Chapter 2 - Cells and Organelles Flashcards
What are the 2 types of cells?
Eukaryotic and Prokaryotic
Nucleus
- contains coded genetic info in the form of DNA molecules
- DNA controls the metabolic activities of the cell
- DNA is contained within a nuclear envelope (double membrane)
- Nuclear envelope has nuclear pores - allow molecules to move in and out the nucleus
- DNA+histones=chromatin-> coil and condense to form chromosomes
Nucleolus
- within the nucleus + responsible for ribosome production
- composed of RNA +proteins
- RNA = produce rRNA, then combine with proteins=ribosomes for protein synthesis
Mitochondria
-site of aerobic respiration, where ATP is produced
- number of mitochondria in a cell reflects how much energy used
-double membrane
the inner membrane is folded to form cristae and fluid interior=matrix
-inner membrane contains enzymes used in aerobic respiration
-can produce their own enzymes and reproduce themselves
Vesicles
- membranous sacs that have storage and transport roles
- only have a single membrane with fluid inside
- transport materials inside the cell
Lysosomes
- specialised vesicles that contain hydrolytic enzymes
- break down waste material in cells
- break down pathogens ingested by phagocytic cells
- programmed cell death- apoptosis
Cytoskeleton
- network of fibres necessary for shape and stability of cell
What are the 4 main functions of the cytoskeleton?
- Microtubules and microfilaments support the cell’s organelles, keeping them in position
- strengthen the cell and main shape
- responsible for movement of materials within the cell
- proteins of cytoskeleton can also cause the cell to move
Microfilaments
-responsible for cell movement and cell contraction during cytokinesis
Microtubules
- globular proteins polymerise to form tubes
- tracks for the movement of organelles around the cell
- spindle fibres are composed of microtubules
Intermediate fibres
-mechanical strength in cells and help maintain their integrity
Centrioles
- small hollow cylinders composed of microtubules
- 2 associated centrioles form the centrosome
Cilia
- small, hair-like structures on surface membrane of some animal cells
- cross section -> outer membrane and ring of 9 pairs of protein microtubules inside, with 2 microtubules in the middle
- microtubules allow cilia to move - used by the cell to move substances along the cell surface
Flagella
- enable cells motility
- stick out from cell surface and surrounded by plasma membrane
- inside is the same as cilia - 9 pair of microtubules around the edge, 2 in the centre
- microtubules contract to make it move
Smooth endoplasmic reticulum
-network of membranes enclosing flattened sacs (cisternae)
-responsible for lipid and carbohydrate synthesis, and storage
(synthesis and processes lipids)
Rough endoplasmic reticulum
- network of membranes enclosing flattened sacs (cisternae)
- ribosomes on its surface
- responsible for synthesis + transport of proteins
- FOLD AND PROCESS PROTEINS
Ribosomes
- free-floating in the cytoplasm/ attached to the ER, forming RER
- constructed of RNA molecules made in the nucleolus of the cell
- site of protein synthesis
Golgi apparatus
- compact structure formed of cisternae+no ribosomes
- modify proteins and package them into vesicles
- secretory vesicles/lysosomes
Protein production
- Proteins are synthesised on the ribosomes bound to the ER
- pass on its cisternae and are packaged into transport vesicles
- vesicles containing the newly synthesised proteins move towards the Golgi via the cytoskeleton transport
- Vesicle fuse with the golgi and protein enter
- protein is modified and leaves the golgi in vesicles
- secretory vesicles carry proteins that are to be released from the cell
- vesicles move towards and fuse with the cell-surface membrane, released by exocytosis
Cell wall
- made of cellulose
- freely permeable-> substances pass in and out of the cell through the cellulose wall
- make it rigid
- supports the plant
- defence mechanism- against invading pathogens
Vacuoles
- membrane lined sacs in the cytoplasm containing cell sap
- many plant cells have permanent vacuoles-> maintenance of turgor
- membrane of vacuole=tonoplast
- selectively permeable-some small molecules can pass through it
Chloroplasts
- responsible for photosynthesis in plant cells
- found in the cells in the green parts of plants like leaves and stems
- double membrane structure
- fluid enclosed in the chloroplast= stroma
- internal network of membranes=thylakoids
- thylakoids stacked together=granum
- grana are joined by a lamellae
- grana contains the chlorophyll
- also contains its own DNA and ribosomes
Features of prokaryotes
PROKARYOTES: (bacterial cells)
- extremely small cells (<2 um diameter)
- DNA is circular
- No nucleus - DNA free in cytoplasm
- Cell wall made of polysaccharide but not cellulose/chitin
- Few organelles and no membrane-bound organelles eg mitochondria
- Flagella made of the protein flagellin, arranged in a helix
- small ribosomes
Eukaryotes features
- larger cells (approx 10-100 um diameter)
- DNA is linear
- Nucleus is present-> DNA is inside the nucleus
- No cell wall
- Many organelles are membrane bound
- flagella made of microtubule proteins
-larger ribosomes
