- bublished by abbystizo ze dexter boy
- Monday, 27 July 2015
Insulin and Genetic Engineering
- Diabetes mellitus is the inability of beta cells of pancreas to produce insulin
- Restriction enzymes/endonuclease cut DNA at specific recognition sites
- This produces either "sticky ends" or "blunt ends"
- DNA ligase can be used to re-join the ends
- Recombinant DNA technology combines the DNA from two different organisms
- Reverse transcriptase catalyses the formation of DNA from mRNA
- Vector is a gene carrier. It will carry a human gene into the cell of a bacterium or yeast that will be used to make human protein. Produces no benefit for viruses / carrier
- Plasmid, circular strand of DNA, are useful vectors to make human protein from bacteria
- Transgenic organisms contain another species DNA
[EXAM] Remove a particular gene from the DNA of an animal cell
- Locate with the use of a gene probe
- Use restriction enzymes
- Use endonucleases to cut at specific base sequence by hydrolysing
- Breaking sugar-phosphate bonds
[EXAM] Insert this gene into the genetic material of a bacterium
- Same restriction enzymes
- Cut at same base sequence in bacterial DNA
- Leaving sticky ends/hydrogen bonds break
- Join/splice with ligase
- Use of plasmid
Task to find and insert the gene into bacterium for Insulin production
- Isolate human gene, e.g. insulin, by using cytoplasmic mRNA (no introns)
- Reverse transcriptase, taken from a retrovirus, makes DNA from mRNA
- DNA is given "sticky ends" by using the enzyme restriction endonuclease
- Insert into a plasmid from a bacterium
- Dissolve cell walls using enzymes
- Centrifuge to separate bacterial chromosome ring from plasmids
- Cut open the plasmid
- Add sticky ends
- Mix plasmid and DNA gene together and use DNA ligase to stick them together
- Mix with bacteria //only ≈1% will take up the engineered plasmids
- Identify by using antibiotic resistance. Add gene for antibiotic resistance next to insulin gene in the plasmid. Add antibiotic to the culture / only bacteria surviving have insulin gene
- Grow transformed cells using industrial fermenters
- Isolate and purify human protein made by these cells
Moral and ethical issues associated with recombinant DNA technology
- Transgenic bacteria or viruses may mutate and may become pathogenic
- Genetically modified crops could "escape"
- Forms a genetically modified population in the environment
- Genetic modification may involve the resistance to herbicides
- Escaped crops may become "superweeds" that are difficult to kill and control
- Transgenic organisms could upset the balance of nature
- Population of transgenic salmon have been produced in which individuals grow rapidly
- These transgenic fish could compete for food with other fish species
- bublished by abbystizo ze dexter boy
Early Development of the Zygote to a Blastocyst (1st Week)
- Ovulation releases ovum/secondary oocyte
- Fertilization in the oviduct → produces zygote
- Zygote undergoes cleavage as it moves along oviduct → produces morula
- As zygote divides, cells become smaller \ Morula stays same size
- Movement by cilia and peristalsis present in oviduct walls
- Morula develops into a blastocyst
- Trophoblast (outer layer of blastocyst) → nourishes future embryo
- Inner cell mass → will become fetus
- Fluid filled cavity → for protection (absorbs shocks, resists compression, ...)
- Blastocyst (≈100cells) implants itself in uterus lining
- Nourished by secretion from uterus
- Microvilli provide large surface area (→gas + nutrients exchange)
Implantation Of The Blastocyst Into The Uterine Lining (2nd Week)
- Trophoblast secretes enzymes → digest tissues and blood vessel of endometrium
- Embryo uses released nutrients/products from digestion
- Blastocyst becomes buried within endometrium
- Microvilli are replaced by placenta
- Trophoblast secretes human chorionic gonadotrophin (hCG) hormone
The Developing Fetus
- During gestation (→length of pregnancy) growth rate is in excess
- Placenta is the first organ to develop when blastocyst embeds itself in uterine lining
- Growth faster than embryo in early pregnancy
- Development increases in complexity
- Differentiating of inner cell mass of blastocyst
- First month → beginning of a gut, developed kidney, brain, beating heart
- Second month → all main organ systems present; embryo is called a fetus
- At the end of gestation placenta is discarded, but essential for the 1st 9 month of life
Features of the Circulatory System of the Developing Fetus:
Placenta is the Fetal Gas Exchange Organ → Fetal Lungs are Non-Functional
- Umbilical vein carries oxygenated blood from placenta to vena cava
- Blood in the heart bypasses through foramen ovale
- Oxygenated blood flows from right into left atria / flap valve prevents back flow of blood
- Some blood in right atria passes to right ventricle into pulmonary artery (to lungs)
- Blood bypasses lungs through ductus arteriosus
- Oxygenated blood flows from pulmonary artery into aorta
- Umbilical arteries carry deoxygenated blood from aorta to placenta
Importance of Pulmonary Circulation
- Carry oxygenated blood to lungs
- To allow respiration in lungs / be ventilated before birth
At Birth the Placenta is Replaced by Lungs as the Organ of Gas Exchange
- Umbilical vein constricts → prevents blood loss
- Ductus arteriosus constricts → blood leaving right ventricle is sent to lungs
- Blood pressure in left atrium exceeds that in right atrium
- Valve closes foramen ovale which fuses within atrial wall
- Prevents mixing of de- and oxygenated blood
- Deoxygenated blood in right ventricle is oxygenated in lungs
- [EXAM] Replacement of fetal to adult Hb takes ≈3months
- Each polypeptide/globin chain is coded by a separate gene
- Gene for fetal (gamma) globin is suppressed
- Gene for adult (beta) globin becomes active
Structure of the Placenta
- Originates from fetal tissues and endometrium
- Fully developed ≈20cm across and ≈3cm thick
- Umbilical cord connects placenta with fetus
- 1 umbilical vein → oxygenated blood from placenta to fetal vena cava
- 2 umbilical arteries → deoxygenated blood from fetal aorta to placenta
- FICK'S LAW: (surface area x difference in conc)/thickness of surface µ rate of diffusion
- Microvilli grow into endometrium
- Each villi contains a network of fetal capillaries
- Surrounded by thin pool of maternal blood
- Supplied by uterine arteries and drained by uterine vein
- Max difference in concentration
- Fetal Hb has a greater affinity for O2 than adult Hb
- Flow of maternal and fetal blood in opposite direction
- Uterine artery to umbilical vein
- Maintains gradient/prevents concs reaching eqm
- Short diffusion path (≈3.5μm)
- Fetal and maternal blood supply is separated by 3 layers
- Capillary endothelium
- Thin layer of connective tissue
- Epithelium covering villi
- Exchange surface only one cell thick
- Maternal and fetal blood come close together but never mix
- Maternal blood may be genetically different from fetal blood
- Fetal and maternal blood supply is separated by 3 layers
- Microvilli grow into endometrium
Function of the Placenta
- Exchange of substances between maternal and fetal blood
- O2 and waste products (urea, CO2) cross placenta by diffusion
- Glucose enters fetal blood by facilitated diffusion
- Amino acids enter fetal blood by active transport
- Placenta contains many mitochondria
- Maternal antibodies are taken into villi by pinocytosis
- Infant has immunity to same diseases as its mother after birth
- Secretes hCG (oestrogen, progesterone) → maintains pregnancy
Maternal Physiology
Effect of Pregnancy on Aspects of Maternal Physiology
- GROWTH OF: uterus from ≈50g to 1kg / secreting tissue in breasts by progesterone
- ENLARGEMENT OF: smooth muscle fibres of uterus wall / ducts of breast tissue by oestrogen
- INCREASE OF:
- Body mass/thirst/metabolic rate/ventilation rate/cardiac output/blood volume/red blood cell number
- Ca2+ and glucose levels in bloodstream
- Dietary requirements of Carbohydrates(energy), Protein(growth), Fe(Hb), Ca(bones), Vitamins
- Minimises stresses imposed on female body → optimum environment for growing fetus
(1) Changes in Thermal Balance
- Respiration + high growth rate increase heat
- Heat excess transferred to cooler maternal blood by heat gradient
- Mother loses this excess heat from her body
(2) Changes in Cardiac Output and Blood Volume and their Significance
- High growth rate of fetus, placenta, maternal tissues (not just breast and uterus)
- This increases O2 consumption/respiration
- As maternal muscles have to work harder to move her increased size
- Increases CARDIAC OUTPUT (= STROKE VOLUME x HEART RATE)
- Heart beats faster
- Increase in stroke volume
- Increase in cardiac muscle / heart chambers enlarge / output increases by 40%
- Increase in maternal blood volume
- Changes in volume of plasma > increase in number of red blood cells
Birth
- Fetus lies with its head down against stretched cervix
- Weak contraction of uterus every ≈30min / increase in strength and frequency
- Caused by hormone oxytoccin secreted by posterior pituitary gland
- When cervix is fully dilated
- Expulsion of baby by contractions of mother's abdominal muscles
- Umbilical cord shuts down, isolating baby from mother
- Rises CO2 content of the blood / stimulates baby's first breath
- Expulsion of placenta → ≈30min after birth
- Pregnancy lasts ≈38 weeks from implantation, 40 weeks from last period
Hormonal Changes During And After Pregnancy
Human Chorionic Gonadotrophin hCG Hormone
- Secreted by trophoblast and developing placenta
- Maintains corpus luteum past the time it normally disintegrates
- Endometrium is maintained and menstruation does not occur
- Female sex hormones still at high level
- Basis for pregnancy test → hCG can be detected in urine
- Peak in bloodstream after ≈2months followed by a slow decline
Progesterone and Oestrogen
- Secreted by corpus luteum for first 3 months
- Maintain endometrium, development of uterus, prevent menstruation
- Inhibit FSH production from anterior pituitary gland
- Prevents development of further mature ovarian follicles in ovary
- Hormone secretion is taken over by placenta
- Corpus luteum degenerates
Oxytocin causes Uterine Contraction (Birth)
- Oestrogen from placenta makes muscles of uterus sensitive to oxytocin
- End of pregnancy, level of oestrogen in blood rises, level of progesterone falls
- Oestrogen promotes uterine contraction, progesterone inhibits it
- Pressure of fetus against cervix stimulates stretch receptors
- Hypothalamus stimulates posterior pituitary glands to secrete oxytocin
- Oxytocin causes contraction of uterus
Lactation and Prolactin
- High levels of progesterone inhibits prolactin
- At birth, progesterone levels fall → prolactin levels increase
- Suckling promotes production and ejection of milk
- Nerve impulses travel to hypothalamus
- Stimulates posterior pituitary gland to secrete oxytocin
- Stimulates muscles in walls of milk ducts to contract, squeezing milk out
- Stimulates anterior pituitary gland to secrete prolactin
- Stimulates production of more milk
- Prevents secretion of FSH and LH
- Thus, ovulation does not happen → mother is less likely to conceive
- Milk is bacteria free/ contains antibodies, essential nutrients, Ca2+ for bone growth, NO fibre/iron → baby will need solid food after ≈3-4months
Skeletal muscles
- bublished by abbystizo ze dexter boy
- Sunday, 15 December 2013
Gross and Microscopic Structure of Skeletal Muscle Including Ultrastructure of a Myofibril
- Skeletal muscle is joined to bone by inelastic tendons
- Muscle contraction / pulls on tendons / bone moves
- Each muscle is made of bundles of muscle fibres surrounded by connective tissue
- An individual muscle fibre
- Has many nuclei → muscle fibre develops from fusion of many cells
- Sarcoplasm (cytoplasm) filled by parallel myofibrils
- Sarcolemma (surface membrane) forms deep tubes (T tubules) into the sarcoplasm along its length
- Network of membranes called sarcoplasmic reticulum (ER)
Roles of Actin, Myosin, Calcium Ions and ATP in Myofibril Contraction
Striations In Skeletal Muscle Are Caused By Filaments Of Two Protein Actin And Myosin
- Actin filament / thinner than myosin → lighter striations
- Myosin filament / thicker than actin filament → darker striation
- Distance between 2 adjacent Z lines: sarcomere / actin filament is attached to Z lines and extended into sarcomeres on either side
- Striation of actin alone → I band
- Striation of myosin alone → H zone
- Length of myosin → A band
- Central thickening of each myosin filament → M line
Structure Of Actin And Myosin Filament
- Actin filament: 2 actin strands twisted around each other
- Troponin-tropomyosin-actin complex blocks binding site for myosin
- Myosin filament: bundles of myosin molecules
- Bundle of myosin tails form a central stalk
- Globular heads attach to specific sites on actin filaments
- Myosin heads contain ATPase that hydrolyses ATP
Neuromuscular Junction
- Synapse between motor neurone and muscle fibre
- \ skeletal muscle fibres are stimulated by motor neurones
- IMPULSE REACHES NEUROMUSCULAR JUNCTION
- Influx of Ca2+ / synaptic vesicles fuse with presynaptic membrane
- Release of acetylcholine (ACh) into synaptic cleft by exocytosis
- Neurotransmitter diffuses across cleft
- Binds with receptors on motor end plate (→postsynaptic membrane of muscle fibre)
- Depolarises sarcolemma
- Threshold stimulates wave of depolarisation along muscle fibre
- Changes permeability of sarcoplasmic reticulum to Ca2+
- Ca2+ move into sarcoplasm / causes contraction of myofibril
Muscles As Effectors
- Motor neurones stimulate glands and muscles into action
- Respond to a stimulus → are effectors
Role of ATP and Phosphocreatine in Providing the Energy Supply During Muscle Contraction
Stimulation Of Muscle Fibres By The Nervous System
- CONTRACTION → myosin heads attach to actin binding sites / form temporary cross bridges / bridges rapidly break and reform / new cross bridges form further along actin filament / causing shortening of each sarcomere
- WHEN STIMULATION STOPS → Ca2+actively taken up by sarcoplasmic reticulum / myosin head detaches from actin / cross bridges reform / muscle relaxes
- NO ATP AVAILABLE → cross bridges cannot detach / muscle becomes stiff / unable to relax / extreme form: rigor mortis / occurs after death
Cycle Of Events During Contraction Of A Myofibril
- Ca2+ ions enter sarcoplasm during wave of depolarisation
- Bind to troponin / changes shape of protein / removes block of tropomyosin / exposes actin binding sites
- ATP binds to myosin / stimulates ATPase / RELEASES ENERGY
- Allows myosin heads to form cross bridges with actin
- Allows POWER STROKE: myosin head changes angle / pulls on actin filaments
- Width of I band, H zone decrease → filaments overlap increases
- Z lines move closer together → length of sarcomere decreases
- No change to A band → lengths of filaments stay constant
- Allows Ca2+ ions to be pumped back in by active transport
- New ATP binds to myosin / allows detachment from actin
- Myosin head changes to original position (cross bridges reform)
- Next attachment to actin filament and power stroke can occur
- Ca2+ and ATP required for cycle to continue
Energy In Active Muscle Cells
- Breakdown of phosphocreatine / releases PI + energy / attach to ADP / forms ATP
- PHOSPHOCREATINE + ADP → CREATINE + ATP
- ATP is used faster than it can be supplied by respiration
- Phosphocreatine allows regeneration of ATP without respiration
- Thus, Muscle cells continue exercise until slower pathways synthesis ATP
- Breakdown of glycogen in muscle cells / aerobic respiration of glucose
- Aerobic respiration of glucose, fatty acids from bloodstream / fatty acids last longer
- Prolonged exercise / not enough O2 for aerobic respiration
- Anaerobic respiration continues
- Lactate may cause cramps
Table 16-9-1: Structure, location and general properties of slow and fast skeletal muscle fibres
Feature | Fast muscle | Slow muscle |
| FUNCTIONAL - Role in body | - Rapid, powerful movements - Short-lasting | - Slow movement - Long-lasting |
| STRUCTURAL - Diameter of fibres - Capillaries - Sarcoplasmic reticulum - Mitochondria | - Large - Few - High - Few | - Small - Many - Low - Many (ETC, Krebs cycle) |
| MECHANICAL - Speed of contraction - Rate of pumping Ca2+ | - Fast - High | - Slow - Slower |
| BIOCHEMICAL - ATPase activity - Respiration - Glycogen content - Myoglobin content - Resistance to fatigue | - High, split ATP quickly - Anaerobic - High - Low - Low | - Low, split ATP slowly - Aerobic - Low - High - High |
| LOCATION | Arms and legs (running and throwing) | Back and neck (postural muscles) |
| Slow muscles contain myoglobin in sarcoplasm → appears bright red | ||
Facts about biology
- bublished by abbystizo ze dexter boy
[- Genetics -]
In a single human cell there are between 10,000 and 100,000 coded messages known as genes. If all the directions contained in all these genes were written down, the words would fill the equivalent of 10,000 volumes of the Encyclopaedia Britannica.
[- Genetics -]
Scientists at the Institute for Cancer Research in Philadelphia have bred mice that have more than one set of parents. Known as "multimice," these creatures are spawned by taking two embryos created by two sets of parent mice, placing them together in such a way that the embryos grow together, then transplanting the entire organism into the womb of a third female mouse. The result is a baby mouse born with genetic characterisitics of both set of parents.
Facts about biology
- bublished by abbystizo ze dexter boy
[- Genetics -]
In a single human cell there are between 10,000 and 100,000 coded messages known as genes. If all the directions contained in all these genes were written down, the words would fill the equivalent of 10,000 volumes of the Encyclopaedia Britannica.
[- Genetics -]
Scientists at the Institute for Cancer Research in Philadelphia have bred mice that have more than one set of parents. Known as "multimice," these creatures are spawned by taking two embryos created by two sets of parent mice, placing them together in such a way that the embryos grow together, then transplanting the entire organism into the womb of a third female mouse. The result is a baby mouse born with genetic characterisitics of both set of parents.
Interesting Facts
- bublished by abbystizo ze dexter boy
Memory
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