Introduction to Cells Flashcards
Features all cell types posses (prokaryotic and eukaryotic)
Cell membrane, DNA, cytoplasm, ribosomes
Function of plasma membrane
A partially permeable barrier between the cytoplasm and external environment that allows movement of few molecules via simple / facilitated diffusion, osmosis, active transport and exo/endocytosis. Retains most organically produced chemicals within the cell. Involved in cell communication using cell-surface receptors.
Structure of plasma membrane
Lipid bilayer consisting of phospholipids (hydrophilic head and hydrophobic tail), cholesterol (embedded in inner area of bilayer and provides membrane integrity which prevents lysis), and proteins (transport of molecules).
Phospholipid structure
Hydrophilic head consists of choline, phosphate and glycerol. Hydrophobic tail made of two fatty acid chains linked to glycerol by ester bond.
Cell membrane pathologies
Haemoglobinopathies (sickle cell anaemia and thalassaemia) which hereditary. Alterations in organisation of lipid bilayer phospholipids decreases RBC lifespan and they are not as effectively replaced.
Nuclear envelope
Double-membrane structure which RNA can pass but not DNA
Nucleolus function
Where ribosomes are produced.
Ribosomes function
Protein translation. 80S ribosomes in eukaryotes and 70S in prokaryotes.
Ribosome structure
Made of a large and small subunit and central protuberance. A site (aminoacyl tRNA binding site) where appropriate amino acid is attached. P site (peptidyl-tRNA binding site) where amino acid is added to the polypeptide chain. E site is exit site. mRNA binding site.
Ribosome pathologies
Ribosomopathies were originally thought to be fatal. Many ribosomopathies are due to defects in ribosome synthesis and are rare.
Example of a ribosome pathology
Treacher Collins Syndrome (TSC) which causes abnormal craniofacial development.
Endoplasmic reticulum structure
Mesh of interconnected membranes which are involved in protein synthesis and transport. The nuclear envelope is connected to the RER which is connected to the SER.
Rough Endoplasmic Reticulum function
Production of proteins, ‘tags’ proteins for appropriate cell distribution, and post-translational modification (correct folding which is crucial for function).
Proteins produced by the RER
Lysosomal (hydrolytic) enzymes, secreted proteins (extracellular), membrane proteins.
Main function of Smooth Endoplasmic Reticulum
Manufacture of lipids
Specialised function of SER in hepatocytes
SER is more abundant. Glycogenolysis - breaks down glycogen to glucose.
Specialised function of SER in adrenal cortex
Produces steroid hormones
Specialised function of SER in muscle
In the form of sarcoplasmic reticulum which stores Ca2+. The orderly release of Ca2+ triggers muscle contraction.
The role of SER in the detox stop
Detoxifies organic chemicals (e.g. alcohol) by converting them into safer water-soluble products. E.g. in hepatocytes the SER can double its SA and then return to its normal size once the assault has subsided.
The result of endoplasmic reticulum dysfunction
defective folding and processing of proteins
What is ER dysfunction associated with?
Ageing and numerous neurodegenerative disorders such as Alzheimer’s, Parkinson’s and epilepsy.
How do correctly folded proteins move from the ER to the Golgi?
Transport vesicles
Function of Golgi apparatus
Further post-translational modification of proteins, stores proteins and packages proteins into vesicles which are transported.
3 possible Golgi dysfunctions
- Impaired trafficking (transport) of proteins through Golgi
- impairments in post-translational modification capacity
- loss of functionality due to mutation of proteins that make up the Golgi.
Effect of impaired protein trafficking in Golgi
If proteins which are important in making myelin are not correctly transported, this results in hypomyelinating disorders (e.g. cataracts)
Effect of impaired post-translation modification in the Golgi
Results in defective glycosylation disorders (glycoproteins and glycolipids) which cause a range of pathologies affecting multiple organs.
Pathology caused by loss of Golgi function due to mutated proteins that make up the Golgi
Muscular dystrophy
Vacuoles formation and structure
Single-membrane organelle formed by fusion of multiple vesicles.
Vacuoles function
Storage area - essentially part of external environment located within the cell.
Function of Vesicles
Transport substances within the cell and to the outside of the cell (exocytosis)
Formation of lysosomes
Large vesicles formed by the Golgi apparatus
Function of lysosomes
Contain hydrolytic enzymes which breakdown/digest extracellular / foreign materials and worn out cell components.
Name of the membrane system that make up organelles and allows compartmentalisation
endomembrane system
Origin of mitochondria
endosymbiotic theory - bacteria-like organisms incorporated into eukaryotic cells. Therefore contain own mDNA (maternal)
Function of mitochondria
Site of energy release and ATP formation via aerobic respiration following glycolysis in cytoplasm.
Structure of mitochondria
Outer membrane is smooth while inner membrane is folded into cristae (surface where ATP is generated during oxidative phosphorylation). Contains matrix.
Cause of mitochondrial dysfunction
Mutations in mtDNA
Diseases associated with mitochondrial dysfunction
Alzheimer’s, Parkinson’s, Huntington’s, diabetes, CVD, stoke, autoimmune diseases (Sjogren’s syndrome - dry mouth), cancer.
Function of cytoplasm
Cytoplasmic streaming - facilitates transport of material around cell (not static)
Name of fluid that makes up cytoplasm
Cytosol
4 functions of cytoskeleton
- maintains cell shape
- anchors organelles
- moves cell (cilia, flagella)
- controls internal movement of organelles
Structure of cytoskeleton
made up of 3 fibrous proteins
- microfilaments: actin monomer
- intermediate filament: fibrous subunit
- microtubule: tubulin
Function of actin monomer (microfilaments) in cytoskeleton
- maintain cell shape
- muscle contraction
- cytoplasmic streaming
- cell division
Function of fibrous subunit (intermediate filament) in cytoskeleton
- maintain cell shape
- anchors nucleus
- nuclear lamina (inside nucleus)
Function of tubulin (microtubule) in cytoskeleton
- cell motility (cilia and flagella)
- chromosome movement
- organelle movement
