Cell Structure And Division Flashcards
Function of a Cell wall in Plants and Fungi
Function: Provides cell with protection to withstand hydrostatic pressure and permeability to allow osmosis of water molecules
Characteristics of cell wall in Plants and Algae
Plants-made of microfibrils of cellulose polymer(the monomer is polysaccaride)
Fungi-made of chitin(nitrogen containing polysaccharide)
Functions of the Golgi Apparatus?
Add carbohydrates to proteins to make glycoprotein
Transports,modifies and stores lipids
Secretes carbohydrates
Forms lysosomes
What is Plasmodesmata?
Specialised channels in the wall of 2 connecting plant cells which allow communication and transport of materials
Structure of chloroplasts and organelles?
Has own DNA and ribosomes to easily manufacture proteins
Has a chloroplast envelope
Thylakoids contains chlorophyll
Membranes= large SA for attachment of chlorophyll
Function and structure of Mitochondria
Double membrane
Cristae- extensions of inner membrane providing large SA for enzymes for proteins
Site of AR and where ATP is made
Vacuole function and structure?
Fluid filled sac bounded by one membrane called a tonoplast
Contains solution of mineral salts
Makes cells turgid and provide protection
Stores sugars and amino acids
What is a nuclear envelope
A double membrane surrounding the nucleus,continuous with endoplasmic reticulum.
Ribosomes on surface
What is nucleolus?
Small sphere in nucleus which is the site of rRNA production and makes ribosomes
Nucleus function?
Site of DNA replication and transcription
Contains genetic code for making each cell
Contains genetic material
Contains pores to allow RNA to move between nucleus and cytoplasm
What is the Rough endoplasmic Reticulum?
Contains folded membranes called cisternae
Has proteins on outer surface
Where protein synthesis occurs
Provides a large SA for proteins and glycoprotein
Provide a pathway for transport of materials
What is the Smooth endoplasmic reticulum?
Synthesis and storage of carbohydrates and lipids
Contains lots of tubules which increases SA for storage of key enzymes
What are lysosomes and function?
Bags of different enzymes(contains lysozymes)
Hydrolyse phagocytic cells
Autolysis-break down cells
Exocytosis-release enzymes to outside of cells to destroy material
Digest worn out organelles for reuse
Fuse with the vesicle
What is the plasma membrane?
Found in all cells
Controls the exit and entrance of molecules
Phospholipid layer-molecules embed within and attach on the outside
What is binary fission?
Method of cell division by prokaryotes involving replication of circular DNA and plasmids
What is the cytoskeleton?
Protein filaments in cells helping to maintain its shape and structure
What are viruses?
They are acellular,non living particles
Size:20 to 300nm
Characteristics of Viruses?
Contains DNA or RNA
Can only multiply through a host cell
Capsid-protein coat protecting DNA
Lipid envelope-surrounds capsid
Attachment proteins-allow virus to attach to host cell
Function of Ribosomes?
Where protein synthesis occurs
70s-small ribosomes found in eukaryotic cells
80s-found in eukaryotic cells
What is cell fractionation?
A technique to separate out the different components/organelles of the cell
What is homogenisation?
Cells are broken up by a homogeniser(to break organelles)
Stage 1 of Cell Fractionation?
Place in cold temperature-to reduce enzyme activity that could damage and cause enzymes to denature and to prevent digestion
Isotonic-so cells do not burst or shrivel by osmosis to prevent lysis
Buffered-to maintain constant pH and prevent damage
Stage 2 of Cell Fractionation?
Is Homogenisation-add tissue into a test tube and use a homogeniser to break organelles
Stage 3 of cell Fractionation?
The homogenate is FILTERED to remove any insoluble material such as cell walls and connective tissue
Stage 4 of Cell Fractionation
Ultracentrifugation:
The filtrate is placed in a centrifuge and spun at a low speed
This causes large organelles to be collected at the bottom of the tube
The fluid at the top(supernatant)and large organelle is removed
Repeat process at higher speeds to get smaller organelles
Compare DNA and mRNA
DNA is double stranded but RNA is single stranded,DNA is longer
DNA has non coding sequences but RNA does not
What is magnification?
How many times larger image size is compared to object size
What is resolution?
Minimum distance between 2 objects at which a microscope can distinguish them as separate entities
Light Microscopes characteristics?
Radiation:Light
Max resolution:200nm
Max Mag:1500x
Benefits and costs of Light microscope?
Cheap
Low mag
Poor resolution
Colour images
Can view living samples
What is the Laser Scanning Microscope?
Radiation:Laser
Resolution:20nm
Mag:1500x
Image:3D
What is a TEM and characteristics?
Radiation:Beam of electrons
Focused by: Magnets
Mag: 100000x
Resolution:0.5nm
A live specimen cannot be used as its placed in a vacuum
Image:2D
What’s an SEM and characteristics?
Radiation:Electrons
Radiation focused by:Magnets
Mag:200000x
Resolution:0.2nm
Cannot be used to view a live specimen
Image:3D
What is the Centrosome and functions?
A microtubule organising centres of eukaryotic cells
Contains 2 centrioles
Involved in creating and extending microtubules that contribute to the cytoskeleton
Involved in the formation of mitotic fibres
What is the centrioles?
Cylindrical microtubule
Forms flagella and cilia
Involved in the formation of mitotic spindle during cell division
What is the eyepiece graticule and its function?
Small piece of glass with a measurement scale on surface inside microscope eyepiece
This allows for precise measurements and analysis of microscopic measurements
What is the eyepiece graticule and its function?
Small piece of glass with a measurement scale on surface inside microscope eyepiece
This allows for precise measurements and analysis of microscopic measurements
Explain why some organisms cannot be viewed with an optical microscope(2)
Requires a greater resolution
Because wavelength of light is too long
Explain why biologists use a blender and then filter(2)
Breaks open cells and produces a homogenate
Remove unbroken cells and larger debris
Describe how to mount a piece of plant tissue to observe starch grains?(4)
Add drop of water to slide
Place thin section on slide
Add iodine
Lower coverslip at an angle
What are prokaryotes?
Single celled organisms with no nucleus
What are eukaryotes?
Complex multicellular organisms with a nucleus
Explain the Principles and limitations of TEM
Principles:
Electrons enter through thin specimen
Denser parts absorb more electrons
Electrons have a short wavelength giving it a high resolution
Limitations:
Thin specimen required
Only 2D images
Cannot view living cells
