Biology Cells 1

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  • Created by: jackjj9
  • Created on: 10-10-16 21:35
What is a eukaryotic cell?
A cell containing a true nucleus with membrane-bound organelles
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What is a prokaryotic cell?
A cell without a true nucleus and no membrane-bound organelles
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Name 6 organelles in a eukaryotic cell
Nucleus/nucleolus/RER/SER/golgi/lysosomes/mitochondria/chloroplasts/ribosomes/plasma membrane/
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Name 3 things present in a prokaryotic cell and not a eukaryotic cell
Mesosome/small ribosome/chromosomal DNA/slime capsule/sometimes a flagellum
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What is a cell wall in a prokaryotic cell usually made of?
Murien
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What is the purpose of the mesosome?
Respiration
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What is the purpose of ribosomes?
Protein synthesis
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What is the purpose of nucleolus?
Produces ribosomes
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What is the purpose of mitochondria?
Respiration
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What is the gap between the two membranes of the nucleus?
Nuclear envelope
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What does the membranes of a nucleus have?
Many pores
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What is a stack of thylakoids in a chloroplast called?
Granum
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What is the fluid present in a chloroplast called?
Stroma
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What proteins network granum together?
Lamella
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What is the green pigment in a chloroplast?
Chlorophyll
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What is the purpose of RER
Fold and move proteins produced by the attached ribosomes to the area of work
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What is the only non-membrane bound organelle in a eukaryotic cell?
Ribosome
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What is the fluid in a mitochondrion known as?
Matrix fluid
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What are the folds on the inside of a mitochondion's inner membrane called?
Cristae
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What is the purpose of lysosomes?
Contain enzymes to digest unwanted intruders and worn out cell components
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What is the purpose of SER
Regulates and releases calcium cations
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What is the purpose of golgi apparatus?
Bundle lipids and proteins ready for excretion from the cell
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What are cell walls in fungi made of?
Chitin
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What are cell walls in plants made of?
Cellulose
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Why might an intestinal epithelial cell contain many mitochondria?
It needs energy to diffuse nutrients from food against the concentration gradient in active transport
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What is a virus' D/RNA core held within?
The capsid
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What is on the surface of a virus particle?
Attachment proteins
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Put in size order, our body cells, viruses and bacteria from biggest to smallest...
Our cells - bacteria - virus particles
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1000um = how many mm?
1mm
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1um = how many nm?
1000nm
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When, and only when, can a virus inject its nuclear material into our cells?
When the attachment proteins have anchored to our cells
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Give the 9 steps of viral infection:
1. Anchor. 2. Entry of capsid. 3. Breakdown of capsid. 4. Release D/RNA. 5. RNA made if DNA was released. 6. Intergrates DNA. 7. Transcription and translation. 8. New virus assembled. 9. Breakout
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What is a sign of viral infection?
Cell death
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When do you feel symptoms of a viral infection?
When they burst out of our cells
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Why is a virus' DNA able to intergrate with ours?
D/RNA is a universal molecule, composed of the same amino acids. The cell just accepts it as its own
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What happens during translation?
Amino acids are strung together into a polypeptide at a ribosome
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What is the formula for magnification?
M = Image / Actual
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What is the process of calculating the value of divisions on an eyepiece graticule using a stage micrometer known as?
Calibration
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How do you prepare a slide for a TEM or SEM?
1. Complex staining process. 2. Cryofixation
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What must a TEM and SEM be in?
A vacuum
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What kind of mount is usally used for an optical microscope?
Wet mount
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How do you prepare a wet mount?
Add 1 drop of water, add 1 drop of iodine to stain. Add cover slip.
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What is an artefact?
A blip in an image from a microscope that we cannot be sure is part of the specimen or not?
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Which slide preparation is more likely to result in artefacts and why?
Electron microscope because it is more a complex
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How do TEMs produce an image?
They TRANSMIT electrons through the cell where electrons are absorbed more in more dense areas, resulting in darker areas on screen
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What extra stage is usually added into the slide preparation for the SEM?
Coating in metal
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How do SEMs produce an image?
Electrons are bounced off the surface and collected in a cathode ray tube, producing an image of the cell's surface on screen
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What is the main difference between the organelles of an algal cell and a plant cell?
Algal cells contain bigger and less chloroplasts
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What is a plasmid?
A small loop of DNA which is present in some prokaryotic cells
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What does acellular mean?
Not a cell (e.g. virus particles)
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What is chromosomal DNA aka?
Loop of DNA
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What does resolution mean?
How well the microscope can distinguish between 2 points that are close together
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What id 0.0004 in standard form?
4*10^-4
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Give 4 things that should be considered when selecting a type of microscope to use
Resolution, living specimen or not, staining process complexity, specimen thickness, type and what you want the image to be of
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Which microscope can only be used on thin specimens?
TEMS
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How can you distinguish between an artefact and an actual part of the specimen?
Repeat the slide preparation process many times and see if the so-called artefact appears on them all. If it does, it is extremely unlikely to be an artefact
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Which has a higher resolution, TEMs or SEMs?
TEMs
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If the wavelength is shorter, is the resolution greater?
Yes
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Which has a smaller wavelength, light or electrons?
Electrons
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What are the 3 main steps of cell fractionation?
Homegenisation. Filtration. Ultracentrifugation
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What is homogenisation?
Breaking the membranes of the cells to release the organelles such that all samples of the homogenate contain equal proportions of organelles
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What kind of solution should the homogenate be?
An ice cold, isotonic, buffer solution
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Why must the homogenate be kept ice cold?
To reduce the activity of enzymes released from lysosomes for example so that they do not digest/damage the organelles
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What is meant by an isotonic solution?
A solution with an equal concentration of chemicals to that of the cell
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Why must an isotonic solution be used for the homogenate?
So that there is no effect on osmosis and organelles do not shrivel or swell
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What is a buffer solution?
A solution that can maintain pH
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Why must a buffer solution be used?
It maintains the pH so that organelles are not damaged by excess acidity or alkalinity
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What is the purpose of filtering the homogenate?
Removes clumps of unbroken cells and lumps of plasma membranes
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What is ultracentrifugation?
When you separate organelles from each other based on mass by spinning them in a centrifuge
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What is the name of the clump that forms at the bottom of the tube after ultracentrifugation called?
A pellet
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What pellet is likely to form first?
Nucleus
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What pellet is likely to form last?
Ribosomes
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What is the remaining liquid above the pellet called?
Supernatant
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How do you isolate mitochondria after a nucleic pellet has formed?
Drain of supernatant and add to a new tube. Spin at a slightly higher speed in a centrifuge
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What type of force does a centrifuge apply?
G-force
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In plant cells, where do chloroplasts form a pellet?
After nuclei but before mitochondria
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What are the four stages of the cell cycle in order?
G1, S, G2, M
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What is the G1 phase?
Gap 1 - When the cell is increasing in size and new proteins are made
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What is the S phase?
Synthesis - When DNA replicates itself
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What is the G2 phase?
Gap 2 - When the cell increases in size, producing new proteins and organelles
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What is the M phase?
Mitosis - The cell divides
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What name can be given to the cycle from G1 to G2?
Interphase
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What happens to ATP levels during the interphase?
Increases because the cell needs energy to divide
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In what process do prokaryotic cells replicate?
Binary fission
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What is step 1 of binary fission?
Circular DNA and plasmids replicate
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What is step 2 of binary fission?
The cell gets bigger and the circular DNA moves to opposite poles (sides) of the cell
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What is step 3 of binary fission?
Cytoplasm beings to divide - new cell wall formed
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What is step 4 of binary fission?
Cytoplasm totally divides, producing 2 daughter cells. Each daughter cell has one copy of the circular DNA but can have a variable number of plasmids, depending on how many there orginally were and how many times they replicated themselves.
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What are the stages of mitosis in order?
Interphase, Propahse, Metaphase, Anaphase, Telophase
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What is a good way to remember the order of mitotic stages?
I Pee More After Tea
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What happens during interphase?
The chromosomes are invisible and the cell is growing
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What happens during prophase?
Pairs. Chromosomes pair up and become visible as long noodle shapes. Nuclear membranes disintergrate.
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What happens during metaphase?
Middle. Chromosomes lie along the equator of the cell and become attached to spindles by their centromeres
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What happens during anaphase?
Apart. Chromosomes are pulled apart to opposite poles of the cell by the spindles, centromere first
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What happens during telophase?
Two. Two nuclei form at either end of the cell, around the chromosomes. The cell is ready to divide.
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What is the exact moment where a cell divides called?
Cytokineses
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How do you calculate mitotic index?
Number of cells undergoing mitosis (visible chromosomes)/total observed cells in FoV
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True or false, the number of chromosomes is constant throughout mitosis?
True
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True or false, the number of chromatids is constant throughout mitosis?
False
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How is cancer caused?
The rate of mitosis is too high
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What do cancer drugs aim to do?
Reduce the rate of mitosis
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How is cancer caused?
The rate of mitosis is too high
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What do cancer drugs aim to do?
Reduce the rate of mitosis
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What is the required practical for this unit?
A root tip squash
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How do you know which cells are undergoing mitosis when observing your prepared slide from the root tip squash?
The chromosomes are visible
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What do you use to stain the cells (and chromosomes) in a root tip squash?
Toluidine
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What colour is toluidine?
Blue
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Why is the root tip placed in 5M HCl acid for 15 minutes?
To kill the cells, freezing them in their current phase of mitosis
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What is maceration?
When the cell is mashed
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What can you use to macerate the cell?
A mounting needle
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Why is the root tip macerated and squashed with a coverslip?
So it is very thin to let as much light pass through as possible as we are using an optical microscope.
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