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
what diseases are associated with intermediate filaments
- Kertain mutation in congenital epidermal
- Blistering diseases for example epidermalysis bullosa, laminopathies
what is the function of microtubules
- Cell scaffold
- Tracks for movement of cell organelles and vesicles
- Mitotic spindle fibres- chemotherapy drugs target this
- form Cilia and flagella
what are microtubules made out of
tublin
what are microfilaments made out of
actin
what disease is associated with microfilaments
- Drug targets for example taxane anit-cancer drugs that stop cell division
what is the structure of plasma membrane
- Phospholipid bilayer
- Embedded protein, transporters, channels, recepotrs, signalling and adhension molecules
- Anchors cytoskeleton
- Cholesterol to modify fluidity
what is the function of plasma membrane
- Selective diffusion
- Transport
- Cell signalling
- Cell adhesion
- Interaction with extracellular matrix
describe the structure of the Golgi apparatus
- Membranes arranged in stacks
- Cis and trans ends – cis is close to nucleus, trans is close to periphery
whats the definition of connective tissue
a tissue that lies between two other tissue which consists of cells and extra cellular matrix
what is connective tissues function
- they are tissues that support other tissues and give organs shape
what is connective tissue made up of
made up of cells, mainly those that secrete the extracellular matrix and the extracelluar matrix itself
what is connective tissue divided into
loose and dense
name the loose connective tissue
- serous membrane
- adipose tissue
- blood
name the dense connective tissue
- dermis of the skin
what are the cells of the connective tissue and the cells that synthesis the extracellular matrix
- fibroblast -
- adipocytes - fat
-chondrocytes - cartilage cells - osteocytes- bone
- haematopoietic blood cells
these maintain and synthesise the ECM
what does the extracellular matrix determine
determines the tissues physical properties for example..
- bone has abundant amount of calcified ECM
- neural tissue has almost no ECM
- tendons have tough rope like ECM
- dermis - pliable acts as a shock absorber
what is the function of the extracellular matrix
- cell scaffold
- cell migration
- shape,
- proliferation,
- survival
- tissue development
what are the two macromolecules of ECM
- Polysaccharide chains called glycosaminoglycans (GAGs) which are linked to a protein – proteoglycans
- Fibrous protein such as collagen, elastin, fibronectin
describe GAGS
- Made form polysaccharides (GAGs) 20 to 100s disaccharides
- Sulphated
- Can bind water and form hydrated gels filling spaces between cells
- GAG gels resist compressive forces
- GAG, permit rapid diffusion of nutrients, hormones and metabolites through them and pass from cell to cell and pass into tissues and through blood capillaries into tissues
- Examples of GAGs are chondroitin sulphate, heparin sulphate, dermatan sulphate, hyaluronic acid
describe proteoglycans
- When GAGs stuck onto proteins they are referred to as proteoglycans
- 1 GAG attached to a core protein
- Aggrecan, biglycan (simple protein with 2 GAGs attached to it) and syndecan are examples of 3 different proteoglycans
name examples of GAGs
- Examples of GAGs are chondroitin sulphate, heparin sulphate, dermatan sulphate, hyaluronic acid
describe hyalurinc acid
- consists of 25,000 disaccharides
- Joints resist compressive forces,
- Acts as a lubricant
- Cell migration- wound healing
name some examples of proteoglycans
- Aggrecan, biglycan (simple protein with 2 GAGs attached to it) and syndecan are examples of 3 different proteoglycans
what are the 3 types of fibrous protein that you need to know
- collagen
- elastin
- fibronectin
whats the function of fibbers proteins
- give rise to the strength of extracellular membranes
describe collagen
- Collagen – most abundant protein in human
- provides tensile strength
- Collagen protein polymerizes and forms collagen fibrils
- Fibroblast – makes collagen and therefore is in the collagen
- Collagen type I is the most common it has structural roles in the bone
- structural roles in skin
describe the diseases associated with collagen
- If there are mutations in collagen then the skin is not held together very well these are called ehiers-danlos syndromes (EDS)
describe elastin and the disease of elastin
- Polymer of tropoelastin which is associated with fibrillin (glycoprotein) they polymerise to form elastic fibres
- Elastic fibres are most common in arteries
- Elastin fibres have a fibrillin sheath
- Abundant in arteries lungs and skin
Disease - Marfin syndrome – fibrillin gene is mutated and this causes the rupture of the arteries
describe fibronectin
- Circulates soluble fibronectin in plasma and body fluids
- Insoluble in many tissues
- Fibronectin fibres binds to cells (integrins – allows it to bind to the surface of the cell, these integrins sit in the plasma membrane of the cell allowing receptors to be formed and signalling into the cell itself) and ECM (collagen)
- Cell attachment and matrix organisation
- Guiding cell migration – development and wound healing
describe the structure of the basement membrane
- Made out of the Lamina densa (dense layer and appears darker and denser)
- lamina lucida (layer that you can see through, appears clearer in microscopy)
- reticular lamina (this is where the basement membrane attaches to the extracellular matrix- separate from the basal lamina itself)
- Goes in the order, lamina lucida, lamina densa and then reticular lamina
- Main collagen type IV
describe the function of the basement membrane
- Underline all epithelial and endothelial cells
- Separates epithelium from the underlying connective tissue
- Supportive anchoring,
- protective role
- selective cell movement
- molecular filtering
- signalling
describe the diseases associated with the basement membrane
- Responsible for genetic diseases such as laminin which is junctional epidermolysis bullosa this blisters at the basement membrane in skin and internal epithelial tissues
- Collagen (type IV) heparan sulphate proteoglycan, laminin, nidogen (entactin) – have mutations associated and have diseases asosicated with them
- malignant carcinoma – when a cancer develops in an epithelial cell it has to break through the basement membrane into the dermis then through the endothelium and into the blood to attach to other organs this is a carcinoma
describe what the epithelial is held together by
- held together by epithelial junctions which control movement from cell to cell
what are the types of epithelial junctions
- Tight - regulate movement of ions and solutes between cells
- Adherens – tether adjacent cells together
- Desmosome – resist mechanical stress -strongest junction, strong attachment in tissues subject to stress
- Gap – allow passage of small molecules between adjacent cells such as amino acids and sugars
- Hemidesmosome – anchor epithelium to basal lamina
what are desmosomes made up of
- made up of cadherin and desmoplakin
what diseases are associated with cadherin being targeted in desmosomes
- In staphylococcus scalded skin syndrome – toxins from S aureus are directed against cadherins causingepidermal blisters
- Autoimmune diseases such as pemphigus vulgarius, these are autoantibodies directed against desmosomal cadherins proteins which break down and result in epidermal blisters
what diseases are associated with desmoplakin being targeted in desmosomes
Desmoplakin is targeted
- In naxos disease that causes skin blisters and cardiomyopathy
what are the two types of cilia
- primary cilia (non-motile)
- motile cilia
name some motile cilia
pseudopedia
lamellipodia
filopodia
describe what primary cilia do
there is only one of them – sensory antennae, chemosensory, photosensors, mechanosensors; signalling
where are motile cilia present.
trachea and fallopian tubes – help stuff move over the surface
what are diseases associated with cilia
- Genetic ciliopathies for example bardet-biedl syndrome
- lack of cilia in fallopian tubes – ectopic pregnancy
describe the function of pseudopodia
- Cell protrusions – actin polymerisation and neutrophils
- For pseudopodia allows cells to move and crawl
what are lamellipodia and filopodia
- function includes cell movement, contact and environmental sensing
describe function lamellipodia
ruffles; epithelial cells; fibroblasts cell migration (moving)
describe function of filopodia
spikes; migrating neural growth cones, fibroblasts
what are there an abundance of in invasive cancer cells
- filopodia
describe microvili
- Cell surface extension of secretory and absorptive epithelia for example kidney and intestinal cells
- Several 1000 microvili on apical surface of a single small intestinal cell this increases surface area 600 fold
describe microvili disease
- Infection by E.coli toxin can destroy the intestinal microvilli leading to malapsorption and osmotic diarrhea
- Toxins destruction or intestinal microvilli and intestinal tight junctions and inhibition of water reabsorption
what are the three layers of the basement membrane
lamina lucida
lamina densa
reticular lamina
