2022 extended response questions

cervical dilation cervix dilates foetus moves more deeply into pelvis

stage of expulsion: amnion bursts and amniotic fluid is released contraction of abdominal muscles occur foetus is expelled from uterus

removal of afterbirth umbilical cord is clamped in two places and cut uterus contractions force out the afterbirth

surface area to volume ratio: Cells are very small, which gives them a large surface area compared to volume This means that the cell can efficiently exchange enough materials through the cell membrane to support its given volume/if the cell was larger it could not supply its given volume with enough materials through the cell membrane

Concentration gradients: A concentration gradient refers to a difference in concentration across the cell membrane Substances tend to passively move down a concentration gradient/from areas of high to areas of low concentration If the concentration gradient across the membrane is maintained this allows for constant exchange of materials across the cell membrane The greater the concentration gradient, the faster exchange of materials (or opposite concept)

Physical nature: Some molecules are larger than others, which affects their ability to pass through the small spaces in the membrane Small molecules can travel directly through the lipid membrane while larger molecules cannot fit/need to pass through carrier or channel proteins

Chemical nature: The cell membrane is made up of lipids/a phospholipid bilayer Therefore lipid-soluble/non-polar molecules can easily diffuse through the lipid portions of the membrane (because they are not repelled by the lipid portion of the membrane) Water soluble/polar molecules cannot pass through and need to use carrier/channel proteins to cross the membrane (because they are repelled by the lipid portion of the membrane)

<p>How enzymes function: They can attach to a specific substrate The active site of the enzyme will combine with the substrate Form an enzyme-substrate complex (before a chemical reaction occurs) Can work based on lock and key model/induced fit model Enzymes act as (organic/biological) catalysts To speed up the rate of chemical reactions in the cell By reducing the activation energy/reducing the energy needed to get a chemical reaction started They are not used up/altered in the reaction themselves and can be reused Effect of temperature on enzyme function: The rate of reaction will initially increase as temperature increases As the temperature reaches above 40°C the enzyme/active site becomes denatured This changes the shape of the enzyme Therefore the enzyme cannot combine with the substrate and the reaction cannot be carried out/the enzyme cannot function as normal</p> Signup and view all the answers

<p>Made up of units called osteons/Haversian systems Osteons run parallel along the axis of the bone A central canal runs through the centre of each osteon The central canal can contain blood capillaries/nerves/lymph capillaries Layers of bony matrix called lamellae surround the central canal Small spaces within the lamellae are known as lacunae Lacunae are occupied by bone cells known as osteocytes Tiny canals known as canaliculi connect the lacunae/spaces in the osteons</p> Signup and view all the answers

<p>Hyaline cartilage contains closely packed/densely packed collagen fibres Hyaline cartilage provides strength and flexibility/provides a smooth surface for movement at the joints Fibrocartilage has a coarse appearance/has collagen fibres that are not packed as densely as hyaline cartilage/parallel bundles of collagenous fibres Fibrocartilage provides support in weight-bearing locations/site of heavy pressure (such as the knee/between the vertebrae) Elastic cartilage had obvious elastic fibres with not so closely packed collagen fibres It provides elastic support in specific locations (such as the outer ear)</p> Signup and view all the answers

<p>Ball and socket joints have a spherical head that fits into a concave/cup-like cavity They allow for movements in all directions (except where inhibited by ligaments)</p> <p>Hinge joints form when a convex surface meets a concave surface They allow for movement on one plane only/allow for flexion and extension only</p> <p>Pivot joints have a pointed/rounded/conical end that connects with a ring made of bone and ligament They allow rotational movements/movement around an axis</p> <p>Gliding joints are made up of irregular bones/exist between two bones that are flat (or nearly flat) at the meeting point They allow side-to-side and back-and-forth movements</p> <p>Saddle joints form from two saddle-shaped bones/form from a concave and convex shape in different directions They allow side-to-side and back-and-forth movements Condyloid/ellipsoid joints have a slightly convex bone combining with a slightly concave bone They allow for up and down and side-to-side movements</p> Signup and view all the answers

<p>Follicle stimulating hormone Causes production of sperm/to regulate spermatogenesis in seminiferous tubules Causes the maturation of the follicle and promote oogenesis in the ovarian cycle Luteinising hormone Cause the production of testosterone from interstitial cells in testes Causes ovulation/formation of the corpus luteum in the ovarian cycle Testosterone Testosterone causes maturation of the sperm/stimulates secondary male sexual characteristics Oestrogen Stimulates the endometrium to thicken and develop in the menstrual cycle Progesterone Causes the thickening and maintains the endometrium in the menstrual cycle</p> Signup and view all the answers

<p>The combined pill contains (synthetic) progesterone and oestrogen It is taken throughout the ovarian &amp; menstrual cycle/progesterone and oestrogen levels remain high throughout the whole cycle When the progesterone and oestrogen levels are high, the levels of FSH and LH are low/the levels of pituitary hormones/gonadotropins are suppressed The low FSH means follicle does not develop/the egg is not matured The low LH means egg/secondary ooctye cannot be released/ovulation never occurs Therefore the egg is never available for fertilisation (in the fallopian tube) The morning-after pill contains high levels of progesterone only If taken within the correct timeframe/before ovulation occurs this high level of progesterone delays the release of an egg/delays ovulation Because sperm can survive for up to 5-7 days this decreases the likelihood of an egg being available for fertilisation</p> Signup and view all the answers

<p>Follicle stimulating hormone Causes production of sperm/to regulate spermatogenesis in seminiferous tubules Causes the maturation of the follicle and promote oogenesis in the ovarian cycle Luteinising hormone Cause the production of testosterone from interstitial cells in testes Causes ovulation/formation of the corpus luteum in the ovarian cycle Testosterone Testosterone causes maturation of the sperm/stimulates secondary male sexual characteristics Oestrogen Stimulates the endometrium to thicken and develop in the menstrual cycle Progesterone Causes the thickening and maintains the endometrium in the menstrual cycle</p> Signup and view all the answers

<p>DNA structure: DNA is made up of two (anti-parallel) strands of nucleotides/double stranded structure 1-5 Nucleotides made up of a phosphate group, a deoxyribose sugar and a nitrogen base The sugar of one nucleotide bonds with the phosphate of another/there is a long chain of alternating sugar and phosphate molecules for each DNA strand/sugar-phosphate backbone Attached to each sugar is a nitrogen base 4 different nitrogen bases named adenine, thymine, guanine and cytosine The bases for each strand are bonded together with hydrogen bonds Adenine only bonds with thymine Cytosine only bonds with guanine The DNA twists into a double helix shape/coiled into a spiral</p> Signup and view all the answers

<p>Hydrogen bonds between bases are relatively weak and easily broken This means the nitrogen bases are easily exposed to allow for replication to occur DNA can replicate itself because of the way its double strands relate to one another/the complementary nature of the two strands Enzyme helicase separates the two strands of DNA Each strand of DNA acts as a template to make new complementary strands of DNA DNA polymerase adds new free-floating nucleotides to form the new strands of DNA DNA ligase combines short sections of DNA This creates two new identical molecules of DNA</p> Signup and view all the answers

<p>Crossing over: When homologous chromosomes pair up (during prophase I) they exchange sections of DNA The chromatids for each pair cross (at the chiasma), break and exchange segments This leads to a new combination of alleles in the gametes that is different from the parent cell/recombination</p> <p>Random assortment When homologous pairs line up/separate they do so at random The way one pair separates is unaffected by another/each pair separates independently This takes place for all 23 pairs of chromosomes and leads to a new combination of chromosomes that will differ from the parent cell</p> <p>Non-disjunction When a pair of chromosomes fails to separate during anaphase I or II One daughter cell will receive an extra chromosome, one will be missing one/gametes will either have 22 or 24 chromosomes (instead of 23) When the gamete with the extra or missing chromosome combines with another gamete during fertilisation this can lead to trisomy – where there are three chromosomes when they should be a pair, or monosomy, where there is one chromosome when there should be a pair</p> Signup and view all the answers

<p>Muscle cells are held together in bundles/surrounded by perimysium Connective tissues/epimysium holds the bundles together Epimysium/connective tissue tapers at end of muscle to form tendons Each muscle cell is an elongated cylinder with many nuclei Each muscle cell contains a sarcolemma and sarcoplasm Within sarcoplasm are myofibril threads Each myofibril is made up of myofilaments Thick filament is made up of myosin Thin filaments is made up of actin Myofilaments make up units called sarcomeres</p> Signup and view all the answers

<p>Kidney is important for regulation of body fluids It allows for reabsorption of water and other essential nutrients And allows for excretion of metabolic wastes (through urine) When kidneys fail the blood cannot be filtered and/or nutrients may be lost in the urine</p> Signup and view all the answers

<p>Energy released from cellular respiration can be stored in ATP ADP/adenosine diphosphate is made up of two phosphates and adenosine When energy is released from respiration a third phosphate bonds to ADP This is a high energy bond and creates a molecule of ATP/adenosine triphosphate The energy stored in ATP can now be released and used when needed by the cell</p> Signup and view all the answers

<p> Anaerobic respiration does not require oxygen  Aerobic respiration requires oxygen</p> <p> Anaerobic takes place in the cytosol  Aerobic takes place in the mitochondria</p> <p> Anaerobic produces pyruvate  Aerobic produces carbon dioxide and water</p> <p> Anaerobic releases enough energy for 2 ATP/can form up 2 ATP molecules from anaerobic respiration  Aerobic releases enough energy for up to 36/38 ATP/can form up to 36/38 ATP from aerobic respiration</p> <p> Anaerobic involves the process of glycolysis  Aerobic involves the Krebs cycle and electron transport system</p> Signup and view all the answers

<p>Digestive system: Breaks down the food we eat Simple substances absorbed into blood Include glucose necessary for anaerobic respiration Plus other nutrients/lists examples needed for enzymes to function through cellular respiration</p> <p>Circulatory system: Carries oxygen and glucose in the blood Oxygen is essential aerobic respiration/glucose is essential for anaerobic respiration Therefore supplying cells with the what needed to complete respiration</p> Signup and view all the answers

<p>Prophase  Nucleolus disappears  Nuclear membrane breaks down  Centrioles migrate to poles  Chromosomes appear as two chromatids/chromatin condenses into chromosomes  Spindle forms from microtubules Metaphase  Chromosomes line up at the equator of the cell Anaphase  Centromeres divide/degenerate  Chromosomes move to opposite ends of spindle Telophase  Spindle disappears  Nuclear membranes and nucleoli form  Centrioles divide  Chromosomes uncoil  Cytokinesis begins</p> Signup and view all the answers

<p>When cells divide uncontrollably this is cancer Cancer cells do not differentiate into normal tissue cells They form a tumour/a mass of cells called a tumour Tumours grow at a rapid rate Therefore normal body tissues cannot get supply of nutrients/cancerous cells ‘take over’ the normal body cells/tumour exerts pressure on organs and surrounding tissues/there can be a build up of wastes in the area</p> Signup and view all the answers

<p>Cervical screening tests identifies abnormal cells before they become cancerous</p> <p>Breast screening uses an X-ray to get a picture of the breasts and identify tumours</p> <p>Some blood tests can identify abnormalities that can be linked to bowel and prostate cancer</p> Signup and view all the answers

<p>pathway of sperm:  Travels through vas deferens  Seminal vesicles release sugar-rich fluid to combine with sperm  Prostate releases alkaline fluid  Semen travels through urethra and exits body  Semen deposited into vagina  Sperm pass through cervix and uterus  To fallopian tube where they meet ovum</p> <p>Fertilisation: Enzyme in acrosome breaks down corona radiata/zona pellucida Nucleus of the sperm enters the ovum Then forms a membrane which prevents entry of other sperm Nucleus of sperm fuses with nucleus of ovum (zygote is formed)</p> Signup and view all the answers