Cell Structure Flashcards
what is cell theory
- both plant and animal tissue is composed of cells
- cells are the basic unit of life
- cells only develop from existing cells
what is dry mount
- solid specimens are viewed
what is wet mount
- specimens suspended in liquid
- cover slip placed at an angle
what are squash slides
- wet mount prepped first
- lens tissue gently presses down cover slip
what are smear slides
- edge of slide is used to smear the slide
- thin even coating
what are positively charged dyes
- crystal violet
- methylene blue
- attracted to negatively charged materials in the cytoplasm
- stains cell components
what are negatively charged dyes
- nigrosin and congo red
-stays outside the cells leaving them unstained - stand out against the stained background
what is differential staining
- distinguish between two types of organisms that would be hard to identify
- differentiate between different organelles of a single organism
- gram stain technique
- acid fast technique
what is the gram stain technique
- separates bacteria into gram positive and gram negative
- crystal violet added to bacterial specimen then iodine added
- slide washed with alcohol
- gram positive retain crystal violet and stay blue
- gram negative lose stain and counterstained with safarin dye to appear red
what is the acid fast technique
- differentiate species of mycobacterium from other bacteria
- lipid solvent carries carbolfuchsin dye into cells
- cells washed with a dilute acid alcohol solution
- mycobacterium retain carbolfuchsin stain
- other bacteria lose the stain and stained with methylene blue
what are the stages of slide preparation
Fixing - chemicals used to preserve specimens in as near-natural state as possible
sectioning - specimens are dehydrated with alcohols and placed in wax/resin to harden
staining - shows different structures
mounting - specimens secured on a microscope and then a cover slip is placed
what is magnification
how many times larger the image is than the actual size of the object being viewed
what is resolution
- the ability to distinguish between two close together points on the same specimen
how do you work with a scale bar
- measure the actual length of the scale bar
- divide it by the length is represents to work out the magnification
how do you calibrate a light microscope
- line up the eyepiece graticule with stage graticule and focus the microscope
- count the number of eyepiece divisions and note the number of micrometres
what are electron microscopes
- uses a beam of electrons to illuminate the specimen
- can show artefacts
what is a transmission electron microscope
- beam of electrons is transmitted through a specimen and focused to produce an image
- gives some contrast
-2D image - resolving power of 0.5nm
- x500 000 magnification
what is a scanning electron microscope
- beam of electrons is sent across the surface and is reflected off
- resolving power 3-10nm
- x100 000 magnification
what are the features of an electron microscope
- expensive
- large and need installing
- complex sample prep
- sample prep may distort the sample
- vacuum required
- black and white images
- x500 000 magnification
- TEM =0.5nm SEM= 3-10nm
- dead specimensw
what are the features of a light microscope
- inexpensive
- small and portable
- simple sample prep
- sample prep doesn’t distort the sample
- no vacuum
- natural colour seen
- x2000 magnification
- 200nm
- living or dead specimens
what is a laser scanning confocal microscope
- moves a single spot of focused light across a specimen
- causes fluorescence from components
- light emitted from the specimen is filtered through a pinhole aperture
- only light radiated close to the focal plane is detected
what is a eukaryote
- any organism consisting of one or more cells that contain DNA in a membrane bound nucleus
what is a nucleus
- contains coded genetic information
- DNA controls metabolic activities
- DNA associated with histones to form chromatin
what is chromatin
- coils and condenses to form structures known as chromosomes
- only visible when the cell is preparing to divide
what is the nuclear envelope
- protects DNA from damage
- contains nuclear pores that allow molecules to move in and out
- dense spherical structure
- double membrane
what is the nucleolus
- produces ribosomes
- composed of proteins and RNA
- RNA produces ribosomal RNA and is combined with proteins to form ribosomes for protein synthesis
what is the mitochondria
- inner membrane is highly folded to form cristae and interior fluid called the matrix
- inner membrane is coated in enzymes which catalyses the reactions of aerobic respiration
- mitochondrial DNA
What are vesicles
- membranous sacs that have storage and transport roles
- single membrane with fluid inside
- used to transport materials inside the cell
what are lysosomes
- specialised vesicles containing hydrolytic enzymes
- digestive enzymes to break down material
- break down pathogens
- role in apoptosis
what is the cytoskeleton
- network of fibres responsible for the shape and stability of a cell
Microfilaments - cell movement and contraction
Microtubules - structural support
what is the endoplasmic reticulum
- network of membranes enclosing flattened sacs called cisternae
Smooth
- lipid and carbohydrate synthesis and storage
Rough
- ribosomes bound to the surface
- synthesis and transport of proteins
what are ribosomes
- can be free floating in the cytoplasm or bound to the rough ER
- no membrane
- site of protein synthesis
what is the golgi apparatus
- compact structure
- doesn’t contain ribosomes
- modifies and packages proteins into vesicles
what is the process of protein production
- proteins synthesised from ribosomes bound on the rough ER
- pass into cisternae and packaged into vesicles
- vesicle moves to golgi apparatus via the cytoskeleton
- vesicles fuse with golgi apparatus and proteins enter
- proteins are structurally modified before leaving the golgi apparatus in vesicles
- vesicles move towards and fuse with the cell membrane
- vesicles release their contents by exocytosis
what is the cellulose cell wall
- provides rigidity to the cell
- acts as a defence mechanism - protect the contents of the cell from invading pathogens
what are vacuoles
- membrane lined sacs in the cytoplasm containing cell sap
- maintain a rigid framework for the cell
what are chloroplasts
- double membrane structure separated by stroma
- internal network of flattened sacs - thylakoids
- grana joined by lamellae
- grana contains chlorophyll pigments
- produces starch in the form of starch grains
- contain their own DNA and ribosomes
- internal membranes provide large surface area for photosynthesis
what are prokaryotic cells
- unicellular organism where the DNA isn’t contained in the nucleus
- organelles aren’t membrane bound
what are the features of prokaryotic cells
- no nucleus
- circular DNA
- organelles not membrane bound
- peptidoglycan cell wall
- 70s ribosomes
- has a cytoskeleton
- reproduce by binary fission
- unicellular
- has a cell membrane
what are the features of eukaryotic cells
- has a nucleus
- linear DNA
- has membrane and non membrane bound organelles
- chitin cell wall in fungi
- cellulose cell wall in plants
- 80s ribosomes
- complex cytoskeleton present
- reproduce sexually or asexually
- unicellular or multicellular
- cell membrane present
