B3 Cell Structure Flashcards
What are the two domains into which all organisms are divided?
Eukaryotes and prokaryotes.
What distinguishes eukaryotic cells from prokaryotic cells?
Eukaryotic cells contain a nucleus and other membrane-bound organelles, while prokaryotic cells do not.
What is the function of the nucleus?
Contains DNA, controlling cell activities by containing instructions to make proteins.
What is chromatin?
DNA associated with histone proteins.
What is the function of the nucleolus?
Ribosome production.
What is the nuclear envelope?
A double membrane surrounding the nucleus with pores.
What is the role of RER?
Folds and processes proteins synthesised in the ribosomes and transport to Golgi apparatus via vesicle
What is synthesized in the smooth endoplasmic reticulum (SER)?
Lipids, including cholesterol and steroid hormones.
What is the function of the Golgi apparatus?
Modifies and repackages proteins and lipids into vesicles; site of lysosome synthesis.
What is the function of ribosomes?
Translation of RNA into protein (protein synthesis).
What is the function of mitochondria?
ATP is released during aerobic respiration.
What are cristae?
Folds in the inner membrane of mitochondria.
What is the function of lysosomes?
Contain digestive enzymes to destroy old organelles or foreign material which are engulfed by the lysosome
What is the function of chloroplasts?
The site of photosynthesis.
What is the plasma membrane made of in eukaryotic cells?
A phospholipid bilayer with proteins and cholesterol.
What is the function of the plasma membrane?
Controls the movement of substances into and out of the cell.
What is the role of centrioles?
Formation of spindle fibers during mitosis and formation of cilia and flagella.
What is the function of the cell wall?
Provides support to the cell.
What is the cell wall made of in plants, fungi and prokaryotes?
Cellulose, chitin, and murein, respectively.
What is the function of flagella?
Propel the cell forward.
What is the function of cilia?
Sweep mucus up the windpipe (in epithelial cells lining the trachea).
What is the function of a vacuole?
Stores cell sap, nutrients, and proteins; helps keep plant cells turgid and rigid by maintaining the cells pressure
What are plasmodesmata?
Channels between plant cells that enable communication.
What is a tissue?
A group of specialised cells working together to perform a function
What is an organ?
A collection of tissues performing a specific function.
What is an organ system?
Multiple organs connected together.
What type of tissue forms capillary walls?
Endothelium.
Name three differences between eukaryotic and prokaryotic cells.
Eukaryotes have membrane organelles, prokaryotes lack membrane-bound organelles
Eukaryotes have linear DNA whilst prokaryotes have circular DNA
Prokaryotes have smaller ribosomes (70S).
What are plasmids?
Small circular rings of DNA in prokaryotes.
What is murein?
A type of glycoprotein that makes up bacterial cell walls.
What is the slime capsule in bacteria?
A capsule that protects bacteria against an immune system attack.
How do bacteria replicate?
Binary fission.
What is the function of the viral capsid?
A protein coat surrounding the nucleic acid (DNA or RNA) and enzymes.
How do viruses infect host cells?
Viruses use their attachment proteins to bind to complementary receptor proteins on the surface of host cells
They then inject their genetic material/ nucleic acids into the host cell
Then host cells ribosomes will replicate the viral particles as the host cells machinery is hijacked
How do prokaryotic cells replicate via binary fission
Circular DNA replicate ( plasmids can replicate as many times as they want )
Cell expands in size and the circular DNA loops move to opposite poles of the cell
Cytoplasm begins to divide
2 daughter cells produced
Magnification Definition
How much bigger the image is than the specimen
Resolution Definition
How well a microscope can distinguish between 2 points that are close together
Magnification Equation
Image size
—————
Size of real object
How do light microscopes work and all about them
They use light to form an image
Only larger organelles can be viewed like ribosomes ER and lysosomes
Low resolution Low magnification
Electron microscopes in comparison to light
Electron microscopes have a higher resolution and higher magnification so give a more detailed image
How do TEMS work
Use electromagnets to focus a beam of electrons which are then transmitted through the specimen
This allows denser parts of the specimen to absorb more electrons so appear darker
+ and - of TEMS
High resolution
Can view internal structure of organelles
Only used on thin specimens
How do SEMs work
Scan a beam of electrons across the specimen which knocks off electrons from the specimen. These are gathered in a cathode ray tube to form an image
+ and - of SEMS
3D
Can be used on thick specimens
Give lower resolutions
How to view specimens using an optical microscope
Pipette small drop of water onto the slide
Place a thin section of specimen on slide using tweezers
Add a drop of stain
Add the cover slip by tilting the slip and slowly lowering it to prevent air bubbles from forming
Cell fractionation Steps
Grind the cells in a blender for homogenisation.
Solution must be kept in a cold isotonic buffer solution
Filter large debris out
Ultracentrifugation by placing solution in a centrifuge and spin at a low speed.
Take tube out and filter out the supernatant.
Place supernatant in another tube and spin in centrifuge at a higher speed
Why cant we see structure of granules with an optical light microscope
Lower resolution
So wavelength of light is too long
