Flashcards in General Deck (517)
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1
What is a glycocalyx?
A carbohydrate rich coating that covers the outside of many eukaryotes and prokaryotes.
2
Compare the nucleus of prokaryotes and eukaryotes.
Prokaryotes - no nuclear membrane.
Eukaryotes - nucleus, nuclear membrane, nucleolus.
3
Compare whether the organelles in prokaryotes and eukaryotes are membrane bound.
Prokaryotes - no
Eukaryotes - Yes e.g lysosomes, mitochondria, chloroplasts.
4
Compare the flagella in prokaryotes and eukaryotes.
Prokaryotes- made with 2 proteins.
Eukaryotes - made with multiple microtubules.
5
Compare the Glycocalyx in prokaryotes and eukaryotes.
Pro- Present as capsule or slime layer.
Eu - Present but chemically simple - cellulose or chitin.
6
Compare the cytoplasm and cytoskeleton of prokaryotes and eukaryotes.
Pro- No cytoplasm and cytoskeleton
Eu- Cytoskelton and cytoplasm.
7
Compare the ribosomes of prokaryotes and eukaryotes.
Pro- small 70s
Eu- 80s and small 70s in organelles.
8
Compare the DNA of prokaryotes and eukaryotes.
Pro- single circular chromosomes with no histones.
Eu- multiple linear chromosomes with histones.
9
Compare the methods of cell division in prokaryotes and eukaryotes.
Pro - Binary fission
Eu- mitosis / meiosis
10
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.
11
What is cytosol?
The intracellular fluid of cytoplasm. Contains dissolved ions, glucose, Aino acids, ATP, lipids and waste products.
Site of enzyme-controlled reactions.
12
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.
13
What are the 3 main filament types in a cytoskeleton?
Microfilaments, intermediate filaments, microtubules.
14
What proteins are microfilaments in the cytoskeleton made from?
Actin and myosin.
15
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.
16
How do microfilaments in the cytoskeleton allow a cell to move?
Microfilaments break and reform constantly to allow the cell to move.
17
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.
18
What proteins are the intermediate filaments of the cytoskeleton made from?
Keratin, vimentin and lamination's.
19
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.
20
What proteins are the microtubules in the cytoskeleton made from ?
Tubulin
21
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.
22
Where are microtubules formed?
In the centrosome then radiate outwards.
23
What is the function of centrosomes?
Growth of mitotic spindles during cell division.
24
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.
25
What are cilia made of?
Microtubule core and surrounded by a membrane.
26
What is the function of cilia?
Transport of fluid along a cell surface.
27
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.
28
Name a human cell where a flagella is necessary
Sperm
29
Where does the endoplasmic reticulum extend from and too?
The nuclear envelope to the cytoplasm.
30
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.
31
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.
32
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.
33
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.
34
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.
35
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.
36
What is the purpose of the smooth ER in muscles?
Stores Ca2+
37
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?
Liver cells.
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.
38
What is the genetic material of ribosomes?
Ribosomal RNA
39
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.
40
Where are ribosomes present in the mitochondria?
Free in the cytoplasm or attached to the endoplasmic reticulum (RER).
41
What is the overall function of ribosomes?
Protein synthesis
42
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.
43
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.
44
What is the general function of the Trans face of the Golgi apparatus?
Shipping
45
What is the general function of the Cis face of the Golgi apparatus?
Receiving
46
What are the main overall functions of lysosomes?
Digestion of substance entering the cell such as worn out organelles (Autophagy) or entire cells (Autolysis).
47
What is the digestion of worn out cells by lysosomes called?
Autophagy
48
What is the digestion of entire cells by lysosomes called?
Autolysis
49
Why is autophagy necessary?
Allows renewal, cellular differentiation and control of growth and tissue remodelling.
50
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.
51
What are the symptoms of Tay Sachs disease ?
Seizures, muscle rigidity, blindness, very early death (Age 5 ish).
52
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.
53
Where are a lot of peroxisomes found?
Liver
54
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.
55
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.
56
What is the main function of proteosomes ?
Degrade cytosolic proteins (un-needed, damaged or faulty).
57
What enzymes do proteosomes contain?
Protease
58
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.
59
What are the main functions of the mitochondria?
Aerobic respiration and ATP production.
60
What is the purpose of the cristae in mitochondria ?
Provide a large surface area for aerobic respiration.
61
Where are enzymes needed for respiration found in the mitochondria.
In the matrix and on the Cristae surface.
62
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.
63
What are the functions of the plasma membrane?
Regulates what enters and exits the cell.
Involved with cell recognition.
Aids cell signalling.
Enzymatic functions.
Aids cell linking and cross-talk
64
Describe generally the structure of the plasma membrane.
Thin, flexible, fluid mosaic model.
65
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.
66
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.
67
What are glycoproteins used for in the phospholipid bi-layer of the cell membrane?
They contain oligosaccharides and form the glacocalyx.
68
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.
69
What are the purpose of transmembrane proteins?
Transport substances from outside and inside the cell.
70
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.
71
What is the main purpose of the phospholipid bi-layer?
Separates hydrophilic and hydrophobic domains.
72
What type of permeability does the phospholipid bilayer have?
Selective permeability
73
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).
74
How does water pass through the phospholipid bi-layer?
Via aqua-porins.
75
What is the overall purpose of the phospholipid bi-layer being semi-permeable?
Allows concentration gradients to be built and pH to be regulated.
76
What are channel intrinsic proteins generally used for?
Used for charged ions usually.
77
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.
78
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).
79
How many molecules can a carrier protein transport at once and why?
1 because they are gated and highly specific.
80
How does temperature affect the rate of diffusion?
As temperature increases, so does rate of diffusion.
81
How does the mass of the substance moving affect its rate of diffusion?
The greater the mass, the slower the rate of diffusion.
82
How does diffusion distance affect the rate of diffusion?
As diffusion distance increases, rate of diffusion decreases.
83
How does concentration gradient affect rate of diffusion?
As concentration gradient increases, so does rate of diffusion.
84
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.
85
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.
86
What is an isotonic solution?
Concentration of ions inside and outside the cell is the same.
87
How is cerebral edema treated?
Hypertonic solution is infused to drain extra water out of the brain.
88
What is the energy source for active transport?
Uses energy from the hydrolysis of ADP.
89
Give an example of a active transport mechanism.
sodium potassium pump.
90
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.
91
What is another name for secondary active transport?
Co-transport
92
What is symport in secondary active transport?
Molecules travel in the same direction.
93
What is antiport in secondary active transport?
When molecules travel in opposite directions.
94
What is the positives of using secondary active transport?
More efficient than primary active transport because less ATP is required - uses alternative energy source.
95
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.
96
What enzymic functions do membrane proteins have?
Act as digestive enzymes.
97
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.
98
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.
99
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.
100
Which cells undergo phagocytosis?
Macrophages and neutrophils.
101
Outline bulk phase endocytosis.
Small droplets of extracellular fluid are taken into the cell by endocytosis.
102
Where does bulk phase endocytosis occur on mass?
Intestines and kidneys.
103
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.
104
What is the main purpose of exocytosis?
Used to transport materials out of the cell.
105
What are the main cells that exocytosis is exhibited by and what do they release?
Secretory cells - digestive enzymes and hormones.
Nerves - neurotransmitters.
106
What is transcytosis ?
A combination of endo and exocytosis used to pass substances through the cell.
107
Where is transcytosis common?
Endothelial cells which line blood vessels.
108
Describe the process of Co-transport of glucose in the small intestine.
In notebook
109
Describe how the second messenger model works with adrenaline.
In notebook
110
What is it called when Glycogen is converted to Glucose
Glycogenolysis
111
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.
112
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.
113
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.
114
What is the purpose of the Cathrin coating in receptor mediated endocytosis?
Cathrin coating buds in towards the cell cytosol to form a vesicle.
115
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.
116
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.
117
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.
118
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.
119
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.
120
Draw the Golgi packaging system.
In notes.
121
How is resolving power affected as frequency of light waves increases?
Resolivng power also increases
122
Name some types of optical microscopy.
Phase contrast, DIC, Dark field, Polarisation, UV, Fluorescent, Light field.
123
Describe the specimen used and images produced by phase contrast microscopy.
Living, unstained cells
Cells appear black and white
124
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.
125
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.
126
How do Dark field microscopy images appear?
Illuminates cells and tissues against a dark background to allow for contrast.
127
How do polarisation microscopy images appear?
Illuminates cells and tissues against a dark background to allow for contrast.
128
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.
129
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.
130
What are highly organised rays in terms of sample specimen? - polarisation microsopy
X
131
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.
132
What is needed to be able to see a UV microscope image?
UV light source
133
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.
134
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.
135
What is confocal fluorescent microscopy?
A method used to cleaner and resolve a fluorescent microscope image.
136
What is the disadvantage of using bright field microscopy?
You must stain the cells which can be damaging.
137
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.
138
What 2 types of microscopy are often combines and why?
Phase contrast and fluorescent. They create a highly structured and coloured specimen image.
139
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.
140
What may interference in microscopy be used for?
Used to quantitatively measure. E.g find the dry mass of a sample.
141
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.
142
What type of specimen are usually stained during microscopy?
Thin specimens which are generally transparent at the visible light wavelengths.
143
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.
144
What are the 2 types of vital dye use in microscopy?
Vital dye exclusions and vital dye uptakes
145
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
146
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.
147
What is the most common type of staining used for microscopy and what does it do?
H&E staining
Haemotoxylin makes the nuclei stain blue.
Eosin stains the cytoplasm pink.
148
What stain is often used to stain neurones in microscopy and what colour does it go?
Golgi silver stain - black
149
What stain is often used to stain nucleic acids in microscopy and what colour does it go?
Nissl stain - purpose
150
What stain is often used to stain DNA in microscopy and what colour does it go?
Feulgen Schiff - Red
151
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.
152
What is the purpose of enzyme histochemistry?
To see the location of enzymes within a cell
153
What is the main purpose of autoradiography?
It uses radioactive sources to blacken desired regions of the photographic plate.
154
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.
155
What is meant by the term 'in vivo'?
Within a living orgaism
156
What is the precursor substrate for proteins during autoradiography?
Amino acids
157
What is the precursor substrate for DNA during autoradiography?
Thymidines
158
What is one of the main uses of microscopy in the clinic environment?
Immunofluorescence
159
What are the 2 types of immunofluorescence?
Direct and indirect
160
Describe direct immunofluorescence.
Specific antibodies against an antigen are labelled with fluorescent due. Antibodies then bind to the antigen and act as a labeller.
161
Describe indirect immunofluorescence.
Specific primary antibodies bind to the antigen. Secondary antibodies labelled with the fluorescent dye then bind to the primary antibodies.
162
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.
Easier process
163
What is tissue fixation?
The cessation of the normal life functions of the tissue and the preservation of the tissue sample.
164
Define resolution
The ability to distinguish between two or more objects which are close together.
165
What is the equation for resolution?
On laptop notes
166
What do the letters D, N and alpha stand for in the resolution equation?
D= resolution
N = refractive index
alpha = angular apeture
167
What is the refractive index of air?
1.0
168
What is the refractive index of oil?
1.5
169
What are arrays in terms of microscopy?
Lots of repeats of the same structure in an area of the cell
170
What is the purpose of the condenser in a microscope?
Focuses light onto the specimen and controls the contrast.
171
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.
172
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.
173
What is the purpose of immersion oil in light microscopy?
Increases resolving power - most frequently used under a high magnification.
174
What are protozoans?
Single-celled, microscopic organisms.
175
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.
176
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.
177
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.
178
What is the purpose of tetrahymena in relation to cilia?
It can re-generate cilia which have been gently removed.
179
How do Colchicine and Colcemid affect cilia?
They inhibit tubular monomers growing in microtubules.
180
When are membranes of adjacent cells most interactive?
During cancer cell metastasis and foetal development.
181
What is Metastasis?
Cancer split off from the primary tumour and travel around the body forming secondary tumours.
182
What controls the interactions between adjacent cell membranes?
Membrane proteins
183
Name some types of junctions which form between adjacent cells.
Desmosomes, Hemi-desmosomes, adherent junctions, tight junctions, gap junctions.
184
How many different types of gap junctions can adjacent cells have between them?
Infinite
185
What tissue types are desmosome gap junctions most frequently found in?
Cardiac and intestinal tissues.
Usually in epithelial cells.
186
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.
187
What type of binding do desmosome gap junctions use?
Homophillic binding
188
What is homophillic binding?
The binding of a receptor molecule to an identical molecule.
189
What type of proteins are used in desmosome gap junctions?
Cadherins
190
What type of adhesions do desmosome gap junctions make?
Cell-to-cell junctions.
191
What is the purpose of hemidesmosomal gap junctions?
Adhere cells to their basal lamina.
192
What is a cells basal lamina?
A layer of extracellular matrix secreted by the epithelial cells. Basement layer that the cells sit on.
193
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.
194
Where are adherent gap junctions most commonly used? (What tissue type?)
Epithelial tissues
195
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.
196
What cell types are tight junctions found in?
Only in epithelial cells.
197
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.
198
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).
199
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.
200
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.
201
In what types of organisms do gap junctions occur in?
Multicellular animals
202
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.
203
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.
204
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.
205
What is the overall purpose of gap junctions between adjacent cells?
Control cell communication
206
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.
207
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.
208
What is cellular synchronisation?
Cells in different phases of the cell cycle are brought to the same phase.
209
What conditions are required to allow cells to reader after they have been separated?
The presence of calcium and magnesium ions.
Optimum temperature.
210
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.
211
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.
212
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.
213
What is the extracellular structure in plant cells and what is it made of ?
Cell wall made of cellulose
214
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.
215
What are the adhesive molecules in the extracellular matrix of animal cells?
Fibronectins and laminas
216
What is the most abundant protein found in animals?
Collagen
217
How many different forms of collagen are present in humans?
10
218
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.
219
Are collagen fibres striated or un-striated?
Can be either.
220
What processing mechanism must happen for a collagen helix to become a collage molecule?
The loose ends of the helix must be removed.
221
How are structural mutations in collagen measured?
The % of helix content.
The more of a mutation, the lower the helix content %.
222
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.
223
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).
224
What type of organisms is elastin present in?
Only in vertebrates
225
Where is elastin present? - generally and give examples
In the extracellular matrix of extensible tissues (Blood vessels, trachea, bronchi, ligaments).
226
What is the general structure of elastin fibres?
Interrupted helix with no disulphide bridges and no cross-linked helices.
227
When and when is elastin made?
Only in embryonic and juvnile fibroblasts.
228
What type of light damages elastin?
UV
229
What makes elastin highly viscous?
It is 95% carbohydrate composed with a protein backbone and hyaluronic acid core.
230
How does elastin act as a sieve?
Proteins and bacteria are unable to penetrate elastin.
231
What is an aneurysm?
A weakening of an artery wall that creates a bulge of the artery.
232
What is a G protein?
A membrane-bound signalling protein that is activated by the binding of GTP.
233
What type of specialised cell junction allows plant cells to coordinate metabolic activity by providing channels for the passage of small molecules?
Plasmodesmata
234
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.
235
Describe the membrane of a nucleus.
Double, bi-lipid membrane
236
What is the space between the inner and outer membranes of the nucleus called?
Peri-nuclear space.
237
How does mRNA move out of the nucleus after transcription?
Via nuclear pores
238
What type of proteins do free ribosomes translate?
Proteins which will be used within the cytosol of the cell.
239
What is cytosol?
The fluid between organelles.
240
Why is the cell cycle required overall?
To replace damaged or dead cells. Enables tissue growth.
241
What is karyokinesis?
Nuclear division
242
What is cytokinesis?
Cytoplasm division
243
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.
244
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.
245
What controls the number of divisions that a cell has?
Suicide genes
246
Define genes.
A specific sequence of nucleotides in DNA or RNA that is located on a chromosome and codes for a particular polypeptide.
247
What is G0 of the cell cycle?
Cell cycle arrest
248
Name a cell type that is always in G0.
Neurones
249
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.
250
Where do checkpoints in the cell cycle occur?
End of G1
End of G2
Metaphase
251
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.
252
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.
253
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.
254
What happens if DNA damage is identified by cell cycle checkpoints?
The cell cycle can be stalled for repairs to be made.
Or
The cells are targeted for destruction via apoptosis.
255
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.
256
What is the overall purpose of kinase enzymes?
Phosphorylate other molecules
257
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.
Nucleoli disappear.
Cytoskeletal microtubules disassemble.
Centriole pairs separate and move towards opposite poles.
258
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.
259
What is the metaphase plate?
A plane of the equator of the cell which orders the way spindles are aligned.
260
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.
261
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.
262
How does cytokinesis occur?
The cytoplasm developed a cleavage furrow that deepens , finally separating the 2 daughter cells.
263
Define centromere
A part of the chromosome that links sister chromatids. During the mitosis, spindle fibres attach to the centromere via the kinetochore.
264
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.
265
Define centrosome.
An organelle that serves as the main microtubule organising centre of the animal cell as well as a regulator of cell-cycle progression.
266
How are G1 and G2 of the cell cycle different ?
G1 = organelle replication, longer process
G2 = DNA replication, shorter process
267
What is the main feature of anaphase?
Sister chromatids are separates and pulled to opposite cell poles.
268
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.
269
What is the purpose of Cyclin dependent kinases?
Regulate the initiation of cell growth. They are switched on and off by cyclins.
270
What regulates the initiation of cell growth?
Cyclin dependent kinases
271
What switches Cyclin dependent kinases on and off?
Cyclins
272
What is required to advance cells through the cell cycle?
Mitogenic signals.
273
What causes mitogenic signals?
Large proteins or large peptides that are often produced by cells that have just died.
274
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.
275
What is anchorage dependence in terms of cell division?
Cells which can only divide when attached to the extracellular matrix.
276
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.
277
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.
278
How many mutations must occur to cause cancer?
Multiple
279
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.
280
What causes the signal transduction pathway?
Binding of the signal messenger to its receptor leading to a cascade of reactions.
281
How does localised cell signalling occur?
Through direct contact or by secreting and receiving local acting growth factors and cytokines.
282
What is direct contact in terms of cell signalling?
The signalling molecule on one cell is complementary to the receptor on another target cell.
283
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.
284
What is used to undergo long cell signalling?
Hormones
285
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.
286
What type of hormones is Aldosterone ? Where is I produced ? What is its purpose?
Mineralcorticoid
Cortex of the adrenal glands
Regulates salt and water balance
287
Where is Thyroxine hormone produced an what is it's purpose?
Thyroid gland
Stimulates metabolism and healthy generation.
288
What are the 4 types of hormones?
Amine
Peptide
Protein
Steroid
289
What are amine hormones?
Amino acids with modified groups
290
What are peptide hormones?
Short chains of linked amino acids
291
What are protein hormones?
Long chains of linked amino acids
292
What are steroid hormones?
Derived from the lipid cholesterol
293
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.
294
What are the types of signalling molecules?
Cytokines
Hormones
Growth factors
295
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.
296
Describe the distance over which cytokines act.
Short
Autocrine/ Paracrine
297
What are the general effects of cell signalling?
Alters cell division
Changes protein production
Apoptosis
Alters metabolism
Cell movement
298
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.
299
Where are signalling receptors found on a cell?
Cell surface membrane
Occasionally on the nucleus.
300
How is cell signalling specific?
One type of signalling molecules is complimentary to one receptor type.
301
How is the cell altered to have a different sensitivity to cell signalling
Receptor density and expression is altered.
302
What are receptors made of?
Proteins
303
What might the effect of a mutation in a growth factor receptor be?
The cells may continually divide and grow therefore causing cancers.
304
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.
305
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.
306
What are the 3 methods of cell signalling pathway?
Ligand gates ion channels
G-proten coupled receptors
Receptor Thyrosine Kinases
307
What does malfunctioning of G-protein coupled receptor signalling lead to
Many diseases such as diabetes, allergies, depression, cardiovascular defects, certain cancers.
308
How many G-protein receptors are in the human genome?
About 800
309
How many polypeptide chains are in a G-protein receptors?
1
310
Describe the structure of G-protein coupled receptors
A single polypeptide which is coiled and crosses the membrane 7 times.
311
Where is the ligand binding domain on G-protein coupled receptors?
The outer N terminal
312
Where is the G protein binding region on a G-protein coupled receptor?
Inner C region
313
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.
314
What does GDP stand for?
Guanine Di-phosphate
315
What does GTP stand for?
Guanine Tri-phosphate
316
When are G proteins turned on and off as signalling molecules within cells.
When bound to GDP - off
When bound to GTP - on
317
What group of enzymes do G proteins belong to ?
GTPases
318
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.
319
What are the constituent subunits of the G-protein coupled receptor?
Alpha
Beta
Gamma
320
What is the purpose of protein kinase C?
Phosphorylates other proteins to activate or inactivate them.
321
What must be true for G proteins to remain active?
Alpha subunits must be bound to GTP.
322
What type of molecule is Thryosine?
Amino acid
323
Describe the affinity of receptor tyrosine kinases to the cell surface receptors.
high affinity
324
How many throne kinase genes are there in the human genome?
90
325
What are receptor Thyrosine Kinases used for in general?
Cell growth
Development
Regulation of cancers
326
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.
327
What is used to deactivate the Receptor Thyrosine Kinases cell signalling pathway?
Phosphatase enzymes remove the phosphate group from the tail of the tyrosine.
328
What are the overall effects of the G-protein coupled cell signalling pathway?
Metabolic, cell movement, growth etc
329
How is the G protein coupled cell signalling pathway de-activaed?
The phosphate is removed from the alpha subunit.
330
What is a typical 2nd messenger for the G-protein signalling pathway?
Cyclic AMP
331
What is the 2nd messenger for the Receptor Thyrosine Pathway of cell signalling?
Kinase enzymes
332
What does receptor tyrosine kinase cell signalling have several different steps?
It is an amplification system
333
How are G-proteins anchored to their plasma membrane ?
Alpha and gamma subunits have covalently bonded lipid tails which join to the plasma membrane.
334
How does the drug Latrunculin A affect cells?
It is a microfilament so affects both phagocytosis and exocytosis. Greater effect on exocytosis.
335
Does the drug Latrunculin A have a greater effect on phagocytosis or exocytosis and why?
Exocytosis.
Inhibits microfilaments which are heavily required for exocytosis.
336
How does the drug 'Colchine' affect cells?
Microtubule inhibitor so reduces exocytosis and phagocytosis. Greater effect on phagocytosis.
337
Does the drug 'colchine' have a greater effect on phagocytosis or exocytosis and why?
Phagocytosis.
Inhibits mictorubules which are heavily required.
338
What effect does Cyclohexamide have on cels?
Protein synthesis inhibits
339
In plants, what tissue types does mitosis occur?
Meristems
340
What are meristem tissues?
Tissues forms from undifferentiated cells in plants where alot of mitosis occurs. Responsible for growth.
341
Where are meristem tissues found in plants?
Root and shoot tips and the cambia between the xylem and phloem of the vascular bundle.
342
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.
343
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.
344
What structure holds the cellulose walls of adjacent plant cells together?
Middle Lamella containing pectin
345
What type of molecule is pectin?
Protein - starch
346
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.
347
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.
348
What is mitotic index a measure of?
The amount of cell division that a tissue is undergoing.
349
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).
350
Define cellular fate.
What a cell will be programmed to turn into.
351
Define cell potency.
The ability of a stem cell to divide into different cell types.
352
Define tetrads.
Pairs of homologous chromosomes.
353
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.
354
When in meiosis does crossing over occur?
Prophase I
355
During prophase I of meiosis, what is it called when homologous chromosomes form tetrads?
Synapsis
356
What is synapsis in meiosis?
The formation of tetrads (pairs of homologous chromosomes).
357
What are the positives of having crossing over in meiosis?
Creates variability (genetic recombination) and is beneficial to evolution.
358
What are homologous chromosomes?
Chromosome pairs which have approximately the same length and centromere position.
359
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.
360
When in meiosis does cytokinesis occur?
Telophase I and Telophase II
361
When in meiosis do the centromeres divide?
Anaphase II
362
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.
363
Describe the genetic information of the daughter cells of mitosis.
2 daughter cells which are genetically identical to the parent cell and each other.
364
What is the official term for a fully developed sperm cell?
Spermatozoa
365
What is the step formation of a fully developed from a sperm cell (spermatozoa)?
Primary Spermocyte
Meiosis I
2 secondary spermatocytes
Meiosis II
4 Spermatids
Spermiogenesis
Spermatozoa
366
What is sermiogenesis?
Structural changes that allow a primary spermocyte to form the final version of a sperm cell (Spermatozoa).
367
How long does it take for a primary spermocyte to develop into a spermatozoa?
75-120 days
368
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.
369
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.
370
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.
371
When do Spermatozoa (sperm cells) gain motility?
When they detatch from the Sertoli cells and enter the lumen of the seminiferous tubules.
372
Describe the DNA of spermatozoa.
Highly condensed and tightly packed.
373
What controls the Production of Sperm cells?
The pituitary glans - FSH and testosterone.
374
What is the production of sperm cells technically called?
Gametogenesis
375
What is gametogenesis?
The production of gates (specifically sperm cells).
376
What is he technical name for egg cell production?
Oogenesis
377
What is oogenesis?
Egg cell production
378
Outline the production of a mature egg cell from a primary oocyte.
Primary Oocyte
Meiosis I
1 secondary oocyte and 1 polar body
Meiosis II
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.
379
When are egg cells produced?
In the foetus
380
When does egg cell production in females stop?
During prophase I in the late foetus then nothing happens until puberty.
381
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.
382
What term is used to describe the process of maturation of an ovarian follice?
Folliculogenesis
383
What is folliculogenesis?
The maturation of an ovarian folicle.
384
What controls oogenesis?
Pituitary glans - FSH and LH.
385
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.
386
When do blastocysts form?
In the early development of mammals.
387
What is the purpose of blastocyst cells?
They have an inner cell mass which eventually forms an embryo.
388
What is the outer layer of a blastocyst called?
Trophoblast
389
What is a trophoblast?
Outer layer of cells of a blastocyst.
390
What are the main purposes of adult stem cells?
Growth, repair, turnover of frequently replenished cells.
391
Where are adult stem cells extracted from?
Bone marrow
Fat
Blood
392
Name some important features of stem cells.
Ability to choose between cellular fates.
Prolonged self-renewal.
Differentiation.
393
What regulates the functioning of stem cells?
Intrinsic signals and external microenvironment.
394
What are the hierarchy levels of pluripotent in stem cells?
Totipotent
Pluripotent
Multipotent
Unipotent
395
What is meant by a stem cell being totipotent?
Can form a zygote (entire individual). Can divide into any cell type.
396
What is meant by a stem cell being pluripotent?
Can differentiate into any of the three germ layers.
397
What are the 3 germ layers that pluripotent stem cells can divide into?
Ectoderm, mesoderm, endoderm
398
What is meant by a stem cell being multipoint?
Can differentiate into several cell types
399
What is meant by a stem cell being unipotent ?
Can differentiate into a single cell type.
400
What cell types can be used for induced pluripotency?
Adult cells
401
What is induced pluripoteny advantageous to cells?
Does not cause rejection by the body via the immune system.
402
Why are adult stem cells expensive and difficult to extract?
There are not many stem cells in a given population.
403
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.
404
What are used on mass to produced induced, pluripotent stem cells?
Transcription factors
405
What can be used to identify stem cells?
CD markers, genes, enzymes proteins.
406
What are CD markers on stem cells?
Surface proteins which can be used to identify cell types.
407
What is meant by the term 'proximal'?
Near/ close to
408
What is meant by the term 'distal'?
Far
409
What is the Placode of an embryo?
Ectodermal thickening over a developing structure.
410
What is Anlage (Embryology)?
Cluster of embryonic cells from which a structure develops.
411
What is Epigenesis theory of development?
The theory that development occurs over time and structures arise via progressive stages.
412
What is the preformation theory of development?
Suggests that all structures exist from the very beginning, they are just getting larger.
413
Who came up with the Homonuclus theory and when?
Nicholas Hartsoeker - 1692
414
What is the homonuclus theory of development
A little human embryo was hidden in the head of every sperm cell.
415
What are the 5 processes of development in cells?
Cleavage division
Pattern formation
Morphogenesis
Cell differentiation
Growth
416
How does cleavage division alter total cell mass in development?
Cells divide but there is no increase in total cell mass.
417
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.
418
What is morphogenesis in development?
Becoming a 3D form
419
What are the 5 cell behaviours?
Cell to cell communication.
Cell shape changes.
Cell movement.
Cell proliferation.
Apoptosis.
420
What is cell proliferation?
Growth and division of cells to keep a constant cell count.
421
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.
422
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.
423
What is the vitelline membrane of an egg cel?
Surrounds the outer layer of the plasma membrane.
424
What is the benefit of having asymmetric distribution of cytoplasm components during cell division?
Allows cells to have different fates.
425
What is inductive cell interaction?
The process by which one group of cells changes the fate of another group of cells.
426
What are the possible methods of inductive cell interaction?
Cell signalling
Diffusion
Direct contact
Gap junctions
427
Why is it beneficial for cells to bind tightly and closely during development?
They have a greater surface contact and therefore cellular interactions increase.
428
What is radial cell cleavage what type of cells does this produce?
Horizontal cleavage producing 2 polarised cells.
429
What is transgenital cell cleavage and what type of cells does this produce?
Vertical cleavage producing 1 polarised cell and 1 non-polarised cell.
430
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.
431
What 2 cell types are present in a blastocyst?
Trophoblasts
Inner cell mass
432
What 2 regions do trophoblasts cells divide into when they come into contact with the endometrium?
Synctioblasts (outer portion)
Cytotrophoblasts
433
Why are syncitioblasts not described as being cellular?
Nuclei share a common cytoplasm
434
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.
435
What are intervillous spaces?
Spaces between the villi containing vessels of the mother and the embryo.
436
What is the endometrium?
The tissue lining the inner cavity of the womb.
437
What is the tissue lining the inner cavity of the womb called?
Endometrium
438
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.
439
How many weeks after fertilisation does gastrulation occur?
3
440
What are the 3 germ layers of the primitive streak?
Ectoderm
Mesoderm
Endoderm
441
Why do significant abnormalities within an embryo often occur during the gastrulation process?
Alot of morphological movement is occurring which could undergo errors.
442
Define Tissues
A group of cells that usually have a common embryo and function together to carry out specialised activities.
443
Define Histology.
The study of tissues.
444
What is a pathologist?
Examines tissues for changes that may indicate disease.
445
What is a biopsy?
The removal of a sample of living tissues for microscopic examination.
446
What are the 4 main types of tissues?
Epithelial tissues.
Connective tissues.
Muscular tissues.
Nervous tissues.
447
What are the main purposes of epithelial tissues (in general) ?
Cover the body surfaces and line hollow organs.
Form glands
448
What are the main purposes of connective tissues (general)?
Protect and support organs.
Store energy.
Act as a route for immune cells to travel through.
449
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.
450
Describe the extracellular matrix present in the epithelial tissues.
No ECM or very little.
451
Describe the blood vessels present in epithelial tissues.
No blood vessels present so relies on blood vessels from other tissues.
452
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.
453
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.
454
Outline the structure of the basement membrane of epithelial tissues.
Thin, fibrous, extra-cellular layer.
455
What is the basemen membrane of epithelial tissues made from?
Proteins
456
Where are the connective tissues cells of an epithelial tissue?
Reticular lamina
457
What are the purpose of hemidesmosomes in epithelial tissues?
Connect the basement membrane to the epithelial and connective tissue layers.
458
What happens to epithelial tissues if diabetes mellitus is untreated?
Basement membrane around capillaries in the eyes and kidneys thicken.
459
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.
460
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.
461
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.
462
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.
463
What are the 2 divisions of epithelial tissues?
Epithelial tissues that cover and line.
Glandular epithelial.
464
What is glandular epithelial tissue.
Makes up secretory parts of glans.
465
Where are striated squamous epithelial cells found and what is their purpose?
Lines the Oesophagus, mouth and vagina.
Protects against abrasion.
466
Where are the striated cuboidal epithelial cells found and what is their purpose?
Sweat glands, salivary glands and mammary glands.
Protective tissue.
467
Where are striated columnar epithelial cells found and what is their purpose?
The male urethra and the ducts of some glands.
Secretes and protects.
468
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.
469
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.
470
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.
471
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.
Absorbes.
Secrets mucous and enzymes.
472
Where are the Pseudostratified columnar epithelial cells and what is their purpose?
Ciliated tissue lines the trachea and upper respiratory tract.
Secretes mucus.
473
What are exocrine glands?
Produce and secrete substances onto an epithelial surface by way of a duct.
474
What are endocrine glands?
Secrete hormones directly into the blood.
475
What are connective tissues?
Tissues that connect, support, bind or separate other tissues or organs.
476
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.
477
What are the main functions of connective tissues?
Bind together to support and strengthen other tissues.
Protect and insulate organs.
Compartmentalise structures.
Serve as a major transport system.
Store energy as fat in the adipose tissue.
478
Where do connective tissues store energy?
As fat in the adipose tissue.
479
What are the 3 main components of connective tissue?
Extracellular fibres.
Ground substance.
Cells.
480
What are the 2 categories of cells in the connective tissues.
Fixed cells
Wandering cells
481
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.
482
What are the 3 types of fibres in the connective tissues?
Collagen
Elastic fibres
Reticular fibres
483
What are the purpose of collagen fibres in the connective tissues of epithelial cells?
Resist pullling forces to maintain structure.
484
What is the structure of reticular fibres in connective tissues?
Collagen n fine bundles with a coating of glycoproteins.
485
What are the purposes of reticular fibres in the connective tissues?
Provide support in blood vessel walls.
486
Explain the distance over which macrophages act in connective tissues.
Mobile over a short distance and act in a local region of connective tissues.
487
How does the number of macrophages alter when the connective tissue is damaged?
Increases alot.
488
Where are mast cells found relative to connective tissues?
Found close to small blood vessels in loose connective tissue.
489
What are the purposes of mast cells in connective tissues?
Contain granules of heparin proteoglycan - anticoagulant.
Contain histamine - promotes the inflammatory reaction.
490
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
491
What is the purpose of granules in mast cells of connective tissues?
Contain heparin proteoglycan which acts as an anticoagulant.
492
What are the types of connective tissue?
Embryonic
Mature
Loose
Dense
493
What is cartilage?
A firm tissue which is softer and more flexible than bone.
494
What is cartilage made up of?
Chondrocytes
495
What is the function of chondrocytes?
Produce large amounts of extracellular matrix
496
How are chondrocytes of cartilage provided with nutrients?
There are no blood vessels nutrients diffuse through a dense connective tissue surrounding the cartilage (Perichondrium).
497
What is the dense connective tissue surrounding cartilage called?
Perichondrium
498
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).
499
What is the main purpose of osteoblast cells?
Form bone
500
What protein do osteoblasts make and what is its composition?
Osteoid - contains Type I collagen which mineralises to become bone.
501
How do osteoblasts form bone?
They form osteoid protein which contains Type I collagen. This then mineralises to form bone.
502
Where do osteocytes originate from?
Osteoblasts that have migrated and become trapped and surrounded by the bone marrow that they produced.
503
What are spaces that osteocytes occupy called?
Lacunae
504
Describe the general structure of osteoclasts.
Large, multinucleate cells.
505
What is the main purpose of osteoclasts?
Breakdown bones by doing bone reabsorption.
506
Describe the structure of areolar tissues.
Loosely organised with diverse cellular and fibrous components.
507
What are the purpose of areolar connective tissues?
Supports organs and vasculators.
Inflammatory response
508
Describe the structure of adipose tissues.
Bubble-like appearance with little matrix.
509
What is the purpose of adipose tissue?
Cushions organs, insulates the body and stores energy.
510
What is the purpose of reticular connective tissues?
Forms network of support for blood cells within h lymph nodes, spleen, liver and bone marrow.
511
What is the structure of dense regular connective tissue?
Waves of collagen fibres allow for limited stretch in a single direction.
512
What is the purpose of dense irregular connective tissues being irregular?
Allows tissues to withstand tension from many directions.
513
What is the purpose of dense regular connective tissues having collagen fibres?§
Limited stretch in a single direction
514
What are the basic components of connective tissues?
Cells, extracellular matrix, protein fibres, ground substances.
515
Marfan syndrome is caused by issues with what tissue type?
Connective tissue
516
What substances does bone store?
Calcium, minerals and fats.
517
