Cell Biology Flashcards
why do doctors need to know about cell biology
- Cellular basis of disease - Failure of cells lead to failure of organs, lead to failure of organ system
- Drug delivery and targets
- Diagnosis
how many times does a light microscope magnify
it magnifies 2000 times
how many times does a electron microscope magnify
it magnifies greater than 500,000 times
what is immunocytochemistry
science of using antibodies on individual cells, to stain difference cells,
what is immunohistochemistry
stains antibodies and proteins so you can see the structure of the tissue, uses whole tissue structures.
describe the structure of the nucleus
- Chromatin (unwound chromosomes, DNA complexed with protein)
- Double membrane – the outer membrane is continuous with the endoplasmic reticulum
- nuclear pores- made up of lamin and ermin
- Nucleolus
- Two types of chromatin these are Heterochromatin and euchromatin
what is euchromatin
- Euchromatin is loosely packed transcribed DNA that’s transcribed to RNA and is therefore expressed
what is heterochromatin
- heterochromatin is densely packed regulatory – it is important in regulating the cell and is not expressed it has a dark grey structure
what is the function of the nucleus
- Contains genetic material
- Only expresses genetic material when it is euchromatin
- The nuclear pores regulate transport allowing steroid hormones into the nucleus and messenger RNA out of the nucleus – have tags such as a nuclear import sequence or nuclear output sequence restricting what goes in and what goes out.
- Nucleolus is responsible for ribosomal RNA transcription and ribosome assembly
what are the diseases caused by failure of the nucleus
- Inherited defects in the inner nuclear membrane proteins (lamin or emerin)
- Laminopathies (associated with lamin nuclear membrane proteins)– 8 rare human disease, diverse manifestations and pathophysiology obscure
- emery-dreifuss muscular dystrophy which effects skeletal and cardiac muscle
- Hutchinson-Gilford progeria syndrome – this is premature ageing and is associated with lamin protein misshapen causing an unstable nuclear envelope
- Treacher Collins syndrome – TCOF1 gene (nucleolar protein)
describe structure of the rough endoplasmic reticulum
- Rough has ribosomes attached whereas smooth does not
- Continuous with the nucleus membrane
describe the function of RER
- RER – makes membrane and organelle protein and all proteins secreted by the cell – PROTEIN SYNTHESIS
- Proteins made by the ribosomes cross the rough ER membrane, once the proteins are made they move into the centre of the RER membrane and that is where they are folded – FOLDING
- Have sugars added and glycosylation to protect proteins and allows them to be transported to the Golgi apparatus - MODIFICATION
describe disease caused by failure of RER
- Linked to cystic fibrosis if the CFTR is misfolded in the RER
- Cystic fibrosis is when folding is not controlled and it is folded over and over again
describe the structure of SER
- No ribosomes attached to surface therefore it is smooth
- Continuous with the nucleus membrane
- Has cisternae
- Fluid filled cavity
describe the function of SER
- Synthesis – carbohydrates and lipids
- Calcium Storage – e.g. calcium in smooth ER of many cells
- Detoxification SER enzymes detoxify absorbed drugs toxins which happens in the liver and kidney
describe the function of the Golgi apparatus
- Packaging of secretions such as hormones and proteins for exocytosis
- Vesicles from ER go to Golgi for maturation and modification of proteins
- Proteins tagged for delivery, tags make sure they are sent to the final place,
- Proteins that are non-functional have another tag put on them and are sent to the lysosome to be broken down and digested
what are the excretory pathways
exocytosis
endocytosis
describe exocytosis
– constitutive which means it is not regulated, e.g. extra cellular matrix proteins by fibroblasts these make up the dermis in the skin and act as a damper and shock absorber in the skin and secrete extracellular matrix proteins
- Secretory vesicles-regulated by signals for example insulin beta cells in islets of Langerhans – hormones and growth factors are examples
describe endocytosis
- process by which cells absorb molecules which are often recycled back into the cell membrane for example growth factor receptors, can be molecules from an extracellular environment or insulin receptors and pathway reacted
how do cells recycle the receptor
- During endocytosis cells need to be able to recycle the receptor, the receptors are occupied by a hormone, the reports that are occupied are absorbed within the cell in a vesicle and the cell then breakdown the receptor by lysosomes or recycles them by endosomes and transported back to the plasma membrane.
describe the structure of the lysosomes
- formed at Golgi
- Contain digestive enzymes
describe the functions of lysosomes
- Defence against disease
- Contain digestive enzymes
- Play a role in phagocytosis – fuse with phagocytotic vesicles to digest contents, they are abundant in macrophages
- Autophagy clean-up of cell organelles and derby within cells
- Take part in Autolysis after cell death
describe the disease associated with lysosomes
- Lysosomal storage disease > 30 childhood diseases for example Tay Sachs failure to breakdown gangliosides (lipids)
describe the structure of peroxisomes
- originate at RER
- membrane bound organelle formed of a lipid bilayer surrounding a crystalline core
describe the function of peroxisomes
- Metabolism of fatty acids
- Metabolism of hydrogen peroxide as it contains catalase
- Metabolism of ethanol
- Detoxifying (free radicals from normal metabolic process such as hydrogen peroxide and alcohol)
describe the diseases of peroxisomes
- Lipid metabolism, nervous system, leukodystrophies
- Zellweger syndrome-failure to form peroxisomes which accumulate high levels of long chain fatty acids, it is a rare autosomal recessive congenital disorder that causes hypomyelination, hepatomegaly (enlarged liver), hypotonia and facial abnormality and developmental delay
describe the structure of mitochondria
- double membrane with an intermembrane space
- Inner membrane
- Cristae – increase surface area
- Matrix
- Makes mitochondrial DNA therefore showing it is from bacterial origin
- 1500 mitochondrial proteins
- 37 mitochondrial genes – most mitochondrial protein is imported
describe the function of mitochondria
- Energy production produces ATP by oxidative phosphorylation
- role in apoptosis
describe the disease of the mitochondria
- maternally inherited
- > 40 diseases, clinically heterogenous
- Tissue with high energy needs often affected
- Genetic diseases mtDNA or nDNA encoding mitchondiral proteins
- Toxins and drugs
- Ageing – mitochondrial free radical production driving mitochondrial degeneration, may damage the mitochondria and lead to ageing of the cell
what are the three components that make up the filaments of the cytoskeleton
- actin microfilaments - 3-6nm
- intermediate filaments - 10nm
- microtubules - 20-25nm
what do actin microfilaments do
- formed of actin subunits
- Actin proteins polymerise in all cells cell movement
- Cell cytoskeleton – cell shape (stress fibres)
- Cell movements with myosin (cytokinesis)
- Cell organelle and vesicle transport
- Alpha actin thin filaments with myosin in muscle movement
what are the diseases associated with actin microfilaments
- Genetic diseases such as gamma actin – congenital deafness
- Muscle actins – cardiomyopathies and skeletal myopathies
what is the function of intermediate filaments
tensile strength
- Structural integrity – found in tissue under stress
- For example keratins and lamins ( in nuclear membrane) – different ties found in different cell types