1.2 Cell Ultrastructure Flashcards
Who created the microscope?
-Robert Hooke
-1665
Who devised the cell theory and what is it?
-Schleiden and Schwann in 1839
-All living organisms are made of one or more cells.
-The cell is the most basic unit of life
-Cells can only arise from pre- existing cells
2 types of microscopes
-Light microscope
-Electron microscope
Light microscope
-x1,500 magnification
-200nm resolving power
-Eyepiece lens magnification x Objective lens magnification = Total magnification
-Common stains = Haematoxylin+ Eosin stain, Methylene Blue, Iodine
Pros + Cons of light microscopes
Pros= Cheap, accessible and portable
-Can look at live cells with little preparation e.g blood samples and sperm
Cons= Limited in terms of magnification and resolution
Electron microscope
-x500,000 magnification
-0.5nm resolving power
-Beam of electrons rather than a beam of light
-Smaller wavelength
-2 types = Transmission electron microscope (TEM) + Scanning electron microscope (SEM)
-TEM = images produced are black + white + 2D but SEM produces 3D images and colour can be added after
Pros + Cons of electron microscope
Pros= massive magnification and massive resolution
Cons= have to examine specimens in a vacuum so they have to be dead and dried of all water
-very expensive
-large
-very specialised skills required to prepare samples
-artefacts likely
Cutting plane
-Determine what you see on the slide
Cells can be split into 2 categories
1- Prokaryotic cells
2- Eukaryotic cells
Viruses
-Do not have cell organelles found in cells
-Made of a protein coat called a CAPSID on the outside and has some DNA or RNA inside
-Not living
-No nucleus
-No metabolism
-Must reproduce inside a living host cell
Nucleus
-largest organelle
-double membrane called the nuclear envelope
-nuclear pores allow ribosomes to travel through
-nucleoplasm contains DNA in the form of chromatin when not dividing and chromosomes when it it
-contains the nucleolus
Nucleolus
-dense darker area of the nucleus
-produces ribosomes and RNA
Ribosomes
-made of ribosomal RNA and protein
-made in nucleus then moved through the cell
-used in protein synthesis to assemble the polypeptide
-found in eukaryotic cells = 80S ribosomes
-made from subunits 60S + 40S
RER
-made from flattened fluid-filled sacs of membrane called cisternae
-location of extracellular protein synthesis
-once a protein has been made the membrane pinches off to form a vesicle which can be transported around the cell
-usually found next to the nucleus + sometimes connected to the nuclear envelope.
SER
-manufacture and then transport lipids and steroids such as certain hormones
-cells that store large quantities of carbs, proteins and fats including liver and secretory cells have extensive ER
Mitochondria
-site of aerobic respiration to produce ATP and energy for the cell
-capsule shaped and made from a double membrane filled with a fluid called matrix
-inner membrane folded into cristae providing a larger surface area for attachment of enzymes
-muscle cells will contain a high number of mitochondria as they need a lot of ATP
Centrioles
-only found in ANIMAL cells
-found in pair near nucleus usually at right angles
-each is a bundle of 9 microtubules making hollow cylinders, sometimes called a centrosome
-used when a cell divides
-move to opposite ends and produce the microtubule spindle that will attach to the chromosomes and pull them apart
Lysosomes
-small temporary unit, membrane bound vacuoles
-contain and isolate digestive enzymes, usually lysozymes
-used for breaking down old organelles
-can fuse with cell membrane and release it’s enzymes out of the cell
-used in programmed cell death, autolysis, when a cell self destructs
Golgi apparatus/body
-stacks of membrane bound sheets
-golgi receives vesicles containing proteins made in the RER
-golgi modifies and packages the proteins
-release the modified proteins into vesicles to be transported around the cell or released at the cell membrane by exocytosis
Exocytosis
-contents of the vesicles e.g enzymes, hormones etc. are released out of the cell
-ACTIVE process REQUIRES ENERGY
Endocytosis
-material that needs to move into the cell becomes surrounded by an area of cell membrane that then buds off into the vesicle
-ACTIVE process REQUIRES ENERGY
Cytoskeleton
-fibrous network that fills the cytoplasm
-gives cells structure
-moves and holds structures like organelles
-made from microtubules and protein microfilaments like actin
Cytoplasm
-most cellular metabolism
-mostly made from water
-cytosol is the ‘soup’ in which the organelles reside
-cytoplasm = cytosol + organelles
Cell wall
-ONLY FOUND IN PLANT CELLS
-provides strength and support
-freely permeable, doesn’t control what comes in and out of the cell
-made of layers- middle lamella which contains pectin and the cellulose microfibrils. Also needs calcium to strengthen structure
-linked together by gaps in cell walls called plasmodesmata
Plasmodesmata
-small channels that directly connect the cytoplasm between two adjacent cells
-allow for direct transport between cells
ONLY IN PLANT CELLS
Functions of cell wall
1- transport- gaps between cellulose fibres make it permeable to water and ions- space outside= apoplast
2- mechanical strength- strong. when vacuole is full, cell contents push against cell wall, it resists expansion and cell is turgid
3- communication between cells- plasmodesma occurs when there is no cellulose thickening between two cells. the network of cytoplasm in connected cells is symplast. important in water transport through a plant
Chloroplasts
-site of photosynthesis, found in large concentration in palisade mesophyll layer
-contain chlorophyll, 70S ribosomes and circular DNA
-double membrane bound capsule, inner membrane folded into thylakoids which are staked up to form granum
-provides a large surface area for chemical reactions to occur
-linked by lamella and surrounded by liquid called stroma.
Vacuole
-animal cells sometimes have small temporary vacuoles, but plant cells have a large permanent vacuole
-filled with cell sap = dissolved substances in water
-used to help maintain the cell shape
-also used for storage
Tonoplast
-name of the membrane that surrounds the vacuole
-controls what enters and leaves the vacuole and therefore controls the cell’s osmotic potential
Prokaryotic- cell wall
-prevents cell bursting
-gives bacteria it’s shape
-made of peptidoglycan which is a combination of polysaccharide and protein
-2 types of cell wall
Prokaryotic - capsule
-only on some bacteria
-made from various different molecules such as starch or glycolipids
-protects bacterium from drying out in certain conditions, or being discovered by the immune system
Prokaryotic - cell membrane
-The cell membrane, also known as the plasma membrane, is a double layer of lipids and proteins that surrounds a cell. It separates the cytoplasm (the contents of the cell) from the external environment.
Prokaryotic - mesosome
-One difference between eukaryotic and some prokaryotic cell membranes is that they can have a section that folds inwards to form a mesosome.
-A mesosome performs the same function as a mitochondrion.
-Prokaryotes don’t have any membrane bound organelles so don’t have mitochondria.
Prokaryotic - Nucleoid
-Prokaryotes don’t have a nucleus.
-But they still have DNA which is in the form of one long single strand called the nucleoid.
-This is not in a membrane but just free in the cytoplasm.
Prokaryotic - plasmids
-Small circular loops of DNA.
-They can be transferred between bacteria.
-Code for a specific trait.
Prokaryotic - ribosomes
-Smaller that eukaryotic ribosomes.
-These are 70S made from a 30S and 50S subunits.
-They have the same function as in eukaryotes
endosymbiont theory
-The endosymbiont theory is a widely accepted theory that explains how Eukaryotic cells evolved from Prokaryotic cells.
-Theory proposed that the main organelles of the eukaryotic cell were actually primitive prokaryotic cells that had been engulfed by a different, bigger prokaryotic cell.
Prokaryotic - flagella and pili
-Some bacteria have flagella for movement.
-Made from protein fibres called flagellin which are spun around like a motor.
-Some bacteria have thousands of small structures called pili on the outside.
-They are use to help the bacteria reproduce and communicate.
Prokaryotic- Gram staining
-able to see the 2 cell walls
-gram positive bacteria and gram negative bacteria
Organelles are interrelated
1.Nucleus – synthesising rRNA (this is used for protein)
2.rRNA released through pore
3.rRNA fuses with RER as a ribosome – site of protein synthesis
4.Vesicle (containing protein) pinched off ER
5.Vesicle fuses with Golgi body – protein is modified and packaged
6.Vesicle pinched off Golgi body – taking modified protein to cell membrane
7. Vesicle fuses with cell membrane for exocytosis to take place – protein leaves cell
4 Types of tissues
1- Epithelial tissue
2- Nervous tissue
3- Muscle tissue
4- Connective tissue
4 Types of epithelial tissue
1-cilliated
2-squamous
3-columnar
4-cuboidal
3 Types of muscle
1-straited
2-smooth
3-cardiac
5 Types of connective tissue
1-dense
2-adipose
3-areolar
4-compact bone
5-blood
stratified
cells are in layers
Squamous epithelial tissue
-A stratified squamous epithelium consists of squamous epithelial cells arranged in layers upon a basal membrane.
-thin, flat cells
-Examples of Simple: Capillary lining, Alveoli
-Examples of Stratified: Lining of Mouth, Lining of Vagina
Cuboidal epithelial tissue
-short, cylindrical cells, appear hexagonal in cross section
-Examples of Simple: Lining of Proximal and Distal Convoluted tubules in Kidney nephrons
-Examples: Mammary glands, Sweat glands, Salivary glands
Columnar epithelial tissue
-Long, or column-like cylindrical cells, which have a nucleus at the base
-Examples of Simple: Digestive tract, Upper respiratory tract
-Examples: rectum, male urethra, ducts of salivary glands
Ciliated epithelial tissue
-Cuboidal or Columnar epithelium can be ciliated. Cilia are fine hair-like projections that move mucus in a specified direction
-Examples: Respiratory tract (bronchioles), Vas deferens, Oviducts (fallopian tubes)
Basement membrane
-The basement membrane is a thin, pliable sheet of extracellular matrix that supports the tissue and acts as an anchoring platform. It sits between the epithelial cells and the connective tissue.
-It is jointly made by the epithelium and the underlying connective tissue
Smooth muscle
-look for smooth appearance and pale nuclei
-examples: walls of arteries and veins, around glands
Striated muscle
-look for striped appearance and darker nuclei
-examples: stomach, small intestine, large intestine, rectum
Cardiac muscle
-look for a more chaotic appearance with intercalated discs, cross striations and branching
