Cell Structure :). Flashcards
What are eukaryotic cells made of?
Eukaryotic cells
What are eukaryotic cells?
Complex include all animals and plants
What are prokaryotic cells?
Small and simpler e.g bacteria
What is more complicated prokaryotic or eukaryotic?
Eukaryotics
Name organelles of animal cells?
Plasma membrane, RER, nucleus, SER, ribosome, lysosome, Golgi appartus, cytoplasm, microchrondria
Explain structure of nucleus?
Nucleolus wrapped in nucleus wrapped in nuclear envelope
What organelles do plant cells have compared to animals?
All the same organelles but with a few extra: the cell wall, vacuole, chloroplasts
What does cell wall have?
Plasmodesmata
Channels for exchanging substances with adjacent cells
Description of plasma membrane?
Found on surface of animal cells and just inside cell wall of plant cells and prokaryotic cells. Made mainly of lipids and protein.
Function of plasma membrane
Regulates movement of substances into and out of cell
Also has receptor molecules which allow it to respond to chemicals like hormones
Description of cell wall?
Rigid structure surrounds plant cells. Made mainly of the carbohydrate cellulose.
Function of cell wall?
Supports plant cells
Description of nucleus?
Large organelle surrounded by a double membrane nuclear envelope containing many pores. Nucleus contains chromatin and the nucleolus
Function of nucleus
Controls cell’s activities
Contains DNA to mind proteins
Pores to allow substances to move between nucleus and cytoplasm
Nucleolus makes ribosomes
Lysosome description
Round or handle surrounded by a membrane with no clear internal structure
Function lyposome
Contains digestive enzymes
Separate from cytoplasm by surrounding membrane and can be used to digest invading cells or break down worn out components of cell
Describe ribosome
Very small organelle that either gloats free in cytoplasm or is attached to RER
Made of protein and RNA not surrounded by membrane
Function of ribosomes?
Site where proteins made
What are prokaryotic organisms made of?
Prokaryotic cells
Rough endoplasmic reticulum describe
System of membranes enclosing a fluid filled space. Surface covered with ribosomes
Rough endoplasmic reticulum function
Folds and processes protein that have been made at the ribosomes
Smooth endoplasmic reticulum describe
Similar to rough endoplasmic reticulum but no ribosomes
Smooth endoplasmic reticulum function
Synthesises and processes lipids
Vesicle description
Small fluid-filled sac in cytoplasm surrounded by a membrane
Vesicle function
Transports substances in and out of cell via plasma membrane and between organelles. Some are formed by Golgi apparatus or endoplasmic reticulum while others are formed at the cell surface
Golgi apparatus describe
Group of fluid filler membrane-bound flattened sacs. Vesicles often seen at edges of sacs
Golgi apparatus function
Processes and packaged new lipids and proteins. Also makes lysosomes
Mitochondrion describe
Usually oval-shaped. Double membrane. Inner one folded into structures (cristae) inside is the matrix which contains enzymes involved in respiration
Mitochondrion function
Site of aerobic respiration where ATP is produced.
Found in large numbers in very active cells and cells requiring a lot of energy
Chloroplasts describe
Small, flattened structure found in plant cells.
Surrounded by double membrane and membrane inside (thylakoid membrane). These membranes are stacked up in some parts of chloroplasts to form grana. Grana linked together by lamellae
Lamellae are?
Thin flat pieces of thylakoid membrane
Chloroplasts function
Site of photosynthesis
Some parts of photosynthesis happen in grana
Other parts in the stroma
Stroma is?
Thick fluid found in chloroplasts
Centrioles describe?
Small, Hollow cylinders made of microtubules (tiny protein cylinders)
Found in animal and some plant cells
Centrioles function
Involved with separation of chromosomes during cell division
Cilia describe
Small hair like structures found on surface membrane of some animal cells
Cross-section have outer membrane and ring of nine pairs of protein microtubules inside with 2 microtubules in the middle
Cilia function
Microtubules allow cilia to move
Movement used by cell to move substances along cell surface
Flagella describe
on eukaryotic cells are like cilia but longer
Stick out from cell surface and surrounded by plasma membrane.
Inside like cilia too two microtubules in centre and nine pairs around the side
Flagella function
Microtubules contract to make flagellum move
Flagella used like outboard motors to propel cells forwards (sperm cells swims)
Where are proteins made?
At the Ribosomes
What do the ribosomes on the rough endoplasmic reticulum do?
Make proteins that excreted or attached to cell membrane
Free ribosomes in cytoplasm make proteins stay in cytoplasm
Where are new proteins produced?
At the rough endoplasmic reticulum and then they are folded and processed (e.gsugar chains added) in rough endoplasmic reticulum
Where are they transported to from RER?
Golgi apparatus in vesicles
What happens at Golgi appartus?
Proteins undergo further processing (sugar chains trimmed or more are added)
What do proteins do?
Enter more vesicles to be transported around cell e.g. Glycoprotein (found in mucus) move to cell surface and are secreted
What are organelles in cells surrounded by?
Cytoplasm
What is cytoplasm?
More than just solution of chemicals
Has networks of protein threads running through it
Protein threads are called?
Cytoskeleton
What are the protein threads in eukaryotic cells arranged as?
Microfilaments (small solid strands) and microtubules (tiny protein cylinders)
Cytoskeleton four main functions?
Support cell’s organelles, keeping them in position
Help strengthen cell and maintain its shape
Responsible for movement of materials within cell
Cause the cell to move
What Support cell’s organelles, keeping them in position
Microtubules and microfilaments
What Help strengthen cell and maintain its shape?
Microtubules and microfilaments
Give example of the cytoskeleton being Responsible for movement of materials within cell
The movement of chromosomes when separate during cell division depends on contractions of microtubules in spindle
Give example of Cause the cell to move?
Movement of cilia and flagella is caused by cytoskeletal protein filaments that run through them. So in cause of single cells that have flagellum (sperm) cytoskeleton propels whole cell
Why can microtubules and microfilaments be prevented from functioning using respiratory inhibitors?
Assembly of microtubules and microfilaments and movement of materials along then requires energy from respiration
Prokaryotic size
Extremely small cells
Less than 2 nanometers diameter
Eukaryotic size
Larger cells (about 10-100 nanometers diameter)
Prokaryotic DNA
Circular
Eukaryotic DNA?
Linear
Prokaryotic nucleus?
No nucleus DNA free in cytoplasm
Eukaryotic nucleus?
Present DNA inside nucleus
Prokaryotic cell wall?
Made of polysaccharide not cellulose or chitin
Eukaryotic cell wall
No cell in animals
Cellulose walk in plants
Chitin cell wall in fungi
Prokaryotic organelles?
Few organelles
No membrane-bound organelles (no Mitochondria)
Eukaryotic cells?
Many organelles
Microchrondria and other membrane-bound organelles present
Prokaryotic flagellum?
When present made of protein flagellum arranged in helix
Eukaryotic flagellum?
When present made of microtubules proteins arranged in “9+2” formation
Prokaryotes ribosome?
Small
Eukaryotic ribosomes?
Larger ribosomes
Prokaryotic example
E.coli bacterium
Eukaryotic example
Human liver cell
Prokaryotes like bacteria rough size?
Tenth of the size of eukaryotic cells
Can a light microscope really see a prokaryotic bacteria?
No
Define magnification
How much bigger the image is than the specimen you’re looking at
Formula to get magnification
Magnification= image size /object size
Resolution is
How detailed the image is
More specially how well a microscope lens can’t separate two objects increasing magnification won’t help
Light microscope
Uses light Lower resolution than electron microscope Maximum resolution 0.2 micrometres Used to look at whole cells/ tissues Maximum useful magnification about x1500
Laser scanning confocal microscope is?
Special type of light microscope
Laser scanning confocal microscope uses what
Uses laser beams (intense beams of light) to scan specimen which is usually tagged with fluorescent dye
What do lasers do Laser scanning confocal microscope
Lasers causes dye to fluoresce. Light focused through pinhole onto detector. Detector hooked up to computer which generates image (can be 3D)
Pinhole Laser scanning confocal microscope means?
Any out-of focus light is blocked so microscopes give clearer image than normal light microscope
Laser scanning confocal microscope used to look at?
Different depths in thick specimen
Electron microscopes?
Use electrons to form image
Higher resolution than light microscope to give more detailed images
Two types: TEM, SEM
Transmission electron microscope uses?
Electromagnets to focus a beam of electrons which is transmitted through specimen
TEM denser parts of specimen
Absorb more electrons making them look darker on the image you end up with
Why are TEM’s good?
High resolution image (so can be used to look at range of organelles) but they can only be used on thin specimens.
Scanning electron microscopes do what?
Scan beam of electrons across specimen knocking off electrons from specimen gathered in cathode ray tube to form an image
Images of Scanning electron microscopes
Show surface of specimen and can be 3D
Give Lower resolution than TEMs
What affects how specimen appear
The angle they are cut at
Light microscope max resolution
0.2 micrometers
Light microscopes max magnification
x1500
TEM max resolution
0.0002 micrometers
TEM max magnification
Can be more than X1,000,000
SEM max resolution
0.002 micrometers
SEM max magnification
Usually less than x500,000
What happens as a result of light microscope or TEM’s the beam of light or electrons pass through the objects being viewed?
An image of produced because some parts of the object absorb more light or electrons than others
What happens if the object being viewed is completely transparent?
It makes the whole thing look white because light rays or electrons just pass straight through
This has to be stained
Staining for light microscopes how
Means using some type of dye
Stain taken up by some parts of object more than others- contrast makes different parts show up
Common stains for light microscopes
Methylene blue and eosin
What are different stains used for?
To make different parts show up
E.g. Eosin used to stain cell cytoplasm
Methylene blue stains DNA
How many stains can be used at once
More than one
Staining samples for electron microscopes
For electron microscopes, objects dipped in solution of heavy metal like lead
Metal ions scatter electron creating contrast- some parts of object show up darker than others
Colourful electron microscope images??
Black and white even with stain. Artificial colour added after image has been made
What’s a slide used for?
If you want to look at specimen under light microscope you need to stick it on a slide first
Slide is
Strip of clear glass or plastic. Slides usually flat but some of them have small dip or well in centre useful if specimens particularly big or a liquid.
Dry mount preparation of slide
Specimen needs to let light through to see it clearly under microscope do if you have a thick specimen take a thin slice to use for slide
Use tweezers to pick up specimen and put in middle of clean slide
Pop on cover slip on top
Wet mount preparation of slide
Start pipetting small drop of water onto slide. Use tweezers to place specimen on top of water drop. Put cover slip on, stand slip upright on slide next to water droplet. Carefully tilt and lower it so covers specimen. Try not to get any air bubbles under there. Once cover slip in position add stain.
How to add stain in wet mount
Put drop of stain next one edge of cover slip then put bit of paper towel next to opposite edge. Stain will get under slip across specimen
Why is it bad to get air bubbles in wet mount?
Will obstruct your view of specimen
What are wet mounts good for?
Looking at tiny organisms that live in water
How to use microscope 1
Start clipping slide containing specimen you want onto stage
How to use microscope 2
Select lowest- powered objective lens (one producing the lowest magnification)
How to use microscope 3
Use coarse adjustment knob to move objective lens down to above slide
How to use microscope 4
Look down eyepiece (containing ocular lens) adjust the focus with fine adjustment knob, until you get a clear image of whatever’s on the slide
How to use microscope 5
If you need to see the slide with greater magnification swap to higher-powered objective lens and refocus
What to remember if draw what’s seen under microscope?
Make sure you write down magnification under which specimen was viewed. You’ll need to laced your drawing
When you would you use eyepiece graticule and stage micrometer?
You might want to know the size of your specimen
They are a bit like a rulers
Explain eyepiece graticule?
Fitted onto eyepiece
Like transparent ruler with numbers but no units
Stage micrometer?
Placed on stage
Microscope slide with accurate scale (has units) and used to work out value of division on eyepiece graticule at particular magnification
How can you measure the size of the specimen
Take stage micrometer away and replace with slide containing specimen
Example of eyepiece graticule
Line up eyepiece graticule and stage micrometer
Each division on stage microscope 0.1mm long
At magnification 1 division on stage microscope same as 4.5 divisions on eyepiece graticule
Work out size of 1 division on eyepiece graticule divide 0.1 by 4.5
0.22mm
So look at object under microscope at magnification and 20 eyepiece division long
At different what will divisions will be different at?
Magnifications so eyepiece graticule so eyepiece graticule needs to be recalibrate do
