Structure of eukaryotic cells Flashcards
What are the distinguishing features of eukaryotic cells?
- cytoplasm containing membrane-bound organelles
- DNA enclosed in a nucleus
What is the structure of the cell-surface membrane?
- hydrophilic phosphate heads attracted to water
- hydrophobic fatty acid tails repelled from water
What are functions of the cell-surface membrane?
- selectively permeable which enables control of passage of substances in & out of cell
- molecules/receptors/antigens on the surface allow cell recognition
What is the structure of the nucleus?
- nuclear envelope which has double membrane & nuclear pores
- nucleoplasm
- nucleolus
- protein bound, linear DNA (chromatin = condensed & chromosome = highly condensed)
What are the functions of the nucleus?
- stores genetic info which codes for polypeptides
- site of DNA replication
- site of transcription which produces mRNA
- nucleolus makes ribosomes/RNA
What is the structure of ribosomes?
- made of ribosomal RNA & protein
- not membrane bound organelle
What is the function of ribosomes?
site of protein synthesis (translation)
What is the structure of the RER?
has ribosomes attached to the surface
What are the functions of the RER?
- ribosomes attached synthesise proteins
- proteins are processed/transported
- proteins packaged into vesicles for transport to Golgi
What is the structure of the SER?
doesn’t have ribosomes attached to it making it appear ‘smooth’
What are the functions of the SER?
- synthesises & processes lipids (e.g. cholesterol & steroid hormones)
What is the structure of Golgi apparatus & vesicles?
- golgi apparatus: flattened membrane sacs
- golgi vesicle: small membrane sac
What are the functions of Golgi?
- modifies proteins & lipids (e.g. adding carbs to it)
- packages proteins/ lipids into Golgi vesicles
- produces lysosomes which is a type of Golgi vesicle
What is the function of the Golgi vesicles?
- transports proteins/lipids to their required destination by fusing with cell-surface membrane
What is the structure of lysosomes?
they are membrane-bound & contain hydrolytic enzymes
What are the functions of lysosomes?
- release hydrolytic enzymes (lysozymes)
- hyrdolyse pathogens & worn-out cell components
What is the structure of mitochondria?
- outer membrane
- cristae (inner membrane fold)
- matrix that contains 70S ribosomes & circular DNA
What are the function of mitochondria?
- site of aerobic respiration
- produces ATP for energy release needed to protein synthesis, vesicle movement & active transport
What is the structure of chloroplasts?
- double membrane
- stroma containing thylakoids, 70S ribosomes, circular DNA & starch granules/lipid droplets
- lamella which links grana
- grana: stacks of thylakoids
What is the function of chloroplasts?
absorbs light energy for photosynthesis to produce organic substances like carbs & lipids
What is the structure of the cell wall?
- mainly made of cellulose (polysaccharide) in plants/algae
- made of chitin (nitrogen containing polysaccharide) in fungi
What is the function of the cell wall?
provides mechanical strength to cell which prevents it from changing shape or bursting under pressure
What is the structure of the cell vacuole?
- tonoplast membrane
- contains cell sap
What are the functions of the cell vacuole?
- maintains turgor pressure in cell which stop the plant wilting
- cell sap stores sugars, amino acids, pigments & any waste chemicals
