B3.1

Question 1

Gas Exchange in Animals

Gas Exchange

Answer 1

Driven by diffusion of molecules from high conc. to their low conc across an exchange surface.

Question 2

Gas Exchange in Animals

Concentration Gradients

Answer 2

The difference in conc. of substances between locations - needed for diffusion to occur.

Question 3

Gas Exchange in Animals

Aveolus

Answer 3

• Located in lungs, microscopic spheres (aveoli) of 1 cell thick, tissue wall bubbles.
• Covered in capillary blood supply

Question 4

Gas Exchange in Animals

Surfactant

Answer 4

• Lines the inner surface of each alveolus.
• Is a phospolipid & protein monolayer film.
• Made by type 2 pnuemocyes
• Helps keep alveoli open and expanded for gas exchange.
• Surrounds wall of aveoli with phospholipid tails facing up, meaning aveoli’s walls won’t stick during an exhale, reduces surface tension that could cause H2O behind the surfactant to lead to lung collapse.

Question 5

Gas Exchange in Animals

Bronchioles

Answer 5

• Air travels down a single tube (trachea) which then divies into 2 bronchi that travel to the lung.
• Bronchi then divide into many small tubes with the alveoli at the end of them (best way to deliver air)
• These small tubes are bronchioles.

Question 6

Gas Exchange in Animals

Properties of Gas Exchange Surfaces

Answer 6

1. Very thin (ideally 1 cell thick) for short distances.
2. Moist for gases to dissolve.
3. Large SA:V ratio for more rapid diffusion.
4. Higher permeability of membrances.

Question 7

Gas Exchange in Animals

SA:V of Large vs Small Organisms

Answer 7

• Larger animals have larger volumes, constituting for larger no. interior cells that are far removed from the external environment.
• Larger organisms and their low SA:V ratio prevent cell exchange directly with environment, thus have organs to obtain and transport gasses.

Question 8

Gas Exchange in Animals

Conc. Gradients in Fish

Answer 8

• Fish swallow water, and thus dissolved oxygen.
• They pump this oxygen over thier gills which have blood supply running through them.
• Water moves along the gills with a higher conc. gradient than the blood travelling in the oxygen direction.
• Water maintains high oxygen conc. in the alveoli than the blood of the gills, causing O2 to diffuse into them (capillaries).
• This is done by ventilation, as O2 conc. drops, fish exhale and replace when the CO2 levels rise in blood.

Question 9

Gas Exchange in Animals

Conc. Gradients in Land Animals

Answer 9

• Each alveolar wall is 1 cell thick & surrounded by a capillary, whose wall is also 1 cell thick.
• Allows for short distance for efficient diffusion.
• Many small alveoli allows for higher SA:V, and increases blood supply access.
• Surfactant prevents alveoli walls from attracting and collapsing it.

Question 10

Ventilation

What is Ventiliation?

Answer 10

• Exchange of air between the lungs and the environment.
• Inhalation brings in O2, exhalation releases CO2.
• Frequent ventiliation maintains conc. gradients.

Question 11

Ventilation

Inspiration?

Answer 11

• Process of inhalation
  1. Based on CO2 levels, the Diaphragm is signalled to contract.
  2. At the same time, external intercostal muscles signalled to contract, pulling up and out.
  3. Lung volume increases.
  4. Due to Boyle’s law (increased pressure correspond to decreased volume and vice versa), pressure drops in lungs.
  5. Air moves in since outside air pressure is higher.

Question 12

Ventilation

Expiration

Answer 12

• Process of Exhalation.
  1. Diaphragm relaxes, pulling back up.
  2. External Intercostel muscle relaxes, pulling in and down. Intercostal mucle can contract further pulling the ribs down (a big exhale)
  3. Lung Volume decreases.
  4. Lung pressure increases.
  5. Air is pushed out the airway.

Question 13

Ventilation

Diaphragm

Answer 13

• A thin, dome shaped mucle that sits below the lungs.
• Attatched to the lungs, rib cage and spine.
• The contraction & relaxtion of the diaphragm enables volume of the lung to change and faciliate breathing.

Question 14

Ventilation

Patrial Vacuum

Answer 14

• Change in pressure, when the lungs increase in volume which causes a decrease in pressure due to the change of volume.
• Causes air to move into the lungs from the environment.

Question 15

Ventilation

Spirometer

Answer 15

• Measures the amount of air breathed in and out & how quickly you breathe out.

Question 16

Ventilation

Tidal Volume

Answer 16

• The volume of fresh air that is inhaled and exhaled during a typical resting breathing pattern.
• Not a maximum potentional of our lungs.

Question 17

Ventilation

Inspiratory Reserve Volume

Answer 17

• Volume of air that a person could inhale forefully beyond the normal tidal volume.

Question 18

Ventilation

Expiratory Reserve Volume

Answer 18

• The volume of air we could exhale beyond the normal tidal volume.
• Not as lage as the inspiratory volume as we retain a small residual volume after a large inhale –> protective way to retain some air in lungs at all times.

Question 19

Ventilation

Vital Capcacity

Answer 19

• Potential lung volume during a deliberate/ forced inhale/ exhale.
• We have a large vital capaicity, an important adaptation for activities (swimming eg.,)
• The sum of the inspiratory reserve volume, tidal volume & expiratorty reserve volume. DOESN’T include small residual volume.

Question 20

Ventilation

Boyle’s Law - Pressure & Volume

Answer 20

• An increase in volume leads to a decrease in pressure, vice versa.
• Explains how expanding the volume of the lungs reduces the pressure, which reduces the pressure to LOWER than the atmospheric pressure, cuasing air to move in during inhalation.
• Increase in pressure by reducing volume is caused by exhalation.

Question 21

Ventilation

Role of Intercostal Muscles

Answer 21

To adjust the ribcage.
* External Intercostal muscles expand the ribcage when the contract. When relaxed, then reduce the volume of the lungs for exhalation to occur.
* Internal Intercostal muslces contract to further shrink the lungs (forced exhale)

Question 22

Haemoglobin

What is Haemoglobin?

Answer 22

• The oxygen transport protein found IN red blood cells. It’s a conjugated protein with 4 polypeptide subunits, each with a Haem group made of Iron.
• The haem group is the binding site of oxygen –> each haemoblogin can transport 4 O2 molcules.
• Each red blood cells has many haemoglobins.

Question 23

Haemoglobin

Saturation of Haemoglobin

Answer 23

• Refers to how many O2 molecules are bound to haemoglobin.
• Each subsequent O2 added makes it easier for the next one to bind.

Question 24

Haemoglobin

Cooporative binding?

Answer 24

• Each O2 molecule that binds to Haemoglobin makes it easer for the next one.
• Due to shape changes in the protein that increase the potentional/ affinity for the next O2 to bind, i.e O2 is most attracted to a haemoglobin with 3 O2 already bound.

Question 25

# Haemoglobin What is allosteric binding?

Answer 25

* The binding of carbon dioxide to haemoglobin at an allosteric binding site. * Like enzyme inhibition, this binding change the shape of the haemoglobin by reduching the attraction to the O2, making it more likely to detatch with CO2 bound

Question 26

# Haemoglobin Fetal Haemoglobin?

Answer 26

* A fetus has haemoglobin for circulating O2 to the growing tissues. * It's haemoglobin is a distinct protein made of two alpha chains and two y chains, as oppose to two beta chains. * It's structural difference cause it to have a higher affinity for O2 than adult haemoglobin. * Fetal haemoglobin thus 'steals' O2 from maternal blood.

Question 27

# Haemoglobin Placenta?

Answer 27

* A highly vascularized tissue that connects the blood streams of the pregnant woman with the fetus. * Within it, thin capillaries of mother & baby come close enough in contact for diffusion to occur. * Due to high affinity of O2 for the fetal haemoglobin ,O2 diffuses out of maternal capillaries into the fetal ones.

Question 28

# Haemoglobin Oxygen Partial Pressure?

Answer 28

* The pressure exerted by a gas in a mixture of gases. * An indicator of available oxygen, and helps represent the relationship between O2 supply and the sauration of haemoglobin.

Question 29

# Haemoglobin The Bhor Shift

Answer 29

* The fact that increased binding of CO2 causes the decreased binding/release of O2 is called the Bohr Shift. * Often represented as a pH change that causes this shift, however the pH change is due to the increase in CO2 binding. (increased CO2, lowers pH, reduces affinity for O2)

Question 30

# Haemoglobin Bohr Shift for Respiring Muscles

Answer 30

* Bohr shift helps understand how different cells can access O2 needed for cellular resp. * Respiring tissues accumulate CO2. * As blood circulates through respiring tissues, CO2 binds to RBCs, causing O2 to lose affinity & hop off haemoblogin, delivering to cells who need it to continue to create energy for acitvity.

Question 31

# Haemoglobin Oxygen Dissociaiton Curve

Answer 31

* A graphical representation of the relationship between O2 availability and the saturation of haemoglobin. * Curve's non-linear shape relates to co-op binding, as O2 availability (pressure) increases & more O2 binds to Hb, it rapidly increases saturation.

Question 32

# Gas Exchange in Plants What is a cuticle?

Answer 32

* Waxy lipid layer that covers the surface of leaves & prevents uncontrolled/ excessive leaf water loss by evaporation. * No gaps in cuticle for the stomata. * Varies in thickness for different plants --> thicker --> adaptation to limit water loss.

Question 33

# Gas Exchange in Plants Epidermis?

Answer 33

* Uppermost cells, in plants, the small layer of cells at the surface of leaves. * Epidermis cells secrete the cuticle that coats the cells providing a waterproof later.

Question 34

# Gas Exchange in Plants Palisade Mesophyll?

Answer 34

* A densely packed region of cylindrical cells in the upper portion of the leaf. * Contain many chloroplasts, located at the top to maximise exposure to sunlight for photosynthesis. * Chloroplasts rich layer gives leaves their green colour & primary site of photosynthesis.

Question 35

# Gas Exchange in Plants Sponge Mesophyll?

Answer 35

* Below the palisade mesophyll. * A loosely packed layer of cells, containing fewer chloroplasts, with space between the cells to allow the gases that entered at the stomata to diffuse through to the palisade cells for photosynthesis.

Question 36

# Gas Exchange in Plants Xylem?

Answer 36

* Tissue (like veins) for transport throughout the plant. * The vessel (one of two for plants, phloem being the other vessel) that transports water and dissolved minerals from the roots up to the rest of the plant (leaves etc.)

Question 37

# Gas Exchange in Plants Phloem?

Answer 37

* A seperate vessel that transports sugars, often with some water that it's dissolved in. * The transport vessel that collects sugars made in photosynthesis and delivers it to the parts of the plant (FRUITS) and below (STORAGE ROOTS) --> THINK rhyme, root and fruit.

Question 38

# Gas Exchange in Plants Stomata?

Answer 38

* **Pores (stoma singular) that are an opening in the epidermis** allowing gases to enter and exit --> needed for photosynthesis. * Helpful because the waxy cuticle reduces permeability of gases to enter through the epidermis. * Stomata has the ability to be opened/ closed by gaurd cells.

Question 39

# Gas Exchange in Plants Gaurd Cells?

Answer 39

* Pairs of cells placed one on each side of the stomata, controlling whether the stoma is closed or open. 1. Turgid Gaurd Cells --> open the stomata during the day, **full vacuole**, allowing gas exchange, photosynthesis and transpiration to occur. Water supply is present (hydrated plants). 2. Flacid Gaurd Cells --> closed stomata, during night, empty vacuole, no gas exhcnage, no photosynthesis or transpiration occurs.

Question 40

# Gas Exchange in Plants Transpiration?

Answer 40

* When **water vapour molecules leave the plant cells out of the stomata**, created by broken hydrogen bonds in liquid water being released into water vapour molecules. Influenced by: 1. **Increased Temperature**: More Transpiration, as increased kinetic enegery of liquid water moleculars increases evaporation to water vapour. 2. **Increased Light:** More transpiration, as gaurd cells are stimulated to open for CO2 & enhance photosynthesis. 3. **Increased Wind**:More transpiration, as wind moves released water away from stomata maintaining low water potential of air. 4. **Increased Humidity:**: LESS transpiration, as increased water potential of air/pulling it less/lower conc. gradient between air and leaf.

Question 41

# Gas Exchange in Plants Stomatal Density?

Answer 41

* The mean no.stomata per unit area of leaf surface in mm^2.

Question 42

# Gas Exchange in Plants Protometer?

Answer 42

* A tool for measuring rate of transpiration. * As plant takes up water from roots, the ubble moves along the capillary tube.