fuckass bio test puberty

IB BIO: Control of the developmental changes of puberty by Gonadotropin-releasing hormone and steroid sex hormones. 

• Puberty is a sequence of developmental changes in transition from childhood to sexual maturity. 

• Puberty is triggered by a part of the brain called the hypothalamus.The hypothalamus secretes a hormone called Gonadotropin Releasing Hormone (GnRH) which travels through a short blood vessel to cells of the pituitary. 

• GnRH is a peptide hormone (i.e protein based), so the target receptor is a transmembrane protein within the cell membrane. ,

• After binding to its receptor, it triggers a signaling cascade within the pituitary cell which makes the pituitary cells respond to the GnRH by activating synthesis and secretion of Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH).

• These two hormones travel through the bloodstream to their targets, the gonads (Testes & Ovaries) which ultimately lead to the effects of puberty in the body. 

Puberty in Typical Males

• Follicle Stimulating Hormone (FSH)

  • Released from pituitary and travels through blood to the testes. 

  • Binds to transmembrane receptors in Sertoli cells, which triggers a signaling cascade that leads to the activation and maintenance of spermatogenesis. 

• Luteinizing Hormone (LH)

  • LH is released from the pituitary and travels through the blood to the testes. 

  • Binds to transmembrane receptor on the Leydig cells, triggering a signaling cascade which leads to the production of testosterone. 

• Testosterone

  • Steroid Hormone

  • Travels through the bloodstream to cells throughout the body with testosterone receptors. 

  • In response to testosterone during puberty, typical males will experience:

    • Enlargement of the penis and balls

    • Deepening of the voice

    • Growth of facial and pubic hair

    • Increase in muscle size and strength

    • Bone Growth

    • Increased Libido

Puberty in Typical Females

• Follicle Stimulating Hormone (FSH)

  • Released from pituitary and travels through blood to the ovaries. 

  • Binds to transmembrane receptors in Granulosa cells in a follicle, which triggers a signaling cascade that leads to the development of the follicle and the production of estrogen.

• Luteinizing Hormone (LH)

  • LH is released from the pituitary and travels through the blood to the testes. 

  • Binds to transmembrane receptors in the follicle and corpus luteum, triggering a signaling cascade which leads to ovulation, the development of corpus luteum, and the production of progesterone.

• Estrogen

  • Estrogen is released from ovaries during the ovarian cycle, which travels throughout the bloodstream to cells throughout the body with estrogen receptors.

  • In response to rise in estrogen during puberty, typical females will experience:

    • Enlargement of vagina and uterus

    • Development of breasts

    • Beginning of menstrual cycle

    • Change in body shape and fat deposition

• Progesterone

  • Progesterone is secreted from cellswin the ovarian corpus luteum during the second-half of the ovarian cycle. During puberty, progesterone’s primary function is development of breasts.

• Overview:

  • LH activates synthesis and secretion of testosterone in typical males.

  • FSH activates synthesis and secretion of estrogen and progesterone in typical females.

Fertilization in Humans

• Once released, egg and sperm will die unless they find each other and fuse in the process of fertilization

Movement of Sperm

• After ejaculation, sperm move through the cervix, into the uterus and swim towards the egg within the oviduct.

  • Sperm are able to direct their movement towards an egg using thermotaxis and chemotaxis.

  • Thermotaxis: Sperm change their swimming direction according to temperature gradient, swimming towards a warmer temp. 

  • Chemotaxis: Sperm moves in response to chemical gradients. Sperm plasma membranes have receptors that detect chemicals released by the egg.

Acrosome Reaction

• Once at a egg, the sperm must maneuver through the cells of the corona radiating around the egg. 

• The corona cells are cells that form around a developing egg in the ovary and remain with it upon ovulation.

  • Corona cells secrete hormones that trigger an acrosomal reaction in the sperm.

  • Enzymes in sperm head digest zona pellucida of the egg.  

Membrane Fusion

• Fertilization occurs with the fusion of the sperm plasma membrane with the egg’s plasma membrane. After the membranes fuse, the sperm’s nucleus enters the egg cell. The sperm cell tail and mitochondria do not enter the egg. 

Cortical Reaction 

• Upon fusion w/ sperm and egg membrane, the zona pellucida hardens to prevent polyspermy. This “cortical reaction” ensures that the egg is not fertilized by multiple sperm and has the appropriate number of chromosomes. 

Formation of Diploid Nucleus

• Once the sperm & egg membranes fuse, the cell is called a zygote. Fertilization is not complete at this stage until the 2 haploid nuclei come together and combine into a single diploid nucleus. 

Mitosis

• It takes b/w 24 to 30 hours after fertilization for the sperm & egg nuclei to find each other for their nuclear membrane to break down. The sperm & egg nuclei each release 23 chromosomes which jointly participate in mitosis as the zygote divides to become an embryo.

Development of a blastocyst and implantation in the endometrium

Embryo Development

• The embryo divides to create a ball of cells called a morula. About 5 days after fert., the cells of the morula begin to differentiate and the morula changes into a blastocyst. This occurs in the oviduct.

  • Blastocyst: A hollow ball of cells. “Hatches” out of zona pellucida  and undergoes implantation, embedding into endometrium.

• The next stage of embryonic dev. Is characterized by the formation of most internal organs and external body structures.

• The heart begins to pump fluid through blood vessels by day 20 and the fast red blood cells appear the next day. Almost all organs are developed after 10 weeks post-fertilization. 

• The brain & spinal cord are the exceptions to this which continue to develop throughout pregnancy. 

• 8th week - embryo is considered a fetus.

IB BIO: Puberty Hormones / Cell Signaling Review

• Receptor Proteins

  • Some Receptors are found on the surface of the cell, these receptors are called transmembrane receptors. 

  • The Intracellular receptors are those found inside the cell. 

    • The signal molecules must be hydrophobic, non-polar molecules that can traverse the membrane to reach the intracellular receptor. 

• Steroid Hormones

  • Steroid hormones are able to pass through the membrane via blood bound transport proteins. Then the hormone binds to the receptor within the cytoplasm or nucleus, forming a hormone-receptor complex. 

  • The hormone-receptor complex goes through a pore of the nucleus and attaches to the DNA at the specific gene. 

  • The hormone-receptor complex acts as a transcription factor which then transcribes the DNA into RNA.

  • The mRNA is translated into a protein at the ribosome which takes effect in the cell. 

• Ex.) Testosterone Response 

  • The binding of testosterone to its receptor leads to muscle growth.

    • Testosterone diffuses through the cell membrane of a muscle cell.

    • Binds to receptor, forming hormone-receptor complex

    • Moves through nuclear pore, and acts as a transcription factor which transcribes DNA into RNA. 

      • The binding of this particular hormone-receptor complex to the DNA activates the transcription of serum response factor gene into mRNA. 

    • The mRNA translates into serum response factor protein which causes growth of the muscle. 

• Steroid Hormones:

  • Estrogen - Ovaries

  • Progesterone - Ovaries and Placenta

  • Testosterone - Testes

IB Bio: Differences between sexual & asexual reproduction

• Reproduction, a shared process of life is the capacity to generate more members of the species. 

  • Sexual or Asexual

• Asexual Reproduction involves only one parent.

  • Ex.) Binary Fission, mitosis & budding

    • Produces offspring genetically identical to parent.

    • Variation only caused by mutation.

    • Most effective in stable, predictable environment.

• Sexual Reproduction involves two parents and the fusion of haploid sex cells from each parent.

  • Ex.) Meiosis

    • Fusion of gametes

    • Most plants & animals reproduce sexually

    • Produces genetically unique offspring and increases genetic variation.

    • Most effective in unpredictable, changing environments.

Adaptations of Sperm and Egg Cells

• Gametes are cells formed in meiosis that contain a haploid nucleus tat  is used to pass on genetic info from parent to offspring. 

  • Males = sperm, Females = Ovum (egg)

• Sperm Cell

  • The function of sperm is to deliver DNA to an egg cell during sexual reproduction. Sperm are adapted to reduce resistance as the cell moves towards the egg. 

    • Head: Cell body packed with haploid nucleus, receptor proteins bind to the zona pellucida on the egg during fertilization. The acrosome is a sac of digestive enzymes that digest the outer layer of the egg. Binding proteins on the acrosome bind to protein on the egg cell where the sperm and egg fuse. 

    • Midpiece: multiple mitochondria wound around microtubules at base of tail perform cellular respiration. Produces ATP to move flagellum.

• Egg Cell

  • Surrounded by structures that protect the egg prior to and after the fertilization. 

    • Zona Pellucida: layer of glycoproteins digested by sperm during the acrosome reaction. Chemically altered in the cortical  reaction to prevent more sperm from penetrating. 

    • Cortical Granules: Vesicles full of enzymes along the inner edge of the cell which are released  via exocytosis after fertilization to make the zona pellucida impenetrable to more than one sperm.

    • Corona Radiata: A layer of follicle cells that form around developing oocyte in the ovary and remain with it upon ovulation.

    • Binding Proteins: Proteins on the plasma membrane of the egg cell that bind to the proteins of the sperm cell acrosome membrane when the egg and sperm fuse during fertilization. 

Differences between male and female sexes in sexual reproduction

• Spem &  egg cells differentiatr to  develop into specfic shapes and sizes that maximize the ability of the cell  to perform its specialized function.  

Nuclear division prior to cell division

• Eukaryotic cell division is divided into two major steps: 

  • 1.] division of nucleus by meiosis & mitosis

  • 2.] division of the cytoplasm by cytokinesis

    • Nuclei must divide before cytokinesis to ensure each daughter cell has a nucleus. 

      • Cells w/o nucleus are termed anucleate

Role of meiosis and fusion of gametes in the sexual life cycle

• Sexual LIfe Cycle:

  • A life cycle is a series of stages of the life of an organism. 

• In order to maintain the correct # of chromosomes in each generation, there must be a reduction in the # of chromosomes in the forming of eggs & sperm—halving from diploid to haploid.

• At fertilization two haploid gametes fuse to form a diploid zygote by uniting two gametes with half the # of chromosomes, the full # of chromos. is restored each generation. 

• Sexual reproduction = VARIATION.

Segregation and Independent Assortment of unlinked genes in meiosis

• A diploid organism has two copies of every gene.

  • 2 copies may be the same or different alleles. 

  • The genotype of an individual is the combination of alleles that are present. 

• Homologous Chromosomes:

  • Same length

  • Same Centromere

  • Same Genes

• Segregation of Alleles

  • Law of Segregation: two alleles of a single gene present in a diploid parent will separate from each other and be distributed to each haploid gamete (egg or sperm). 

• Segregation of Alleles during Meiosis

Meiosis as a source of variation

• Variation is a defining feature of life.

•  Variation within a species is called “intraspecies variation”.

• Genetic variation is inheritable (Parent to Offspring)

  • Enables some organisms to survive better than others and thus pass their beneficial variation down to their offspring. 

  • Part of the process of natural selection.

• Genetic Variation within a species can result from:

  • Mutation

  • Gene Flow

    • The movement of genes b/w different groups of organisms

  • Meiosis

  • Sexual Reproduction

• Meiosis generates genetic diversity in two ways:

  • Crossing over b/w non-sister chromatids of homologous chromosomes during prophase 1 of meiosis creates new combinations of alleles that are on the same chromosome.

    • Synapsis is when the homologous chromosomes pair up during prophase 1.

    • Chiasma (pl. chiasmata) is the location where the fragments switch.

    • Crossing over produces recombinant chromosomes, or chromosomes with new combinations of alleles not present in either parent. 

  • Random Orientation and independent assortment of bivalents during metaphase 1 of meiosis creates gametes with new combinations of alleles that are on different chromosomes. 

    • Random assortment:

      • Bivalent: Pair of homologous chromosomes

      • During anaphase 1, two chromosomes of the bivalent will each move and attach to a random pole. 

    • Independent Assortment:

      • The orientation of the bivalent does not affect the other bivalents.

      • There are 2n possible ways chromosomes can independently assort into gametes.

• Spermatogenesis 

  • Germ cells called spermatogonia divide by mitosis. Half become sperm cells and the other half remain germ cells to keep a constant source of ___.

  • Spermatogonia destined to develop into mature sperm cells will grow to become primary spermatocytes. Primary spermatocytes move from the outer part of the seminiferous tubule to a more central part and attach to Sertoli cells. 

  • After growing, the primary spermatocytes complete meiosis 1 to form a secondary spermatocyte. Goes from being a diploid to a haploid. 

  • Stimulated by testosterone secreted by leydig cells, the secondary spermatocytes complete meiosis 2 to form a spermatid. This creates 4 haploid cells. 

  • The secondary spermatocytes differentiate to become spermatozoa. Once the sperm has differentiated, it is transported through the seminiferous tubules and stored in the epididymis until ready to be released.

• Oogenesis - prenatal

  • Germ cells called Oogonia in the outer edge of the fetal ovary divide by mitosis. Oogonia destined to develop into egg cells will grow to become primary oocytes within a primordial follicle in the ovary. Primary Oocytes start the process of meiosis but stop at prophase 1. 

  • Influenced by FSH from the pituitary each month an ovarian follicle will grow. Just before ovulation, the primary oocyte within the follicle will complete meiosis 1. The cytokinesis is unequal and results in one ;large secondary oocyte and one small polar body. The secondary oocyte, now a haploid is still in the follicle, will begin meiosis 2 but stop at metaphase 2. 

  • Influenced by LH from the pituitary, each month a follicle will rupture and ovulation will occur. When ovulated, the egg is still a secondary oocyte that is paused at metaphase 2 of meiosis. If fertilization occurs If fertilization occurs the secondary oocyte will complete meiosis 2 and another polar body will be created, the ovum. 

Equal & unequal Cytokinesis

• Cytokinesis is the division of cytoplasm and organelles into 2 daughter cells

  • In most cases, the cytoplasm and organelles are equally partitioned b/w the daughter cells. 

• Sometimes, cytoplasm is unequally divided.

  • Budding is an asymmetric division mechanism used by most yeast cells to reproduce asexually.

  • Oogenesis is the production of an egg cell in which the cytoplasm is unequally divided to produce one large egg cell  and three polar cells. The single egg cell contains the cytoplasm.  

Hormones of the Menstrual Cycle:

Changes during the Ovarian and Uterine Cycles and their Hormonal Regulation

• Menstrual cycle starts at puberty and lasts until a woman experiences menopause (stopping of menstrual cycle).

  • Series of changes in the uterus where the endometrium (inner lining of uterus) is built in anticipation of implantation of an embryo.

  • Sheds if no pregnancy occurs.

• The Ovarian cycle refers to the series of changes in the ovary during which the follicle matures and an egg is released and the corpus luteum develops. 

• The typical menstrual cycle is a median of 28 days.

• The Ovarian cycle is divided into 2 main phases.

  • Follicular Phase: 

    • 1-14 days, Follicle is stimulated to start developing and at day 14, the hormone level is just right where the egg is released. 

      • This is called Ovulation.

  • Luteal Phase:

    • 15-28 days, the walls of the ruptured follicle develop into a temporary mass of cells within the ovary called the corpus luteum.

• In the brain, the hypothalamus releases gonadotropin releasing hormone (GaRH) throughout the body through the circulatory system 

• When it gets to the pituitary, the pituitary secretes follicle stimulating hormone (FSH) so that the follicle may start developing and thus estrogen is produced.

  • Ovulation: Rupturing of the follicle and release of the egg cell. 

    • Triggered by the rapid rise in Luteinizing Hormone (LH) triggered by gonadotropin releasing hormone (GnRH) from the hypothalamus. At the ovaries it causes the walls of the follicle to be digested, causing the release of the egg. 

  • The luteal phase begins after ovulation, where the cells of the corpus luteum secrete estrogen and progesterone which cause the thickening of the uterus endometrium. The corpus luteum is broken down if fertilization does not occur. 

• Feedback is when the effect of an action influences whether or not the action continues. 

  • Negative Feedback - The effect decreases the action; more of the product causes less of an action.

  • Positive Feedback - The effect increases the action; more of the product causes more of the reaction. 

    • This is how hormones act.

• Estrogen provides negative feedback to the hypothalamus, which lowers the levels of FSH and LH being secreted and subsequently the levels of estrogen produced. 

• During the days 12-14 of the Ovarian cycle, estrogen switches to provide positive feedback to the hypothalamus. This causes an increase in the level of LH being secreted in the ___.

Hormone replacement therapy and the risk of coronary heart disease

• Menopause is the stage of life when a woman permanently stops having menstrual cycles. This is caused by a rapid decline in the hormones progesterone and estrogen. 

• Symptoms include:

  • Hot flashes

  • Night sweats

  • Reduced sex drive

  • Vaginal dryness

• Hormone replacement therapy

  • Women can be prescribed medications of estrogen and progesterone as a way to treat menopause symptoms. 

  • Early epidemiological studies also suggested that hormone replacement therapy reduced risk of coronary heart disease in postmenopausal women.

  • New data from controlled studies suggested that HRT among healthy postmenopausal women was associated with a slightly elevated risk of coronary heart disease. 

  • A spurious correlation is a correlation in which 2 variables are associated but not causally related. 

Use of hormone in vitro fertilization (IVF) treatment

• In Vivo and in Vitro fertilization 

  • In vivo: Occurs inside the body.

  • In Vitro: A form of medically assisted reproduction, where fertilization occurs outside the body. 

• The first step in the IVF process is called down regulation. Injections of medications are administered daily for about two weeks. These drugs stop the pituitary gland from secreting FSH and LH which suspends the normal menstrual cycle. 

• The second step is to administer high doses of FSH via 7-12 days of daily injection. The FSH triggers development of multiple follicles rather than the typical single follicle.

• Once multiple follicles have developed, the eggs can be received from the ovaries. A needle is then stuck in the vagina with a suction at the end that sucks the eggs out. An ultrasound device is used to guide the needle.

• Each egg is mixed with a sample of sperm in a shallow dish to allow for fertilization. The cells are incubated for 1-2 days to see if a zygote forms and begins to divide into an embryo.

• In order to prepare the uterus for reception of an IVF embryo, estrogen and progesterone are prescribed. These medications stimulate the thickening of the endometrium in preparation for implantation of an embryo. 

• If fertilizagtion was successfful, one or moore embryos are placed into the uterus when they are between 2 and 6 days old. 

D3.1.6 Fertilization in human

• Once released, egg and sperm will die unless they find each other

  • Sperm can live about 5 days within the female reproductive tract

  • After ovulation the egg can live for 12 to 24 hours

• External fertilization

  • Sea Urchins (Spawning) releasing both egg and sperm into water 

• Movement of Sperm

  • Sperm move through the cervix into the uterus and swims towards the egg within the oviduct

  • Sperm are able to direct their movement towards an egg using thermaxis and chemotaxis 

    • Thermatotaxis: sperm change their swimming direction according to a temperature gradient, swimming toward warmer temperature 

    • Chemotaxis: sperm move in response to chemical gradient; sperm plasma membranes have receptors that detect chemical released by the egg

• Acrosome Reaction

  • Sperm must move through the cells of the corona radiata around the egg

  • Corona cells secrete hormones that trigger acrosomal reaction in sperm; sperms head digests the zona pellucida of the egg

• Membrane Fusion 

  • Fertilization occurs with the fusion of the sperm plasma membrane with the egg plasma membrane; sperm enters the egg cell; sperm tail and mitochondria do not enter the egg

• Cortical Reaction

  • Zona pellucida hardens to prevent entry of more sperm; ensure egg is not fertilized by multiple sperm and that the zygote will have the correct number of chromosomes

    • Juno protein helps trigger the reaction

• Mitosis

  • 24 to 30 hours after fertilization for sperm and egg to find each other and break down plasma membranes 

  • Each release 23 chromosomes which participate in mitosis; zygote divides to an embryo 

D3.1.16 Development of a blastocyst and implantation in the endometrium 

• Zygote: fusion of egg and sperm

  • Divides by rapid mitosis to form an embryo composed of genetically identical cells 

• Embryo Development (oviduct)

  • Embryo divides to create a solid ball of cells called morula

  • Five days after fertilization the cells of morula begin to differentiate and morula changes in blastocyst 

    • Blastocyst is a hollow ball about 250 cells; inner mass will develop into the fetus (end of 8th week) and the outer layer of cells develop into amniotic sac and placenta 

• Implantation

  • Blastocyst hatches out of the zona pellucida

  • Seven days after fertilization, the blastocysts undergoes implantation embedding into the endometrium of uterine wall  

• Embryo Development 

  • Formation of most internal organs and external body structures

    • Day 16: Heart and major blood vessels

    • Day 20: Heart pumps fluids through blood vessels

    • Day 21: First red blood cells appear

    • Week 10: almost all organs besides brain and spinal cord

D3.1.18 Role of the placenta in fetal development inside the uterus 

Mammals

• Vertebrates, have hair, milk production in mammary glands, and three bones in the inner ear

  • Monotremes: egg-laying mammals (platypus + echidna)

  • Marsupials: give birth to underdeveloped offspring that climb into mother’s pouch to complete development (Kangaroos, koalas, opossums)

  • Placentals: mothers carry fetus in uterus where its nourished via the placenta (cat, rodents, humans); uterus supports growing fetus but its very energy demanding for the mother

• Placenta

  • Temporary organ that develops from the blastocyst shortly after implantation; placenta is connected to the fetus via the umbilical cord and to the mother at the uterus

  • Composed of a combination of fetal and maternal tissues 

• Placenta Structure

  • Fetal half: Blood from fetus arrives at the placenta via blood vessels in the umbilical cord; blood vessels branch into chorionic villi

    • Cell that line chorionic villi  separate the maternal from fetal blood creating a selectively permeable barrier between the fetal and maternal blood supplies

    • The branching structure increases surface area through which nutrient and waste can be exchanged between fetal and maternal blood 

  • Maternal half: blood from mother flow to and from the paces surrounding the villus

    • The nutrition and oxygen in the mother’s blood moves into the chorionic villi and into the fetal blood supply

    • Waste products and CO2 from fetus are passed from the fetal blood in the chorionic villi into the mother’s blood 

• Placenta Function

  • Endocrine organ, producing hormones that regulate both maternal and fetal physiology during pregnancy

    • Human Chorionic Gonadotropin: maintains the ovarian corpus luteum to ensure a new follicle does not mature and another egg is not ovulated; suppress mother’s immune system so the embryo is not rejected 

    • Oestradiol and progesterone: maintains the endometrium during pregnancy and stimulates mammary gland development 

• From mother to fetus (Umbilical vein)

  • Glucose, Amino acids, lipids, oxygen, water, antibodies, hormones, ions

• From Fetus to mother (Umbilical arteries)

  • Carbon dioxide, water, ions, Urea and other waste products 

• Placenta Transport -  Simple diffusion 

  • Simple diffusion: substance moves from higher to lower concentration directly through membrane; movement of gases (O2 and CO2).

    • O2 moves from maternal blood to fetal blood

    • CO2 move from fetus’s blood into maternal blood

• Placenta Transport- osmosis

  • Osmosis: movement of water across a semipermeable membrane from an area of high water concentration to an area of low water concentration.

    • Can move directly through the cell membrane or aquaporins, which are integral membrane proteins that serve as channels in the transfer of water using facilitated diffusion

• Placenta Transport- facilitated diffusion

  • Facilitated diffusion: passive movement of molecules from high to lower concentration through a channel protein

    • Simple carbohydrates (glucose) are transported by facilitated diffusion from mother to fetus through Glucose transport channel proteins in the cells of the chorionic villi

      • Fetus has lower glucose levels, mother has higher levels

• Placenta Transport-active transport

  • Active transport: movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration; requires cellular energy (ATP) to power pump proteins

    • Amino acids (proteins): brought to fetus through active transport 

• Placenta Transport- bulk transport

  • Antibodies: proteins the immune system produces to help protect the body against infections

    • These are taken into the cells of chorionic villi by endocytosis; the cell uses vesicles to transport the antibodies to the opposite side where they are released into fetal blood by exocytosis. (ACTIVE)

D3.1.17 Pregnancy testing by detection of human chorionic gonadotropin secretion

• Human Chorionic Gonadotropin: hormones produced during pregnancy

  • Produced by outer ring of cells of the embryo and from the placenta 

• Function: 

  • Stimulate the corpus luteum and placenta to continue to produce progesterone; which maintains the endometrium of the uterus

• Pregnancy Tests

  • They use monoclonal antibodies to detect hCG, the monoclonal antibodies (Y) are proteins that are synthesized in a lab and are capable of binding to ONE specific target molecules 

  • Monoclonal antibodies bound to enzymes that trigger a color change 

1. Start:  A sample of urine is placed on the surface of the test strip; if the person is pregnant hCG is present. If they aren’t then hCG isn’t present.

2. Reaction zone: Urine sample moves to free antibody(Y) complementary to shape of hCG; if the hCG is present it will bind to the free antibody as the urine move

3.  Test zone: A different antibody (Y) is immobilized at the test window; if hCG is present in the sample it will bind to the antibody causing a color change and a line. No hCG no line

4. Control zone: contains different immobilized antibodies bind directly to antibody from step B (Y); if the test works the enzyme is activated and a line will appear for all samples; ensure test strip is functioning 

IB BIO: Viruses

Viruses are very Diverse

• Viruses vary in:

  • Size 

  • Shapeir

  • Genetic Material

  • Genes Present

  • Enveloping

• Structures Common to Viruses

  • All viruses:

    • Use Nucleic Acid as their genetic material. Some viruses use DNA or RNA

    • Have an outer coating (“Capsid”) made of protein.

• Viruses are small so they can infect cells and because they have few (or no) enzymes and do not have cytoplasm. 

• Viruses have no cell cycle, so they don't grow. 

• Need help from a living cell to reproduce.

Lytic Cycle of Viruses

• A capsid is the protein shell of a virus, enclosing its genetic material. 

  • Predominantly one of two  shapes, helical or icosahedral, though a few have a complex architecture. 

• Viruses are either “enveloped” or “non-enveloped”. This distinguishes their presence of a lipid bilayer membrane on the outer part of the virus. 

  • Viral envelopes are acquired from host cell membranes during the maturation of the virus by the process known as “budding”. 

• Ex.] Bacteriophage Lambda

  • Host: E.coli bacteria

  • Genetic Mat.: Double-stranded linear DNA

  • Structure: Icosahedral head bound to a helical tail. Non-enveloped.

• Ex.]  HIV

  • Host: Primate T-cells with a CD4 receptor protein

  • Gen. Mat: Two copies of single stranded RNA (Retrovirus)

  • Icosahedral capsid with an envelope.

  • LIfestyle: Lytic

  • Associated Human Disease: AIDS!

• The virus’s mission is to hijack cellular machinery to force the cell to:

  • Make more virus nucleic acid (DNA or RNA)

  • Make more virus proteins

  • Assemble new virus molecules

• Bacteriophage Lambda 

  • Obligate intracellular viruses that specifically infect bacteria.

  • Lambda can alternate between two approaches of infection:

    • Lysogenic Cycle: The virus assimilates the genome within the host cell’s genome to achieve replication without killing the host

    • Lytic Cycle: The virus reproduces and bursts out of the host cell, killing it. 

• 7 steps to lytic cycle:

  • Phage attachment to the host cell.

  • Phage DNA entry into host cell

  • Phage DNA replication

  • Phage protein synthesis

  • Assembly of a new phage viruses

  • Lysis

  • Spread