3.4 Eukaryotic cell structure Flashcards
(28 cards)
What are the distinguishing features of eukaryotic cells
● Cytoplasm containing membrane-bound organelles
● So DNA enclosed in a nucleus
Describe the general structure of eukaryotic cells (what organelles do they have) (8)
Cell surface membrane
Mitochondrion
Nucleus
Ribosomes
Rough endoplasmic reticulum
Smooth endoplasmic reticulum
golgi apparatus
Lysosome
What are the organelles specific to plant cells (3)
Chloroplasts-in plants and algae
Cell wall-in plants algae and fungi
Cell vacuole- only in plants
Describe the structure of the cell surface membrane (3)
- Hydrophilic phosphate heads-points to/ are attracted to water
- Hydrophobic fatty acid tails-point away/repelled from water
- Forms a phospholipid bilayer
Describe the function of the cell surface membrane
● Selectively permeable → enables control of passage of substances in / out of cell
● Molecules / receptors / antigens on surface → allow cell recognition / signalling
Describe the structure of nucleus (5)
- Has a nuclear envelope
-Double membrane
-Nuclear pores - Nucleoplasm-Granular jelly like material
- Nucleolus-Dense region
- Protein/histone bound, linear DNA
-Chromatin=condensed
-Chromosome=Highly condensed
Describe the function of the nucleus (4)
● Holds / stores genetic information which codes for polypeptides (proteins)
● Site of DNA replication
● Site of transcription (part of protein synthesis), producing mRNA
● Nucleolus makes ribosomes / rRNA
Describe the structure of RER and SER
Has lots of ribosomes-RER
Both made of a system of membranes called cisternae
Describe the function of RER (3) and SER
RER:
● Ribosomes on surface synthesise proteins
● Proteins processed / folded / transported inside rER
● Proteins packaged into vesicles for transport eg. to Golgi apparatus
SER:
● Synthesises and processes lipids
● Eg. cholesterol and steroid hormones
Describe the strcuture of a ribosome
● Made of ribosomal RNA and protein (two subunits)
● Not a membrane-bound organelle
describe the function of a ribosome
Site of protein synthesis (translation)
What is the difference between 80s and 70s ribosomes
80s-Found in euk is arouond 25nm in diameter
70s-Found in prok smaller than 80s
Describe the structure of golgi apparatus and golgi vesicles
Golgi A is flattened membrane sacs
Golgi V are small membrane sacs
Describe the fucntion of golgi A (4) and Golgi V (2)
Golgi apparatus:
● Modifies protein, eg. adds carbohydrates to produce glycoproteins
● Modifies lipids, eg. adds carbohydrates to make glycolipids
● Packages proteins / lipids into Golgi vesicles
● Produces lysosomes (a type of Golgi vesicle)
Golgi vesicles:
● Transports proteins / lipids to their required destination
● Eg. moves to and fuses with cell-surface membrane
Describe the structure of lysosomes
Membrane
Hydrolytic enzymes
Describe the function of lysosomes (3)
- Fuse with vesicle
● Release hydrolytic enzymes (lysozymes)
● To break down / hydrolyse pathogens or worn-out cell components
Describe the strcucture of mitochondria (3)
- Has a outer membrane
- Cristae-extensions of the inner membrane-provides a large surface area for the attachment of enzymes
- Matrix-Contains 70s ribosomes and circular DNA
Describe the function of mitochondria
● Site of aerobic respiration
● To produce ATP for energy release
● Eg. for protein synthesis / vesicle movement / active transport
Describe the structure of chloroplasts in plants and algae (6)
- Double membrane
- Stroma, containing:
*Thylakoid membrane
*Small / 70S ribosomes
*Circular DNA
*Starch granules / lipid droplets - Lamella - thylakoid linking grana
- Grana - stacks of thylakoid
grana is also where the first stage of phptosyntehsis takes place
Describe the function of chloroplasts in plants and algae
● Absorbs light energy for photosynthesis
● To produce organic substances eg. carbohydrates / lipids
How are chloroplasts adapted to thier function (3) dont even need to know this
- The granal membrane provides a large surface area for the attatchment of chlorophyll
- The fluid of the stroma possess all the enzymes needed to make sugars
- Chloroplasts contain DNA and 70s ribosomes so they can quickly manufacture the proteins needed for photosynthesis
Describe the structure of the cell wall in plants algae and fungi
● Composed mainly of cellulose (a polysaccharide) in plants / algae
● Composed of chitin (a nitrogen containing polysaccharide) in fungi
Describe the function of the cell wall in plants algae and fungi
● Provides mechanical strength to cell
● So prevents cell changing shape or bursting under pressure due to osmosis
Describe the structure of the vacuole in plants
Has a tonoplast membrane and contains cell sap
WHen talking about the cell sap talk about the contents in the cell sap
