cellular components Flashcards
describe the structure of the nucleus
- surrounded by a nuclear envelope, a semipermeable double membrane
- nuclear pores allow substances to enter/exit
- dense nucleolus made of RNA and proteins
describe the function of the nucleus
- contains DNA coiled around chromatin into chromosomes
- controls cellular processes: mitosis, semi-conservative replication, mRNA transcription, gene expression etc.
describe the structure and function of the endoplasmic reticulum
- cisternae: network of tubules and flattened sacs that extends from the cell membrane and connects to the nuclear envelope
- two types:
. rough (RER): has many ribosomes attached for protein synthesis and transport
. smooth (SER): lipid synthesis
describe the structure and function of the golgi apparatus
- planar stack of membrane-bound flattened sacs
- ‘cis’ face aligns with the RER and vesicles form new layers, ‘trans’ face is where vesicles bud off via exocytosis
- molecules are processed in the cisternae
- modifies and packages proteins for export
- synthesises glycoproteins
describe the structure and function of ribosomes
- formed of protein and rRNA
- two subunits: large - joins amino acids, small - has mRNA binding site
describe the structure of a mitochondrion
- surrounded by a double membrane
- folded inner membrane forms cristae: site of electron transport chain
- fluid matrix; contains mitochondrial DNA, respiratory enzymes, lipids and proteins
state the function of mitochondria
site of aerobic respiration to produce ATP
describe the structure of a chloroplast
- vesicular plastid with double membrane
- contain thylakoids: flattened discs that stack to form grana, contains photosystems with chlorophyll
- intergranal lamellae; tubes that attach to thylakoids in adjacent grana
- contain stroma - fluid filled matrix
state the function of chloroplasts
site of photosynthesis to convert solar energy into chemical energy
describe the structure and function of a lysosome
- sac surrounded by single membrane
- contains embedded H+ pump that maintains acidic conditions
- contains digestive hydrolase enzymes
- glycoprotein coat protects cell interior
- fuse with other vesicles that contain something that needs to be digested e.g. bacterium
- exocytosis of digestive enzymes
describe the structure and function of a plant cell wall
- made of cellulose microfibrils for mechanical support
- plasmodesmata form part of apoplast pathway to allow molecules to pass between cells
- middle lamella separates adjacent cell walls
what are bacterial cell walls made of?
peptidoglycan (murein)
what are fungal cells walls made of?
chitin
describe the structure and function of centrioles
- spherical group of 9 microtubules arranged in triples
- located in centrosomes
- migrate to opposite poles of cell during prophase and spindle fibres form between them
describe the structure and function of the cell surface plasma membrane
- ‘fluid-mosaic’ phospholipid bilayer with extrinsic and intrinsic proteins embedded
- isolates cytoplasm from extracellular environment
- selectively permeable to regulate transport of substances
- involved in cell signalling / cell recognition
state the role of cholesterol in the cell surface membrane
steroid molecule that connects phospholipids and reduces fluidity
state the role of glycoproteins in the cell surface membrane
cell signalling, cell recognition (antigens) and binding cells together
state the role of glycolipids in the cell surface membrane
cell signalling and cell recognition
describe the structure and function of flagella
- hollow helical tube made of the protein flagellin
- rotates to propel the organism
describe the structure and function of cilia
-hair-like protrusions on eukaryotic cells
- move back and forth rhythmically to sweep foreign substances e.g. dust or pathogens away, or enabling the cell to move
why is the cytoskeleton important?
- provides mechanical strength
- aids transport within cells
- enables cell movement
describe the process of production of proteins
- DNA is transcribed in the nucleus and converted to mRNA
- mRNA strand leaves the nucleus via a nuclear pore
- mRNA attaches to ribosomes on the RER where the code is read and translate into an amino acid sequence
- amino acid sequence is transported to the golgi apparatus where it is modified and packaged into a protein
- this protein is then transported via secretory vesicles to the cell surface membrane - this movement is aided by the cytoskeleton
- vesicle fuses with cell surface membrane and protein is secreted via exocytosis
