Cell structure Flashcards
What is homogenation
- when cells get broken down and the cells organelles get released
- the resultant fluid is homogenate which gets filtered to remove any debris
What is ultracentrifugation
a process where fragments from filtered homogenate get separated in a centrifuge
What is the use of a cold isotonic buffer
cold - reduce enzyme activity
buffer - so that pH doesn’t fluctuate and result in organelle structure
What is the process of ultracentrifugation
e.g. isolating chloroplasts from a lettuce leaf
- sample is cut up in cold buffered solution
- further broken down in a homogeniser
- homogenised sample (tissue) is spun in a ultracentrifuge at low speed
- heavy organelles (nuclei) forced to the bottom of the tube forming a thin sediment
- the fluid on top, called the supernatant is removed and put in another tube, leaving just the sediment of nuclei
- the supernatant gets spun in the centrifuge at medium speed
- the next heaviest organelles like mitochondria are forced to the bottom of the tube
- this process is continued till the next heaviest organelle is sedimented at higher speeds
What is the formula for magnification
magnification = size of observed / size of real
Compare Light, Transmission Electron and Scanning Electron Microscopes
LM 500nm:
-low resolution
- short wavelengths of light
TEM 10nm:
- beam of electron pass through thin non living specimen
- specimen has to be prepared which can result in limitations of resolution
SEM 2nm:
-same limitations as the TEM however higher resolution and non living specimen doesn’t need to be as thin
Evaluate the use of Electron Microscopes to study cells
Advantages - higher resolution and magnification
Disadvantages - very large and are costly to make/use
Eukaryotes VS Prokaryotes
Eukaryotes: Prokaryotes:
- linear DNA -circular DNA
- introns -no introns
- nucleus -no nucleus
- membrane bound organelles -non membrane bound
- 80’s ribosomes -70’s ribosomes
- divide my mitosis/meiosis -divide by binary fission
- cell wall made from murein -cell wall cellulose/chitin
Describe the structure of a nucleus
- nuclear envelope
- nuclear pours
- nucleocytoplasm
- chromosomes of protein bound linear DNA
Describe the structure of a mitochondrion
- outer membrane
- inner membrane
- cristae (extensions on the inner membrane)
- matrix
Describe the structure of a chloroplast
- outer membrane
- inner membrane
- thylakoids (light dependent reaction)
- granum (stacks of thylakoids)
- stroma (light independent reaction)
What are the functions of the Rough and Smooth Endoplasmic Reticulum
RER: ribosomes present on its outer membrane
- provides large surface area for the synthesis of proteins and glycoproteins
- provide pathway for transport of materials e.g. proteins throughout the cell
SEM: lacks ribosomes and is tubular
- synthesise, store and transport lipids
- synthesise, store and transport carbohydrates
What are the functions of the Golgi Apparatus
- processes triglycerides
- add carbohydrates and proteins to form chylomicrons
- packaged for exocytosis into lymph capillary
How do cells become specialised
by differentiation the genes needed for the role of the cell get expressed
What is a tissue
a collection of similar cells that perform a specific function
What is an organ
a collection of tissues that perform a variety of functions
What is an organ system
a group of organs the work together as a unit to perform a function more efficiently
What are 3 organ systems
- digestive system
- respiratory system
- circulatory system
What is the use of Pillus and Capsule of a bacterium
pillus - bacterial adhesion and conjunction
capsule - protects bacterium from other cells
Structure of a virus
- they are acellular, non living particles
- contain nucleic acid enclosed in a protein coat called a capsid
- have attachment proteins that allow virus to bind to host cells
What is mitosis
the devision of a cell that results on 2 daughter diploid cells being genetically identical to the parent cell
What is Interphase
when a cell is getting ready to divide and the S, G1, G2 and DNA replication stages take place
What are the 4 stages of Mitosis
Prophase - centrioles move towards poles and spindles begin to form
Metaphase - chromosomes line up along the equator and spindles attach to the centromeres
Anaphase - chromosomes separate and chromatids get pulled towards the poles
Telophase - nuclear envelope forms around the chromosomes which uncoil into chromatin
-followed by cytokinesis, the devision of the cytoplasm
How do prokaryotic cells divide (bacteria)
binary fission:
- the circular DNA and plasmids replicate
- cell membrane begins to grow between the 2 circular DNA molecules dividing the cytoplasm into two
- new cell wall forms between the two forming 2 new identical daughter cells
How is cancer similar to mitosis
its a process where cells divide however cancer cells have no restriction to how much they can replicate also they damage surrounding cells
How could a drug prevent the growth of a tumour
preventing the DNA from replicating by inhibiting metaphase of mitosis by interfering with spindle formation
