Cell Structure & Division (Chapter 3) Flashcards
What is a eukaryotic cell?
Animal cell
Plant cell
Algal cells
Fungal cells
What is a prokaryotic cell?
Bacteria lol
Function of the cell surface membrane?
Regulates movement of substances in and out of the cell.
Has receptors which allow it to respond to hormones etc
Structure of the nucleus?
Large organelle surrounded by a nuclear envelope which contains pores.
Nucleus contains chromosomes (made from protein bound linear DNA)
Function of the nucleus?
Controls cells activities
DNA of course babe
Contains instructions to make proteins
Structure of mitochondria?
Double membrane- inner highs folded (cristae)
Matrix- contains enzymes involved in respiration
Function of mitochondria?
Site of aerobic respiration
ATP produced
Structure of chloroplasts?
Small flattered structure
Double membrane
Thylakoid membranes- stacked up to form grana
Lamella
Function of chloroplasts?
Photosynthesis
Structure of Golgi vesicle?
Small fluid filled sac in the cytoplasm surrounded by a membrane
Produced by Golgi apparatus
Function of Golgi vesicle?
Stores lipids and proteins made by Golgi apparatus
Transports these out the cell
Lysosome structure?
Round organelle
Membrane
Function of lysosomes?
Contains hydrolysis enzymes
Used to digest invading cells or break down worn out cell parts
Ribosome structure?
Small organelle made up of proteins and RNA
NO MEMBRANE
Ribosome function?
Proteins are made
Rough endoplasmic reticulum structure?
System of membranes enclosing fluid filled space
Covered with ribosomes
Function of RER?
Folds and processed proteins
Smooth endoplasmic reticulum structure?
Membranes enclosing a fluid filled space
SER function?
Synthesises proteins and lipids
Cell wall structure?
Rigid structure surrounds cells in plants, algae, fungi
What Is the cell wall in plants and algae made of?
Cellulose
What is the cell wall made of in fungi?
Chitin
Cell wall function?
Give support- preventing from changing shape
Cell vacuole structure?
Membrane bound found in cytoplasm of plant cells
Contains cell sap
Function of cell vacuole?
Maintain pressure inside cell and keep cell rigid
Where do cells become specialised?
In complex multicellular organisms
How are specialised cells organised?
Cells —> tissues —> organs —> organ systems —> organisms
Give one example of a specialised cell?
Epithelial cells in small intestine- food absorption
List 4 ways prokaryotic cells differ to eukaryotic cells?
Cytoplasm lacks membrane bound organelles
Smaller ribosomes
No nucleus- instead they have loop & plasmids (sometimes)
Cell wall that contains Muriein (glycoproteins)
What are the three things that only certain prokaryotic cells have?
One or more plasmid
Capsule surrounding the cell
One or more flagella
Are viruses cells?
NO they are acellular
Structure of a virus? And what do they contain?
Nucleic acids surrounded by a protein coat
Genetic material
Capsid
Attachment proteins
Magnification equation?
Magnification = size of image / size of real object
What is magnification?
How much bigger the image is than the specimen
What is resolution?
How well a microscope can distinguish between two points that are close together
Optical microscopes max resolution?
0.2 um
What is the max useful resolution on an optical microscope?
X1500
What is the max resolution on an electron microscope?
0.0002 um
What is the max useful magnification on an electron microscope?
X 1 500 000
How do transmission electron microscopes work?
Use electromagnets to focus a beam of electrons, which is then transmitted through the specimen.
Denser parts of the specimen absorb more electrons which makes them look darker on the image
Advantage of transmission electron microscope?
High resolution images, so can see things like organelles (eg. Chloroplasts)
Disadvantage of transmission electron microscopes?
Can only be used on thin specimens
How do scanning electron microscopes work?
Scan a beam of electrons across the specimen which knocks off electrons from the specimen. These knock off electrons from the specimen which are gathered in a cathode ray tube to form an image.
Are SEMs images 3D or 2D?
3D
Advantage of SEMs?
Can be used on thick specimens
Disadvantage of SEMs?
Lower resolution than TEMs
If you wanted to look at organelles under an electron microscope what technique would you use?
Cell fractionation
List the three steps involved in cell fractionation?
Homogenisation
Filtration
Ultracentrifugation
What is involved in homogenisation?
Breaking up the plasma membrane and releases the organelles into the solution
What is the solution in homogenisation and why?
Ice cold- reduce enzyme activity
Isotonic- prevent damage through osmosis/ stop osmosis
Buffered- maintain pH
What is involved in filtration?
Homogenised cell solution is filtered through a gauze to separate any large debris eg. Connective tissue
Describe the three steps of ultracentrifugation?
Cell fragments poured into a tube, then added to a centrifuge and spun at low speed. Heaviest organelles go to the bottom (nuclei) and form the pellet. The other organelles and solution is called the supernatant.
Supernatant drained off and poured into another tube. Then spun again in the centrifuge at a higher speed. Heaviest form pellet (this time mitochondria).
Process repeated again at higher and higher speeds until all organelles separated out.
What are artefacts?
Things that you can see down the microscope that aren’t part of the cell or specimen eg. Dust or fingerprints etc
Where are artefacts most common?
In electron micrographs
Can we distinguish between artefacts and the specimen?
Kinda, there was a considerable period of time when we couldn’t tho
What is mitosis?
Cell division in eukaryotes that produces genetically identical cells
What are the four stages of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What is mitosis needed for?
Growth of multicellular organisms and repairing damaged tissues
What is the period of cell growth, DNA replication and ATP content increased called?
Interphase
What is a centromere?
The bit in the middle where the chromatids join
What happens in prophase? (3 point)
Chromosomes condense and get shorter and fatter
Centrioles start moving to opposite ends of the cell, forming spindle fibres
Nuclear envelope breaks down (chromosomes free in cytoplasm)
What happens in metaphase?
Chromosomes (each with two chromatids) line up along the middle of the cell and become attached to the spindle by their centromere
What happens in anaphase? (3 points)
Centromeres divide, separating each sister chromatids.
Spindles contract pulling chromatids to opposite poles (centromere first)
Chromatids appear v shaped
What happens in telophase? (5 points)
Chromatids reach opposite poles
Uncoil and become long and thin again (now called chromosomes)
Nuclear envelope forms (now two nuclei)
Cytokinesis finished in telophase
Two daughter cells formed
What is cancer the result of?
Uncontrolled cell division
What is cancer?
Tumour that invades surrounding tissue
What are both mitosis and the cell cycle controlled by?
Genes
What are cancer treatments usually aimed at?
Control the rate of the cell cycle
What is chemotherapy targeted at (chemical drugs)?
Prevents synthesis of enzymes needed for DNA replication- forcing cell to kill itself
What is radiation targeted at?
Damage DNA which when the body checks for damage the cell will kill itself
How do prokaryotic cell replicate?
Binary fission
How do viruses replicate themselves?
They use host cells- inject their DNA or RNA into host cell LOL
Inject nucleic acid as well
Host cell replicates virus particles
List the 4 steps involved in binary fission?
Circular DNA and plasmids replicate, main loop only replicated once
Cell gets bigger and DNA loops move to opposite poles
Cytoplasm begins to divide and new cell walls begin to form
Cytoplasm divides and two daughter cells are produced (each has one copy of circular DNA but variable NO of plasmids)
What is the equation for mitotic index?
Mitotic index = number of cells with visible chromosomes / total number of cells observed
What required practical is used for mitosis?
Preparation of stained squashes of cells from plant root tips and using an optical microscope to identify stages of mitosis
Calculate mitotic index
What is an eyepiece graticule used for?
Calculate the size of cells
Does an eyepiece graticule need to re-calibrated at each magnification?
Of course