1. Cells and Cell Techniques Flashcards
What do all Cells Contain?
- Plasma Cell Surface Membrane
- Genetic Material
- Cytoplasm
Prokaryotes e.g
Bacteria
Eukaryotes e.g
Cells found in:
- Plants
- Animals
- Fungi
- Algae
That HAVE INTERNAL MEMBRANES, forming organelles
What are Organelles?
“little organ”
Small subcellular structure that has a specific function
Billions of years ago the first organelles were__ .
They are much smaller than _____ cells and do not contain any _________ organelles in their cytoplasm
- Prokaryotes
- Eukaryotes
- Membrane-Bound
How do prokaryotes form new cells?
Binary Fission
What is the structure of Prokaryotes?
(Different Parts)
- DNA + Plasmid DNA
- Cytoplasm
- Small 70s Ribosomes
- Cell Surface Membrane + Cell Wall + Capsule
- Flagellum
Definition of DNA + Plasmids?
(Pro)
DNA:
Definition: Short circular molecules of DNA, not associated with protein and free in cytoplasm
Function: Carries Genetic Code for Protein
Plasmids:
Defintion: One or more loops of DNA, away from main circular DNA, that can replicate independently
Function: Can exchange/pass on genetic info to other bacteria to gain favourable characteristics via CONJUGATION e.g Antibiotic Resistance for Bacteria
Definition of Cytoplasm + 70s Ribosomes
(Pro)
Cytoplasm:
Definition: solution where many dissolved substances are found, no membrane bound organelles for prokaryotes
Function: Site of Metabolic Reactions
Ribosomes (70s):
Definition: small structures in cytoplasm 70s
Function: Protein Synthesis
Definition of Cell Membrane + Cell Wall
(Pro)
Cell Membrane :
Definition: Phospholid bilayer containing embedded proteins
Function: Controls passage of substances across exchange surfaces by passive or active transport
Cell Wall:
Definiton/Function: Murein (glycoprotein) wall, preventing osmotic lysis and rigidly strengthens and supports the cell
Capsule + Flagellum Definiton/Function:
(Pro)
Capsule:
Definition: Extra Layer outside cell wall
Function: protects against:
-desiccation
- phagocytosis
- some pathogens
Flagellum:
Definition: thin rotating fibre
Function: allows movement of cell
Which of the Prokaryote structures aren’t found in Eukaryotes?
-DNA/Plasmids as there is DNA in Eukaryotes but surrounded by membranes in a nucleus
-Flagellum
-Capsule
Eukaryotes has ____ features than prokaryotes, providing indirect ______ of ______
1.More
2. Evidence
3. Evolution
What is the benefit of membrane-bound compartments (Eukaryotes)?
- Compartmentalisation allows different reactions to occur at different conditions which is more efficient
How do Eukaryotes form new Cells?
Mitosis
Meiosis
Organelles of Eukaryotes: (Plasma Membrane) -
Definition: Phospholid bilayer with embedded proteins that’s found on cell surface and MOST internal organelles
Function: Selectively Permeable allowing entry and exit of substances across exchange surfaces depending on cells needs and conditions surrounding cells
Nucleus
(Eu)
Defintion: Contains long chromosomes of linear DNA, associated with histones (PROTEIN), surrounded with a nuclear envelope (double membrane), nuclear pores and nucleoli
Function:
- Contains genetic code for making protein
- Nucleolus manufactures ribosomes
Mitochondria
(EU)
Defintion: Oval shaped organelle, with 2 membranes; the inner folded into cristae.
Contain Matrix (fluid containing ions enzymes and metabolic products which also contains circular DNA like prokaryotes)
Function: Produces ATP from aerobic respiration (energy store used by cells for processes e.g active transport and proteinsynthesis)
Rough Endoplasmic Reticulum
Definition: series of tubes in the cytoplasm with “rough” due to the ribosomes attached
Function: synthesis, modification and transport of protein in the cell
Why is the inner membrane of Mitochondria folded into cristae?
+++++ surface area to allow more exhange of gases for more respiration
Smooth Endoplasmic Reticulum
Definition: Series of tubes in the cytoplasm of cell with NO RIBOSOMES
Function: synthesises and transports lipids
Ribosomes
(Eu)
Small Organelle made from RNA and protein, not membrane bound and 80s (larger than prokaryotes)
Golgi Body
Definition: Stack of flattened sacs with Vesicles budding off the ends of the sacs
Function:
1.Modification of proteins that ae made in the cell into useful proteins by folding and adding other substances onto it (converting proteins into glycoproteins)
2. Packages proteins into Vesicles ready for export from the cell
3. Vesicles form Lysosomes
Lysosomes
Made in the Golgi Vesicles, containing hydrolytic enzymes that digest unwanted material in the cell, e.g unwanted organelle and pathogens
Cytoplasm
Solution where many dissolved substances are found, and is the site of many metabolic reactions, including anaerobic respiration
Plant Cell Differences
- Large Vacuole
- Cell Wall
- Chloroplast
Definitions of Plant Cell: (Cell Wall)
Made of CELLULOSE, (so is algae cell walls), providing high tensile strength preventing osmotic lysis
What are fungi cell walls made from?
Chitin
Vacuole
Filled with Cell Sap - giving rigidity
Chloroplast
Site of Photosynthesis
What cells are Chloroplasts found in?
Plant + Algal Cells
In Green plants in the mesophyll layer
What are the 5 structures in a chloroplast?
- Envelope
- Granum
- Stroma + Starch Grains
- DNA
- Ribosomes
Envelope (Chloroplast)
Double membrane surround chloroplasts
Granum (Chloroplast)
Stack of membrane bound discs called “thylakoids”:
- membranes of the thylakoids contains chlorophyll
- membranes have large S.A for light absorption which maximises rate of photosynthesis
Stroma (Chloroplast)
Fluid like solution, containing enzymes needed for photosynthesis and stores starch grains
DNA (Chloroplast)
short circular non-protein associated DNA (like prokaryotes) that contains genetic code for protein
Ribosomes (Chloroplast)
70s, synthesises proteins for enzymes needed for photosynthesis
In complex _______ organisms, eukaryotic cells may become _____, for specific functions.
- multicellular
- specialise/differentiate
Tissue Definition
Group of similar cells e.g muscle cells
Organ Definition
Group of tissues e.g heart
Organ System Definition
Group of interacting interdependent and interrelated organs forming a whole. e.g circulatory system
Are Viruses Cells?
No, they are ACELLULAR
Can Viruses undergo cell divison?
No, because they ain’t cells
How do Viruses replicate?
They attach and enter host cells and us the hosts machinery to replicate
How many and what components does a Virus consist of?
- Genetic Material: DNA or RNA
- Capsid: protein coat
- Attachment Protein: allows virus to attach to host cell, (complementary to receptors on host cells membrane)
2 Types of Microscope
- Optical
- Electron
2 types of Electron Microscope
- transmission electron microscope
- scanning electron microscope
Define Magnification
Number of times bigger the image appears compared to actual size
Define Resolution
Minimum distance between two objects at which they can be seen as separate
Resolution of Optical Microscope is determined by __________-
wavelength of light
Resolution of Electron Microscope is determined by ____________________
the wavelength of the BEAM of electrons
How do Optical Microscopes work?
Use “light” to “illuminate the specimen”, whilst using the “glass lenses” to focus the light
What are the two lenses that determine the magnification of Optical Microscopes?
- eyepiece lens (fixed mag.)
- objective lens (usually has multiple options of which different mags.)
Why must the Specimen be thin for an Optical Microscope?
- specimens must be thin as they need light to be transmitted (pass through), e.g. ideally around one cell thick for tissues
Does Optical Microscopes have High or Low Resolution, and why?
- low resolution
–> since light has a long wavelength
Maximum Magnification of Optical?
1500x
Optical Microscopes are powerful enough to see:
-cells
-larger organelles
-individual bacteria
Optical Microscopes aren’t powerful enough to see:
-smaller structures
-internal detail
Total Magnification = ?
Objective Lens Mag. x Eyepiece Lens Mag.
How do Electron Microscopes Work?
-uses beams of electrons, which are then focussed through electromagnets
Do Electron Microscopes have High or Low resolution and why?
-High
–> Electrons have a short wavelength
Highest Magnification of Electron?
500,000x
Optical Microscope VS Electron Microscoe
-»>
How do they work?
Optical + Electron Mc
Optical: uses light to illuminate specimen, followed by glass lenses to focus the light
Electron: uses beams of electrons, which are then focussed using electromagnets
Resolution? Optical VS Electron
Electron Res> Optical Res
Mag? Optical VS Electron
Electron: 500,000x
Optical: 1500x
Colour or B & W
Optical VS Electron
Electron: B & W no light absorbed
Optical: Colour
Optical Microscopes can view ____ samples, but in Electron Microscopes they must be _____-
1.Live
2.Dead
Optical Microscopes have ____ set-ups for the specimen, but Electron Microscopes have _____ set-ups
1.Easy
2. Difficult
Why do Electron Microscopes need to be Vacuumed?
Electrons would be absorbed by air, which means they wouldn’t reach the sample to produce an image
Why are Electron Microscopes B & W?
Only electrons no light waves used
How do TEMs work?
-the beam of electrons are transmitted (passed through) the specimen:
-some electrons are absorbed by the specimen and some are passed through, the more electrons absorbed the more the are appears dark in the image
Why does the specimen need to be thin in Electron Microscopes?
-so the electrons can be transmitted (pass through)
TEMs have a very ____ resolution, which means more ___ of smaller ______ and internal details such as ______
1.high
2.detail
3.organelles
4.cristae
Are TEMs 2D or 3D?
2D
How do SEMs work?
- beam of electrons onto the surface of sample, and are reflected and scattered depending on contours
Are SEMs 3D?
Yes
Does SEM show internal structures or surface?
Surface of object
Why aren’t SEMs samples always thin?
They don’t need to be as there isn’t transmission
What is an “Artefact”?
Something that results from the way a specimen is prepared, which could appear on micrograph without being apart of the natural specimen, e.g airbubble
Conversions:
Meters (M) (1 x 10^0) –> Millimetres (MM) (1 x 10^-3) –> Micrometres (μm) (1 x 10^-6) –> Nanometres (NM) (1 x 10^-9)
Image Size = ?
Actual Size x Magnification
You should always measure in _______
Millimetres (MM)
When estimating you cannot us the _______ Formula
I = AM
When viewing cells using an optical microscope, it is possible to ________ their size
- Estimate
FOV Estimate Explanation
- Measure diameter of your FOV using a stage micrometer (slide with scale on) or a transparent ruler.
- Estimate the proportion of one cell
e.g. FOV- A sample of muscle tissue was observed by an optical microscope. The diameter was 0.2mm.
A group of 3 fibres occupied approximately 75% of the FOV, estimate the diameter of one fibre.
Full Diameter = 0.2mm
3 fibres occupy 75%: 3/4
therefore 1 fibre =
1/4 x 0.2mm = 0.05mm
Eyepiece Graticule explanation.
- The eyepiece graticule scale is first calibrated against a stage micrometer scale (of known length).
- This allows you to work out the length that each eyepiece graticule division represents at a particular magnification
- This can then be used to measure an object under the microscope
Why is cell fractionation and ultracentrifugation required?
-EM’s shows us detailed structures of cells and organelles however it doesn’t help us understand information about its structure
What is Cell Fractionation?
-Cells are broken open using a homogeniser, breaking cell membranes (cell-surface membranes, NOT ORGANELLE MEMBRANES
-Cell Debris (e.g large bits of cell walls/membranes) and whole cells are filtered off to leave a suspension
What is a Suspension?
mixture of all organelles
What is Ultracentrifugation?
-resultant suspension is centrifuged at a low speed
-the most dense organelle, the nucleus, separated at the bottom of the tube
-the rest of the organelles are still suspended in the supernatant (solution with the suspension)
-supernatent is poured into a fresh tube and spun at a higher speed to separate off the mitochondria (next dense)
- in Plant Cells the Chloroplast separated before mitochondria as it is more dense
-this process is repeated at progressively increasing speeds to separate the less dense organelles
Why would the ribosome need a high-speed centrifugation?
Very less dense
_______ during the separation need to be controlled to prevent damage to organelles
-Conditions
Why do conditions need to be controlled?
-to prevent damage to organelles, since if they are damaged it could give false data
What are the 3 conditions that need to be controlled?
-cold temp
-buffer
-isotonic
Cold Temp
-reduces enzyme activity
-which prevents digestion of organelle
Buffer
-maintains constant pH
-which prevent denaturation of enzymes (which prevents false data)
Isotonic
-same water potential as organelle to prevent ‘osmotic lysis’ of organelle or shrinking
