A2 Biology Topic 7 Hormones

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Transcript A2 Biology Topic 7 Hormones

A2 Biology Topic 7 Performance enhancing drugs

Banned substances and practices

Anabolic steroids Stimulants Hormone agonists Hormones and releasing factors Beta-2 agonists Narcotics Beta blockers Diuretics Blood doping Gene doping Is it an infringement of athletes human rights to be required to give blood and urine samples?

Page reference: 178-179 Edexcel A2 Biology (concept) textbook

Steroid hormones

Pass through the plasma membrane and stimulate protein synthesis Steroid hormones Other steroid molecules

Mechanism of action of steroid hormones: steroid hormone cell surface membrane Hormone enters cell and binds with receptor Complex binds to DNA and acts as a transcription factor receptor enters nucleus hormone-receptor complex Switches on a gene for synthesis of a protein nuclear membrane

Testosterone

Stimulates protein synthesis Results in bigger and stronger muscles

Anabolic steroids

Natural testosterone is quickly broken down.

Testosterone is modified to produce drugs that remain for longer in the body These synthetic anabolic steroids are illegal.

testosterone nandrolone

Side-effects of using anabolic steroids

Infertility due to disruption of normal hormone production: - disrupted menstrual cycle - reduced sperm production -impotence In addition: - liver damage - high blood pressure - heart attacks - increased aggression 21 year old body builder: A and B Severe acne conglobata C After 8 weeks off steroids and with antibiotics

Peptide hormones

Peptide hormones do not enter the cell. They bind to receptors on the cell surface membrane.

They also act to switch genes on or off.

Human erythropoietin

Mechanism of action of peptide hormones: peptide hormone receptor cell surface membrane Inactive secondary messenger eg. cAMP Secondary messenger activated: initiates a protein kinase cascade acts as a transcription factor which switches on gene for a specific protein

Erythropoietin

Erythropoietin is synthesised in the kidneys Causes the synthesis of enzymes required for synthesis of red blood cells (erythrocytes) in bone marrow.

Useful for treating anaemia.

Use of erythropoeitin

Increases number of blood cells and therefore enhances oxygen supply to muscles.

Improvement of 10% in aerobic performance Use is popular with endurance athletes and cyclists

Side-effects of overuse of erythropoietin Excess of red blood cells can lead to strokes and heart attacks .

Attacks most common at night due to low heart rate.

Thought to have caused the unexpected deaths of 18 european cyclists between 1987 1991 .

Abuse difficult to prove as it is naturally occurring.

Ethics of performance-enhancing drugs

Problems with deciding on what is illegal: Creatine is not banned: Classed as a nutritional supplement Can cause kidney damage and high blood pressure Erythropoietin is banned: Is a naturally occurring hormone Can cause strokes and heart attacks Ethical questions: Is everything acceptable in the pursuit of sporting excellence?

Isn ´ t it the choice of the athlete to risk using drugs or not?

Blood doping banned: Donating, storing and transfusing own blood before competition High altitude training not banned: Increases number of red blood cells.

Caused by natural increase in erythropoietin production.

Do use of performance enhancing drugs improve or ruin competition?

Are there circumstances when drug use is acceptable?

Essay

Read pages 182 – 183 (of concept approach textbook) and answer question 2 on page 183: Describe an absolutist and a relativist ethical position on the proposal to set a maximum total red blood cell count for athlete rather than measure erythropoietin levels.