Cell Structure Flashcards
What is the function of the Golgi apparatus?
To process and and package proteins into vesicles and lipids to be sent elsewhere
What is the function of ribosomes?
Where proteins are made
What is the function of the nucleus?
Contain DNA
What is the function of nucleolus?
To make ribosomes
What is the function of the smooth endoplasmic reticulum?
Synthesis and processes lipids
What is the function of mitochondria?
Produces ATP and releases energy and is the site of respiration
What is the function of the cell surface membrane?
To regulate the movement of substances in and out the cell
What is the function of centrioles?
To form the spindle for cell division
What is the function of the rough endoplasmic reticulum?
To Fold and process proteins made at ribosomes
What is the function of the nuclear pore?
Allows RNA to move between the nucleus and cytoplasm
What is the function of the Golgi vesicle ?
Stores lipids and proteins made by the Golgi apparatus and transports them out the cell
What is the function of a lysosome?
Contains digestive enzymes called lysozymes
What is the function of the cell wall?
To support cells and prevent them from changing shape
What is the function of the cell vacuole?
Helps maintain pressure inside the cell and keep the cell rigid
What are the similarities of eukaryotic cells vs prokaryotic cells?
•cell wall
•ribosomes
•cytoplasm
•cell membrane
•cell surface membranes are made from a phospholipid bilayer
What are the differences between eukaryotic cells vs prokaryotic cells?
•cell wall in prokaryotic cells are made from murein whereas cell wall in eukaryotic cells are made of cellulose
•DNA is circular in prokaryotic cells whereas it is linear in eukaryotic cells
•Ribosomes are larger in eukaryotic cells
•DNA is enclosed in nucleus in eukaryotic cells whereas it is free in the cytoplasm in prokaryotic cells
•Organelles are membrane bound in eukaryotic cells
•No capsule or pili in eukaryotic cells whereas it is present in prokaryotic cells
What is the structure of a virus?
•viruses are made up of nucleic acids
•the nucleic acids are surrounded by a protein called a capsid
•viruses are smaller than bacteria
•attachment glycoproteins
What are viruses not considered as living ?
•they have no nucleus, plasma membrane, cytoplasm or ribosomes
• they are not made as cells
•they cannot reproduce independently
What are the function of viruses?
1) to replicate, viruses have to invade and hijack the reproductive mechanism of a living cell
2) viruses have attachment glycoproteins that bind to complementary receptors on host cells
3) they then inject DNA or RNA into the host cell
4) the host cell divides as normal and the virus is replicated
What is the definition of resolution?
How well a microscope can distinguish between two points close together
What is the definition of magnification?
How much bigger an image from a microscope is compared to the specimen
What are the principles of a optical (light microscope) ?
Light is directed on to a specimen using mirrors
What is an advantage of a optical microscope?
•dead or alive specimens
•uses colour
What is a disadvantage of a optical microscope?
Lower resolution and magnification
What are the principles of a transmission electron microscope (TEM)?
Electromagnets focus a beam of electrons through a thin slice of specimen, denser parts of the specimen absorb more electrons than other parts
What are the advantages of a TEM microscope?
•generates image on computer (false colour can be added after)
•resolution and magnification is good
What are the disadvantages of a TEM microscope?
•only in black and white
•can only view dead specimens
•2D images only
•can contain artefacts
What are the principles of scanning electron microscope ( SEM) ?
An electron beam is scanned across a specimen, knocks electron off the specimen and gather in a cathode ray tube to form a image
What is an advantage of a SEM microscope?
•image shows the 3D surface
•generates image on a computer
•specimens do not have to be thin
•good resolution and magnification (but lower than TEM)
What is a disadvantage of a SEM microscope?
•only in black and white
•dead specimens only
•can contain artefacts
How do you measure the actual length of a specimen?
1) calibrate the eyepiece graticule (in eyepiece)
2) micrometer of known length on stage
3) line them up to work out the scale of divisions
Why do electron microscopes have a higher resolution and magnification than light?
Electron microscopes have shorter wavelength
What is the equation of magnification?
Magnification= size of image/actual size of specimen
Describe the process of cell fractionation and ultracentrifugation.
1) homogenisation
First you blend/break up the cells to release organelles into a solution, this solution need to be ice cold to reduce the activity of the enzymes it also need to be isotonic to have the same water potential to prevent water from moving via osmosis and it also need to be buffered to prevent damage to the organelles, we are then left with a homogenised solution
2)Filtration
Homogenised cell solution is filtered through a gauze to separate large cell debris from organelles
3) Ultracentrifugation
Cell fragments are poured into a tube and then spun at a low speed, heaviest organelles are moved to the bottom of the tube to form a thick sediment called the pellet, the rest of the organelles dart suspended in the fluid above the pellet (supernatant), the process is repeated at higher and higher speeds until all the organelles are separated out
