2022 extended response questions
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Describe the three stages of labour

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

Explain how surface area to volume ratio, concentration gradients can affect the exchange of materials across the cell membrane.

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)

(a) Explain how surface area to volume ratio, concentration gradients and the physical and chemical nature of substances can affect the exchange of materials across the cell membrane. (10 marks)

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)

Describe how enzymes function to optimise metabolism in the cells and explain the effect an increase in body temperature from 37°C to above 40°C can have on normal enzyme function.

<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

Describe the microscopic structure of compact bone

<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

describe the structure and function of the three different types of cartilage in body

<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

(b) Describe the structure and range of movement of four different types of synovial joints. (8 marks)

<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

Name and describe the function of the hormones that normally regulate the male reproductive system and the ovarian and menstrual cycle in females.

<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

(b) Explain how the combined oral contraceptive pill, and emergency hormonal contraceptives (the morning-after pill), influence the hormonal control of the ovarian and menstrual cycle to prevent fertilisation. (8 marks)

<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

(a) Name and describe the function of the hormones that normally regulate the male reproductive system and the ovarian and menstrual cycle in females. (12 marks)

<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

describe structure DNA

<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

Why DNA structure allows for replication of DNA + steps in DNA replication

<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

(b) Describe three processes that occur during meiosis that lead to variation. (10 marks)

<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

(a) Describe the macroscopic and microscopic structure of skeletal muscle. (10 marks)

<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

(c) Explain the effect of kidney failure on the chemical composition of body fluids. (4 marks)

<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

Cellular respiration is one of many essential metabolic processes that occurs in all cells. (a) Explain the role of ATP in the process of cellular respiration.

<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

(b) Contrast anaerobic and aerobic respiration. (8 marks)

<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

(c) Explain how the functions of the digestive and circulatory system allow cellular respiration to take place in all cells in the body. (7 marks)

<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

(a) Name and describe the four phases of mitosis. (10 marks)

<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

(b) Describe what is meant by the term cancer and explain how the development of malignant tumours can be detrimental to the functioning of normal body tissues.

<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

Describe how cervical screening tests, breast screening and blood tests have made early detections of some cancers possible

<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

Outline the path of the sperm from the epididymis to the point where conception occurs. Include in your answer a description of the process of fertilisation.

<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

Study Notes

Stages of Labour

  • Stage 1: Early Labour
    • Cervix dilates from 0 to 10cm
    • Water may break
  • Stage 2: Pushing
    • Baby moves through the birth canal
    • Ends with the birth of the baby
  • Stage 3: Delivery of the Placenta
    • Placenta is expelled from the uterus

Surface Area to Volume Ratio, Concentration Gradients, and Cell Membrane Exchange

  • Surface Area to Volume Ratio: Cells with higher surface area to volume ratios have more efficient exchange of materials, as there is more membrane surface area exposed to the environment
  • Concentration Gradient: Substances move from an area of high concentration to an area of low concentration
  • Physical and Chemical Nature of Substances: The size, shape, and chemical properties of substances affect their ability to cross the cell membrane
    • Small, lipid-soluble molecules pass easily through the cell membrane
    • Large, polar molecules require transport proteins to cross the cell membrane

Enzyme Function and Metabolism

  • Enzymes: Biological catalysts that speed up metabolic reactions by lowering activation energy
  • Optimizing Metabolism: Enzymes work best at their optimal temperature and pH, facilitating efficient metabolic reactions
  • Temperature Effects on Enzyme Function:
    • Increased Temperature (37°C to 40°C): Enzyme activity initially increases, but excessive heat can denature the enzyme, disrupting its shape and function

Compact Bone Structure

  • Bone Matrix: Composed of collagen fibers and mineral salts (hydroxyapatite)
  • Osteons: Basic structural units of compact bone, containing a central canal with blood vessels and nerves, surrounded by concentric rings of bone matrix (lamellae)
  • Lacunae: Small spaces within the lamellae where osteocytes reside
  • Canaliculi: Tiny channels connecting lacunae to the central canal, allowing for nutrient and waste exchange

Cartilage Types

  • Hyaline Cartilage:
    • Structure: Smooth, glassy appearance, found in nose, trachea, articular cartilage
    • Function: Reduces friction in joints, supports respiratory passages
  • Elastic Cartilage:
    • Structure: Contains elastic fibers, found in ears and epiglottis
    • Function: Provides flexibility and support
  • Fibrocartilage:
    • Structure: Strong, contains collagen fibers, found in intervertebral discs, menisci
    • Function: Provides strong support and shock absorption

Synovial Joints

  • Ball and Socket Joint:
    • Structure: Ball-shaped head fits into a cup-shaped socket
    • Movement: Wide range of motion: flexion, extension, abduction, adduction, rotation
    • Example: Shoulder, hip
  • Hinge Joint:
    • Structure: Convex surface fits into a concave surface
    • Movement: Flexion and extension
    • Example: Elbow, knee
  • Pivot Joint:
    • Structure: Round bone rotates within a ring of bone and ligament
    • Movement: Rotation only
    • Example: Between radius and ulna in the forearm
  • Condyloid Joint:
    • Structure: Oval-shaped condyle fits into an elliptical cavity
    • Movement: Flexion, extension, abduction, adduction
    • Example: Wrist

Hormones Regulating Reproduction

  • Male Reproductive System:
    • Testosterone: Promotes development of male secondary sexual characteristics, stimulates sperm production
    • Luteinizing Hormone (LH): Stimulates testosterone production
    • Follicle-Stimulating Hormone (FSH): Promotes sperm production
  • Female Reproductive System:
    • Estrogen: Promotes development of female secondary sexual characteristics, regulates menstrual cycle
    • Progesterone: Prepares the uterus for pregnancy, maintains pregnancy
    • LH: Triggers ovulation, stimulates corpus luteum formation
    • FSH: Stimulates follicle development and estrogen production

Hormonal Contraceptives

  • Combined Oral Contraceptive Pill: Contains synthetic estrogen and progesterone
    • Mechanism of Action: Suppresses ovulation by inhibiting LH and FSH, thickens cervical mucus to prevent sperm entry
  • Emergency Hormonal Contraceptives (Morning-After Pill): High dose of progesterone or a combination of estrogen and progesterone
    • Mechanism of Action: Delays ovulation, prevents fertilization, may prevent implantation

DNA and Cell Replication

  • DNA Structure:
    • Double helix: Two strands of nucleotides wound around each other
    • Nucleotides: Composed of a sugar (deoxyribose), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, guanine)
    • Base pairing: Adenine pairs with thymine, cytosine pairs with guanine
  • DNA Replication Steps:
    • Unwinding: DNA helix unwinds
    • Base pairing: New nucleotides are added to each strand, following base pairing rules
    • Elongation: Two new DNA molecules are formed, each with one original and one new strand
    • Termination: Replication completes, resulting in two identical DNA molecules

Meiosis and Genetic Variation

  • Crossing Over: Exchange of genetic material between homologous chromosomes, resulting in new combinations of alleles
  • Independent Assortment: Random separation of homologous chromosomes during meiosis I, leading to different combinations of maternal and paternal chromosomes in gametes
  • Random Fertilisation: Any sperm cell can fertilize any egg cell, contributing to genetic diversity

Skeletal Muscle Structure

  • Macroscopic:
    • Structure: Muscles composed of bundles of muscle fibers (muscle cells)
    • Fascia: Connective tissue that surrounds muscles and helps organize muscle fibers
    • Tendons: Connective tissue that attaches muscles to bones
  • Microscopic:
    • Muscle fibers: Long, cylindrical cells with multiple nuclei
    • Myofibrils: Thread-like structures within muscle fibers responsible for muscle contraction
    • Sarcomeres: Repeating units of myofibrils containing actin (thin filaments) and myosin (thick filaments)

Kidney Failure and Body Fluid Composition

  • Kidney Function:
    • Filtration: Removal of waste products (urea, creatinine) and excess water from blood
    • Reabsorption: Return of essential substances (glucose, amino acids) to the bloodstream
  • Kidney Failure:
    • Waste accumulation: Build-up of urea, creatinine, and other waste products in the blood
    • Electrolyte imbalances: Abnormal levels of sodium, potassium, and other electrolytes in the blood
    • Fluid retention: Excess fluid in the body, causing edema

Cellular Respiration

  • ATP Role: Energy currency of the cell, providing energy for metabolic processes
    • ATP Production: Cellular respiration breaks down glucose to generate ATP
    • ATP Use: Used for muscle contraction, active transport, protein synthesis, and other cellular processes
  • Anaerobic vs. Aerobic Respiration:
    • Anaerobic Respiration: Occurs in the absence of oxygen, produces a small amount of ATP and lactic acid
    • Aerobic Respiration: Occurs in the presence of oxygen, produces a large amount of ATP, water, and carbon dioxide

Digestive and Circulatory System Role in Cellular Respiration

  • Digestive System: Breaks down food into smaller molecules that can be absorbed and transported to cells
  • Circulatory System: Transports nutrients (glucose, oxygen) and removes waste products (carbon dioxide) from cells
  • Oxygen Delivery: Red blood cells transport oxygen to cells for aerobic respiration
  • Glucose Delivery: Glucose absorbed from the digestive system is transported to cells as fuel for cellular respiration

Stages of Mitosis

  • Prophase: Chromosomes condense and become visible, nuclear envelope breaks down
  • Metaphase: Chromosomes align at the metaphase plate, spindle fibers attach to the centromeres of chromosomes
  • Anaphase: Sister chromatids separate and move to opposite poles of the cell
  • Telophase: Nuclear envelope reforms around each set of chromosomes, chromosomes uncoil, cytokinesis begins

Cancer and Development of Malignant Tumours

  • Cancer: Uncontrolled cell growth and division due to mutations in genes that regulate cell cycle
  • Malignant Tumours: Can invade surrounding tissues, metastasize to other parts of the body, and disrupt normal tissue function

Early Cancer Detection

  • Cervical Screening: Pap smear test screens for precancerous cells in the cervix
  • Breast Screening: Mammography screens for breast cancer
  • Blood Tests: Some cancers can be detected by identifying specific proteins or markers in the blood

Sperm Path and Fertilization

  • Epididymis: Sperm matures and stores
  • Vas deferens: Carries sperm from epididymis to the urethra
  • Urethra: Carries sperm and urine through the penis
  • Ejaculation: Sperm are expelled from the penis
  • Fertilization: Spermatozoon fertilizes an egg cell in the fallopian tube, resulting in a zygote

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