Organelles Flashcards
what are organelles?
Membrane bound structures within the cell
What is the nucleus?
Relatively large, normally spherical organelle. Contains cell genome controlling cellular activities.
-contains double membrane nuclear envelope with numerous nuclear pore complexes that control passage
What happens inside the nucleus?
- Chromatin condenses to from chromosomes at cell division
- RNA Synthesis
What is the endoplasmic reticulum?
System of membranous tubules and sacs acting as ‘intracellular highway’ for movement and processing of molecules in cells.
two types:
- Rough ER (studded with ribosomes to process proteins for export from cell)
- Smooth ER (lipid/carbohydrate processing, steroid synthesis and main site of cell membrane synthesis
How does the amount of ER vary between cells?
Varies due to cell activity, with higher levels in secretory cells
What are the golgi apparatus?
Piled system of membrane sacs (cisternae) and vesicles.
What do the vesicles do in the golgi?
Vesicles from the ER fuse with the cis face and further modification of proteins occurs in Golgi such as addition of sugars. Final vesicles bud off for distribution in cell or exported out of the cell
What are Endosomes and Lysosomes?
Single membrane-bound compartments in the cell.
Vesicles from ER/Golgi pass via endosomes(transport pathway) to lysosomes.
Lysosomes have an acidic internal environment allowing digestion of external and internal material.
What are mitochondria?
‘Powerhouse of the cell
- Site for metabolic processes such as ATP Production.
- Contain two membranes:
- Inner membrane is highly invaginated forming cristae with embedded proteins for metabolic processes such as ATP production - Contain circular DNA that encodes some but not all genes for metabolic activities
Numbers of Mitochondria in cells vary based on cell type/activity eg. muscle cells have high activity so high levels of mitochondria
What are plastids?
Found in plants and algae with a Chloroplast being the most common type
- Double border membrane
- Inner space ‘stroma’
- Membrane sacs ‘thylakoids’ arranged in stacks of ‘grana’
- Thylakoid membrane is where chlorophyll and site of photosynthesis and ATP production
- Contain some circular DNA genome encoding some genes for metabolism
Other plastids usually lack chlorophyll and used for storage eg, leucoplast
What is the endosymbiont theory?
Mitochondria and Chloroplasts were originally independent prokaryotes engulfed by ancestral eukaryotic cells
What are vacuoles?
Fluid-filled membrane sacs
- prominent in plant cells
- Storage area which may contain pigments or toxins
- Bound by tonoplast membrane with protein pumps to transport contents
- Turgor pressure gives plant cell strength
-In animal cells, vacuole used for food digestion
What are ribosomes?
Numerous small granules which is the site of protein synthesis
What are centrioles?
Involved with cell division and microtubule formation
-found in animal cells
What is a cytoskeleton?
Composed of proteinaceous microtubules, microfilaments and intermediate filaments
- Give the cell framework and motility
- can form cilia and flagella
