How is glucose reabsorbed?
Reveal answer
Active transport in proximal tubule → energy from mitochondria → back into blood.
Key words: active transport
3(i) EXCRETION · RECALL
3.27B Selective reabsorption of glucose
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Why is reabsorption called selective?
Reveal answer
Only useful substances (glucose, amino acids, some salts and water) return to the blood.
Key words: useful
Why does glucose appear in diabetic urine?
Reveal answer
Blood glucose very high → carriers saturated → not all reabsorbed.
Key words: reabsorbed
Which cell feature increases the area for reabsorption?
Reveal answer
Microvilli.
Key words: microvilli
Why do tubule cells need many mitochondria?
Reveal answer
Release energy (ATP) → active transport of glucose.
Key words: active transport
What is meant by the term proximal convoluted tubule?
Reveal answer
First coiled tubule where most selective reabsorption occurs.
Key words: proximal convoluted tubule
What is meant by the term co-transport?
Reveal answer
Linked movement of two substances through one membrane protein.
Key words: co-transport
What is meant by the term transport maximum?
Reveal answer
Highest rate at which available carriers can move a substance.
Key words: transport maximum
Filtration and glucose recovery: for Glomerulus, give the mechanism and the glucose outcome.
Reveal answer
Mechanism: Pressure/size-based filtration. Glucose outcome: Glucose enters filtrate.
Key words: Glomerulus
Filtration and glucose recovery: for Proximal tubule membrane, give the mechanism and the glucose outcome.
Reveal answer
Mechanism: Carrier-mediated selective transport. Glucose outcome: Glucose enters epithelial cells.
Key words: Proximal tubule membrane
Filtration and glucose recovery: for Surrounding capillary, give the mechanism and the glucose outcome.
Reveal answer
Mechanism: Transfer to tissue fluid/blood. Glucose outcome: Glucose returns to circulation.
Key words: Surrounding capillary
Filtration and glucose recovery: for Transport maximum exceeded, give the mechanism and the glucose outcome.
Reveal answer
Mechanism: Carriers saturated. Glucose outcome: Some glucose may remain in urine.
Key words: Transport maximum exceeded
True or false, and why? “Glucose should never be filtered because it is useful.”
Reveal answer
False. It is filtered by size, then recovered selectively.
True or false, and why? “Glucose is reabsorbed in the bladder.”
Reveal answer
False. It is recovered mainly in the proximal tubule.
True or false, and why? “Glucose in urine always proves one specific disease.”
Reveal answer
False. It can have several causes and requires clinical assessment.