cells Flashcards
What is cell ultrastructure?
The study of organelles
What is the structure of the nucleus?
. Spherical, 10-20um
. Phospholytic bilayer membrane
. Nucleolus
. Nuclear membrane has many pores
. Outer membrane folded to form RER
What is the function of the nucleus?
. Store DNA (preventing damage in cytoplasm)
. Nucleolus manufactures rRNA and ribosomes
. Controls cell activities through production of mRNA
. nuclear pores allow mRNA to leave nucleus
What information leads scientists to believe mitochondria had a bacterial origin?
. Loops of DNA
. Shape and size
. No membrane- bound organelles
What tissues contain lots of mitochondria?
Muscle tissue and epithelial tissue (SI)
What is the structure of the mitochondria?
. Rod shaped, 1-10um
. Has cristae- folds of inner membrane
. Membrane- bound organelles
. Prokaryotic style DNA and ribosomes
What is the function of the mitochondria?
. To produce energy through cellular respiration
. Synthesise ATP
. Oxidative phosphorylation
. Own DNA for replication
. Cristae provide large SA for enzymes
What is the function of lysosomes?
. To degrade material taken up from outside the cell and to digest obsolete components of the cell itself
. Formed by golgi apparatus
. Up to 1um in diameter
. Contains hydrolytic enzymes (proteases and lipases)
. Breaks down materials from phagocytosis
. Enzyme exocytosis
. Cell autolysis
. Isolate harmful enzymes from rest of cell
what is the structure of RER?
. folds of membrane, encrusted with ribosomes
. large SA- proteinsynthesis
. connected to nucleus membrane
. membranes enclosed, flattened sacs called cisternae
what is the function of RER?
. proteinsynthesis (cells destined for export are synthesised)
. provides large SA
. provides pathway for transport of proteins
what is the structure of SER?
. similar to RER but more tubular
. continuous to RER
what is the function of SER?
. synthesise, store and transport lipids and carbohydrates
what is the structure of golgi apparatus?
. similar to SER but more compact
. flattened sacks called cisternae and small, hollow vesicles
. found extensively in epithelial cells
what is the function of golgi apparatus?
. recieving, sorting and delivering proteins and lipids
. modifying by adding non-protein components
. forms lysosomes
. vesicles carry finished product to fuse with cell surface membrane
what is the structure of ribosomes?
. located in RER or free in cytoplasm
. smallest organelle
. prokaryotes have 80s ribosomes
. eukaryotes have 70s ribosomes
. have a large and small subunit (rRNA and protein)
. can account for 25% of dry mass of a cell
what is the function of ribosomes?
. proteinsynthesis
. ribosomes on RER produce proteins designed for export
. free ribosomes in cytoplasm
. produce proteins for cellular use
what plant cell has no chloroplasts and why?
. root hair cell
. underground and so doesnt recieve any sunlight
what is the structure of a chloroplast?
. disc-shaped plant organelle around 2-10nm length and 1nm diameter
. double phospholipid membrane
. stroma- like cytoplasm
. thykaloid discs contain chlorophyll forming stacks of granum up to 100 discs
. intergranullar lamella
. ribosomes, loop of DNA, starch
what are the function of chloroplasts?
. production of glucose stored as starch
. ribosomes and DNA allow chloroplasts to quickly produce proteins needed
. LDR- 1st stage, takes place on glana (large SA and attached chlorophyll, enzymes)
. LDR- takes place in stoma , enzymes
what is the structure of leaf pallisade cells?
. elongated
. large numbers of chloroplasts
. migrate to areas of greatest LI
. thin cell walls for efficient diffusion of co2
what is the structure of a vacuole?
. large and central
. composed of membranes containing cell sap
. helps to maintain turgour pressure
. used for storage
what is G1?
cell increases in size (growth phase)
what is S phase?
cell replicates DNA
what is G2?
the cell increases further in size and replicates organelles
what is M phase?
mitosis
what is interphase?
cell doing its usual jobs
what are the stages of mitosis?
. prophase
. metaphase
. amaphase
. telephase
. cytokenesis
what are the steps of ultracentrifugation?
. break up cell to create hemogenate
. filter to remove any whole cells
. increase G force
. densest parts form pellet
. repeat
. liquid on top called supernatant
what is the structure of bacteria?
. have cell walls- made of murein
. some have outer layer called capsule for protection and to stick to other bacteria
. plasmids contain genes that improve survival
. plasmids can be easily exchanged between bacteria
What is the magnification equation?
I = A × M
What are the principles of a light microscope?
Visible light passes through the specimen and is bent through the lense system, allowing the user to see a magnified image
What are the advantages of a light microscope?
. Living and dead material can be viewed
. Doesn’t require specialist training in order to operate
. Small and portable
. Unaffected by magnetic fields
What are the limitations of a light microscope?
. Low resolution: limit is 200nm and so objects smaller cannot be viewed
. Low magnification: maximum is 1500x so is useless for small organelles
. Specimen may be disfigured while being prepared
. Most cells need to be stained to be seen
What are the principles of TEM?
Used to examen thin slices of cell tissues, it projects an electronic beam through a sample and a 2D image is formed
What are the advantages of TEM?
. They provide high resolution images with more detail
. They have a magnification of 1000000x
. They can view the internal structures of cells
What are the limitations of TEM?
. Must be positioned in a vacuum, very detailed images of cell organelles and living specimens cannot survive so cannot visualise living material
. Can only be used for thin tissues as thick specimens easily absorb the electrons
. Can only use dead specimens
What are the principles of SEM?
Scan a beam of electrons across the specimen, the beam bounces off the surface and electrons are detected, forming an image
What are the advantages of SEM?
. They can be used on thick or 3D specimens
. They allow the external, 3D structure of specimens can be observed
. Large depth of field, examination of surface structure
. Resolution as low as 15nm
. Chemical analysis
What are the limitations of SEM?
. Lower resolution than TEM
. They cannot be used to observe live specimens
. They do not produce a colour image
. Expensive to buy and run
. Small risk of radiation exposure
What is binary fission?
Bacterial cell division is much more simple than mitosis because instead of chromosomes, they have a singular, circular DNA molecule
Plasmids are also replicated and passed on
What are the stages of binary fission?
- dna replication of bacterial chromosome and plasmids
- cell divides into two, each receiving half the cytoplasm, one chromosome and some plasmids
What is replication in viruses?
. Acellular and non-living so do not carry out cell division in any form
. Instead, they inject nucleic acid into a host cell
. The host cells dna-replicating and protein-synthesising systems make more virus particles
. Eventually, they are released when host cell bursts, or by each new virus leaving through cell membrane
. The host can be prokaryotic or eukaryotic
