Bio Topic 6- Blood Glucose Concentration Regulation

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26 Terms

1
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Define Homeostasis:

the regulation of internal conditions to maintain optimal conditions for enzyme action and cell function

2
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State things that need to be regulated in our bodies:

  • blood glucose concentration

  • water potential of the blood

  • blood pH

  • body temperature

3
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What is a negative feedback loop?

counteract changes and bring the body back to its set point

4
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What is a positive feedback loop?

they amplify changes and move the body further away from the set point

5
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What would happen if blood glucose concentration was too high or too low?

  • lower/higher water potential than cells

  • water moves out/in by osmosis

  • causes cells to shrivel/lyse

6
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What is the outcome of negative feedback?

  • the stimulus is constantly monitored

  • system is restored to its original level

  • reduce initial effect of stimulus

7
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Positive feedback in bone repair (do not need to memorise but good out of spec knowledge)

osteocalcin is a protein secreted by osteoblasts, they are inactive when secreted

  • The osteoclasts secrete acid

  • lowers the pH

  • cause the osteocalcin to become activated

    • The low pH alters the hydrogen and ionic bonds in the protein which changes the tertiary structure

  • osteocalcin binds to a receptor on beta (β) cells in the pancreas

  • stimulates them to release insulin

  • Osteoblast cells possess insulin receptors which when stimulated causes them to release more inactive osteocalcin

  • The osteoblast cells enhance the effect of the original stimulus (insulin)

8
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Where are insulin and glucagon secreted from?

  • pancreas

  • endocrine tissue

  • tissue is made up of cells called islets of Langerhans

  • a cells secrete glucagon

  • B cells secrete insulin

  • a cells and B cells act as receptors

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Which cells act as the effectors in blood glucose conc regulation?

  • liver cells

  • muscle cells

  • fat cells

have glucose transporter proteins on cell surface (limits rate of glucose uptake by cells)

10
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What is gluconeogenesis?

produces glucose from amino acids, pyruvate, lactate

triggered by glucagon by activating enzymes within the liver

  • These enzymes convert other molecules, such as fatty acids and amino acids, into glucose molecules

11
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What is glycogenesis?

glycogen is synthesised from glucose

glucose molecules added to glycogen chains

triggered by insulin

12
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What is glycogenolysis?

breakdown of glycogen (n) to glucose-1-phosphate and glycogen (n-1)

triggered by glucagon

13
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How does insulin increase uptake of glucose by liver cells?

  • stimulates glycogenesis

  • attach to receptors on liver/muscle cells

  • changes structure of channel proteins, more glucose absorbed by facilitated diffusion

  • more protein carriers incorportated into cell membranes, more glucose absorbed from body cells

  • activates enzymes involved in conversion of glucose to glycogen

14
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How are more protein carriers incorporated into cell membranes?

  • insulin bound to insulin receptor

  • intracellular chemical released

  • causes vesicles containing glucose channel proteins to fuse with cell surface membrane

15
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Describe what occurs when there is a decrease in blood glucose concentration:

SECOND MESSENGER MODEL

GLYCOGENOLYSIS

  • detected by a cells and b cells in pancreas

  • a cells secrete glucagon

  • b cells stop secreting insulin

  • decrease in insulin = decrease in use of glucose by liver and muscle cells

  • glucagon binds to receptors on liver cells

  • causes conformational change in receptor protein

  • activates G protein

  • activated G protein activates enzyme Adenylyl Cyclase

  • activated Adenylyl Cyclase catalyses conversion of ADP to cyclic AMP

  • cAMP binds to protein kinase enzymes, activating them

  • Active protein kinase A enzymes activate phosphorylase kinase enzymes by adding phosphate groups to them

  • Active phosphorylase kinase enzymes activate glycogen phosphorylase enzymes

  • Active glycogen phosphorylase enzymes catalyse the breakdown of glycogen to glucose

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What is the result of the second messenger model process?

  • breakdown of glycogen into glucose

  • releasing of extra glucose by the liver to increase the blood glucose concentration back to a normal level

  • enzyme cascade amplifies the original signal from glucagon

ONLY OCCURS IN LIVER CELLS

17
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Outline how regulation of blood glucose is a negative feedback loop process:

  • When blood glucose concentration is low, more glucagon is secreted and less insulin is secreted

  • When blood glucose concentration is high, more insulin is secreted and less glucagon is secreted

18
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State the different cells, proteins and enzymes involved in the second messenger model:

  • a cells and B cells

  • liver cell receptor

  • G protein

  • Adenylyl Cyclase enzyme

  • ADP to cAMP (second messenger)

  • protein kinase enzymes

  • glycogen phosphorylase enzymes

19
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Describe the role of adrenaline in blood glucose regulation:

  • when secreted, increases concentration of blood glucose

  • binds to same receptors on liver cell as glucagon to stimulate enzyme cascade

  • also stimulates the breakdown of glycogen stores in muscle during exercise

  • glucose in the muscle cells in then used for respiration

20
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What are the three ways glucose can enter the bloodstream?

  • Absorption in the gut following carbohydrate digestion

  • Hydrolysis of glycogen stores

  • Non-carbohydrates such as lipids, lactate and amino acids that have been converted to glucose

21
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What causes type 1 diabetes?
What are the treatments?

  • pancreas cannot secrete sufficient insulin to control blood glucose levels

  • immune system (T cells) attack B cells

  • lack of insulin affects glycogen stores- individual feels fatigued

  • control diet, insulin injections- can be fast or slow acting

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What causes Type 2 diabetes?

What are the treatments?

  • pancreas still produces insulin but the receptors have reduced in number or no longer respond to it

  • occurs in liver and fat storage tissues

  • reduced glucose uptake = higher concentration = β cells to produce larger amounts of insulin which ultimately damages them

  • exercise, sugar and fat reduced diet

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Why do diabetic people often have high blood pressure?

  • high concentration of glucose in blood

  • water moves out of cell

  • increases volume of blood

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Why do diabetic patients often suffer from dehydration?

  • high concentration of glucose in blood

  • kidneys cannot filter out excess glucose

  • kidneys produce large quantities of urine

25
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What is the method and process to calculate concentration of glucose in urine?

Producing a dilution series and a calibration curve


set up standard solutions with known concentration of glucose

do benedicts test on all, control variables

carry out on urine sample(s)

use colorimeter

find unknown value

26
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How do we set up the colorimeter?

  • set colorimeter wavelength to red (complementary to blue, blue solution will absorb red wavelength the best)

  • calibrate colorimeter using cuvette with only distilled water (blank: 100% transmission of light)