Flashcards in General Deck (517)
What is a glycocalyx?
A carbohydrate rich coating that covers the outside of many eukaryotes and prokaryotes.
Compare the nucleus of prokaryotes and eukaryotes.
Prokaryotes - no nuclear membrane.
Eukaryotes - nucleus, nuclear membrane, nucleolus.
Compare whether the organelles in prokaryotes and eukaryotes are membrane bound.
Prokaryotes - no
Eukaryotes - Yes e.g lysosomes, mitochondria, chloroplasts.
Compare the flagella in prokaryotes and eukaryotes.
Prokaryotes- made with 2 proteins.
Eukaryotes - made with multiple microtubules.
Compare the Glycocalyx in prokaryotes and eukaryotes.
Pro- Present as capsule or slime layer.
Eu - Present but chemically simple - cellulose or chitin.
Compare the cytoplasm and cytoskeleton of prokaryotes and eukaryotes.
Pro- No cytoplasm and cytoskeleton
Eu- Cytoskelton and cytoplasm.
Compare the ribosomes of prokaryotes and eukaryotes.
Pro- small 70s
Eu- 80s and small 70s in organelles.
Compare the DNA of prokaryotes and eukaryotes.
Pro- single circular chromosomes with no histones.
Eu- multiple linear chromosomes with histones.
Compare the methods of cell division in prokaryotes and eukaryotes.
Pro - Binary fission
Eu- mitosis / meiosis
What are the benefits of an organism being multi-cellular (Eukaryotes).
Multi-cellular organisms are prey for fewer predators, can eat a wider variety of prey, longer life span, specialism for adaption and efficiency.
What is cytosol?
The intracellular fluid of cytoplasm. Contains dissolved ions, glucose, Aino acids, ATP, lipids and waste products.
Site of enzyme-controlled reactions.
What is the purpose of the cytoskeleton?
Provides structural support to maintain the shape and size of the cells and enable their specific function.
Provides anchorage for organelles so they don't get moved around and damaged.
Allow cell locomotion for example in cillia and flagella.
Also important to cell communication.
What are the 3 main filament types in a cytoskeleton?
Microfilaments, intermediate filaments, microtubules.
What proteins are microfilaments in the cytoskeleton made from?
Actin and myosin.
What are the purpose of microfilaments in the cytoskeleton?
Surround the edge of the cell, help generate movement, provide mechanical support needed for cell strength and shape, create microvilli.
How do microfilaments in the cytoskeleton allow a cell to move?
Microfilaments break and reform constantly to allow the cell to move.
How do microfilaments in the cytoskeleton help when forming blood clots?
Microfilaments break and move out to form new adhesions and increase the size of platelets. This creates a large surface area and allows a blood clot to form.
What proteins are the intermediate filaments of the cytoskeleton made from?
Keratin, vimentin and lamination's.
What are the purpose of intermediate filaments of the cytoskeleton.
They are very strong and are found in parts of the cell which are under mechanical stress such as the skin. They help stabilise the positions of the organelles within the cell.
What proteins are the microtubules in the cytoskeleton made from ?
What is the purpose of the microtubules in the cytoskeleton?
Help with cell strength and movement of organelles such as vesicles during cell division. Provide structure to the flagella.
Where are microtubules formed?
In the centrosome then radiate outwards.
What is the function of centrosomes?
Growth of mitotic spindles during cell division.
What do centrosomes consist of ?
2 centrioles (cylindrical structures composed of 9 clusters of microtubule triplets, both at right angles to each other. )
Pericentriola material (protein material) surrounds the centrioles.
What are cilia made of?
Microtubule core and surrounded by a membrane.
What is the function of cilia?
Transport of fluid along a cell surface.
How does smoking contribute to ectopic pregnancy in women (explain in terms of cilia).
Smoking destroys the cilia, resulting in building-up of mucus, dust and bacteria within the lungs. This build up pass the oocyte towards the uterus and so increases risk during pregnancy.
Name a human cell where a flagella is necessary
Where does the endoplasmic reticulum extend from and too?
The nuclear envelope to the cytoplasm.
Briefly describe the structure and look of the endoplasmic reticulum.
A network of membranes in the form of flattened sacs and tubules extending from the nuclear envelope to the cytoplasm.
What is the purpose of the rough endoplasmic reticulum ? And what feature allows this?
Ribosomes are on the surface of the RER and allow protein synthesis.
What happens to proteins that have been made by the RER?
Some enter the ER space for processing and sorting - by the Golgi body.
Some enzymes may attach carbohydrate groups to the proteins or attach the proteins to phospholipids. These molecules are incorporated into membranes of organelles or the plasma membrane.
Compare the presence of ribosomes and enzymes on the smooth and rough ER.
The smooth ER contains no ribosomes but the rough ER contains Alot of ribosomes.
The smooth ER has a greater range of different enzymes.
How does the wide range of enzymes on the smooth ER aid its function ?
Allows it to synthesise fatty acids and steroids such as oestrogen and testosterones.
What is the purpose of the smooth ER in the liver?
Helps release glucose from glucose-6-pand to detoxify lipid soluble drugs such as alcohol and pesticides.
What is the purpose of the smooth ER in muscles?
How does taking drugs such as phenobarbital cause changes in the smooth ER and what are the side effects of this ?And where in the body is the smooth ER that has these changes?
The cells produce more smooth ER to counteract the poison, meaning the person has to take more of the drug to feel the effect. Causes drug addiction.
What is the genetic material of ribosomes?
What do ribosomes consist of structurally?
A large subunit and a small subunit which are both synthesised separately in the nucleus. Consist of about 50 different protein types.
Where are ribosomes present in the mitochondria?
Free in the cytoplasm or attached to the endoplasmic reticulum (RER).
What is the overall function of ribosomes?
What do the cis and trans faces of the Golgi body face in the cell?
Cis/ convex entry- faces the endoplasmic reticulum.
Trans / concave exit - faces the plasma membrane.
How to the Golgi complex transport and process proteins?
Proteins are surrounded by the endoplasmic reticulum membrane
Transport vesicles containing polypeptide bud off smooth endoplasmic reticulum and fuse with the cis face of the Golgi apparatus, releasing polypeptide into the lumen of the Golgi apparatus.
Proteins are modified and move into medial cistern.
Proteins then move towards the exit face where they are either formed into Golgi vesicles and then lysosomes, secretory vesicles which release polypeptide by exocytosis or membrane proteins which are inserted into the plasma membrane as a vesicle.
What is the general function of the Trans face of the Golgi apparatus?
What is the general function of the Cis face of the Golgi apparatus?
What are the main overall functions of lysosomes?
Digestion of substance entering the cell such as worn out organelles (Autophagy) or entire cells (Autolysis).
What is the digestion of worn out cells by lysosomes called?
What is the digestion of entire cells by lysosomes called?
Why is autophagy necessary?
Allows renewal, cellular differentiation and control of growth and tissue remodelling.
What is the cause of Tay-Sachs disease?
The absence of Hex A lysosomal enzyme.
Hex A normally breaks down the glycolipid 'Ganglioside GM2'. Without being broken down it builds up and begins to destroy nerve cell function.
What are the symptoms of Tay Sachs disease ?
Seizures, muscle rigidity, blindness, very early death (Age 5 ish).
What is the function of peroxisomes and how do they do this?
Peroxisomes are involved with the metabolism of amino acids and fatty acids. They contain oxidases which oxidise toxic substances such as alcohol by removing a hydrogen atom.
Also contain enzymes to fight the toxic effects of hydrogen peroxide.
Where are a lot of peroxisomes found?
What is the cause of Zellweger syndrome ?
Autosomal recessive condition. Mutations in genes cause the peroxisomes to become non-functioning. This causes the myelin on neurones to breakdown and prevents the transmission of nerve impulses.
What are the symptoms of Zellweger syndrome and when is it developed?
Develop symptoms during the new-born period.
Wek muscle tone, feeding problems, hearing loss, vision loss, seizures.
What is the main function of proteosomes ?
Degrade cytosolic proteins (un-needed, damaged or faulty).
What enzymes do proteosomes contain?
How do proteosomes contribute to causing Alzheimers disease?
Caused by the build-up of misfiled proteins in brain cells.
On-going research to discover why these proteins are not degraded by Proteosomes.
What are the main functions of the mitochondria?
Aerobic respiration and ATP production.
What is the purpose of the cristae in mitochondria ?
Provide a large surface area for aerobic respiration.
Where are enzymes needed for respiration found in the mitochondria.
In the matrix and on the Cristae surface.
What might be the effect of centrosome inhibitors on cancer?
Centrosomes form the protein spindle fibres which are a necessity in cell division. They are therefore highly important when regulating cell division. If the centrosomes can’t form spindle fibres, cell division will become irregular and this can lead to the formation of some malignant tumours.
What are the functions of the plasma membrane?
Regulates what enters and exits the cell.
Involved with cell recognition.
Aids cell signalling.
Aids cell linking and cross-talk
Describe generally the structure of the plasma membrane.
Thin, flexible, fluid mosaic model.
How is the bi-layer able to be fluid and what is this fluidity used for?
Neighbouring phospholipids can swap places within the bi-layer. Allows movement of membrane components required for cell movement, growth, division, secretion and the formation of cellular junctions.
What is the purpose of cholesterol in the fluid mosaic model of the cell membrane?
Cholesterol immobilises the first few hydrocarbon groups of phospholipid molecules. This makes the lipid bi-layer less deformable and decreases its permeability to water soluble molecules.
What are glycoproteins used for in the phospholipid bi-layer of the cell membrane?
They contain oligosaccharides and form the glacocalyx.
How are glycoproteins helpful in red blood cells?
They help form the glacocalyx which acts as a slippery layer and helps red bloody cells move smoothly into the capillaries.
What are the purpose of transmembrane proteins?
Transport substances from outside and inside the cell.
If a membrane was depleted of cholesterol what would happen to the membrane structure?
The membrane bi-layer would be more deformable due to becoming less rigid. Permeability to water-soluble molecules would also increase.
What is the main purpose of the phospholipid bi-layer?
Separates hydrophilic and hydrophobic domains.
What type of permeability does the phospholipid bilayer have?
What molecules is the phospholipid bilayer permeable and I'm-permeable to?
Permeable = non-polar, lipid soluble (oxygen and carbon dioxide)
Impermeable = ions and large molecules (Glucose).
How does water pass through the phospholipid bi-layer?
What is the overall purpose of the phospholipid bi-layer being semi-permeable?
Allows concentration gradients to be built and pH to be regulated.
What are channel intrinsic proteins generally used for?
Used for charged ions usually.
What are carrier channel proteins generally used for and name some of their features?
Carrier proteins are specific to the substance they and transporting. They require a constant concentration gradient.
Used for larger molecules such as glucose.
What is the use of carrier proteins subject to?
Transport maximum (how many carrier proteins are actually present), saturation (the quantity of carrier proteins which are already occupied).
How many molecules can a carrier protein transport at once and why?
1 because they are gated and highly specific.
How does temperature affect the rate of diffusion?
As temperature increases, so does rate of diffusion.
How does the mass of the substance moving affect its rate of diffusion?
The greater the mass, the slower the rate of diffusion.
How does diffusion distance affect the rate of diffusion?
As diffusion distance increases, rate of diffusion decreases.
How does concentration gradient affect rate of diffusion?
As concentration gradient increases, so does rate of diffusion.
What happens to a cell when placer in a hypertonic solution and why?
The concentration of ions inside the cell is lower than outside the cell. Water moves out of the cell by osmosis. Cell shrinking.
What happens to the cell when placed in a hypotonic solution?
Concentration of ions inside the cell is higher. Water moves into the cell. Osmotic lysis.
What is an isotonic solution?
Concentration of ions inside and outside the cell is the same.
How is cerebral edema treated?
Hypertonic solution is infused to drain extra water out of the brain.
What is the energy source for active transport?
Uses energy from the hydrolysis of ADP.
Give an example of a active transport mechanism.
sodium potassium pump.
Does active transport require inter membrane proteins and if so which?
Yes - carrier proteins.
ATP changes the shape of carrier proteins and allows substances to be pumped against the concentration gradient.
What is another name for secondary active transport?
What is symport in secondary active transport?
Molecules travel in the same direction.
What is antiport in secondary active transport?
When molecules travel in opposite directions.
What is the positives of using secondary active transport?
More efficient than primary active transport because less ATP is required - uses alternative energy source.
How do intrinsic channel and carrier proteins differ?
Carrier proteins are gated and specific and also carry only one molecule at a time.
Channel proteins are non-specific and are constantly open.
What enzymic functions do membrane proteins have?
Act as digestive enzymes.
What will happen in receptor mediated endocytosis if no Cathrin is present?
Vesicles cant form and no LDL's will be taken into the cell.
How do viruses often take advantage of the receptor mediated endocytosis process?
Viruses attach to the receptor proteins on the cell surface membranes and are taken into the cell by receptor mediated endocytosis. HIV attaches to CD4 receptors.
Outline the process of phagocytosis.
Chemotaxis of microbe to phagocyte.
Ingestion of microbe by phagocyte by endocytosis.
Formation of phagosome.
Fusion of phagosome with a lysosome to form a phagolysosome.
Digestion of ingested microbes by enzymes.
Formation of residual body containing indigestible material.
Discharge of waster material by exocytosis.
Which cells undergo phagocytosis?
Macrophages and neutrophils.
Outline bulk phase endocytosis.
Small droplets of extracellular fluid are taken into the cell by endocytosis.
Where does bulk phase endocytosis occur on mass?
Intestines and kidneys.
Does bulk phase endocytosis require receptors and is it selective?
No receptors required.
All solutes in the extra-cellular fluid are brought in. Non-selective.
What is the main purpose of exocytosis?
Used to transport materials out of the cell.
What are the main cells that exocytosis is exhibited by and what do they release?
Secretory cells - digestive enzymes and hormones.
Nerves - neurotransmitters.
What is transcytosis ?
A combination of endo and exocytosis used to pass substances through the cell.
Where is transcytosis common?
Endothelial cells which line blood vessels.
Describe the process of Co-transport of glucose in the small intestine.
Describe how the second messenger model works with adrenaline.
What is it called when Glycogen is converted to Glucose
Describe the two possible ways vesicles can form during Receptor-mediated endocytosis.
Stimulated endocytosis- Vesicles form on the cell surface membrane when ligands bind to receptors.
Constitutive endocytosis - All receptors are taken into vesicles whether they are bound by ligands or no.
Describe how the vesicles form during receptor-mediated endocytosis.
The phospholipid PIP2 binds to AP2 adaptor proteins and allows their confirmation to change. A Cathrin coating is now able to bind to the AP2 receptors. The Cathrin buds in towards the cytosol to form a vesicle. Dynamic allows complete vesicle fusion and causes the vesicle to become un-attached from the cell surface membrane.
What is the purpose of dynamic in receptor- mediated endocytosis vesicle formation?
It allows complete vesicle fusion and allows the vesicle to become un-attached from the cell surface membrane.
What is the purpose of the Cathrin coating in receptor mediated endocytosis?
Cathrin coating buds in towards the cell cytosol to form a vesicle.
Describe the sorting process of vesicles in receptor-mediated endocytosis.
Vesicles fuse with early endoscopes. The acidic pH of the endoscopes cause AP2 receptors to release the ligands they are bound to into the endosome lumen.
Some ligands are degraded by the endosome whilst the receptors are packaged int more vesicles and returned to the plasma membrane.
However, any left over ligands and receptors form late endosomes.
Describe the maturation of the early endosomes in the receptor mediated endocytosis process.
Regions of the early endosome membrane cave into the lumen an bind off to form luminal vesicles. This creates multi vesicular bodies within the endosome. Now all of the endosome cargo (phospholipids) is contained within the lumen and is accessible to prolytic enzymes.
Describe the glycosylation of endosomes in the receptor- mediated endocytosis process and what is the purpose of this?
Transferase enzymes within the endosome covertly bond carbohydrates to proteins in the endosome membrane. This creates a thick, protective glycocalyx which cannot be degraded by lysosome enzymes.
Describe the acidification of late endosomes in receptor-mediated endocytosis.
Endosomes contain proton pumps that continually transport H+ into the endosome, making it more acidic. By the time the late endosome is formed, the endosome is highly acidic.
What happens after the late endosomes are formed in receptor-mediated endocytosis?
Late endosome fuses with a lysosomes. Lysosomal enzymes degrade proteins, lipids, DNA and RNA into smaller components. There smaller components are transferred into the cell cytosol and re-purposed. The left over lysosome can then fuse with another endosome.
Draw the Golgi packaging system.
How is resolving power affected as frequency of light waves increases?
Resolivng power also increases
Name some types of optical microscopy.
Phase contrast, DIC, Dark field, Polarisation, UV, Fluorescent, Light field.
Describe the specimen used and images produced by phase contrast microscopy.
Living, unstained cells
Cells appear black and white
How does phase contrast microscopy happen?
2 beams of light are used - one goes through the specimen and the other doesn't. They eventually meet. This exaggerates the difference in the refractive index of the specimens and the surroundings.
How do Normarski/ DIC microscopy images appear?
They have a high resolution and give a 3D appearance which shows the structure of the sample well.
How do Dark field microscopy images appear?
Illuminates cells and tissues against a dark background to allow for contrast.
How do polarisation microscopy images appear?
Illuminates cells and tissues against a dark background to allow for contrast.
How are Polaroid microscopy images produced?
The specimen is places between crossed polaroids. Areas where the plane of polarisation has been rotated are seen as brighter than the background. This method detects areas of highly organised rays.
How do polaroid microscopy images appear?
They detected areas of highly organised rays and illuminates cells and tissues against a dark background to allow for contrast.
What are highly organised rays in terms of sample specimen? - polarisation microsopy
How does UV microscopy work and what do UV images appear like?
Uses fluorescent molecules to observe structures. Certain substances within the cell strongly absorb UV and can be detected when illuminated with a UV light source.
What is needed to be able to see a UV microscope image?
UV light source
How does fluorescent microscopy work and what do the images look like?
Certain substances appear fluorescent at a particular wavelength of light or can be made fluorescent by the use of histochemical reactions. This makes the cell become visible.
What is multiple fluorescent microscopy?
Where each organelle appears a different fluorescent colour due to the wavelength of light or the use of histochemical reactions.
What is confocal fluorescent microscopy?
A method used to cleaner and resolve a fluorescent microscope image.
What is the disadvantage of using bright field microscopy?
You must stain the cells which can be damaging.
Describe how confocal microscopy works and what type of image this creates.
Lasers and optical modification are used to focus light onto a single plane. This produces a highly precise, small slice of the specimen in an image.
What 2 types of microscopy are often combines and why?
Phase contrast and fluorescent. They create a highly structured and coloured specimen image.
What is interference in terms of microscopy?
2 beams are used - one of them passes through the specimen and the other doesn't. The light may therefore undergo phase changes due to the difference in the 2 refractive indexes that the light travels through.
What may interference in microscopy be used for?
Used to quantitatively measure. E.g find the dry mass of a sample.
What are phase changes in light?
Light waves changes by 180 degrees when they reflect from the surface of a medium with a higher refractive index than that of the medium to which they are travelling.
What type of specimen are usually stained during microscopy?
Thin specimens which are generally transparent at the visible light wavelengths.
What are vital dyes used for in microscopy?
They are used to assess culture viability by visualising how many of the cells in a culture are live and dead.
What are the 2 types of vital dye use in microscopy?
Vital dye exclusions and vital dye uptakes
What is vital dye exclusions in microscopy?
They are impermeable to live cells but permeable to dead cells. The dead cells will become visible and therefore countable
What is vital dye uptake in microscopy?
They are permeable to living cells and therefore make the living cells become visible and therefore countable. Not able to penetrate dead cells.
What is the most common type of staining used for microscopy and what does it do?
Haemotoxylin makes the nuclei stain blue.
Eosin stains the cytoplasm pink.
What stain is often used to stain neurones in microscopy and what colour does it go?
Golgi silver stain - black
What stain is often used to stain nucleic acids in microscopy and what colour does it go?
Nissl stain - purpose
What stain is often used to stain DNA in microscopy and what colour does it go?
Feulgen Schiff - Red
Outline the process of enzyme histochemistry.
Incubate a tissue sample with a specific substrate. The enzymes within the tissue sample react with the substrate. The complex formed has a coloured appearance and therefore identifies where enzymes are present in your sample.
What is the purpose of enzyme histochemistry?
To see the location of enzymes within a cell
What is the main purpose of autoradiography?
It uses radioactive sources to blacken desired regions of the photographic plate.
Outline the process of autoradiography.
Precursor substances containing labeled 14C or 3H are injected into the organism. The radioactive precursor substance is then used to make radioactive versions of the desired substance.
When the sections are later prepared and placed on a photographic pate or coated with photographic emulsion, black grains will appear where the radioactivity is present.
What is meant by the term 'in vivo'?
Within a living orgaism
What is the precursor substrate for proteins during autoradiography?
What is the precursor substrate for DNA during autoradiography?
What is one of the main uses of microscopy in the clinic environment?
What are the 2 types of immunofluorescence?
Direct and indirect
Describe direct immunofluorescence.
Specific antibodies against an antigen are labelled with fluorescent due. Antibodies then bind to the antigen and act as a labeller.
Describe indirect immunofluorescence.
Specific primary antibodies bind to the antigen. Secondary antibodies labelled with the fluorescent dye then bind to the primary antibodies.
What are the advantages of indirect immunofluorescence over direct immunobluorescnc?
Allows more binding of secondary antibodies to the primary antibodies. Therefore more fluorescent markers and present and a stronger colour image is produces.
It is a lot cheaper.
What is tissue fixation?
The cessation of the normal life functions of the tissue and the preservation of the tissue sample.
The ability to distinguish between two or more objects which are close together.
What is the equation for resolution?
On laptop notes
What do the letters D, N and alpha stand for in the resolution equation?
N = refractive index
alpha = angular apeture
What is the refractive index of air?
What is the refractive index of oil?
What are arrays in terms of microscopy?
Lots of repeats of the same structure in an area of the cell
What is the purpose of the condenser in a microscope?
Focuses light onto the specimen and controls the contrast.
What is the purpose of the objective in a microscope?
Collects light from the image and focuses it to form an image within the barrel of the microscope.
Define resolution limit.
The smallest distance a which two separate items can be distinguished.
Depends on the wavelength of light used and the properties of the optical components.
What is the purpose of immersion oil in light microscopy?
Increases resolving power - most frequently used under a high magnification.
What are protozoans?
Single-celled, microscopic organisms.
What are axonemes on cilia?
A bundle of microtubules formed from tubular and their associated proteins extend from the base to the tip of the cilia.
What is meant by the "9+2" array structure in cilia?
The microtubules in the axoneme are arranged in a pattern of nine doublets in a ring around a central pair of microtubules.
What causes the cilia to be able to move and how is this triggered?
The bending of the axoneme stimulated by Calcium and ATP.
Adjacent microtubules slide with respect to each other to create a sliding activity and therefore a coordinated wave like movement.
What is the purpose of tetrahymena in relation to cilia?
It can re-generate cilia which have been gently removed.
How do Colchicine and Colcemid affect cilia?
They inhibit tubular monomers growing in microtubules.
When are membranes of adjacent cells most interactive?
During cancer cell metastasis and foetal development.
What is Metastasis?
Cancer split off from the primary tumour and travel around the body forming secondary tumours.
What controls the interactions between adjacent cell membranes?
Name some types of junctions which form between adjacent cells.
Desmosomes, Hemi-desmosomes, adherent junctions, tight junctions, gap junctions.
How many different types of gap junctions can adjacent cells have between them?
What tissue types are desmosome gap junctions most frequently found in?
Cardiac and intestinal tissues.
Usually in epithelial cells.
Describe the structure of desmosome gap junctions.
They have a central glycoprotein core. This is then joined to connecting filaments which join to desmosomal plaques. Tonofilaments then join the desmosomal plaques to the cell's cytoskeleton and organelles.
What type of binding do desmosome gap junctions use?
What is homophillic binding?
The binding of a receptor molecule to an identical molecule.
What type of proteins are used in desmosome gap junctions?
What type of adhesions do desmosome gap junctions make?
What is the purpose of hemidesmosomal gap junctions?
Adhere cells to their basal lamina.
What is a cells basal lamina?
A layer of extracellular matrix secreted by the epithelial cells. Basement layer that the cells sit on.
How do adherent gap junctions cause cell to cell adhesion?
Adherents junctions use cadherins transmembrane proteins which are tethered via linker proteins to actin filaments. The cadherins on the plasma membranes of adjacent cells interlock and cause adhesions.
Where are adherent gap junctions most commonly used? (What tissue type?)
What is the main importance of adherents junctions in the body?
They are used in development to form the neural tube and lens vesicles which allow round lenses to be formed in the eye.
What cell types are tight junctions found in?
Only in epithelial cells.
What are the purposes of tight gap junctions?
They prevent passage of materials between cells and therefore force materials to travel directly through cells. This tightly controls the movement of substances into and out of the blood.
Also contributes to membrane asymmetry to allow active and passive processes to be separated.
What structures do tight junctions occur at?
At intervals or encircling cells ( a cell tightly attaches to all of its neighbouring cells in a circular formation).
What would happen if tight junctions were not present in the gut?
Glucose would be lost during co-transport from the lumen of the small intestine into the capillaries. Therefore, glucose would never enter the blood capillaries.
What evidence has been found that tight junctions act as permeability barriers? Describe the experiment.
Electron-opaque tracer is added to one side of the cell layer. If tight junctions are present, the electron-opaque tracer will only travel part way between the cells and will be unable to pass through the gaps in the cells.
In what types of organisms do gap junctions occur in?
Describe the structure of gap junctions.
Connexons are hexagonal proteins that form a ring structure with a central pore. These then join each adjacent cell.
How are gap junctions controlled to control movement into and out of the adjacent cells?
Connexons can be rotated to change the size of the central pore between adjacent cells.
How are gap junctions beneficial if a neighbouring cell is undergoing apoptosis?
The connexions would rotate and make the central pore between adjacent cells close. Therefore the cell undergoing apoptosis will not pass any harmful toxins to the adjacent cells.
What is the overall purpose of gap junctions between adjacent cells?
Control cell communication
What is ionic coupling and what is its purpose in gap junctions in adjacent cells?
The movement of ions between cells via the pores produced. This allows metabolic cooperation and cellular synchornisation.
What is metabolic cooperation?
Cell communication method in which the mutant phenotype of an enzyme deficient cell is correctly cultured by contact with normal cells.
What is cellular synchronisation?
Cells in different phases of the cell cycle are brought to the same phase.
What conditions are required to allow cells to reader after they have been separated?
The presence of calcium and magnesium ions.
What are the purpose of cell adhesion molecules and when are they present in a cell?
They are present before cell junctions are formed and aid the cell junction formation process.
What are the negatives of using cell adhesion molecule to help form cell junctions?
Bacterial pathogens can easily bind to the adhesion molecules and therefore increase the risk of infection to the organism.
What is the overall main purposes of the extracellular matrix?
Bears the mechanical stress and tension of compression in cells.
Give shape and form to the cell.
Protects from pathogens and physical damage.
What is the extracellular structure in plant cells and what is it made of ?
Cell wall made of cellulose
What is the extracellular structure in animal cells an what is it made of ?
Extracellular matrix of collagen and elastin fibres
Also contains proteoglycans, fibronectins and laminins.
What are the adhesive molecules in the extracellular matrix of animal cells?
Fibronectins and laminas
What is the most abundant protein found in animals?
How many different forms of collagen are present in humans?
Describe the structure of collagen.
Collagen molecules are formed by the twisting of 3 precursor alpha collagen polypeptide chains into a helix. Many collagen molecules then join to form collagen fibrils. Many collagen fibrils then join to form collagen fibres.
Are collagen fibres striated or un-striated?
Can be either.
What processing mechanism must happen for a collagen helix to become a collage molecule?
The loose ends of the helix must be removed.
How are structural mutations in collagen measured?
The % of helix content.
The more of a mutation, the lower the helix content %.
How is vitamin D deficiency caused by mutations in collagen?
Cofactor for collagen hydroxylates is not present meaning that the triple helix of alpha precursor collagen polypeptides cannot form.
How does Ehlers-Danlose syndrome arise due to mutations in collagen?
Enzyme defects in collagen mean that collagen is not cross-linked.
(Eye defects, scoliosis, hyper extensible skin and joints).
What type of organisms is elastin present in?
Only in vertebrates
Where is elastin present? - generally and give examples
In the extracellular matrix of extensible tissues (Blood vessels, trachea, bronchi, ligaments).
What is the general structure of elastin fibres?
Interrupted helix with no disulphide bridges and no cross-linked helices.
When and when is elastin made?
Only in embryonic and juvnile fibroblasts.
What type of light damages elastin?
What makes elastin highly viscous?
It is 95% carbohydrate composed with a protein backbone and hyaluronic acid core.
How does elastin act as a sieve?
Proteins and bacteria are unable to penetrate elastin.
What is an aneurysm?
A weakening of an artery wall that creates a bulge of the artery.
What is a G protein?
A membrane-bound signalling protein that is activated by the binding of GTP.
What type of specialised cell junction allows plant cells to coordinate metabolic activity by providing channels for the passage of small molecules?
What is the difference between stimulated and constitutive receptor-mediated endocytosis?
Stimulated requires receptors to be bound by ligands before a vesicle is formed. Constitutive does not require ligands.
Describe the membrane of a nucleus.
Double, bi-lipid membrane
What is the space between the inner and outer membranes of the nucleus called?
How does mRNA move out of the nucleus after transcription?
Via nuclear pores
What type of proteins do free ribosomes translate?
Proteins which will be used within the cytosol of the cell.
What is cytosol?
The fluid between organelles.
Why is the cell cycle required overall?
To replace damaged or dead cells. Enables tissue growth.
What is karyokinesis?
What is cytokinesis?
Outline the process of necrosis.
Small bleb structure form and the structure of the nucleus changes. The blebs fuse and become larger, no organelles are located in the blebs. The cell membrane ruptures and releases the cell content; the organelles are no longer functional.
Outline the process of apoptosis.
Small blebs form. The nucleus begins to break apart, and the DNA breaks into small pieces. The organelles are also located in the blebs. The cell breaks into several apoptotic bodies. The organelles are still able to function. Bcl-2 prevents apoptosis unless it is disrupted.
What controls the number of divisions that a cell has?
A specific sequence of nucleotides in DNA or RNA that is located on a chromosome and codes for a particular polypeptide.
What is G0 of the cell cycle?
Cell cycle arrest
Name a cell type that is always in G0.
What happens in G1 of the cell cycle?
Cellular content excluding the chromosomes are duplicated. Protein synthesis and vigorous growth also occurs and centrosome replication begins.
Where do checkpoints in the cell cycle occur?
End of G1
End of G2
What happens in the S phase of the cell cycle?
Each of the 46 chromosomes in the cell are duplicated.
New histones are synthesised.
New chromatin is assembled.
What happens in G2 of the cell cycle?
Organelle replication completed.
Centriole replication completed.
Synthesis of enzymes and proteins that are essential for cell division.
What are the purposes of cell cycle checkpoints?
They act as control mechanisms to ensure the reliability of cell division. DNA damage is assessed and can be stalled for repairs to be made.
What happens if DNA damage is identified by cell cycle checkpoints?
The cell cycle can be stalled for repairs to be made.
The cells are targeted for destruction via apoptosis.
What is the difference between cyclin and cyclin dependent kinases?
Cyclins are proteins have no biological activity alone.
Cyclins bind to docking sites of cyclin dependent kinases and activate them to phosphorylate other molecules.
What is the overall purpose of kinase enzymes?
Phosphorylate other molecules
Outline what occurs in prophase of the cell cycle.
Chromatin condenses and coils to form chromosomes. Chromosomes consist of 2 sister chromatids held together by a centrosomes.
Cytoskeletal microtubules disassemble.
Centriole pairs separate and move towards opposite poles.
Outline what occurs in metaphase of the cell cycle.
The microtubules line up the chromosomes on the cells equator with the centromeres aligned at the metaphase plate.
Chromosomes undergo maximum coiling.
What is the metaphase plate?
A plane of the equator of the cell which orders the way spindles are aligned.
Outline what occurs in anaphase of the cell cycle.
The sister chromatids separate and the new chromosomes move towards opposite cell poles due to the interactions between the kinetochore and microtubules.
The kinetochore of each chromatid splits. The separated chromatids are now termed as daughter chromosomes.
Outline what occurs in telophase of the cell cycle.
The separate chromosomes reach the cell poles.
The nuclear envelopes re-form around the chromatin mass and the chromatin decondenses.
Chromosomes start uncoiling and transform into chromatin.
Nucleoli reappear and mitotic spindles disappear.
How does cytokinesis occur?
The cytoplasm developed a cleavage furrow that deepens , finally separating the 2 daughter cells.
A part of the chromosome that links sister chromatids. During the mitosis, spindle fibres attach to the centromere via the kinetochore.
What is the kinetochore and what is it's purpose?
The protein structure on chromatids where spindle fibres attach during cell division. If spindles attached directly to the chromosomes they could cause damage.
An organelle that serves as the main microtubule organising centre of the animal cell as well as a regulator of cell-cycle progression.
How are G1 and G2 of the cell cycle different ?
G1 = organelle replication, longer process
G2 = DNA replication, shorter process
What is the main feature of anaphase?
Sister chromatids are separates and pulled to opposite cell poles.
What are chromatids and where fo they come from?
2 sister chromatids joined by a centromere from a chromosome. One arm of a chromosome formed due to DNA replication.
What is the purpose of Cyclin dependent kinases?
Regulate the initiation of cell growth. They are switched on and off by cyclins.
What regulates the initiation of cell growth?
Cyclin dependent kinases
What switches Cyclin dependent kinases on and off?
What is required to advance cells through the cell cycle?
What causes mitogenic signals?
Large proteins or large peptides that are often produced by cells that have just died.
How does contact inhibition prevent cell growth?
A layer of cells which are stuck together may signal each other and prevent growth because there is no room for the cells to grow further.
What is anchorage dependence in terms of cell division?
Cells which can only divide when attached to the extracellular matrix.
How do mutated oncogenes affect the cell cycle?
Oncogenes are growth inducing genes. Mutated oncogenes can cause excessive growth by producing excess cyclin or inhibiting inhibitors of cyclin and cyclin independent kinases. This causes the cell cycle to continue when it shouldn't.
How do mutated tumour suppressor genes affect the cell cycle ?
Growth inhibiting genes.
Prevent inhibitors of cyclin being produced and prevent expression of promoters of p53. So the cell cycle is un-restrained and apoptosis does not occur.
How many mutations must occur to cause cancer?
How are mitotic inhibitors used to treat dance?
They are used to treat tumours by preventing microtubule disassembly This means chromosomes can't be aligned and separated out.
What causes the signal transduction pathway?
Binding of the signal messenger to its receptor leading to a cascade of reactions.
How does localised cell signalling occur?
Through direct contact or by secreting and receiving local acting growth factors and cytokines.
What is direct contact in terms of cell signalling?
The signalling molecule on one cell is complementary to the receptor on another target cell.
What are cytokines and what is their effect?
Small secreted proteins which are release by cells and have a specific effect on the interactions and communications between cells.
What is used to undergo long cell signalling?
What is cortisol , where is it produced and what is its purpose?
A Glucocorticoid hormone produced in the cortex of the adrenal glands.
Alters carbohydrate metabolism and suppressed the immune system.
What type of hormones is Aldosterone ? Where is I produced ? What is its purpose?
Cortex of the adrenal glands
Regulates salt and water balance
Where is Thyroxine hormone produced an what is it's purpose?
Stimulates metabolism and healthy generation.
What are the 4 types of hormones?
What are amine hormones?
Amino acids with modified groups
What are peptide hormones?
Short chains of linked amino acids
What are protein hormones?
Long chains of linked amino acids
What are steroid hormones?
Derived from the lipid cholesterol
What is the purpose of having many different types of hormone ? (amine, peptide etc)
They allow specificity to activated many different types of substances but only at the specific times they are required.
What are the types of signalling molecules?
Describe the regulation of cytokine production and when this production is most likely.
Production is highly regulated and short lived.
Usually secreted after activation of a particular cell.
Describe the distance over which cytokines act.
What are the general effects of cell signalling?
Alters cell division
Changes protein production
What is contact dependent signalling?
Signal molecules in the plasma membrane of the signal cell interact with membrane bound receptors on the target cell. These signals are therefore restricted to cells which are in direct contact.
Where are signalling receptors found on a cell?
Cell surface membrane
Occasionally on the nucleus.
How is cell signalling specific?
One type of signalling molecules is complimentary to one receptor type.
How is the cell altered to have a different sensitivity to cell signalling
Receptor density and expression is altered.
What are receptors made of?
What might the effect of a mutation in a growth factor receptor be?
The cells may continually divide and grow therefore causing cancers.
How can cells alter the number of receptors they have?
More proteins can be produced by the RER and transported to the cell surface by vesicles. These act as receptors on the cell surface.
How can signalling pathways be turned off?
Use protease enzymes to degrade signalling molecules.
Prevent protein synthesis of cell signalling molecules.
Return cell signalling molecules from the cell surface back inside the cell using vesicles.
Use proteins to sequester cell signalling molecules.
What are the 3 methods of cell signalling pathway?
Ligand gates ion channels
G-proten coupled receptors
Receptor Thyrosine Kinases
What does malfunctioning of G-protein coupled receptor signalling lead to
Many diseases such as diabetes, allergies, depression, cardiovascular defects, certain cancers.
How many G-protein receptors are in the human genome?
How many polypeptide chains are in a G-protein receptors?
Describe the structure of G-protein coupled receptors
A single polypeptide which is coiled and crosses the membrane 7 times.
Where is the ligand binding domain on G-protein coupled receptors?
The outer N terminal
Where is the G protein binding region on a G-protein coupled receptor?
Inner C region
Outline G-prottein couple receptor signalling.
When a signalling molecule binds to the G protein receptor, the G protein undergoes a conformational change and is activated.
The alpha subunit exchanges GDP for GTP.
The alpha subunit dissociates from the beta and gamma subunits. This triggers a cellular response.
GTP is hydrolysed to GDP and the signalling molecule comes off the receptor.
The alpha subunit comes back together with the receptor and the beta and gamma subunits.
What does GDP stand for?
What does GTP stand for?
When are G proteins turned on and off as signalling molecules within cells.
When bound to GDP - off
When bound to GTP - on
What group of enzymes do G proteins belong to ?
How is a new cycle of G-protein coupled receptor cell signalling able to occur?
The alpha subunit will hydrolyse GTP into GDP and allow the alpha subunit to re-associate with the beta and gamma subunits.
What are the constituent subunits of the G-protein coupled receptor?
What is the purpose of protein kinase C?
Phosphorylates other proteins to activate or inactivate them.
What must be true for G proteins to remain active?
Alpha subunits must be bound to GTP.
What type of molecule is Thryosine?
Describe the affinity of receptor tyrosine kinases to the cell surface receptors.
How many throne kinase genes are there in the human genome?
What are receptor Thyrosine Kinases used for in general?
Regulation of cancers
Outline how the Receptor Throsine Kinases cell signalling pathway works.
Ligand binds to recetor on Thyrosine receptor.
2 adjacent receptors bind and dimerise.
Dimerizaion activates the Thyrosine kinase.
Receptor phosphorylates the adjacent throsine residue.
The phosphorylate tyrosine residue activated intracellular signal proteins.
Intracellular signalling cascade occurs.
What is used to deactivate the Receptor Thyrosine Kinases cell signalling pathway?
Phosphatase enzymes remove the phosphate group from the tail of the tyrosine.
What are the overall effects of the G-protein coupled cell signalling pathway?
Metabolic, cell movement, growth etc
How is the G protein coupled cell signalling pathway de-activaed?
The phosphate is removed from the alpha subunit.
What is a typical 2nd messenger for the G-protein signalling pathway?
What is the 2nd messenger for the Receptor Thyrosine Pathway of cell signalling?
What does receptor tyrosine kinase cell signalling have several different steps?
It is an amplification system
How are G-proteins anchored to their plasma membrane ?
Alpha and gamma subunits have covalently bonded lipid tails which join to the plasma membrane.
How does the drug Latrunculin A affect cells?
It is a microfilament so affects both phagocytosis and exocytosis. Greater effect on exocytosis.
Does the drug Latrunculin A have a greater effect on phagocytosis or exocytosis and why?
Inhibits microfilaments which are heavily required for exocytosis.
How does the drug 'Colchine' affect cells?
Microtubule inhibitor so reduces exocytosis and phagocytosis. Greater effect on phagocytosis.
Does the drug 'colchine' have a greater effect on phagocytosis or exocytosis and why?
Inhibits mictorubules which are heavily required.
What effect does Cyclohexamide have on cels?
Protein synthesis inhibits
In plants, what tissue types does mitosis occur?
What are meristem tissues?
Tissues forms from undifferentiated cells in plants where alot of mitosis occurs. Responsible for growth.
Where are meristem tissues found in plants?
Root and shoot tips and the cambia between the xylem and phloem of the vascular bundle.
In mitosis investigation, why are root tips used?
This is where meristem tissue is present (the site of mitosis). Also easily accessible and grow rapidly.
Why are root tips placed in hydrochloric acid at 40 degrees for 5 mins before being used for mitosis investigation?
The middle lamella between cells will be hydrolysed and therefore the cellulose walls of each cell will separate therefore allowing the stain to diffuse into the cells.
At 40 degrees increases the rate of hydrolysis of the middle lamella.
What structure holds the cellulose walls of adjacent plant cells together?
Middle Lamella containing pectin
What type of molecule is pectin?
Protein - starch
Why are root tips being investigated fro mitosis placed in toludine blue stain for 2 mins?
Binds to chromatin DNA and stains it deep blue to make chromosomes visible.
2 mins allows chromosomes to be clearly defined.
Why are root tips gently squashed before being investigated for mitosis?
To produce a layer that is one cell thick and doesn't have any overlapping which could obscure the view of the chromosomes.
Gently so doesn't rupture ells and prevents the microscope slide and cover slip from cracking.
What is mitotic index a measure of?
The amount of cell division that a tissue is undergoing.
What is the formula for finding mitotic index of a tissue ?
(Number of cells in the field of view undergoing cell division)/ (Number of cells in the field of view).
Define cellular fate.
What a cell will be programmed to turn into.
Define cell potency.
The ability of a stem cell to divide into different cell types.
Pairs of homologous chromosomes.
How many cells are produced in meiosis and describe their resemblance to the parent cell.
4 daughter cells produced.
All genetically different from the parent and each other due to crossing over.
When in meiosis does crossing over occur?
During prophase I of meiosis, what is it called when homologous chromosomes form tetrads?
What is synapsis in meiosis?
The formation of tetrads (pairs of homologous chromosomes).
What are the positives of having crossing over in meiosis?
Creates variability (genetic recombination) and is beneficial to evolution.
What are homologous chromosomes?
Chromosome pairs which have approximately the same length and centromere position.
What is the difference between Anaphase I of meiosis and anaphase of mitosis?
Metaphase I - homologous chromosomes move to opposite cell poles.
Metaphase - Sister chromatids move to opposite cell poles.
When in meiosis does cytokinesis occur?
Telophase I and Telophase II
When in meiosis do the centromeres divide?
Describe the genetic information within the daughter cells of meiosis.
4 daughter cells which are genetically different from each other and the parent cell.
Half the DNA of the parent cell - haploid.
Describe the genetic information of the daughter cells of mitosis.
2 daughter cells which are genetically identical to the parent cell and each other.
What is the official term for a fully developed sperm cell?
What is the step formation of a fully developed from a sperm cell (spermatozoa)?
2 secondary spermatocytes
What is sermiogenesis?
Structural changes that allow a primary spermocyte to form the final version of a sperm cell (Spermatozoa).
How long does it take for a primary spermocyte to develop into a spermatozoa?
What cell types are used to protect the production of Sperm and how do they do this?
Sertoli cells. Create tight junctions to create a barrier within the testes for sperm production. This means they are not reached by the immune system.
Why are Sperm cells held within a protective barrier in the testes?
Sperm cells are only produced within puberty so the immune system is not used to them.
Barrier prevents the immune system attacking and killing sperm cells.
What structures are used to form the tail of sperm ? And when does this occur ?
Microtubule axonemes for the Spermatozoa tails of the sperm when it detaches from Sertoli cells into the lumen of seminiferous tubules.
When do Spermatozoa (sperm cells) gain motility?
When they detatch from the Sertoli cells and enter the lumen of the seminiferous tubules.
Describe the DNA of spermatozoa.
Highly condensed and tightly packed.
What controls the Production of Sperm cells?
The pituitary glans - FSH and testosterone.
What is the production of sperm cells technically called?
What is gametogenesis?
The production of gates (specifically sperm cells).
What is he technical name for egg cell production?
What is oogenesis?
Egg cell production
Outline the production of a mature egg cell from a primary oocyte.
1 secondary oocyte and 1 polar body
Secondary oocyte produces one mature ovum and 1 polar body.
Polar body divides into 2 polar bodies.
Overall 1 mature ovum (egg cell) and 3 polar bodies are formed.
When are egg cells produced?
In the foetus
When does egg cell production in females stop?
During prophase I in the late foetus then nothing happens until puberty.
When happens in terms of the cell cycle of egg cells once puberty starts in females?
Some complete meiosis I every month.
Secondary oocytes enter Meiosis II but halt at Metaphase II unless fertilisation occurs.
What term is used to describe the process of maturation of an ovarian follice?
What is folliculogenesis?
The maturation of an ovarian folicle.
What controls oogenesis?
Pituitary glans - FSH and LH.
What is a blastocyst?
(What are they formed from, when are they formed, structure, what they form).
A structure formed in the early development of mammals. Possesses an inner cell mass which forms an embryo.
The outer layer of the blastocyst consists of cells collectively called Trophoblasts.
When do blastocysts form?
In the early development of mammals.
What is the purpose of blastocyst cells?
They have an inner cell mass which eventually forms an embryo.
What is the outer layer of a blastocyst called?
What is a trophoblast?
Outer layer of cells of a blastocyst.
What are the main purposes of adult stem cells?
Growth, repair, turnover of frequently replenished cells.
Where are adult stem cells extracted from?
Name some important features of stem cells.
Ability to choose between cellular fates.
What regulates the functioning of stem cells?
Intrinsic signals and external microenvironment.
What are the hierarchy levels of pluripotent in stem cells?
What is meant by a stem cell being totipotent?
Can form a zygote (entire individual). Can divide into any cell type.
What is meant by a stem cell being pluripotent?
Can differentiate into any of the three germ layers.
What are the 3 germ layers that pluripotent stem cells can divide into?
Ectoderm, mesoderm, endoderm
What is meant by a stem cell being multipoint?
Can differentiate into several cell types
What is meant by a stem cell being unipotent ?
Can differentiate into a single cell type.
What cell types can be used for induced pluripotency?
What is induced pluripoteny advantageous to cells?
Does not cause rejection by the body via the immune system.
Why are adult stem cells expensive and difficult to extract?
There are not many stem cells in a given population.
Why is induced pluripotency used over adult stem cells?
Adult stem cells are difficult and expensive to extract because there are not many in a population of cells.
What are used on mass to produced induced, pluripotent stem cells?
What can be used to identify stem cells?
CD markers, genes, enzymes proteins.
What are CD markers on stem cells?
Surface proteins which can be used to identify cell types.
What is meant by the term 'proximal'?
Near/ close to
What is meant by the term 'distal'?
What is the Placode of an embryo?
Ectodermal thickening over a developing structure.
What is Anlage (Embryology)?
Cluster of embryonic cells from which a structure develops.
What is Epigenesis theory of development?
The theory that development occurs over time and structures arise via progressive stages.
What is the preformation theory of development?
Suggests that all structures exist from the very beginning, they are just getting larger.
Who came up with the Homonuclus theory and when?
Nicholas Hartsoeker - 1692
What is the homonuclus theory of development
A little human embryo was hidden in the head of every sperm cell.
What are the 5 processes of development in cells?
How does cleavage division alter total cell mass in development?
Cells divide but there is no increase in total cell mass.
What is pattern formation in cell development?
The formation of a coordination system in the body and finding the locations of each region of the body.
What is morphogenesis in development?
Becoming a 3D form
What are the 5 cell behaviours?
Cell to cell communication.
Cell shape changes.
What is cell proliferation?
Growth and division of cells to keep a constant cell count.
Outline the process of fertilisation of an egg cell by a sperm cell.
1. Sperm binds to 'Zona pellucid' on the egg cell.
2. Acrosome reaction
3. Penetration of zone pellucid.
4. Fusion of sperm to plasma membrane of egg cell.
5. Sperm nucleus enters egg cytoplasm.
Outline how the egg cell prevents penetration of more than one sperm cell.
After the sperm enters the egg cell, cortical granules discharge from the egg cell and the vitelline membrane is raised.
The cortical granule membrane and the vitelline membrane then form the fertilisation membrane which prevents further penetration by another sperm cell.
What is the vitelline membrane of an egg cel?
Surrounds the outer layer of the plasma membrane.
What is the benefit of having asymmetric distribution of cytoplasm components during cell division?
Allows cells to have different fates.
What is inductive cell interaction?
The process by which one group of cells changes the fate of another group of cells.
What are the possible methods of inductive cell interaction?
Why is it beneficial for cells to bind tightly and closely during development?
They have a greater surface contact and therefore cellular interactions increase.
What is radial cell cleavage what type of cells does this produce?
Horizontal cleavage producing 2 polarised cells.
What is transgenital cell cleavage and what type of cells does this produce?
Vertical cleavage producing 1 polarised cell and 1 non-polarised cell.
What junctions join trophoblasts (outer cells) of a blastocyst and what is the purpose of this?
Tight junctions - allows the outside environment to be separated from the inside of the blastocyst. Means fluid can accumulate to form a blastocoel.
What 2 cell types are present in a blastocyst?
Inner cell mass
What 2 regions do trophoblasts cells divide into when they come into contact with the endometrium?
Synctioblasts (outer portion)
Why are syncitioblasts not described as being cellular?
Nuclei share a common cytoplasm
What allows the mothers blood to reach the developing foetus?
Lacunae gives rise to intervillous spaces containing maternal blood and therefore the blood can reach the developing embryo.
What are intervillous spaces?
Spaces between the villi containing vessels of the mother and the embryo.
What is the endometrium?
The tissue lining the inner cavity of the womb.
What is the tissue lining the inner cavity of the womb called?
What is the purpose of gastrulation in foetal development?
Develops a 2 layered embryonic disk into a 3 layered embryonic disk.
Also helps to allow coordination of the developing embryo due to the formation of the primitive streak.
How many weeks after fertilisation does gastrulation occur?
What are the 3 germ layers of the primitive streak?
Why do significant abnormalities within an embryo often occur during the gastrulation process?
Alot of morphological movement is occurring which could undergo errors.
A group of cells that usually have a common embryo and function together to carry out specialised activities.
The study of tissues.
What is a pathologist?
Examines tissues for changes that may indicate disease.
What is a biopsy?
The removal of a sample of living tissues for microscopic examination.
What are the 4 main types of tissues?
What are the main purposes of epithelial tissues (in general) ?
Cover the body surfaces and line hollow organs.
What are the main purposes of connective tissues (general)?
Protect and support organs.
Act as a route for immune cells to travel through.
Outline the structure of epithelial tissues.
Many cells tightly packed together to form a continuous sheet with little or no extracellular matrix.
No blood vessels.
Describe the extracellular matrix present in the epithelial tissues.
No ECM or very little.
Describe the blood vessels present in epithelial tissues.
No blood vessels present so relies on blood vessels from other tissues.
What are the main functions of the epithelial tissues?
Selective barriers that control substance movement in and out of the body.
Secretory surfaces that release products of cells to their free surfaces.
Protective surfaces that resist abrasive environmental influences.
What is the purpose of the basement membranes of epithelial tissues?
Separate the lining of an body surface from the underlying connective tissues.
Prevents the passage of large molecules.
Outline the structure of the basement membrane of epithelial tissues.
Thin, fibrous, extra-cellular layer.
What is the basemen membrane of epithelial tissues made from?
Where are the connective tissues cells of an epithelial tissue?
What are the purpose of hemidesmosomes in epithelial tissues?
Connect the basement membrane to the epithelial and connective tissue layers.
What happens to epithelial tissues if diabetes mellitus is untreated?
Basement membrane around capillaries in the eyes and kidneys thicken.
Why do the basement membranes around the capillaries in the eyes and kidneys thicken when diabetes mellitus is untreated?
Hyperglycaemia - signalling causing more collaged deposition.
Why do epithelial tissues have a high rate of cell division?
They are repeatedly subjected to physical stress and injury so must be able to quickly renew any damaged tissues.
What are the implications of thickening of the basement membrane of epithelial tissues in the capillaries around the kidneys and the eyes?
Affects kidney filtration - kidney disease.
Affects light getting to the photoreceptors in the eyes meaning vision will be impaired. Because blood vessels sit onto of photoreceptors.
Why are epithelial cells often damaged in people with cancer and what are the effects of this?
Chemotherapy targets rapidly dividing cells, epithelial cells have a high rate of division.
This often leads to kidney and gastrointestinal damage.
What are the 2 divisions of epithelial tissues?
Epithelial tissues that cover and line.
What is glandular epithelial tissue.
Makes up secretory parts of glans.
Where are striated squamous epithelial cells found and what is their purpose?
Lines the Oesophagus, mouth and vagina.
Protects against abrasion.
Where are the striated cuboidal epithelial cells found and what is their purpose?
Sweat glands, salivary glands and mammary glands.
Where are striated columnar epithelial cells found and what is their purpose?
The male urethra and the ducts of some glands.
Secretes and protects.
Where are the transitional epithelial cells found and what is their purpose?
Lines the bladder, uretha and ureters.
Allows the urinary organs to expand and stretch.
Where are the simple squamous epithelial cells found and what is their purpose?
Air sacs of lungs, lining of the heart, blood vessels and lymphatic vessels.
Allows materials to pass through by diffusion and filtration.
Secretes lubricating substances.
Where are the simple cuboidal epithelial cells found and what is their purpose?
In ducts and secretory portions of small glands and in kidney tubules.
Secretes and absorbs.
Where are the simple columnar epithelial cells found and what is their purpose?
Ciliated tissues are in the bronchi, uterine tubes and uterus. Also in the digestive tract and bladder.
Secrets mucous and enzymes.
Where are the Pseudostratified columnar epithelial cells and what is their purpose?
Ciliated tissue lines the trachea and upper respiratory tract.
What are exocrine glands?
Produce and secrete substances onto an epithelial surface by way of a duct.
What are endocrine glands?
Secrete hormones directly into the blood.
What are connective tissues?
Tissues that connect, support, bind or separate other tissues or organs.
Describe the general structure of connective tissues.
Relatively few cells embedded in an amorphous matrix (lacking clear structure).
Often contain collagen and other fibres that contain cartilaginous, fatty and elastic tissues.
What are the main functions of connective tissues?
Bind together to support and strengthen other tissues.
Protect and insulate organs.
Serve as a major transport system.
Store energy as fat in the adipose tissue.
Where do connective tissues store energy?
As fat in the adipose tissue.
What are the 3 main components of connective tissue?
What are the 2 categories of cells in the connective tissues.
What are the ground substances of the connective tissues and what is their purpose?
Can be fluid, semi-fluid, gelatinous or calcified.
Support cells, binds cells together, stores water.
Also aid tissue development, migration and metabolic activity.
What are the 3 types of fibres in the connective tissues?
What are the purpose of collagen fibres in the connective tissues of epithelial cells?
Resist pullling forces to maintain structure.
What is the structure of reticular fibres in connective tissues?
Collagen n fine bundles with a coating of glycoproteins.
What are the purposes of reticular fibres in the connective tissues?
Provide support in blood vessel walls.
Explain the distance over which macrophages act in connective tissues.
Mobile over a short distance and act in a local region of connective tissues.
How does the number of macrophages alter when the connective tissue is damaged?
Where are mast cells found relative to connective tissues?
Found close to small blood vessels in loose connective tissue.
What are the purposes of mast cells in connective tissues?
Contain granules of heparin proteoglycan - anticoagulant.
Contain histamine - promotes the inflammatory reaction.
What happens when histamine is released from connective tissues?
Causes endothelial cells lining venues to contract. This weakens the junctions between cells and allows proteins and cells from the plasma to leak through the connective tissues
What is the purpose of granules in mast cells of connective tissues?
Contain heparin proteoglycan which acts as an anticoagulant.
What are the types of connective tissue?
What is cartilage?
A firm tissue which is softer and more flexible than bone.
What is cartilage made up of?
What is the function of chondrocytes?
Produce large amounts of extracellular matrix
How are chondrocytes of cartilage provided with nutrients?
There are no blood vessels nutrients diffuse through a dense connective tissue surrounding the cartilage (Perichondrium).
What is the dense connective tissue surrounding cartilage called?
Why does cartilage grow and repair more slowly than other tissues?
It has no blood vessels so has to wait for nutrients to diffuse in via the perichondrium (dense surrounding connective tissue).
What is the main purpose of osteoblast cells?
What protein do osteoblasts make and what is its composition?
Osteoid - contains Type I collagen which mineralises to become bone.
How do osteoblasts form bone?
They form osteoid protein which contains Type I collagen. This then mineralises to form bone.
Where do osteocytes originate from?
Osteoblasts that have migrated and become trapped and surrounded by the bone marrow that they produced.
What are spaces that osteocytes occupy called?
Describe the general structure of osteoclasts.
Large, multinucleate cells.
What is the main purpose of osteoclasts?
Breakdown bones by doing bone reabsorption.
Describe the structure of areolar tissues.
Loosely organised with diverse cellular and fibrous components.
What are the purpose of areolar connective tissues?
Supports organs and vasculators.
Describe the structure of adipose tissues.
Bubble-like appearance with little matrix.
What is the purpose of adipose tissue?
Cushions organs, insulates the body and stores energy.
What is the purpose of reticular connective tissues?
Forms network of support for blood cells within h lymph nodes, spleen, liver and bone marrow.
What is the structure of dense regular connective tissue?
Waves of collagen fibres allow for limited stretch in a single direction.
What is the purpose of dense irregular connective tissues being irregular?
Allows tissues to withstand tension from many directions.
What is the purpose of dense regular connective tissues having collagen fibres?§
Limited stretch in a single direction
What are the basic components of connective tissues?
Cells, extracellular matrix, protein fibres, ground substances.
Marfan syndrome is caused by issues with what tissue type?
What substances does bone store?
Calcium, minerals and fats.