BiologywithOlivia Notes

• Red blood cells contain lots of haemoglobin (Hb) - no nucleus, biconcave, high surface area to volume ratio, short diffusion path
• Haemoglobin associates with/binds/loads O2 at gas exchange surfaces where partial pressure of O2 (pO2) is high
• Oxyhaemoglobin transports O2 (each can carry 4O2 - one at each Haem group)
• Haemoglobin dissociates from/unloads O2 near cells/tissues where pO2 is low
• Haemoglobin is a protein with a quaternary structure
• Haemoglobin is made of 4 polypeptide chains
• Each chain contains a Haem group containing an iron ion (Fe2+)
• Areas with low pO2 (respiring tissues):

  • Hb has a low affinity for O2
  • O2 readily unloads/dissociates with Hb
  • % saturation is low
• Areas with high pO2 (gas exchange surfaces):

  • Hb has a high affinity for O2
  • O2 readily loads/associates with Hb
  • % saturation is high
• Binding of first oxygen changes tertiary/quaternary structure of haemoglobin

  • This uncovers Haem group binding sites, making further binding of oxygens easier
• At a low pO2, as oxygen increases there is little/slow increase in % saturation of Hb with oxygen

  • When first oxygen is binding
  • At higher pO2, as oxygen increases there is a big/rapid increase in % saturation of Hb with oxygen
  • Showing it has got easier for oxygens to bind
• Bohr effect:

  • Effect of CO2 concentration on dissociation of oxyhaemoglobin
  • Curve shifts to the right
• Increasing blood CO2 e.g. due to increased rate of respiration

  • Lowers blood pH (more acidic)
  • Reducing Hb’s affinity for oxygen as shape/tertiary/quaternary structure changes slightly
  • More/faster unloading of oxygen to respiring cells at a given pO2
• More dissociation of oxygen → faster aerobic respiration/less anaerobic respiration → more ATP produced
• Different types of Hb are made of polypeptide chains with slightly different amino acid sequences

  • Resulting in different tertiary/quaternary structures/shape → different affinities for oxygen
• Curve shift left → Hb has higher affinity for O2

  • More O2 associates with Hb more readily
  • At gas exchange surfaces where pO2 is lower
  • Eg. organisms in low O2 environments - high altitudes, underground, or foetuses

  Curve shift right → Hb has lower affinity for O2

  • More O2 dissociates from Hb more readily
  • At respiring tissues where more O2 is needed
  • Eg. organisms with high rates of respiration/metabolic rate (may be small or active)
• Closed double circulatory system - blood passes through heart twice for every circuit around body:

  • Deoxygenated blood in right side of heart pumped to lungs; oxygenated returns to left side
  • Oxygenated blood in left side of heart pumped to rest of body; deoxygenated returns to right
• Prevents mixing of oxygenated/deoxygenated blood

  • Blood pumped to body is fully saturated with oxygen for aerobic respiration
  • Blood can be pumped to body at a higher pressure (after being lower from lungs)
  • Substances taken to/removed from body cells quicker/more efficiently
• Vena cava – transports deoxygenated blood from respiring body tissues → heart

  • Pulmonary artery – transports deoxygenated blood from heart → lungs
  • Pulmonary vein – transports oxygenated blood from lungs → heart
  • Aorta – transports oxygenated blood from heart → respiring body tissues
• Renal arteries – oxygenated blood → kidneys

  • Renal veins – deoxygenated blood to vena cava from kidneys
• Coronary arteries - located on surface of the heart, branching from aorta
• Thicker muscle to contract with greater force

  • To generate higher pressure to pump blood around entire body
• • Semilunar valves shut when pressure in arteries exceeds pressure in ventricles
  • Atrioventricular valves open when pressure in atria exceeds pressure in ventricles
  • So blood fills atria via veins & flows passively to ventricles
• Atrial systole

  • Ventricular systole
  • Diastole
  • Atria contract → volume decreases, pressure increases
  • Atrioventricular valves open when pressure in atria exceeds pressure in ventricles
  • Semilunar valves remain shut as pressure in arteries exceeds pressure in ventricles
  • Ventricles contract → volume decreases, pressure increases
  • Atrioventricular valves shut when pressure in ventricles exceeds pressure in atria
  • Semilunar valves open when pressure in ventricles exceeds pressure in arteries
  • Atria & ventricles relax → volume increases, pressure decreases
• SL valves closed

  • Pressure in [named] artery higher than in ventricle
  • To prevent backflow of blood from artery to ventricles

  SL valves open

  • When pressure in ventricle is higher than in [named] artery
  • So blood flows from ventricle to artery

  AV valves closed

  • Pressure in ventricle higher than atrium
  • To prevent backflow of blood from ventricles to atrium

  AV valves open

  • When pressure in atrium is higher than in ventricle
  • So blood flows from atrium to ventricle
• Cardiac output (volume of blood pumped out of heart per min) = stroke volume (volume of blood pumped in each heart beat) x heart rate (number of beats per min)
• Heart rate (beats per minute) = 60 (seconds) / length of one cardiac cycle (seconds)
• Arteries:

  • Function: carry blood away from heart at high pressure
  • Thick smooth muscle tissue can contract and control/maintain blood flow/pressure
  • Thick elastic tissue can stretch as ventricles contract and recoil as ventricles relax, to reduce pressure surges/even out blood pressure/maintain high pressure
  • Thick wall withstands high pressure/stop bursting
  • Smooth/folded endothelium reduces friction/can stretch
  • Narrow lumen increases/maintains high pressure
• Arterioles:

  • Function: direct blood to different capillaries/tissues
  • Thicker smooth muscle layer than arteries contracts narrows lumen (vasoconstriction) reduces blood flow to capillaries, relaxes widens lumen (vasodilation) increases blood flow to capillaries
  • Thinner elastic layer pressure surges are lower
• Veins:

  • Function: carry blood back to heart at lower pressure
  • Wider lumen than arteries less resistance to blood flow
  • Very little elastic and muscle tissue blood pressure lower
  • Valves prevent backflow of blood
• Capillaries:

  • Function: allow efficient exchange of substances between blood and tissue fluid (exchange surface)
  • Wall is a thin (one cell) layer of endothelial cells reduces diffusion distance
  • Capillary bed is a large network of branched capillaries increases surface area for diffusion
  • Small diameter/narrow lumen reduces blood flow rate so more time for diffusion
  • Pores in walls between cells allow larger substances through
• Formation of tissue fluid:

  • At the arteriole end of capillaries:

  1. Higher blood/hydrostatic pressure inside capillaries than tissue fluid (so net outward force)

  2. Forcing water (and dissolved substances) out of capillaries

  3. Large plasma proteins remain in capillary
• Return of tissue fluid to the circulatory system:

  • At the venule end of capillaries:

  1. Hydrostatic pressure reduces as fluid leaves capillary (also due to friction)

  2. Increasing concentration of plasma proteins lowers water potential in capillary below that of tissue fluid

  3. Water enters capillaries from tissue fluid by osmosis down a water potential gradient

  4. Excess water taken up by lymph capillaries and returned to circulatory system through veins
• Causes of excess tissue fluid accumulation:

  • Low concentration of protein in blood plasma or high salt concentration reduces water potential gradient, more tissue fluid formed at arteriole end/less water absorbed at venule end by osmosis
  • High blood pressure increases outward pressure from arterial end and reduces inward pressure at venule end, more tissue fluid formed at arteriole end/less water absorbed at venule end by osmosis, lymph system may not be able to drain excess fast enough
• Risk factor:

  • An aspect of a person’s lifestyle or substances in a person’s body/environment
  • Linked to an increased rate of disease
  • Examples: age, diet high in salt or saturated fat, smoking, lack of exercise, genes
• Precautions for dissection:

  • Cover any cuts with a waterproof dressing
  • Cut away from body onto a hard surface when using a scalpel
  • Use a sharp blade when using a scalpel
  • Carry scalpel with blade protected/pointing down
  • Wear disposable gloves and disinfect hands/wash with soap
  • Disinfect surfaces/equipment
  • Safe disposal - put gloves/paper towels/organ in a separate bag/bin to dispose
  • Work in a well-ventilated environment if poisonous chemicals/toxins involved
• Ethical consideration when dissecting animals:

  • Morally wrong to kill animals just for dissection
  • Use animals for dissection that have already been killed (humanely) for meat
• Preparing a temporary mount of a piece of plant tissue for observation with an optical microscope:

  1. Add a drop of water to glass slide

  2. Obtain a thin section of specimen and place on slide

  3. Stain (eg. with iodine/potassium iodide to view starch)

  4. Lower coverslip at angle using mounted needle without trapping air bubbles
• Rules of scientific drawing:

  • Look similar to specimen/image, draw all parts to same scale/relative size
  • No sketching/shading - only clear, continuous lines
  • Include a magnification scale (eg. x 400)
  • Label with straight, uncrossed lines