A-Level Biology: Gas Exchange, Heart, and Plant Transport Flashcards

What is the surface area to volume ratio of an organism?

It is the surface area of an organism divided by its volume; larger organisms have a smaller ratio.

How does increased surface area aid in gas exchange?

Increased surface area, such as projections on root hair cells, facilitates more efficient diffusion.

What factors affect the rate of diffusion?

Diffusion distance, surface area, concentration gradient, and temperature.

What is the role of the diaphragm during inspiration?

The diaphragm contracts and flattens, increasing lung volume and decreasing pressure.

What happens during expiration?

Air pressure in the lungs increases as lung volume decreases, causing air to flow out.

What is tidal volume?

The maximum volume of air an individual can inhale or exhale during a deep breath.

What is the formula for calculating ventilation rate?

Ventilation rate = tidal volume x breathing rate.

What is the structure of fish gills?

Fish gills are stacks of gill filaments, each covered with gill lamellae at right angles.

Why do large organisms need specialized exchange surfaces?

They have a small surface area to volume ratio and higher metabolic rates, necessitating efficient gas exchange.

What is countercurrent flow in fish gills?

It is the mechanism where water flows over gill lamellae in the opposite direction to blood flow, maximizing oxygen uptake.

What adaptations do tracheoles in insects have for gas exchange?

Tracheoles are highly branched and filled with fluid to enhance gas movement.

What is the significance of the alveoli structure?

Alveoli are tiny air sacs that provide a large surface area for gas exchange.

How does the open circulatory system function?

In an open circulatory system, the transport medium does not stay in vessels at all times.

What is the role of the intercostal muscles during ventilation?

They work antagonistically to control the movement of the ribs during inhalation and exhalation.

What is the effect of a steeper concentration gradient on gas exchange?

A steeper concentration gradient increases the rate of diffusion, enhancing gas exchange efficiency.

Why is the alveoli wall thin?

The alveoli wall is one thin layer of squamous epithelial cells to shorten the diffusion pathway.

What happens to air pressure in the lungs during inhalation?

Air pressure in the lungs drops below atmospheric pressure as lung volume increases.

What is the function of the gill arches in fish?

Gill arches support the gill filaments and help maintain their structure for efficient gas exchange.

How does lactate production in insects affect gas exchange?

Lactate production during anaerobic respiration lowers water potential in cells, promoting gas movement from tracheoles.

What is the primary function of the respiratory system in large organisms?

To facilitate efficient gas exchange due to their higher metabolic demands.

What type of circulatory system do fish have?

Single closed circulatory system

What type of circulatory system do most mammals have?

Double closed circulatory system

What is the role of tissue fluid?

Enables delivery of useful molecules to cells and removal of waste

What components are found in tissue fluid?

Water, glucose, amino acids, fatty acids, ions, and oxygen

What is the structure and function of capillaries?

Capillaries have a narrow diameter (1 red blood cell wide) to slow blood flow and have small pores for liquid/small molecules to be forced out.

What are arterioles and their function?

Arterioles branch off from arteries and have the thickest muscular layer to restrict blood flow.

What is the structure of arteries?

Arteries have a thick muscular layer, thick elastic layer, and thick outer layer.

What is unique about the capillary endothelium?

It has a small lumen and no valves, allowing small molecules to pass through.

What happens to the hydrostatic pressure in capillaries towards the venule end?

There is a lower hydrostatic pressure due to a loss of liquid and a higher oncotic pressure.

What is the function of the coronary arteries?

They supply cardiac muscle with oxygenated blood.

What is the significance of the pericardial membranes?

They prevent the heart from filling and swelling with blood.

What is the difference between the left and right ventricles?

The left ventricle has a thicker muscular wall compared to the right ventricle.

What do the vena cava and pulmonary vein do?

Vena cava carries deoxygenated blood from the body to the right atrium; pulmonary vein carries oxygenated blood from the lungs to the left atrium.

What do the pulmonary artery and aorta do?

Pulmonary artery carries deoxygenated blood from the right ventricle to the lungs; aorta carries oxygenated blood from the left ventricle to the rest of the body.

What is cardiac output?

Volume of blood which leaves one (usually left) ventricle in one minute; calculated as cardiac output = heart rate x stroke volume.

What is stroke volume?

Volume of blood that leaves one ventricle (usually left) each beat.

What are the phases of the cardiac cycle?

Diastole, atrial systole, and ventricular systole.

What occurs during atrial systole?

Atrial muscular walls contract, increasing pressure and allowing blood to flow into the ventricles.

What occurs during ventricular systole?

Ventricular muscular walls contract, increasing pressure and forcing blood out of the heart.

Why don't small organisms need breathing systems?

They can rely on diffusion for gas exchange due to their small size.

What is tachycardia?

A condition where the heart rate is faster than normal.

What is bradycardia?

A condition where the heart beats consistently less than 60 beats per minute.

What is fibrillation?

An irregular chaotic rhythm of the heart.

What is an ectopic heartbeat?

Additional heartbeats that are not in rhythm, usually seen on an ECG.

What is the sinoatrial node (SAN)?

The pacemaker of the heart located in the right atrium that releases waves of depolarization across the atria.

What is the function of the atrioventricular node (AVN)?

Located near the border of the right and left ventricle, it releases another wave of depolarization after a short delay.

What is the Bundle of His?

A structure that runs through the septum and conducts impulses from the AVN to the ventricles.

What are Purkinje fibers?

Fibers that distribute the electrical impulse to the ventricles, causing them to contract.

What is the role of non-conductive tissue in the heart?

It prevents the wave of depolarization from traveling directly to the ventricles, allowing for a delay.

Why is there a short delay between SAN and AVN activation?

To ensure that the atria have enough time to pump all blood into the ventricles before they contract.

What is hemoglobin (Hb)?

A quaternary structure protein composed of 2 alpha chains and 2 beta chains that transports oxygen.

What is the oxyhemoglobin dissociation curve?

A graph that shows the relationship between the partial pressure of oxygen and hemoglobin saturation.

What happens when the oxyhemoglobin curve shifts to the left?

Hemoglobin has a higher affinity for oxygen, allowing it to bind more oxygen at the same partial pressure.

What is the Bohr effect?

The phenomenon where hemoglobin's affinity for oxygen decreases in the presence of high carbon dioxide levels.

How is carbon dioxide transported in the blood?

It is transported dissolved in plasma, as carbaminohemoglobin, or as hydrogen carbonate ions.

What is the chloride shift?

The process where hydrogen carbonate ions diffuse out of red blood cells and chloride ions diffuse in to maintain electrical balance.

What causes the AV valves to open?

Higher pressure in the atria than in the ventricles.

What causes the semi-lunar valves to open?

Higher pressure in the ventricles than in the arteries.

Describe the structure of veins.

Veins have a thin muscular layer, thin elastic layer, thin walls, and valves.

What is the role of carbonic anhydrase?

An enzyme that catalyzes the reaction between water and carbon dioxide to form carbonic acid.

What is the role of companion cells in phloem?

Companion cells assist in the transport of sucrose and other assimilates, allowing reduced resistance to flow.

What hypothesis explains the translocation of nutrients in plants?

The mass flow hypothesis explains the transport of assimilates from the source to the sink.

What is the cohesion-tension theory in plant transport?

It describes how cohesive water molecules create a column of water in xylem, which is pulled upwards due to negative pressure from evaporation.

How does wind affect the rate of transpiration?

As wind increases, the rate of transpiration increases due to the removal of water vapor around the plant.

What is the effect of humidity on transpiration?

Higher humidity decreases transpiration as it increases the water potential outside the leaf.

How does temperature influence transpiration?

Increased temperature creates a steep water potential gradient, enhancing evaporation and thus increasing transpiration.

What is the relationship between light intensity and transpiration?

As light intensity increases, the rate of transpiration increases due to more stomata opening, providing a larger surface area for evaporation.

What are the symplast and apoplast pathways in plant water transport?

The symplast pathway involves water moving from cell to cell through cytoplasm, while the apoplast pathway involves movement through cell walls.

What adaptations do xerophytic plants have for water conservation?

Xerophytic plants have features like curled leaves, thick cuticles, and sunken stomata to reduce water loss.

What is the function of guard cells in plants?

Guard cells regulate the opening and closing of stomata to control water loss and gas exchange.

What are hydrophytic plants and their adaptations?

Hydrophytic plants are adapted to wet environments, with features like thin/no cuticles, permanently open stomata, and large leaves for photosynthesis.

What is the mass flow hypothesis?

It describes how assimilates, such as sucrose, move in solution from leaves to respiring cells in a source to sink direction.

How is pressure generated for translocation in plants?

Pressure is generated by pumping hydrogen ions out of companion cells, lowering water potential and causing water to move in from xylem via osmosis.

What is the heart rate?

Heart rate is the number of beats per minute.

Describe the transverse section of a root.

The xylem is at the center, resembling a star shape, with phloem found between the points of the star.

Describe the transverse section of a stem.

Similar to the root, the xylem is at the center in a star shape, with phloem between the points.

Describe the transverse section of a leaf.

The xylem is located on the inner edge of each bundle, closest to the center of the stem.