Insulin is a protein hormone. Explain why it acts at the cell surface rather than inside the cell.

As a large, water-soluble protein it cannot cross the phospholipid bilayer, so it binds to specific receptors on the outer surface of the cell surface membrane and brings about changes inside the cell indirectly.

Name three types of target tissue on which insulin acts.

Liver cells, skeletal muscle cells and adipose tissue.

How does insulin increase the rate at which a muscle cell takes up glucose?

Insulin binding to its receptor causes vesicles carrying GLUT4 glucose transporter proteins to fuse with the cell surface membrane, so there are more channels through which glucose can enter by facilitated diffusion.

OCR A-Level Biology B H422

The Developing Cell: Cell Division and Cell Differentiation

Topic overview The cell cycle and mitosis Apoptosis in growth and repair Stem cells and cell differentiation

The Developing Individual: Meiosis, Growth and Development

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Water and Its Importance in Plants and Animals

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Proteins and Enzymes

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Nucleic Acids

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Patterns of Inheritance

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Population Genetics and Epigenetics

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Gene Technologies

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The Principles and Importance of Homeostasis

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The Hormonal Control of Blood Glucose and the Management of Diabetes

Topic overview The pancreas as an endocrine gland The regulation of blood glucose by negative feedback Types of diabetes and diagnostic testing Treating and managing diabetes

Kidney Functions and Malfunctions

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Fertility and Assisted Reproduction

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The Effects of Ageing on the Reproductive System

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Plant Reproduction

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The Nervous System and the Identification and Consequences of Damage

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The Effect of Ageing on the Nervous System

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The Heart and Monitoring Heart Function

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Transport Systems in Mammals

Topic overview The closed double circulatory system Blood vessels and their microscopic structure Tissue fluid and capillary exchange Measuring and interpreting blood pressure

Gas Exchange in Mammals and Plants

Topic overview Tissues of the mammalian gas exchange system Gas exchange in the alveoli Pulmonary ventilation and lung volumes Expired air resuscitation Gas exchange and stomata in terrestrial plants

Transport Systems in Plants

Topic overview The need for transport systems in plants Vascular tissue in roots, stems and leaves Water uptake and movement through the plant Transpiration and Its Measurement Translocation in the Phloem

The Hormonal Control of Blood Glucose and the Management of Diabetes

The regulation of blood glucose by negative feedback

3 things to know
Components 01, 02 and 03

Overview

Recall questions on how β cells secrete insulin, insulin receptors, GLUT4 and target tissues, glycogenesis, glucagon from α cells, glycogenolysis through cyclic AMP, gluconeogenesis, why muscle glycogen cannot raise blood glucose, and insulin and glucagon as antagonistic hormones.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

How does a rise in blood glucose concentration cause a β cell to secrete insulin?

Key term

Why is the control of insulin secretion described as negative feedback?

Key term

Which cells of the pancreas detect a rise in blood glucose concentration?

Questions from this subtopic

Each one with the model answer underneath.

1
Which cells of the pancreas detect a rise in blood glucose concentration?
Model answer
The β cells of the Islets of Langerhans.
2
How does a rise in blood glucose concentration cause a β cell to secrete insulin?
Model answer
Glucose enters the β cell and is respired, and the extra ATP closes potassium ion channels in the cell surface membrane; the membrane depolarises, voltage-gated calcium ion channels open, and the calcium ions entering cause vesicles of insulin to fuse with the membrane and release it by exocytosis.
3
Why is the control of insulin secretion described as negative feedback?
Model answer
The rise in blood glucose is the stimulus for insulin release, and insulin lowers the glucose concentration, which removes the stimulus and stops further secretion.
4
Insulin is a protein hormone. Explain why it acts at the cell surface rather than inside the cell.
Model answer
As a large, water-soluble protein it cannot cross the phospholipid bilayer, so it binds to specific receptors on the outer surface of the cell surface membrane and brings about changes inside the cell indirectly.
5
Name three types of target tissue on which insulin acts.
Model answer
Liver cells, skeletal muscle cells and adipose tissue.
6
How does insulin increase the rate at which a muscle cell takes up glucose?
Model answer
Insulin binding to its receptor causes vesicles carrying GLUT4 glucose transporter proteins to fuse with the cell surface membrane, so there are more channels through which glucose can enter by facilitated diffusion.

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