The Normal Cell: Ultrastructure Flashcards
Who identified the cell and in what year
Robert Hooke
1665
Cell theory (1885) states that
All living things are composed of one or more cells
Cells are the basic unit of structure and function in an organism.
Cells come from replication of pre-existing cells.
Who identified cell and in what year
Robert Hooke
1665
2 Examples of prokaryotes
Bacteria
Blue green algae
Difference between prokaryotes and eukaryotes
Characteristics
Prokaryotic cells
Eukaryotic cells
Nucleus
No
Yes
Membrane bound organellles
No
Yes
Ribosomes size
70S
80S
Cell wall/Composition
Peptidoglycan is present
No peptidoglycan
Mitotic division
No
Yes
DNA with Histones
No
Yes
No of chromosomes
One
More than one
Cell membrane composition
No sterols (Except in mycoplasmas)
Sterols present
Number of cells
Unicellular
Multicellular
Size of cells
Smaller (1-5 μm)
Larger (10-100 μm)
The plasma membrane is a mosaic of 4 things
Phospholipids
Cholesterol
Proteins
Carbohydrates
The phospholipid bilayer is amphipathic in that
Hydrophilic heads
Hydrophobic tails
The polar heads are mainly derived from ________ conjugated to a ______________ ____________such as _______, ____________ or ______ via a phosphate bridge
Glycerol
Nitrogenous compound
Choline, ethanolamine, serine
The non-polar tail consists of two long-chain _____ ______, each __________ linked to the glycerol component of the polar head.
Fatty acids
Covalently
Cholesterol and phospholipids are in the ratio
And they are both
1:1
Amphipathic
The proteins in the plasma membrane have 6 functions
Intercellular joinings
Enzymatic activity
Transport
Cell to cell recognition
Attachment
Signal transduction
Glycocalyx is the umbrella name for
Glycoproteins & glycolipids
The glycocalyx may be involved in 4 things
•cell recognition phenomena,
•formation of intercellular adhesions •adsorption of molecules to the cell surface; •mechanical and chemical protection for the
plasma membrane
Plasma membrane functions
•Protection
•Communication
•Selectively allow substances in •Respond to environment •Recognition
____________ is the most obvious feature of the cell seen under the light microscope
Nucleus
The structure of the nucleus encompasses 4 things
Nuclear membrane
Nucleoplasm (karyoplasm)
Chromosomes
Nucleolus
Double layered organelles in the cell
Nucleus
Mitochondria
(Chloroplast)
Chromosomes in the nucleus are present in form of
DNA and histones called chromatins
The chromatin is further classified into heterochromatin and euchromatin. What are the differences between them
Heterochromatin:Silenced Genes
- More condensed
- Silenced genes (methylated)
- Gene poor (high AT content)
- Stains darker
• Euchromatin: Gene expressing
- Less condensed
- Gene expressing
- Gene rich (higher GC content)
- Stains lighter
Give one example of enucleate cell
Multinucleate cell
RBCs
Osteoclasts
The principal organelles 2 involved in protein synthesis are:
Nucleus
Ribosome
I’m the nucleus, transcription happens. What’s that?
DNA template is copied to form a complementary messenger RNA (mRNA)
Translation which occurs in the cytoplasm is the process by which?
mRNA is converted into protein by the ribosomes
Functions of mitochondria
•Mitochondria are an important source of reactive oxygen species (e.g., oxygen free radicals, hydrogen peroxide)
•Mitochondria provide the enzymatic machinery for oxidative phosphorylation (efficient generation of energy from glucose and fatty acid substrates).
•Plays a fundamental in regulating both apoptosis and necrosis
Mitochondrial DNA is __________ inherited
Maternally
The inner membrane of the mitochondria contains?
the enzymes of the respiratory chain folded into cristae.
The intermembrane space is the site of
ATP synthesis
The core (matrix space) of the mitochondria harbors
certain metabolic enzymes, such as the enzymes of the citric acid cycle
The ER is the site of synthesis of?
All the transmembrane proteins
Lipids for plasma membrane
Cellular organelles including itself
The rough ER is involved in
Synthesis & Secretion of protein
The principal functions of the Smooth ER is
Lipid biosynthesis
Membrane synthesis & repair
The SER is abundant in the adrenals and gonads because
It produces hormones: steroids
Steroidogenesis
sER in muscle cell is called
Sarcoplasmic reticulum
Sarcoplasmic reticulum?
is responsible for the release and sequestration of calcium ion responsible for muscle contraction and relaxation respectively
Gkycosylation of proteins starts in the _______ and is completed in the _____________
Endoplasmic reticulum
Golgi apparatus
Lysosomes contain more than _____ digestive enzymes collectively known as ____ __________ (proteases, nucleases, lipases, phosphatases, sulfatases) involved in the degradation of particulate material ingested by ___________
40
Acid hydrolases
Endocytosis
Peroxisomes are also known as
Micro bodies
Peroxisomes contain
Oxidases and catalases
Oxidase enzyme leads to the production of _____ useful for __________ ___________ ___________________
H2O2
Killing ingested micro organisms
Catalase enzyme has 2 functions
regulates H2O2 concentration
oxidizes toxic substances such as phenol and alcohol
3 major classes of cytoskeleton
A. Actin
B. Intermediate filaments
C. Microtubules
___________. are the most abundant cytosolic protein in cells
Actin microfilaments
Intermediate filaments are used for
Tumor marking
Types of intermediate filament
•Lamin A, B, and C: nuclear lamina of all cells
•Vimentin: mesenchymal cells (fibroblasts,
endothelium)
•Desmin: muscle cells, forming the scaffold on which actin and myosin contract
•Neurofilaments: axons of neurons, imparting strength and rigidity
•Glial fibrillary acidic protein: glial cells around neurons
•Cytokeratins: at least 30 distinct varieties, subdivided into acidic (type I) and neutral/basic (type II); different types present in different cells, hence can be used as cell markers
Microtubules are ______ thick fibrils composed of dimers of ______ & _______
25-nm
α- and β-tubulin
Microfibers have been adapted to form motile cilia (bronchial epithelium) or flagella (sperm)
True
Within cells, microtubules can serve as _________ ________for “molecular motor” proteins that use ATP to move vesicles, organelles, or other molecules around cells along microtubules
Connecting cables
Types of plasma membrane protein
Intrinsic : incorporated within the membrane
Extrinsic/ peripheral: attached to inner it outer surface by weak electrostatic forces
Transmembrane: intrinsic proteins which span the entire thickness of the membrane exposed to each surface
The Cytoplasm: protein synthesis function
• This mRNA is transported out of the nucleus and is converted into protein by the ribosomes (translation)
•Ribosomes are minute cytoplasmic organelles, each composed of two subunits of unequal size.
•Each subunit consists of a strand of RNA (ribosomal RNA, rRNA) with associated ribosomal proteins forming a globular structure.
Ribosomes align mRNA strands so that transfer RNA (tRNA) molecules may be brought into position and their amino acids added sequentially to the growing polypeptide chain (Translation). Translation takes place in the cytoplasm.
Mitochondria structure and function
•Mitochondria are also an important source of reactive oxygen species (e.g., oxygen free radicals, hydrogen peroxide)
•Mitochondria provide the enzymatic machinery for oxidative phosphorylation (efficient generation of energy from glucose and fatty acid substrates).
•Plays a fundamental in regulating both apoptosis and necrosis
The ER consists of
The ER consists of an interconnecting network of membranous tubules, vesicles and flattened sacs
Vesicles structure & function
Vesicles containing newly synthesized protein separate from the ends of the rER.
•The vesicles are used to ship them to other parts of the cell or to the outside of the cell.
•These proteins can also be shipped to the Golgi apparatus for modification, sorting and packaging
The sER in most cells is relatively sparse and primarily exists as
the transition zone from RER to transport vesicles moving to the Golgi.
The sER is also responsible for
The sER is also responsible for sequestering intracellular calcium; subsequent release from the sER into the cytosol can mediate a number of responses to extracellular signals (including apoptotic cell death)
Golgi apparatus: structure & function
The Golgi apparatus consists of stacked, saucer-shaped membrane-bound cisternae.
•Proteins synthesised in the rough ER are transported to the Golgi apparatus in coated vesicles.
•In the Golgi apparatus, the glycosylation of proteins, begun in the rER, is completed.
•The proteins are packaged into membrane-bound vesicles which detach at the trans Golgi network and are transported to their final destinations (export).
_________ are membrane bound organelle similar in size and ultra structure to lysosomes
Peroxisomes
What is cytoskeleton
The ability of cells to adopt a particular shape, maintain polarity, organize the relationship of intracellular organelles, and move about depends on the intracellular scaffolding of proteins called the cytoskeleton
Intermediate filaments are
• 10-nm diameter fibrils that comprise a large and heterogeneous family.
• Individual types have characteristic tissue-specific patterns of expression that can be useful for assigning a cell of origin for poorly differentiated tumors
Pathologies
Plasma membrane
Plasma membrane is affected in necrosis and apoptosis (cell death)
• Necrosis: Plasma membrane is destroyed
• Apoptosis: Plasma membrane is intact
Membrane proteins
Hereditary stomatocytosis in RBCs: Marked increase of
intracellular sodium because the cell is unable to
regulate cation homeostasis.
• Cystic fibrosis: Mutation in CFTR gene leading to
production of abnormally folded membrane protein
which is degraded by the cell.
• WIlson’s disease: Mutation in Wilson disease protein
(ATP7B) gene. Leads to Cu accumulation.
Ribosomopathies
Diamond Blackfan Anaemia: Macrocytic anaemia, short stature. Defects in RPS 19, 24 etc
• 5q syndrome. RPS 14 defect. Macrocytic anaemia may progress to AML.
Mitochondria
Leigh syndrome:
• mtDNA m.8993T > G mutation. Clinical features of
regression in motor skills etc.
Golgi body
• Structural and functional changes of the Golgi apparatus are associated with neurodegenerative diseases including Alzheimer’s, Parkinson’s disease etc.
Lysosome
Lysosomal Storage Diseases: Inborn errors of metabolism leading to accumulation of substrates in the cells due to defective lysosomal function. E.g. Gaucher’s disease, Niemann Pick disease.
