are:
1. Archea Bacteria
- found in extreme environments (e.g extremophiles)
types of extremophiles
1. Halophiles (salt-loving)
2. THermophiles (heat-loving)
3. Methanogeon (without oxygen)
- Eubacteria
- are traditional bacteria (including pathogens such as E. coli etc)
State the functions of the 8 cellular components (parts) of a Prokaryote?
- Cytoplasm – medium for chemical reactions within the cell (made mostly of water)
- Nucleoid – region of the cytoplasm where the DNA is located (DNA strand is circular and called a genophore)
- Plasmids – autonomous circular DNA molecules that may be transferred between bacteria (produce resistant bacteria)
- Ribosomes – complexes of RNA and protein that make proteins (prokaryote ribosome = 70S)
- Cell membrane – Semi-permeable surrounding the cell that regulates what goes in and out of the cell
- Cell wall – rigid outer structure made of peptidoglycan; maintains the shape of the cells and prevents the cell from bursting (lysis)
- Slime capsule – a thick polysaccharide layer used for protection against drying out (loss of moisture) and phagocytosis (a type of endocytosis — where a cell called Pathogcytes ingests and engulfs particles)
- Flagella – a propeller used for movement (singular: flagellum)
- Pili – involved in cell identity (enable
attachment to surfaces and to other bacteria)
Explain how Prokaryotes reproduce?
Prokaryotes reproduce by binary fission, a form of asexual reproduction. The circular DNA of a prokaryote (the bacterial chromosome) is copied to form two identical copies. These are then moved to opposite ends of the
cell and the cell wall and plasma membrane are then pulled
inwards so the cell pinches apart to form two identical
cells.
Give an example of a Prokaryote?
Salmonella bacteria is a bacteria that can cause Salmonellosis. Symptoms include fever, headache, diarrhea, stomach cramps, nausea, and sometimes vomiting
What are Eukaryotes?
Eukaryotes are organisms that contain a nucleus and have membrane-bound organelles
(Eukaryotes are believed to have evolved from prokaryotes via endosymbiosis)
State the 4 distinct kingdoms of Prokaryotes
- Animalia (no cell wall)
- Plantae (have a cell wall made of cellulose)
- Fungi (have a cell wall made of chitin)
- Protista (unicellular organisms; or multicellular organisms without specialised tissue)
State 6 Eukaryotic organelles with a single membrane and 3 Eukaryotic organelles with a double membrane
Organelles with a single membrane:
- Rough endoplasmic reticulum
- (don’t have ribosomes attached on them & Make protein that will be exported to other cells)
- Smooth endoplasmic reticulum
- (have ribosomes attached on them & Make protein for use within the cell) - Golgi apparatus
- Lysosomes
- Vesicles
- vacuoles
Organelles with a double membrane:
- Nucleus
- Mitochondrion
- Chloroplast
State the function of 2 Universal Organelles and 5 Eukaryotic Organelles?
Universal organelles (found in both pro & eukaryotes)
- Ribosomes (RER & SER) – produce proteins (the process is through translation)
- Cyoskeleton — provides internal structure and maintains the shape of cell
Vesicles —- store and transport materials with the cell.
Eukaryotic Specific Organelles
- Nucleus —stores genetic material (DNA)
- nucleous (part of the nucleus that produces ribosomes)
- – nucleoplasm (cytoplasm of nucleus)
- Endoplasmic Reticulum (ER – Containing both RER & SER) — Transports proteins (SER within the cell & RER to other cells)
- Golgi Apparatus — sorts, stores, modifies and exports secretory products
- Material sorted within the Golgi apparatus will either be secreted externally or may be transported to the lysosome - Lysosome —- breakdown macromolecules with enzymes (carbohydrates, lipids, proteins, and nucleic acids) and plays a role in cell recycling
- Vacuole — maintain turgur pressure of cell
(e. g Contracile Vacuole – type of vacuole that regulates the quantity of water inside a cell (expels excess water)
List 5 differences between Eukaryotes and Prokaryotes
- Prokaryotes have circular and naked DNA
Eukaryotes have linear DNA which is wrapped around histone protein - Prokaryotes have 70s ribosomes
Eukaryotes have 80s ribosomes - Prokaryotes don’t have membrane-bound organelles
Eukaryotes have membrane-bound organelles - Prokaryotes reproduce by binary fission
Eukaryotes reproduce by mitosis and meiosis - Prokaryotes have no no nucleus
Eukaryotes have a nucleus
State 3 similarities between plant and animal cells
- Both have DNA stored within a nucleus
- Both have 80s ribosomes
- Both have a variety of membrane-bound organelles (e.g. mitochondria, ER, golgi apparatus)
State 6 differences between animal and plant cells
- Plant cells have a cell wall
Animal cells don’t have a cell wall - Plant cells have plastids
Animal cells don’t have plastids - Animal cells have centrioles (two pairs)
plants cells don’t have centrioles - Animals cells have cholesterol in their membrane
Plants cell don’t have cholesterol in their membrane - Plant cells have a large central vacuole
Animal cells have many small vacuoles - Plant cells have a regular shape
Animal cells have an irregular shape
Name a Vacuole that isn’t responsible for maintaining turgur pressure within a cell. Given examples of organisms that it’s present in. State its function as well as how it forms
1) Food vacuoles are present in unicellular protozoans such as amoeba, plasmodium
2) Food vacuole responsible for digesting food particles in a cell (work as an intracellular stomach, digesting the ingested food)
3) Endocytosis is the method which forms food vacuoles.
Can Eukaryotes be Unicellular organisms?
While prokaryotes are always unicellular organisms, eukaryotes can be either unicellular or multicellular.
