Cell Biology - 1.2 Ultrastructure of cells Flashcards
Prokaryotic cells
Bacteria and Archaea
- No nuclear membrane (ie a nucleoid) (no definite nucleus) - DNA is stored in the cytoplasm
- DNA is not bound to proteins
- Division by binary fission (ie asexual)
- all unicellular (single-celled)
- VERY SMALL
Pili – shown as single lines
Flagella – shown as thicker and significantly longer lines than the pili
Ribosomes – labelled as 70S
Cell wall – labelled as being composed of peptidoglycan; thicker than cell membrane
Shape – appropriate for bacteria chosen
Organelles
Tiny structures within the cytoplasm that preform specific jobs eg. ribosomes
Eukaryotic cells
All other life (BUT BACTERIA AND ARCHAEA) eg. animals/plant/Protoctista (protist)/Fungal cells
- has a nucleus.
- bigger than a prokaryote
- division by binary fission, mitosis or meiosis
- unicellular or multicellular
- contain membrane-bound organelles (and form spindles during mitosis and meiosis)
- have a compartmentalized cell structure
- eukaryote chromosome (enclosed within a nuclear membrane) is a folded length of SNA - wound around proteins called histones
Cell membrane
Responsible for regulating what materials move into and out of the cell
Nucleoid
DNA with ends that come together to form a circle (and its NOT wrapped around proteins)
Cytoplasm
Gel-like fluid substance (mostly water with many dissolved molecules), site of metabolic reactions
Ribosomes
complexes of RNA and protein that are responsible for polypeptide synthesis and build proteins during translation
Plasmid (Structure found in SOME but not ALL prokaryotic cells)
Extra pieces of small circular DNA that can be shared between bacteria (by conjugation), often contain genes for antibiotic resistance
Cell wall
provides shape and allows the cell to withstand turgor pressure with bursting
Pili (Structure found in SOME but not ALL prokaryotic cells)
enable the cell to attach to surfaces, swap DNA with other cells and may be used to harpoon DNA in the environment
(slime) Capsule (Structure found in SOME but not ALL prokaryotic cells)
A thick polysaccharide layer Helps the cell keep from dehydrating (desiccation), phagocytosis and adhere to surfaces
Flagellum (Structure found in SOME but not ALL prokaryotic cells)
Long extensions containing a motor protein that enable movement - used in cell locomotion
Cytoplasm
The internal fluid component of the cell
Cytoplasm
The internal fluid component of the cell - gives the cell shape
Compartmentalized
= a separate section of a structure (cell) in which certain items ( can be kept separate from others) - occurs in Eukaryotic cells BUT NOT prokaryotic cells
Advantage = an organelle can create a compartment with controlled conditions - tailored to the specific functions of the organelle (a microenvironment)
- they are super-efficient
Process of binary fission
- Prepare for division (must have enough energy and resources)
- DNA is replicated semi conservatively (and depends on the complementary base pairing
- the two DNA loops attach to the membrane + cell growth
4/5. the membrane elongates and pinches off (cytokinesis) forming two separate cells - Two cells = The two daughter cells are genetically identically
= In ideal conditions this can occur every 20 minutes
Asexual reproduction
= offspring arise from a single parent cell or organism
= the offspring are genetically identical to the parent
(Binary fission and mitosis are mechanisms of asexual reproduction)
eukaryote cells -> Animal cells eg. skin, muscle, nerve etc. cells
- Multicellular, specialized cells
- Possess nucleus and membrane-bound organelles
- lack cell walls
- heterotrophic
eukaryote cells -> Plant cells eg. leaf, root, skin etc. cells
- Multicellular, specialized cells
- possess nucleus and membrane-bound organelles
- contain chloroplasts
- cell walls of cellulose
- Autotrophic
eukaryote cells -> Protoctista (protist) cells eg. amoeba, paramecium, chlorella etc. cells
- mostly free-living single cells
- some autotrophic, some heterotrophic
eukaryote cells -> Fungal cells eg. yeasts, mushrooms, mould etc. cells
- possess a nucleus and membrane-bound organelles
- cell walls of chitin
what does membrane-bound organelles mean?
The small structure inside the cell membrane that carries out various important cellular functions - organelles are bound by a membrane that allows for things to move in and out of the cell
Nucleus
the control centre containing all genetic information (DNA) for the cell which controls all cell activities - contains the nucleolus
ROUGH endoplasmic reticulum
series on connected flattened membranous sacs that play a central role in the synthesis and transport of proteins
- has ribosomes
- closer to the nucleus
SMOOTH endoplasmic reticulum
smooth ER lacks ribosomes and is not involved in protein synthesis
MAIN FUNCTIONS = the synthesis of phospholipids and cholesterol and the syntheses and repair of membranes
Golgi apparatus
Package and release proteins from the cell:
- modifies, sorts, concentrates and packs proteins from the RER into sealed droplets called vesicles - dispatched into either the lysosomes (organelles in the cell), Plasma membrane of secretion to outside of the cell
Lysosome
- Small spherical organelles enclosed by a single membrane
- contain enzymes that work in o2 poor areas and lower pH
- Enzymes digest large nutrient molecules and/or degrade and recycle the components of the cell’s own organelles when they are old/damaged (or the cell is starving - lack of nutrients)
Mitochondria
- Location of aerobic cellular respiration which is used to make ATP - ATP is then used to duel the exocrine gland cells protein synthesis, active transport and exocytosis
(cells convert food to energy via respiration)
Small vacuoles (vesicles) - can not be seen on lab microscope
store food and chemicals and floating in the cytoplasm (Animals cells = many small)
(Plan cells = ONE large central vacuole)
Centrioles
Makes spindle for cell division
Animal cells (organelle list)
Cell membrane cytoplasm nucleus mitochondria ribosomes lysosome smooth ER rough ER Golgi bodies centrioles small vacuoles nucleolus
Plant cells (organelle list)
Cell membrane cytoplasm nucleus chloroplasts cell wall large vacuole mitochondria smooth ER rough ER ribosomes lysosome golgi bodies nucleolus
Fungal cells (organelle list) = can be unicellular or multicellular
- have complex cellular organisation –> DON’T HAVE chloroplasts or chlorophyll
Cell membrane cytoplasm nucleus mitochondria ribosomes small vacuoles cell wall golgi bodies
Protist cells (organelle list)
Cell membrane cytoplasm nucleus mitochondria ribosomes small vacuoles chloroplasts eyespot cilia or flagella golgi bodies contractile vacuole
Cell size
Cells are usually measured in micrometres (μm) (1000 μm = 1 mm)
Very small structures (and/or virsus) are measured in nanometers (nm) (1,000,000nm = 1mm or 1000nm = 1μm)
(Plant cells are normally larger than animals cells)
Resolution (in terms of microscopes)
= is the smallest interval distinguishable by the microscope which then corresponds to the degree of detail visible in an image created by the instrument
ie. magnification is = but the resolution is better with the electron microscope
Resolution is the shortest distance between two points that can be distinguished
Ultrastructure
fine structure, especially within a cell, that can be seen only with the high magnification obtainable with an electron microscope.
Light microscopes
- combination of lenses to magnify objects up to 1000x (eg. 10x eyepiece and e 40x objective = 400x magnification)
- Specimens viewed must be thin and mostly transparent as light is focused up through the specimen
- live specimens (eg. bacteria) can be viewed
- Resolution is the shortest distance between two points that can be distinguished (resolution is 0.2μm)
Electron microscopes
- uses a beam of electrons (rather than light) to produce an image
- magnification = 100,000-250,000 x
- specimens must be sections/placed on a special disc in a vacuum (live specimens can NOT be viewed)
- Resolution is 0.001μm
Two types:
1) Transmission EM (which can view organelles and micro-structure of cells)
2) scanning EM (which can view the outside surface features of cells and tissues
Calculation of Magnification:
To calculate the linear magnification of a drawing or image, the following equation should be used:
Magnification = Image size (with ruler) ÷ Actual size (according to scale bar)
Calculation of Actual Size:
To calculate the actual size of a magnified specimen, the equation is simply rearranged:
Image size (with ruler)/measured length ÷ Magnification = Actual/total Size
