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Form and function - Transport

Grade 12IBBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Transpiration in plants is the loss of water vapor from the leaves and stems, creating a transpiration stream driven by a water potential gradient from roots to leaves (H2OH_{2}O).

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The Cohesion-Tension Theory explains xylem transport: water molecules are cohesive due to hydrogen bonding and adhesive to the xylem walls, allowing columns of water to be pulled under tension (P<0P < 0).

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Phloem translocation moves organic solutes like sucrose (C12H22O11C_{12}H_{22}O_{11}) from sources (e.g., leaves) to sinks (e.g., roots/fruits) via active loading and hydrostatic pressure gradients.

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The human circulatory system is a closed, double system. Blood moves through the pulmonary circuit to the lungs for gas exchange (O2O_{2} and CO2CO_{2}) and the systemic circuit to the rest of the body.

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The cardiac cycle consists of atrial systole, ventricular systole, and diastole, regulated by electrical impulses from the Sinoatrial (SA) node and Atrioventricular (AV) node.

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Capillary exchange involves the interplay between hydrostatic pressure, which pushes fluid out, and osmotic pressure (oncotic pressure), which pulls fluid back in.

📐Formulae

Ψ=Ψs+Ψp\Psi = \Psi_{s} + \Psi_{p}

Cardiac Output (CO)=Stroke Volume (SV)×Heart Rate (HR)Cardiac\ Output\ (CO) = Stroke\ Volume\ (SV) \times Heart\ Rate\ (HR)

SA:V=Surface AreaVolumeSA:V = \frac{\text{Surface Area}}{\text{Volume}}

Rate of Transpiration=Volume of Water LostTimeRate\ of\ Transpiration = \frac{\text{Volume of Water Lost}}{\text{Time}}

💡Examples

Problem 1:

A patient has a heart rate (HRHR) of 72 bpm72\ bpm and a stroke volume (SVSV) of 70 mL70\ mL. Calculate the cardiac output (COCO) in liters per minute (L/minL/min).

Solution:

CO=72×70=5040 mL/minCO = 72 \times 70 = 5040\ mL/min CO=50401000=5.04 L/minCO = \frac{5040}{1000} = 5.04\ L/min

Explanation:

Cardiac output is the total volume of blood pumped by the heart per minute. It is calculated by multiplying the heart rate (beats per minute) by the stroke volume (volume per beat). To convert mLmL to LL, divide by 10001000.

Problem 2:

Calculate the water potential (Ψ\Psi) of a plant cell with a solute potential (Ψs\Psi_{s}) of −0.7 MPa-0.7\ MPa and a pressure potential (Ψp\Psi_{p}) of 0.3 MPa0.3\ MPa. If the surrounding solution has Ψ=−0.6 MPa\Psi = -0.6\ MPa, determine the direction of water movement.

Solution:

Ψcell=−0.7+0.3=−0.4 MPa\Psi_{cell} = -0.7 + 0.3 = -0.4\ MPa Since −0.4>−0.6 is false (actually −0.4>−0.6 means cell potential is higher), water moves from Cell to Solution.\text{Since } -0.4 > -0.6 \text{ is false (actually } -0.4 > -0.6 \text{ means cell potential is higher), water moves from Cell to Solution.}

Explanation:

Water moves from a region of higher (less negative) water potential to a region of lower (more negative) water potential. Since the cell's potential is −0.4 MPa-0.4\ MPa and the solution is −0.6 MPa-0.6\ MPa, water will move out of the cell toward the solution.