Mammalian Cell Structure and Organelles Flashcards
What does the nucleus do?
It controls all the cellular activities - the brain of the cell
What is the site of DNA replication?
Nucleus
What is the site of the synthesis of different essential RNA molecules (rRNA, mRNA etc )
The Nucleus
The nucleus diagram
What is the nucleus surrounded by?
A nuclear envelope
What is the nuclear envelope?
It is a double membrane (inner and outer) where both membranes fuse at a nuclear pore.
What is the inner nuclear membrane?
It defines the nucleus
What is the outer nuclear membrane?
Is continuous with the endoplasmic reticulum
What are the ring-like gates composed of in the nuclear envelope?
Composed of proteins allowing regulated movements of molecules between the nucleus and the cytosol
What is found inside the nucleus ?
-The Nucleolus
-Nuclear Lamina
What is the Nucleolus ?
- A dense sub-compartment and is the site of synthesis of ribosomal RNA and where ribosome subunits are assembled
What is the Nuclear Lamina ?
It lines the inner nuclear membrane and is composed of intermediate filaments and membrane associated proteins.
It provides mechanical support and regulates events (DNA replication, cell division)
What is the genome arrangement inside the nucleus ?
It is arranged in single linear DNAs which are highly condensed and wrapped around histones and other fibres proteins to form chromatin (DNA-protein complexes)
What are nucleosomes?
They are chromatin units
What are Chromatin Units?
What is the cell cycle?
What is the Endomembrane System?
What organelles are present in the Endomembrane System ?
Some organelles are connected by continuous membranes or by transport vesicles like the endomembrane system which is linked to a secretary pathway of the proteins.
This involves; The nucleus, Endoplasmic Reticulum, Gogli Apparatus, Lysosomes and vesicles
In order to manufacture and package proteins and lipids, what else does the endomembrane system allow?
Cell organisation
What is the Endoplasmic Reticulum?
It is a distinct component which is connected to the nuclear envelope where it forms an extensive network or membranous tubes and flattened sacs made up of membranes called cisernae running throughout the cytoplasm
There are two components, Rough ER and Smooth ER
What are the two components of the Endoplasmic Reticulum?
The Rough ER
The Smooth ER
What is cisternae?
flattened membrane vesicle found in the endoplasmic reticulum and Golgi apparatus
What is the Smooth Endoplasmic Reticulum (Smooth ER)? what is its function?
-Lacks ribosomes
-Function includes the production of lipids such as fatty acids, phospholipids, steroid hormones
-It stores and releases calcium ions, which control various cell activities such as muscle contraction of cardiac muscle cells
-Detoxification of drugs and alcohol in liver cells (drug metabolism)
What do calcium ions do in the body, released by the smooth endoplasmic reticulum?
controls various cell activities like muscle contraction of cardiac muscle cells
What are lipids?
What is the Rough Endoplasmic Reticulum (Rough ER) and what are its functions?
-Involves Ribosomes
-Functions include Protein synthesis, protein post-translation
-Remaining proteins are synthesised by ribosomes in the cytoplasm.
-Glycosylation
- oligomerisation
-Protein sorting/trafficking (signal sequence)
What is Glycosylation ?
What is protein sorting/trafficking
The transport and movement of proteins
What is Oligomerisation?
oligomerization allows proteins to form large structures without increasing genome size and provides stability,
What cells would be known to be rich in Rough ER?
Cells that secrete large amounts of proteins are rich in rough ER (e.g gland cells secreting insulin or lymphocytes producing antibodies in the blood.
What does secretion mean?
Substances are produced and discharged from a cell
What are Transport Vesicles?
-They are enclosed membranous compartments (tiny sacs)
–The lipid bilayer nature of membranes allows the detachment to and fusion with other membranes.
- It is the cell transport mechanism for proteins
-from rough ER to Golgi apparatus
-from Golgi apparatus to the cell membrane
-from Golgi apparatus to other compartments of the endomembrane system
What is the Golgi Apparatus?
Stacks of flattened, membranous sacs (cistern)
What are the three main distinct regions of the Golgi apparatus?
-Cis Face
-Medical
-Trans face
What is the cis face of the Golgi Apparatus?
the end of the organelle where substances enter from the endoplasmic reticulum for processing,
What is the medical of the Golgi Apparatus?
What is the Trans face of the Golgi Apparatus?
where substances exit in the form of smaller detached vesicle
What is the function of the Golgi Apparatus?
-Protein modification into mature proteins
-Glycoslylation
-Phosphorylation
-Proteolysis
-Lipid modification
-Protein sorting or exported outside (from trans Golgi)
What is Protein sorting or exported outside (from trans Golgi)?
What is Lipid Modification?
What is Proteolysis?
What is Phosphorylation?
Attachment of a phosphate group
What is Glycoslylation ?
Addition of sugar molecule
What is protein sorting or exported outside (from trans Golgi)?
-lysosomal protein transported to lysosome
-protein exported outside (e.g. hormones by secretory vesicles -exocytosis)
-cell surface proteins (same exocytosis process)
What are known as ‘suicidal bags’?
Lysosomes
What are Lysosomes?
Found in cytoplasm contains digestive enzymes
