The cell ultrastructure Flashcards
Nucleus What does the nucleus do?
> stores genetic material
-> site of DNA replication
->transcription – tRNA, mRNA, rRNA
nuclear envelope structure
Contains a nuclear envelope:
-> OUTER envelope contains ribosomes
-> INNER envelope contains Lamins - numerous mutations in the human A-type lamin gene (LMNA) cause Progeria.
Nuclear pores role
Transport to and from cell to cytoplasm
Nucleolus function
rRNA synthesis
-> combine proteins
-> important for making ribosomes
type sof Chromatin (DNA + Histones) in nucleus
Euchromatin - loose and active
-> Heterochromatin – condensed and inactive
nucleus definition and roles
The nucleus is the control centre of the cell and contains the genetic material, DNA. It directs cellular activities and is responsible for the replication and transmission of genetic information.
Cell Membrane structure and role
Acts as a barrier which controls simple, facilitated and vesicular transport.
Structure:
1)Phospholipid Bilayer
Consists of a phospholipid head (hydrophilic)
2)Fatty acid tails (hydrophobic)
where does cholesterol in the cell membrane come from and what’s its role in the cell membrane?
2) comes from SER (lipid synthesis) to golgi to Cell Memebrane
- Contains cholesterol which controls the fluidity and aids solubility of the membrane
what is the function of proteins in the cell membrane?
ionic and molecular transport, electron transport, signal transduction, enzymatic reactions and intercellular communication.
Rough Endoplasmic Reticulum function
a site of protein synthesis, lipid metabolism, and detoxification.
Cell membrane definition
The cell membrane is a selectively permeable barrier that encloses the cell, separating its internal environment from the external surroundings. It regulates the movement of substances in and out of the cell.
The RER has
ribosomes
fate of protein synthesis in the RER
These proteins will become:
Lysosomes
To go to the Membrane proteins
Excretes proteins
how does the RER assist with protein folding?
Assists with protein folding:
The RER also consists of enzymes that catalyze the formation of disulfide bonds necessary for a protein’s tertiary and quaternary structure. If the protein does not fold correctly, the molecular chaperons rebind onto the polypeptide and attempt to fold the protein into the correct shape.
Glycosylation in the RER
Protein Glycosylation. Glycosylation, the attachment of sugar moieties to proteins, is a post-translational modification (PTM) that provides greater proteomic diversity than other PTMs.
what is synthesised in the SER
1) Lipid Synthesis
-> fatty acids
->phospholipids
->cholesterol
CYP540 Enzymes role
CYP enzymes are mainly found within the endoplasmic reticulum of liver cells.
detoxification from the liver e.g. alcohol, liver has high concentrations of these enzymes ->
Biotransformation – breakdown at the liver using these enzymes at the SMR
what mineral does the SER store?
> stores calcium
SER definition and roles
The ER is a network of membranous tubules and sacs involved in protein synthesis, lipid metabolism, and detoxification.
Golgi Apparatus definition and role
the Golgi apparatus modifies, sorts, and packages proteins and lipids for transport to their specific destinations within or outside the cell.
Where does the Golgi recieve vesicles (proteins and lipids) from?
1)Receives vesicles from the RER and SER
Cis Golgi – enters: closest to nucleus
Trans Golgi – leaves: furthest away to the nucleus
what Post translational Modifications occur in the Golgi body?
> Glycosylation - N and O Type
->Phosphorylate
What does the Golgi do with vesicles received from the ER
The Golgi apparatus, or Golgi complex, functions as a factory in which proteins received from the ER are further processed and sorted for transport to their eventual destinations: lysosomes, the plasma membrane, or secretion.
Lysosomes definition and role
Lysosomes contain digestive enzymes that break down waste materials, cellular debris, and foreign substances.
They play a crucial role in cellular recycling and defence mechanisms.
What type of enzymes do lysosomes contain?
They contain Hydrolytic enzymes which breakdown macromolecules
-> such as proteases
-> lipases
->nucleases
->glycosidases
What organelle plays a key role in autophagy?
lysosomes - Plays a key role in autophagy of organelles
What organelle plays a key role in Autolysis of Damaged cells
lysosomes
explain why the membrane of lysosomes is highly glycosylated
The membrane is Highly glycosylated to protect the lysosomes from the hydrolytic enzymes inside
what cells are lysosomes common in?
White blood cells
Peroxisomes contain what enzymes?
1) Contain oxidative Enzymes
->catalase
->oxidase
->metabolic enzymes– alpha and beta
what oxidation do peroxisomes play a role in?
2) Fatty acid oxidation
A major function of the oxidative reactions performed in peroxisomes is the breakdown of fatty acid molecules. In a process called β oxidation, the alkyl chains of fatty acids are shortened sequentially by blocks of two carbon atoms at a time, thereby converting the fatty acids to acetyl CoA.
peroxisomes make what?
3)Make lipids and cholesterol
Peroxisome quality control and dysregulated lipid metabolism
In addition, peroxisomes contribute to the biosynthesis of essential lipid molecules, such as bile acid, cholesterol, docosahexaenoic acid, and plasmalogen.
->plasmalogen which is in white matter
what kind of metabolism are peroxisomes involved in?
4)Alcohol metabolism
Catalase, located in peroxisomes, plays only a minor role in alcohol metabolism, possibly accounting for <2% of overall alcohol oxidation, although there is some evidence for increased metabolism of alcohol by peroxisomes in chronic drinkers.
what is adrenoleukodystrophy
Adrenoleukodystrophy (ALD) is a genetic condition that damages the membrane (myelin sheath) that covers nerve cells in the brain and spinal cord. Myelin acts as insulation around the nerve fibers.
Impaired peroxisomal beta-oxidation of saturated very long chain fatty acids (VLCFA, >/=C22:0) results in increased VLCFA levels in the tissues and body fluids of patients with disorders of peroxisomal biogenesis (i.e., Zellweger syndrome and neonatal adrenoleukodystrophy) and single peroxisomal protein defects
Mitochondria definition and role
Mitochondria are the powerhouses of the cell, responsible for generating energy in the form of ATP through cellular respiration. They have their own DNA and are involved in various metabolic processes.
what synthesis occurs in the mitochondria
1) ATP Synthesis
-> electron transport chain
->oxidative phosphorylation
pathways in mitochondria
Krebs Cycle and other pathways Urea, glucogenesis, ketogenesis
what genetic material is contained in the mitochondria?
3) Mitochondrial DNA
Mitochondrial DNA is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate
how does the mitochondria assist in apoptosis ?
assists in apoptosis by sensing cellular stress and release cytochrome C which can initiate apoptosis.
Bcl-2 family members regulate the release of proteins from the space between the mitochondrial inner and outer membrane that, once in the cytosol, activate caspase proteases that dismantle cells and signal efficient phagocytosis of cell corpses.
