2.1 cell structure definitions Flashcards
Centrioles
Hollow cylinder structures found in the cytoplasm containing a ring of microtubules arranged at right angles to each other that produce spindle fibres during mitosis
Chloroplasts
Organelles found in plants and algae that are the site of photosynthesis. Contain their own DNA and ribosomes so can make their own protiens
Cilia
Small hair-like structures that project from the surface of cells made of 9 + 2 arrangement of microtubules.
Laser Confocal microscopy
A type of microscopy that uses lasers to scan a specimen point by point to produce an image
Cytoskeleton
A mesh of protein fibres found in the cytoplasm of eukaryotic cells providing mechanical strength/ support as well as aiding transport within cells (intracellular transport) and enabling cell movement
Differential staining
Using multiple different stains to distinguish different parts of a specimen.
Eukaryotic cell
A type of cell that contains a nucleus along with membrane bound organelles.
Flagella
A whip-like structure found on bacterial cells that is used for cell movement.
Golgi apparatus
An organelle found in eukaryotic cells that is involved in the modification and packaging of proteins and lipids. It is a fluid filled, flattened & curved sacs with vesicles surrounding the edges. It also produces lysosomes.
Light microscope
A type of microscope that uses a series of lenses to magnify the visible light reflecting off a specimen
Lysosomes
Membrane-bound vesicles found in the cytoplasm that contains a hydrolytic (digestive) enzyme called lysozyme
Magnification
How much bigger an image appears compared to the original object.
Mag = image/actual
Mitochondrion
An organelle found in eukaryotic cells it is oval shaped, bound by a double membrane called the envelope. The inner membrane is folded to form projections called cristae with matrix on the inside containing all the enzymes needed for aerobic respiration
Nuclear envelope
A double membrane that surrounds the nucleus
Nucleolus
A structure found inside the nucleus that contains proteins and RNA and is involved in synthesizing new ribosomes
Nucleus
Found in eukaryotic cells. stores the genetic information of the cell as chromosomes and is surrounded by a double membrane called the nuclear envelope. contains pores which allow molecules to enter and leave the nucleus. also contains nucleolus and chromatin
Plasma membrane
A semipermeable lipid bilayer studded with proteins that surrounds the cell and many organelles.
Prokaryotic cell
A unicellular that does not contain any membrane bound organelles or a nucleus but do contain DNA
Resolution
The ability to distinguish two different points in a specimen
Ribosomes
Organelles found either free in the cytoplasm or membrane bound to the RER that are the site of protein production. composed of two sub units. Found in both prokaryotes and eukaryotes (70s in prokaryotes and 80s in eukaryotes)
Rough endoplasmic reticulum (RER)
A membrane-bound organelle that is involved in the synthesis and packaging of proteins by folding and processing them. It is a series of flattened sacs enclosed by a membrane with ribosomes on the surface.
Scanning electron microscope (SEM)
A type of microscope that passes a beam of electrons over the surface of a specimen to produce an image
Smooth endoplasmic reticulum (SER)
A system of membrane-bound sacs. an organelle involved in lipid synthesis.
Transmission electron microscope (TEM)
A type of microscope that passes a beam of electrons through a sample to produce an image.
cell wall (prokaryote)
Rigid outer covering made of peptidoglycan
Capsule (prokaryote)
Protective slimy layer which helps the cell to retain moisture and adhere to surfaces
Plasmid DNA (prokaryotes)
Circular loop of DNA
Flagellum (prokaryotes)
a tail like structure which rotates to move the cell made of 9+2 microtubules
Pili (prokaryotes)
Hair-like structures which attach to other bacterial cells
Transport of proteins (6-9 marks)
Proteins are synthesised on the ribosomes bound to the endoplasmic reticulum (1).
They then pass into its cisternae and are packaged into transport vesicles (2).
Vesicles containing the newly synthesised proteins move towards the Golgi apparatus via the transport function of the cytoskeleton (vesicles)(3,4).
The vesicles fuse with the cis face of the Golgi apparatus and the proteins enter.(5)
The proteins are structurally modified before leaving the Golgi apparatus in vesicles from its trans face (6).
Secretory vesicles carry proteins that are to be released from the cell. (7)
The vesicles move towards and fuse with the cell-surface membrane, releasing their contents by exocytosis.(8)
Some vesicles form lysosomes these contain enzymes for use in the cell (9)
Outline how a student could prepare a temporary mount of tissue for a light microscope
1) slice thin section of tissue using ultratome or by maceration
2) place plant tissue in a drop of water
3) stain using iodine (or equivalent) to make structures visible
4) add cover slip at 45degrees ensuring not to trap air bubbles. (mounted needle could be used for this)
Describe how a light microscope works
1) lenses focus rays of light and magnify the view of a thinly sliced specimen
2) different structures absorb different amounts and wavelengths of light
3) reflected light is transmitted to the observer via the objective lens and eyepiece
Describe how a transmission electron microscope (TEM) works
1) high energy beams of electrons are fired and pass through the thin sliced specimen
2) more dense structures seem darker as they absorb more electrons
3) focus image onto fluorescent screen or photographic plate using magnetic lenses
Describe how a scanning electron microscope (SEM) works
1) focus a beam of electrons onto a specimens surface using electromagnetic lenses
2) reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate
Describe how a laser scanning confocal microscope works
1) focus a laser beam onto a small area of a sample’s surface using objective lenses
2) fluorophores (fluorescent chemical compound) in the sample emit photons
3) photomultiplier tube amplifies the signal onto a detector where the image is then produced pixel by pixel in the correct order
Rules when doing a biological drawing
Sharp pencil no sketching lines/shading include scale bar annotate visible structure use a ruler for lines no arrow heads Use more than 50% of the paper given Ensure correct proportions Label lines should no cross Label lines should be parallel to the top of the page
why do samples need to be stained for light microscopes
coloured dye binds to cell structures
facilitates absorbtion of wavelengths of light to produce an image
differerntial staining: contrast between heavy and lightly stained areas to distinguish structures
State the mag and res of a compound optical microscope
mag x2000
res 200nm
state the mag and res of a TEM
mag x500,000
res 0.5nm
state the mag and res of a SEM
mag x500,000
res 3-10nm
How do you calculate a graticule division
Number of eyepiece divisions / number of micrometres
Permanent Vacuole (plant cells)
Membrane lined sacs in the cytoplasm containing cell sap. Maintain turgor pressure and Ridgid structure
Tonoplast
Membrane of a vacuole in a plant cell that is selectively permeable allowing small molecules to pass
Stroma
Fluid enclosed in a chloroplast
Thylakoids
Internal network of membranes which form flattened sacs
Granum
Several thylakoids stacked together joined together by lamellae. They contain the chlorophyll pigments
Where is starch produced by photosynthesis present
Starch grains within the chloroplast
Similarities and differences between prokaryotes and eukaryotes
PROKARYOTE No nucleus Circular DNA (plasmids) Non membrane bound organelles Cell wall = peptidoglycan 70s ribosomes Simple cytoskeleton Reproduce via binary fission Unicellular Cell surface membrane present
EUKARYOTES Nucleus present Linear DNA extra DNA only present in mitochondra and chloroplasts Membrane bound and non membrane bound Cell wall = chitin in fungi, cellulose in plants and not present in animals 80s Ribosomes Complex cytoskeleton Reproduced asexually or sexually Unicellular and multicellular Cell surface membrane present
Theory of endosymbiosis
Mitochondria and chloroplasts were formerly free living prokaryotes that got taken inside another cell as an endosymbiont which lived within the cell leading to the evolution of eukaryotic cellss
