2.1 CELL STRUCTURE Flashcards
Four types of microscopes
1) light
2) scanning electron
3) transmission electron
4) laser scanning confocal
Define resolution
- minimum distance between two objects in which they can still be seen as separate
Define magnification
- how many times larger the image is compared to the actual object
Formula for magnification
Image = Actual x Magnification
State the 3 steps to calibrate an eye piece graticule
1) line up the stage micrometer and eyepiece graticule whilst looking through the eyepeice
2) count how many divisions on the eyepiece graticule (ruler below) fit into one division of the micrometer scale (ruler above)
3) length of one division on the micrometer (ruler above) DIVIDED BY how many divisions of the eyepiece graticule (ruler below) fit into it
Name the four types of slides/mounts used in light microscopy
1) Dry mount
2) Wet mount
3) Squash slides
4) Smear slides
Describe how dry mounts are prepared
- Place a cover slip on top of specimen
Describe how wet mounts are prepared
- Add water to specimen
- Lower cover slip with mounted needle to prevent air bubble formation
Describe how squash slides are prepared
- Add water to specimen
- Lower cover slip with mounted needle to prevent air bubble formation
- Squash cover slip down to ensure thin enough layer of specimen formed
Describe how smear slides are prepared
- Use edge of another slide to smear sample across the slide to produce even, thin coat
- Place a cover slip on top
Define differential staining
- using many chemical stains to stain different parts of a cell different colours in light microscopy
Why is differential staining important? (2)
- provides increased contrast for differentiation
- to make cells/cell organelles visible
State the relative magnification of all the microscopes
(lowest magnification) Light < LSCM < SEM < TEM (highest magnification)
State the relative resolutions of all the microscopes
(lowest resolution) TEM < SEM < Light < LSCM (highest resolution)
Describe the type of image produced by a Light microscope
- 2D
- Coloured
Describe the type of image produced by a Laser Scanning Confocal microscope
- 2D OR 3D
- Coloured
Describe the type of image produced by a Scanning Electron microscope
- 3D
- Black and white
Describe the type of image produced by a Transmission Electron microscope
- 2D
- Black and white
What do Light microscopes observe?
- Alive, thin
- Whole cells/tissues
What do Laser Scanning Confocal microscopes observe?
- Alive, thick or thin
- Objects within certain depths of cells
What do Transmission Electron microscopes observe?
- Dead, thin
- Organelles
What do Scanning Electron microscopes observe?
- Dead, thick or thin
- Cell surfaces
4 key rules of drawing images from microscopes
1) state the magnification
2) no overlapping lines
3) annotations of components
4) title the specimen
Why are eukaryotic organelles membrane bound and which one isnt?
- separates organelle from cytoplasm
- ribosomes arent membrane bound
Nucleus structure and function
- Nuclear envelope with pores to separate nucleus from rest of cell and so mRNA can leave and hormones can enter
- Nucleolus containing RNA, where ribosomes produced
- Chromatin as the genetic material consisting of DNA wrapped around histone protein
Rough Endoplasmic Reticulum (RER) structure and function
- ribosome coated membrane system
- synthesising proteins
Smooth Endoplasmic Reticulum (SER) structure and function
- membrane system
- synthesising lipids
Golgi Apparatus structure and function
- flattened membrane sacs
- modifying proteins
Mitochondria structure and function
- surrounded by inner and outer membrane and a fluid-filled inner matrix with highly folded cristae membrane
- site of ATP production during aerobic respiration
Chloroplast structure and function
- surrounded by inner and outer membrane and a fluid-filled matrix (stroma) with stacks of thylakoids (grana) connected by intergranal lamallae
- site of photosynthesis
Ribosome structure and function
- made of rRNA and proteins
- site of translation during protein synthesis
Lysosome structure and function
- contain digestive enzymes that are separate from rest of cell
- can engulf old cell organelles and digest foreign material
Plasma cell surface membrane structure and function
- phospholipid bilayer embedded with protein, cholestrol, glycolipids and glycolipids
- partially permeable to control what enters and leaves cell
Centriol structure and function
- small microtubules made of tubulin
-produces spindle fibres for mitosis
Cellulose cell wall structure and function
- made of cellulose in plants and surrounds plasma cell surface membrane
- prevents lysis, provides strength/support
Flagella/Cilia structure and function
- small hairlike extentions of plasma cell surface membrane
- wafts/moves things or moves the cell
Uses of the cytoskeleton (5)
- provides stability/mechanical strength
- forms a track for motor proteins to drag along/transport organelles
- enables cell movement
- form spindle fibres for mitosis
- extends between cells to enable cell signalling
Steps of secretion of proteins by organelles
1) Genes on chromatin in nucleus is transcribed into mRNA and leave via nuclear envelope pores to RER’s ribosomes
2)Polypeptide chains are translated at the ribsomes on RER then packaged in transport vesicles to Golgi Apparatus
3) In Golgi apparatus, protein is modified then packaged into secretory vesicles which move along cytoskeleton
4) Secretory vesicle containing protein fuses with plasma cell surface membrane and secreted via exocytosis
Similarities between prokaryotes and eukaryotes (4)
- Plasma cell surface membrane
- Cytoplasm
- Ribosome
- DNA and RNA
Differences of prokaryotes against eukaryotes (5)
- much smaller
- no nucleus
- no membrane bound organelles
- peptidoglycan cell wall
- less developed cytoskeleton
