Topic 2.1 Eukaryotic Cells Flashcards
Fluid mosaic model
-Phospholipids
-Carrier proteins
-Channel proteins
-Peripheral proteins
-Glycoproteins
-Cholesterol
-Cytoskelaton
How do the hydrocarbon fatty acid tails contribute to the ‘fluidity’ of cell membrane?
-Fatty acid parts contain double bonds
-Therefore phospholipid molecules are loosely packed
-So its ‘fluid’.
How hydro properties determine the structure of the bilayer?
-Phosphate groups attracted to water and face outwards
-Fatty acid parts repelled by water and face inward
-Therefore phospholipids spontaneously form a stable bilayer in water.
Light microscope (optical)
Light passes through the specimen and on through the lenses to give an image that is magnified and upside down.
Magnification: 1500x life size.
Advantages and disadvantages of light microscopes
Advantages:
-Can see living plants and animals
-Relatively cheap
-Relatively light so easy to move
Disadvantages:
-Limited powers of resolution
Transmission electron microscope (TEM)
1) A beam of electrons passes through (thin slice of) specimen
2) More dense structures appear darker since they absorb more electrons
3) Focus image onto fluorescent screen or photographic plate using magnetic lenses.
Produces a 2D image.
Magnification: x 500,00
Resolution: 0.5 nm
Advantages and disadvantages of an electron microscope
Advantages:
-Huge powers of magnification and resolution, many details of cell structure have been seen for the first time
Disadvantages:
-Examined in a vacuum so tissues look fuzzy (impossible to look at living material)
-Extremely expensive
-Large and has to be kept at constant temperature.
Scanning electron microscope (SEM)
1) Focus a beam of electrons onto a specimen’s surface using electromagnetic lenses
2) Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate.
Produces a 3D image.
Magnification: x 500,000
Resolution: 3-10 nm
(Same advantages and disadvantages as TEM).
Function of a lysosome
-If organelles become worn out they need to be destroyed
-If they fuse with the outer cell membrane and release digestive enzymes to destroy the cell
-Releasing their digestive enzymes to destroy the entire contents of the cell; this is known as apoptosis
-Lysosomes also destroy bacteria and are self-destroying.
Reasons for apoptosis
-Worn out cell
-Mutation
-Defence mechanism
Extremities of apoptosis
Too much- neurodegenerative diseases (Alzheimer’s, Parkinson’s)
Too little- cancer, tumors
Ribosomes
-Translate mRNA into a polypeptide chain
-Found in both cells 70s + 80s
-Aren’t surrounded by a phospholipid bilayer
Smooth endoplasmic reticulum
Cisternae: network of tubules and flattened sacs extensors from cell membrane and connects to nuclear envelope.
-Involved in the synthesis of steroids, lipids and carbohydrates
-Converts toxins into less toxic compounds which can be excreted from the body
-Tubular passages
Rough endoplasmic reticulum
Cisternae: network of tubules and flattened sacs extensors from cell membrane and connects to nuclear envelope.
-Involved in protein synthesis; isolates and transports proteins made by the ribosomes
-Fold protein molecules into their final shape
-Flat passages joined to the nucleus
Golgi apparatus (body)
-Flattened membrane sacs with close link with rough ER
-Modifies and packages correct combinations of proteins, lipids and other chemicals, delivers them to area of the cell where they’re needed
-Eg. Some proteins have carbohydrates added to them to form glycoproteins such as mucus.
Vesicles
Small membrane bound package of materials within the cell
Transport vesicles:
Moves molecules between locations in the cell (eg. from rough ER to the Golgi body)
Secretory vesicles:
Excretes materials from the cell (eg. to release waste or release chemicals in a process known as exocytosis).
Vacuole
Surrounded by single phospholipid membrane called tonoplast.
Stores cell sap, which contains mineral ions, water, enzymes, soluble pigments.
Controls turgor pressure.
Absorbs and hydrolyses potentially harmful substances to detoxify cytoplasm.
Multicellular/unicellular
Unicellular:
-(mainly) protist
-fungi
-prokaryote
Multicellular:
-plant
-animal
-protist
-(mainly) fungi
Organelles role in the formation of enzymes
Rough ER- isolates and transports proteins
Vesicles- transports the proteins from the rough ER to the golgi body
Golgi body- packages the correct combinations of proteins and delivers to area of cell where needed and modifies.
What is the plasmodesmata?
The cytoplasmic connections between one plant cell and another.
State the principal of cell theory
Cells are fundamental structural units in all living organisms.
They determine the function and organism of biological systems.
Relationship between a system and specialised cells
Specialised cells –> tissue that perform specific function –> organs made of several tissue types –> organ systems
Structure of nucleus
Surrounded by nuclear envelope, a semi-permeable double membrane.
Nuclear pores allow substances to enter/exit.
Dense nucleolus made of RNA and proteins assembles ribosomes.
Structure of mitochondrion
Surrounded by double membrane folded inner membrane forms cristae: site of electron transport chain.
Fluid matrix: contains mitochondrial DNA , respiratory enzymes, lipids, proteins.
Structure of a chloroplast
-Vesicular plasmid wit double membranes
-Thylakoids: flattened discs stack to form grana; contain photosystems with chlorophyll.
-Intergranal lamellae: tubes attach thylakoids in adjacent grana
-Stroma: fluid-filled matrix
Structure of plant cell wall
-Made of cellulose microfibrils for mechanical support
-Plasmodesmata form part of app-last pathway to allow molecules to pass between cells
-Middle lamella separates adjacent cell walls
Structure and function of centrioles
Spherical group of 9 microtubules arranged in triples.
Located in centrosomes.
Migrate to opposite poles of cell during prophase and spindle fibres form between them.
Magnification definition
Factor by which the image is larger than the actual specimen.
Resolution definition
Smallest separation distance at which 2 separate structures can be distinguished from one another.
How to use an eyepiece graticule and stage micrometer to measure the size of a structure
1) Place micrometer on stage to calibrate eyepiece graticule.
2) Line up scales on graticule and micrometer. Count how many graticule divisions are 100μm on the micrometer.
3) Length of 1 eyepiece division= 100μm/number of divisions
4) Use calibrated values to calculate actual length of structures.
