Digestion and Absorbtion 2 Flashcards
What does maltose break down into and which enzyme is this reaction catalysed by
Glucose and glucose via maltase
What does sucrose isomaltase break down into and which enzyme is this reaction catalysed by
Glucose and fructose by sucrose isomaltase
Which two substances are converted to glucose in the liver
Fructose and galactose
What does catabolism of glucose produce
ATP
What is glycogenesis and where does this process occur
The conversion of glucose to glycogen and occurs in skeletal muscle and liver
What is glycogenolysis
The breakdown of glycogen to glucose
What is gluconeogenesis
When glucose is made from non-carbohydrate precursors such as fats and proteins
What are fully saturated glycogen stores
Where glucose is converted to free fatty acids and stored in adipocytes in the form on truglycerides
What are carbohydrates broken down by
Salivary and pancreatic amylase and brush border enzymes in the SI
What is glucose anabolism
Glucose storage and release, formation of glucose from proteins and fats, excess glucose stored as fat
Which cells rely almost entirely on glucose
CNS, retina and germinal epithelium cells
What are normal fasting blood glucose levels
3.5-7.5mmol-1
What is the predominant tissue in responding to reduced/ elevated blood glucose levels
The liver
What is persistently high blood glucose levels called
Hyperglycaemia
What is persistently low blood glucose levels called
Hypoglycaemia
What happens if blood glucose levels fall below 3mmol-1?
Loss of conciousness (coma)
What happens if blood glucose levels rise above 10mmol-1?
Glucose would appear in the urine, pH of blood would fall lead to coma
What happens if there are inadequate levels of glucose in the blood
Cells immediately shift to the catabolism of fats for energy
What happens if starvation occurs
Proteins are also used for energy after carbohydrate and fats are depleted
Which factors influence blood glucose levels
When eating takes place/ type of food eaten. The amount of physical and mental activity. The presence of hormones
Which two hormones are involved in the short term regulation of blood glucose levels
Insulin and glucagon
Which 4 hormones are involved in the long term regulation of blood glucose levels
Adrenaline, glucocorticoids, growth hormones, thyroid hormones.
What is the glycaemic index (GI) and what does it show
It is a rating system for foods containing carbohydrates and shows us how rapidly each food affects blood glucose levels (when that food is eaten on its own)
What are acniar cells and what do they secrete
They are in the pancreas and are part of the exocrine system so secrete digestive enzymes
What percentage of the pancreas is made up of Islet of Langerhans
2%
Which three types of cells is the Islet of Langerhans made up of
Alpha, beta and delta
How much of the islet of Langerhans consists of alpha cells
20%
What do alpha cells secrete
Glucagon
How much of the islet of Langerhans consists of beta cells
75%
What do beta cells secrete
Insulin
How much of the islet of Langerhans consists of delta cells
5%
What do delta cells secrete
Somatostatin
How long is insulin’s half-life and what impact does this have on it’s regulation of glucose
Insulin has a 5 minute half-life which means that it provides short term regulation
What type of protein is insulin
Globular
How many amino acids is insulin made from
51 amino acids
What does insulin respond to
High blood sugar levels
Which hormone responds to high blood sugar levels
Insulin
What impact does raised blood glucose levels have on cells in the Islets of Langerhans
Raised plasma glucose levels results in depolarisation of the beta cells
How long after a meal does plasma glucose reach max levels
Approximately 60 minutes after
Which elicits a greater response- oral glucose or intravenous glucose
Oral glucose
What do gastrointestinal hormones ‘incretins’ do
They enhance beta cell response to glucose
What are the 6 actions of insulin
- Major targets= liver, adipose tissue and muscle mass
- Increases glucose uptake by cells
- Stimulates liver to convert glucose into glycogen (glyconeogenesis)
- Inhibits gluconeogenesis
- Stimulates excess glucose to be converted into fat (lipogensis)
- Blood glucose levels drop
What is important to note about the CNS and insulin
Glucose uptake by the CNS is independent of insulin
Which is the most potent hyperglycaemic hormone
Glucagon
How many amino acids is glucagon made of
29 amino acids
What is the half life of glucagon
6 minutes
Describe the actions of glucagon in relation to insulin
The actions of glucagon directly oppose insulin
Why is glucagon secreted
In response to lowered plasma glucose to raise glucose levels
Which hormone inhibits glucagon secretion
Insulin
What are the nine actions of glucagon
- If blood glucose falls to dangerous levels the alpha cells release glucagon
- Glucagon exerts its effects on carbohydrate. fat and protein metabolism
- The major target of glucagon is the liver
- Glucagon converts glycogen into glucose (glycogenolysis)
- It inhibits glycogen synthesis
- It activates amino acid uptake and gluconeogenesis
- It increases lipolysis
- It provides a ready supply of metabolic substances
- It enables glucose to be spared for the CNS
Changes in plasma glucose that occur during fasting then glucose rich meal
First 90 minutes= absorptive state of metabolism, insulin dormant
3-4 hours= post absorptive state of metabolism, glucagon dominant
Which hormones apart from insulin and glucagon are involves in the regulation of plasma glucose
Adrenal glucocorticoids, growth hormone, catecholamines, thyroid hormone
What functions do the hormones other than insulin and glucagon do
Maintain glycogen stores, stimulate gluconeogenesis, stimulate the metabolism of fatty acids and proteins. They play a significant role during prolonged fasting and conserve glucose for the CNS
What 2 metabolic effects does stomatostain have
- Suppresses glucagon release from alpha cells
2. Suppresses release of insulin, pituitary tropic hormones, gastrin and secretin
What 2 metabolic effects does epinephrine (adrenaline) have
- Enhances release of glucose from glycogen
2. Enhances release of fatty acids from adipose tissue
What 2 metabolic effects does cortisol have
- Enhances gluconeogenesis
2. Antagonises insulin
What 2 metabolic effects does ACTH have
- Enhances release of cortisol
2. Enhances release of fatty acids from adipose tissue inhibiting uptake by extrahepatic tissues
What metabolic effect does growth hormone have
Antagonises insulin, inhibiting uptake of extrahepatic tissues
What 2 metabolic effects does thyroxine have
- Enhances release of glucose from glycogen
2. Enhances absorption of sugars from intestine
Which is the only hormone that lowers blood glucose levels
Insulin
What effect do all hormones (apart from insulin) have on blood glucose levels
They raise blood glucose levels
What is diabetes mellitus
A condition in which the body either does not produce enough, or does not properly respond to insulin or both
What are the 10 symptoms of diabetes mellitus
- Always tired
- Always hungry
- Sexual problems
- Sudden weight loss
- Wounds that won’t heal
- Vaginal infections
- Numb/ tingling hands or feet
- Always thirsty
- Frequent urination
- Blurry vision
What are the other names for Type 1 diabetes
‘Juvenile’ diabetes/ insulin dependent diabetes mellitus (IDDM)
What are the other names for Type 2 diabetes
‘Adult onset’ diabetes, noninsulin dependent diabetes mellitus (NDDM)
Why is type 1 diabetes an organ specific immune disorder
It leads to the destruction of pancreatic beta cells resulting in the complete loss of insulin secretion
What 4 pros does exercise have in relation to diabetes risk
- Decreased insulin resistance
- Decreased risk of obesity and T2DM
- Exercise may enhance insulin’s binding to receptors on the muscle fibre
- Thyfault and Booth 2011- increased sitting time leads to a reduction in insulin sensitivity
What is type 2 diabetes strongly linked to
Obesity
What is type 2 diabetes caused by
A reduction in pancreatic insulin or an increasing failure of tissues to respond to insulin
How can type 2 diabetes be controlled
Through diet
What is temporary glycaemia
Benign and asymptomatic
What does long term glyceamia lead to
Increased secretion of glucagon (insulin suppression), increase in glycogen breakdown, increase in rate of gluconeogenesis and increased lipolysis. Leads to further raising of blood glucose levels
What are the 3 consequences of hyperglycaemia
Polyuria, polydipsia, polyphagia
What is polyuria
Frequent and excessive urination. Osmotic pressure due to glucose in the urine