Ib Biology Study Guide Topic 11
An attached antigen is recognised by a B-cell. Each B-cell has a corresponding antigen that they can produce antibodies against. The selected B-cell is stimulated to divide rapidly. These cells grow in size and become plasma cells. Plasma cells produce antibodies and release them into the blood. Antibodies bind to attached antigens and destroy the invading microbe.
Amazon.com: ib study guide. IB Biology Study Guide: 2014 edition: Oxford IB Diploma Program Sep 30, 2014. $11.40 $ 11 40 $36.99.
Some of the B-cells become memory cells that live for a very long time and 'remember' the antigen (can respond very rapidly=you are immune to that particular microbe). Plasma cells live for about 5 days while memory cells can live for as long as you live. Pathogen enters body and causes disease. Pathogen/antigen ingested by macrophages (endocytosis). Antigen exposed on surface of macrophage. T-helper cells bind to these macrophages.
Those T-helper cells become activated. Activated T-cells bind to inactive B-cells (this activates the B-cells). Activated B-cells divide and form plasma cells and memory cells. Plasma cells then produce more free antibodies (antibodies secreted by exocytosis). Causes immunity (excessive amount of antibodies+existing memory cells). Bones (humerus, ulna, radius): rigid structures providing anchors for muscles. Muscles (biceps-flexor muscle/bends joint.
Triceps-extensor muscle/straightens joint): provide forces to move joint and act as antagonistic pair. Tendons: join muscle to bone. Cartilage: smooth strong covering on articulating surfaces of joint. Synovial fluid: lubricates articulating surfaces of cartilage+shock absorber. Band ligaments: tough inelastic structures holding bones in joints together.
Capsular ligament: encloses joint to protect it. Nerve impulse reaches neuromuscular junction. Acetylcholine released from vesicles fusing with end plate membrane.
Initiates action potential in muscle cell membrane. Action potential carried throughout muscle cell and travels down T-tubules to reach sarcoplasmic reticulum. Action potential causes sarcoplasmic reticulum to release calcium into myofibrils.
Calcium ions bind to troponin. Troponin changes shape and moves tropomyosin away from myosin head binding sites.
Myosin heads become attached to actin filament. ADP+Pi released causing myosin heads to bend.
ATP binds to the myosin head, causing the cross bridge to detach. ATP becomes ADP+Pi and returns myosin head to original position. The myosin head binds to a new myosin head receptor to form a cross bridge. ADP+Pi is released, causing it to bend.
ATP binds, causing cross bridge to detach, etc, etc. This process drags the actin filaments further towards the Z lines, shortening the sarcomere. This is how the muscle contracts. Calcium ions actively absorbed back into sarcoplasmic reticulum.
Troponin then reverts to original shape, causing tropomyosin to block myosin head binding sites on actin filament again. Ultrafiltration-the filtration under pressure at the molecular level. Occurs inside bowmans capsule and is passive and unselective. Blood pressure very high-part of blood plasma escapes through fenestrated wall of capillaries to bowmans capsule. Blood pressure high because efferent vessel is narrower than afferent vessel. Small molecules pass through fenestrated wall but big molecules don't, e.g.
Basement membrane acts as an ultra-filter and allows small solute molecules to pass through, e.g. Glucose, NaCl, H2O, urea, amino acids, etc. Layer of podocytes outside capillary wall-podocytes have long and fine 'fingers' which act as a filtering layer, reducing size of molecules that can leave the blood. The loop of Henle: -salt is actively transported out of the ascending limb in order to create an osmotic gradient.because the ascending limb is impermeable to water, the osmotic gradient causes the water from the descending limb (which is permeable to water) to be released into the capillary next to the descending limb.the salt is absorbed into the descending limb and is then stuck in a cycle. The collecting duct: -main site of osmoregulation.water levels in blood monitored by hypothalamus.little water=ADH released.lots of water=ADH released.ADH is a hormone released from the pituitary gland.ADH opens the aquaporines in the collecting duct-water reabsorbed. Mitosis: germinal epithelium cells (2n) divide by mitosis to produce more diploid cells.
Cell growth: diploid cells grow larger-now called primary spermatocytes. Meiosis I: primary spermatocytes go through meiosis I and produce secondary spermatocytes (n).
Ib Biology Study Guide Book
Meiosis II: secondary spermatocytes go through meiosis II and produce spermatids (n). Cell differentiation: spermatids become associated with Sertoli cells, helps them develop into spermatozoa (n)-example of cell differentiation. Sperm detach from Sertoli cells and are eventually carried out of testis by fluid in the centre of seminiferous tubule. Mitosis: germinal epithelium cells (2n) divide by mitosis to form more diploid cells. Growth: diploid cells grow larger and become primary oocytes (2n). Meiosis I: primary oocytes start meiosis I but stop at prophase I. Primary follicle is formed by primary oocyte and single layer of follicle cells around.
When a baby girl is born ovaries contain 400,000 primary follicles. Unequal division: every menstrual cycle a few primary follicles start to develop; completes meiosis I and forms two haploid nuclei. Cytoplasm of primary oocyte divided unequally forming large secondary oocyte (n) and small polar cell (n). Meiosis II: secondary oocyte starts meiosis II but stops at prophase II. Mature follicle bursts, releasing the still secondary oocyte. After fertilisation secondary oocyte completes meiosis II to form an ovum (with sperm nucleus already inside), and a second polar cell.
First and second polar cell don't develop and eventually degenerate. Epididymus: stores sperm before ejaculation. Sperms mature here and become motile.
Seminal vesicles: produce seminal fluid with fructose as an energy source for the sperm. Also contains protecting mucus and prostaglandins (helps movement of sperm by stimulating contractions of female reproductive tract). Prostate gland: produces slightly alkaline fluid that neutralises vaginal acids; helps protect sperm from hostile vagina environment and also contains clotting enzyme that converts the protein in seminal fluid into a gelatinous mass. Spermatogenesis/oogenesis Differences: -produces millions of cells daily/one cell produced per cycle -process begins at puberty/process begins in foetus -spermatogenesis continues until death/fertility limited until menopause -spermatogenesis involves equal cell divisions/oogenesis involves unequal cell divisions -no polar bodies formed/polar bodies formed -ejaculation of sperm can happen at any time/ovulation only happens in middle of menstruated cycle.
Similarities: -LH and FSH involved in both -both involve mitosis, growth, and meiosis. Arrival of sperm: are attracted to chemical signal and swim up oviduct to reach egg.
Binding: first sperm to break through the layer of follicular cells binds to zona pellucida (triggers acrosome reaction). Acrosome reaction: contents of acrosome released by separation of acrosome cap from sperm. Protease from acrosome digests a way through zona pellucida; sperm reaches plasma membrane of egg. Fusion: plasma membrane of sperm and egg fuse (triggers cortical reaction).
Sperm nucleus enters egg and joins egg nucleus. Cortical reaction: cortical granules move to plasma membrane of egg and fuse with it, releasing their contents by exocytosis. Causes cross-linking of glycoproteins in zona pellucida, making it hard and preventing more sperm entry. Fertilisation membrane forms over surface of plasma membrane of egg. Second oocyte completes meiosis II.
Egg and sperm nuclei fuse and form a diploid zygote. Structure of placenta: -acts as a barrier between maternal and fetal blood.disc shaped structure connected to fetus by umbilical cord.placental villi increase surface area for exchange.fetal capillaries in placental villi are surrounded by maternal blood.short distance between fetal and maternal blood.
Functions of placenta: 1. Exchange of materials between mother and child: placenta is the site where exchange if molecules occur between fetal and maternal blood. Hormone production: placenta is an endocrine organ (produces hormones).
It produces HCG, estrogen, progesterone, and human placental lactogen (stimulates breast development). Exchange across placenta: From mother to fetus-nutrients, oxygen, antibodies, hormones.
From fetus to mother-carbon dioxide, urea, hormones (HCG, placental progesterone). During last month of pregnancy there's a drop in estrogen and progesterone levels-causes increased uterine contractions-stimulates release oxytocin secreted from posterior pituitary-increased contractions of uterus-pressure of baby on cervix stimulates release of more oxytocin. =positive feedback.fetus responds to contractions by producing hormones from placenta, prostaglandins, which causes further uterine contractions.contractions cause opening of cervix (the water breaks=amniotic membranes burst and amniotic fluids come out).delivery of baby takes place through the vagina.later placenta is released from the uterus.
IB Biology Revision Notes-Topic 11 animal physiology (HL). 1. Stihl chainsaw 010 service manual. Topic 11: Animal physiology (HL) 11.4 Sexual reproduction U1 Spermatogenesis and oogenesis both involve mitosis, cell growth, two divisions of meiosis and differentiation. U2 Processes in spermatogenesis and oogenesis result in different numbers of gametes with different amounts of cytoplasm. U3 Fertilization in animals can be internal or external. U4 Fertilization involves mechanisms that prevent polyspermy. U5 Implantation of the blastocyst in the endometrium is essential for the continuation of pregnancy.
U6 HCG stimulates the ovary to secrete progesterone during early pregnancy. U7 The placenta facilitates the exchange of materials between the mother and fetus. U8 Estrogen and progesterone are secreted by the placenta once it has formed.
U9 Birth is mediated by positive feedback involving estrogen and oxytocin. A1 The average 38-week pregnancy in humans can be positioned on a graph showing the correlation between animal size and the development of the young at birth for other mammals. S1 Annotation of diagrams of seminiferous tubule and ovary to show the stages of gametogenesis.
S2 Annotation of diagrams of mature sperm and egg to indicate functions. Spermatogenesis:. Spermatogenesis is basically the production of sperm (male gametes) through meiosis. Occurs in the testes of male.
Spermatogonia (stem cells of the sperm - 2n) are located at the periphery of each seminiferous tubules. Developing sperm move towards the central opening of the tubule (lumen) as they undergo meiosis and differentiation. Mature sperm will be stored in epididymis. Spermatogonia is first divided by mitosis to form more 2n cells, called primary spermatocytes.
Primary spermatocytes undergo meiosis I to form two secondary spermatocytes. Two secondary spermatocytes undergo meiosis II to form four early spermatids. Early spermatids will go through cell differentiation and form mature sperms. Sperms are released into the lumen of the seminiferous tubules where they are transported to the epididymis. The sperm attain full motility in the epididymis. Cells in between the developing spermatocytes called Leydig cells, which produce testosterone in the presence of LH (luteinizing hormone) to aid in the development of the sperm.
Sertoli cells nourish the spermatids as they mature and differentiate into sperms. Spermatogonia Spermatogonia. Oogenesis:. Oogenesis is basically the production of female eggs (female gametes) through meiosis. Germ cells (2n) in the fetal ovary divide by mitosis to produce many 2n germ cells called oogonia. Oogonia will grow in the cortex until they are large enough and ready to go through meiosis; they are called primary oocytes.
The primary oocytes begin to go through the first division of meiosis, which is arrested (stopped) in prophase I. This is called the primary oocytes (about 400,000 in a female when she is born). These oocytes remain in the first stage of meiosis until the girl reaches puberty and begins her menstrual cycle. Every month a primary follicle finishes meiosis I to form two haploid (n) cells (one haploid cell is much larger than the other cell). This development is stimulate by FSH. The large cell is a secondary oocyte and the small cell is called the polar body.
The secondary oocyte develops inside what is known as the mature follicle. As the large secondary oocyte begins to go through the second meiotic division, it is released from the ovary. It will not complete the second meiotic division unless the oocyte is fertilized. When meiosis II is complete you have an ovum and another polar body. Follicle cells are providing nourishment. Structure of sperms and eggs Fertilisation:.
Fertilization is the combining of the male and female gametes to produce a zygote. Sperm are ejaculated into the vagina of a female and are stimulated to swim by calcium ions in the vaginal fluids. The sperm follow chemical signals produced by the egg, until they reach the fallopian tubes, which is where the majority of fertilizations take place.
When the sperm reaches the egg, a reaction called the acrosome reaction takes place that allows the sperm to break through the layer of glycoproteins. The acrosome in head of the sperm releases hydrolytic enzymes onto the glycoprotein layer surrounding the egg called the zona pellucida. This digests the layer allowing the sperm to force their way through the zona pellucida through vigorous tail beating. The first sperm that makes it through comes into contact and fuses with the egg’s membrane (The membrane at the tip of the sperm has special proteins that can bind to the now exposed membrane of the egg), releasing the sperm’s nucleus into the egg cell.
The entry of sperm will stimulate meiosis II and release Ca2+ ions, which will stimulate the release of cortical granules. When the membranes fuse together, cortical granules near the surface of the egg membrane are released by exocytosis. The chemicals in the granules combine with the glycoproteins in the zona pellucida.This causes the glycoproteins in the zona pellucida to cross-link with each other, creating a hard layer impermeable to the other sperm. This prevents fertilization of an egg by more than one sperm.