3.2.1 Cell Structure Flashcards
define the terms eukaryotic and prokaryotic cell.
eukaryotic - has a nucleus, contains membrane-bound specialised organelles
prokaryotic - no nucleus, DNA ‘free’ in cytoplasm, no organelles e.g. bacteria & archaea
state the relationship between a system and specialised cells
specialised cells –> tissues that perform
specific function –> organs made of several tissue types –> organ systems
describe the structure and function of the cell-surface membrane
- isolates cytoplasm from extracellular environment
- selectively permeable to regulate transport of substances
- involved in cell signalling / cell recognition
explain the role of cholesterol, glycoproteins & glycolipids in the cell-surface membrane
cholesterol: steroid molecule connects phospholipids & reduces fluidity
glycoproteins: cell signalling, cell recognition (antigens) & binding cells together
glycolipids: cell signalling & cell recognition
describe the structure of the nucleus
- surrounded by nuclear envelope, a semi-permeable double membrane
- nuclear pores allow substances to enter/exit
- dense nucleolus made of RNA & proteins assembles ribosomes
describe the function of the nucleus
- contains DNA coiled around chromatin into chromosomes
- controlled cellular processes: gene expression determines specialisation & site of mRNA transcription, mitosis, semiconservative replication
describe the structure of a mitochondrion
surrounded by double membrane folded inner membrane forms cristae: site of electron transport chain
fluid matrix: contains mitochondrial DNA, respiratory enzymes, lipids, proteins
describe the structure of a chloroplast
- vesicular plastid with double membrane
- Thylakoids: flattened disks stack to form grana; contain photosystems with chlorophyll
- Intergranal lamellae: tubes attach thylakoids in adjacent grana
- Stroma: fluid-filled matrix
state the function of mitochondria and chloroplasts
Mitochondria: site of aerobic respiration to produce ATP
Chloroplasts: site of photosynthesis to convert solar energy to chemical energy
describe the structure and function of the Golgi apparatus
planar stack of membrane-bound, flattened sacks cis face aligns with rER
molecules are processed in cisternae vesicles bud off trans face via exocytosis:
- modifies and packages proteins for export
- synthesises glycoproteins
describe the structure and function of a lysosome
Sac surrounded by single membrane embedded H+ pump maintains acidic conditions
contains digestive hydrolase enzymes glycoprotein coat protects cell interior:
- digests contents of phagosome
- exocytosis of digestive enzymes
describe the structure and function of a ribosome
Formed of protein & rRNA free in cytoplasm or attached to ER
- site of protein synthesis via translation: large subunit: joins amino acids
small subunit: contains mRNA binding site
describe the structure and function of the endoplasmic reticulum (ER)
cisternae: network of tubules & flattened sacs extends from cell membrane through cytoplasm & connects to nuclear envelope
Rough ER: many ribosomes attached for protein synthesis & transport
Smooth ER: lipid synthesis
describe the structure of the cell wall
Bacteria: made of the polysaccharide murein
Plants: made of cellulose microfibrils plasmodesmata allow molecules to pass between cells, middle lamella acts as boundary between adjacent cell walls
state the functions of the cell wall
- mechanical strength and support
- physical barrier against pathogens
- part of apoplast pathway (plants) to enable easy diffusion of water