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Biology A Level > Hormonal Communication > Flashcards

Hormonal Communication Flashcards

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1
Q

What is the endocrine system?

A

A communication system using hormones as signalling molecules

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2
Q

How are hormones transported throughout the body?

A

In the blood

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3
Q

What are the two types of hormone?

A

Peptide/protein hormone and steroid/lipid hormone

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4
Q

How do protein hormones work?

A

Protein hormones can’t ass through the phospholipid bilayer, they have to bind to a receptor on the cell surface membrane of the cell. They release a second messenger into the cell

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5
Q

How do lipid hormones work?

A

Lipid hormones can pass directly through the phospholipid bilayer as they can move through the fatty acid tails of the bilayer. They enter the cell and have a direct effect on the cells nucleus

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6
Q

What is an endocrine gland?

A

Hormones are released directly into the blood from endocrine glands. These glands are ductless and consist of a group of cells that manufacture and release the hormone directly into the capillaries running through the gland

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7
Q

How does a peptide hormone effect the correct cells?

A

It has a shape that is complementary to the shape of the receptor on the cell surface membrane fo the target cell. The hormone will only be able to bind to this receptor and release a second messenger into this cell meaning they can only effect the target cell

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8
Q

How does a steroid hormone effect the correct cells?

A
  • The steroid hormone is secreted from a gland and binds to transporter proteins in the blood that keep it soluble, when it reaches the target cell, the transporter proteins release the hormone
  • The steroid hormone passes through the plasma membrane of the target cell
  • The steroid hormone binds with a specific receptor with a shape that is complementary to the shape of the signalling molecule
  • The receptor-steroid complex enter the nucleus and binds to another specific receptor on the chromosomal material
  • Binding stimulates the production of mRNA which leads to the production of proteins
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9
Q

What is a first messenger?

A

A protein hormone, signalling molecules that bind to a receptor on the cell surface membrane and initiate a response inside the cell. This is usually the release of a second signalling molecule in the cell, this is the second messenger

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10
Q

What is a second messenger?

A

A molecule that is released inside the cell as a result of a signalling molecule binding to a receptor on the cell surface membrane

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11
Q

Describe the sequence of events inside the target cell

A

The peptide hormone binds to the receptor molecule on the target cell, this activates a G protein in the plasma membrane of the target cell, the G protein activates an effector molecule such as adenyl cyclase which converts ATP into cAMP. cAMP is the second messenger. The second messenger may open or close an ion channel or activate an enzyme to cause a cascade of enzyme controlled reactions that have an effect on the cell

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12
Q

What is the adrenal cortex?

A

The adrenal cortex consists of an outer capsule and three layers of cells:

  • zona glomerulosa, the outermost layer which secretes mineralocorticoids such as aldosterone
  • zona fasciculata, the middle layer that secretes glucocorticoids such as cortisol
  • zona reticularis, the inner layer that secretes precursor molecules that are used to make sex hormones
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13
Q

What are the adrenal glands?

A

An endocrine gland that is located just above (anterior to) the kidneys, one above each kidney. We have two adrenal glands

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14
Q

What is the adrenal medulla?

A

The adrenal medulla is found at the centre of the adrenal gland and secretes adrenaline and noradrenaline

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15
Q

What is the function of mineralocorticoids?

A

To maintain concentration of Na+ and K+ in the blood, aldosterone (a mineralocorticoid) acts on the cells of the DCT and collecting ducts, it increases absorption of Na+ into the blood, decreases absorption of K+ and increases water retention.

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16
Q

What is the function of glucocorticoids?

A

Help to control metabolism of carbohydrates, fats and proteins in the liver. Cortisol (a glucocorticoid) is released when you are stressed or when you have low blood glucose concentration. It stimulates the production of glucose from fats proteins and glycogen. This reduces metabolism of stored compounds and increases blood glucose concentration

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17
Q

Where is cortisol released from?

A

The zona fasciculata and it can also be released from the zona reticularis but if the correct enzymes for the release fo cortisol aren’t present then the zona reticularis will release precursor androgens that are taken up by the ovaries or testes and converted to sex hormones such as testosterone or oestrogen/progesterone

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18
Q

Where is adrenaline released from?

A

The adrenal medulla

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19
Q

Is adrenaline a peptide hormone?

A

Yes, adrenaline is a peptide hormone derived from the amino acid tyrosine. Adrenaline is a polar molecule due to its OH groups

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20
Q

How does adrenaline affect a wide range of cells?

A

Many cells have receptors for adrenaline on their plasma membrane. This means that adrenaline can bind to receptors on many cells and cause a second messenger to be released in the cell that can have an effect on cell activity

21
Q

What are the effects of adrenaline on the body?

A
  • Relaxation of smooth muscle in bronchioles to increase airflow
  • Increased stroke volume of the heart to increase volume of oxygen delivered to tissues
  • Increased heart rate
  • Vasoconstriction to raise blood pressure
  • Conversion of glycogen to glucose
  • Dilating pupils to take in more light
  • Increased mental awareness
  • Inhibition of gut action to conserve energy
  • Body hair stands erect to preserve body heat
22
Q

Where is the pancreas located and what are its two main secretions?

A

Just below the stomach and its two main secretions are:

  • Pancreatic juices containing enzymes into the small intestine
  • Hormones into the blood, these are secreted from the islet of Langerhans
23
Q

What is the exocrine system?

A

Where glands secrete hormones or enzymes into a duct that leads straight to the target site

24
Q

What is the exocrine function of the pancreas?

A

The pancreas synthesises and secretes digestive enzymes into the pancreatic duct that carries the fluid containing the enzymes to the first part of the small intestine

25
Q

What are acini in the pancreas?

A

Small groups of exocrine cells surrounding tiny tubules

26
Q

What do the tubules of acini come together to form?

A

Interlobular ducts that eventually combine to form the pancreatic duct

27
Q

What is the islet of Langerhans made up of?

A

alpha and beta cells

28
Q

What digestive enzymes does the pancreatic fluid contain?

A
  • Pancreatic amylase- digests amylose to maltose
  • Trypsinogen, inactive form of trypsin that is activated when it reaches the small intestine
  • Lipase, digests lipid molecules.
  • The fluid also contains Na2CO3 which is alkaline, this helps to neutralise the contents of the digestive system that have just left the acidic environment of the stomach
29
Q

What is the endocrine function of the pancreas?

A
  • The islet of langerhans which is surrounded by acini contains alpha cells and beta cells
  • Beta cells secret insulin and alpha cells secrete glucagon
30
Q

Describe the process of the release of insulin

A
  • When glucose concentration is high in the blood, glucose moves into the cell
  • Glucose is metabolised to produce ATP which binds to the ligand gated K+ channels, this shuts the channels
  • Accumulation of K+ increases the potential difference across the cell membrane, the inside of the cell becomes less negative
  • The increased potential difference opens the voltage gated Ca2+ channels allowing Ca2+ to enter the cell
  • Ca2+ ions activate motor proteins that walk vesicles containing insulin along the cytoskeleton to the plasma membrane where the contents of the cell is released into the blood by exocytosis
31
Q

What is the normal blood glucose concentration?

A

4-6 mmoldm-3

32
Q

What is hypoglycaemia?

A

When blood glucose drops below 4 mmoldm-3 for a prolonged period of time and there is insufficient glucose for the body’s tissues, especially the brain. This can lead to seizures and unconsciousness as brain function is impaired

33
Q

What is hyperglycaemia?

A

Where blood glucose concentration rises above 6mmoldm-3 for a prolonged period of time, it can lead to severe organ damage and damage of blood vessels. A blood glucose concentration of over 7 is the diagnosis for diabetes.

34
Q

Describe how insulin affects a target cell

A

When blood glucose concentration increases too much, the beta cells in the islet of Langerhans detect this change and secrete insulin into the blood. This insulin is a peptide hormone meaning it can’t pass through the plasma membrane. When insulin reaches the plasma membrane from by travelling in the blood, it binds to a receptor on the cell surface membrane and activates the enzyme tyrosine kinase, tyrosine kinase causes the phosphorylation of inactive enzymes in the cell which activates the enzymes and causes a cascade of enzyme controlled reactions. This cascade of reactions activates a vesicle with glucose transporter proteins in its membrane, this vesicle fuses with the plasma membrane and inserts these glucose transporter channel proteins into the cell surface membrane. This increases the volume of glucose entering the cell. This causes glucose to be converted into glycogen, fats or to be used in respiration. The increased uptake of glucose by the cells reduces the blood glucose concentration

35
Q

What are the target cells of insulin?

A

Hepatocytes, brain cells, muscle and other body cells

36
Q

What is glycogenesis?

A

Where glucose is converted into glycogen

37
Q

What is glycogenolysis?

A

Where glycogen is converted into glucose

38
Q

What is gluconeogenesis?

A

Amino acids and fats are converted into additional glucose

39
Q

Describe the effect of glucagon on target cells

A

When blood glucose concentration falls too low, alpha cels secrete glucagon into the blood. Glucagon travels to the target cells, the hepatocytes in the liver and binds to the cell surface receptor. This stimulates a G protein inside the membrane which activates adenyl cyclase that convertes ATP into cAMP, cAMP then activates a series of enzyme controlled reactions in the cell. This causes glycogen to be converted into glucose and be released into the blood, more fatty acids to be used in respiration so that glucose doesn’t need to be taken into the cells as much and amino acids and fats to be converted into additional glucose

40
Q

What are the target cells for glucagon?

A

Hepatocytes

41
Q

What is diabetes mellitus?

A

A condition where the body is no longer able to produce sufficient insulin to control the blood glucose levels

42
Q

What is type 1 diabetes?

A

Where a autoimmune response or viral attack destroys all of someone’s beta cells meaning they can’t produce any insulin

43
Q

What happens to someone with diabetes when their blood glucose concentration rises too much?

A

Glucose levels in the blood can’t be quickly brought down as they can’t produce sufficient insulin meaning the cells can’t take up glucose and convert it to glycogen. However when blood glucose concentration does fall, they have no store of glycogen as the cells couldn’t take up glucose in the first place, this is when a diabetic may experience hypoglycaemia

44
Q

What is type 2 diabetes?

A

Where the person can still produce insulin but not enough du to the person having too many cells due to obesity, or where a person’s cells become resistant to insulin due to specific receptors on the hepatocytes and muscle cells becoming less responsive with old age and therefore the cells can’t respond to insulin

45
Q

What are the factors that bring early onset type 2 diabetes?

A
  • Obesity
  • Lack of regular exercise
  • A diet in high sugars
  • Being of asian or Afro-Caribbean origin
  • Family history
46
Q

How is type 1 diabetes treated?

A
  • Insulin injections
  • Insulin pump therapy, insulin is pumped into the blood at a constant rate by a needle that is permanently inserted under the skin
  • Islet cell transplant, healthy beta cells from the pancreas of a deceased donor are implanted into the pancreas of someone with type 1 diabetes
  • A complete pancreas transplant
  • Stem cell treatment, stem cells from the placenta/bone marrow can be used to grow new islet of Langerhans in the pancreas (stem cells are not yet differentiated so can be induced to develop into a variety of cells)
47
Q

How can type 2 diabetes be treated?

A
  • Lifestyle changes and medication that reduces the amount of glucose released by the liver, or medication that increases the amount of insulin released by the pancreas
  • Insulin injections in the cases where cells have become resistant to insulin due to receptors becoming less sensitive to insulin
48
Q

What is the source of insulin for treatment of diabetes?

A
  • Usually from the pancreas of animals such as pigs as it matches human insulin most closely
  • Using e.coli bacteria that has undergone genetic modification to manufacture human insulin
49
Q

What are the advantages of using insulin from genetically modified bacteria as opposed to insulin from animals with similar insulin to humans?

A
  • Exact copy of human insulin, therefore it is more effective
  • Less chance of developing tolerance to the insulin
  • Less chance of rejection due to an immune response
  • Lower risk of infection
  • Cheaper to manufacture than insulin than it is t extract from animals
  • Manufacture process is more adaptable to demand
  • No ethical issues with manufacturing the insulin using the bacteria

Biology A Level (21 decks)

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