Problem 10 - Campbell Biology Concepts & Connections

Question

Match each of the following components of blood (on the left) with what happens to it as the blood is processed by the kidney (on the right). Note that each lettered choice may be used more than once. a. passes into filtrate; almost all excreted in urine b. remains in blood c. passes into filtrate; mostly reabsorbed d. secreted and excreted Plasma protein

Step-by-Step Solution

Answer

b. remains in blood

Step 1: Identify the component

The component to be matched is 'plasma protein'.

Step 2: Analyze the options

Review each option given to understand what it implies:a. Passes into filtrate; almost all excreted in urineb. Remains in bloodc. Passes into filtrate; mostly reabsorbedd. Secreted and excreted

Step 3: Understand the role of plasma proteins

Plasma proteins are large molecules that are essential for various functions in the blood, including maintaining osmotic pressure and transporting substances.

Step 4: Determine if plasma proteins are filtered

Due to their large size, plasma proteins generally do not pass through the filtration barrier of the kidney. Instead, they remain in the bloodstream.

Step 5: Match with the correct option

Based on the filtration properties of plasma proteins, they do not pass into the filtrate and remain in the blood. Thus, the correct match is option b: 'remains in blood'.

Key Concepts

plasma proteins

Plasma proteins are crucial components of our blood, playing various roles in maintaining our health. These large molecules, including albumins, globulins, and fibrinogen, perform key functions such as:

• Maintaining osmotic pressure, which helps keep fluid in our blood vessels
• Transporting substances like hormones, vitamins, and drugs
• Participating in immune responses

Due to their size, plasma proteins are usually too large to pass through the kidney's filtration barrier.

This means they remain in the bloodstream and are not filtered out into the urine.

filtration barrier

The filtration barrier of the kidney is essential for determining what substances pass from blood into the kidney tubules. This barrier is made up of several layers:

• Endothelial cells of the glomerular capillaries, which have small pores
• A dense basement membrane that acts like a sieve
• Podocytes, which are special cells with foot-like projections

These layers work together to filter blood based on the size and charge of molecules. While small molecules and water can pass through, larger molecules like plasma proteins are typically too big and are kept in the blood.

This selective process ensures that essential proteins and large molecules are retained, while waste products and excess substances are filtered out for excretion.

reabsorption

After filtration, the kidneys perform reabsorption, which is crucial for conserving valuable substances and maintaining balance in the body. During reabsorption:

• Filtered substances like glucose, amino acids, and ions are transported back into the blood
• Water is reabsorbed to maintain hydration and blood volume
• It mostly occurs in the renal tubules and collecting ducts

In healthy individuals, nearly all of the filtered glucose and amino acids are reabsorbed, as are significant amounts of water and ions like sodium and potassium.

Reabsorption helps the kidneys efficiently manage the body's needs by selectively returning necessary substances to the bloodstream, ensuring that waste products get excreted in the urine.