Excretion Flashcards
What is excretion?
Process by which toxic waste products of metabolism/substances in excess of requirement are removed from the body
Example of excretion?
Lungs excrete CO2 (waste product) by gas exhale /exhalation
Kidneys produce urine that contains waste product, urea, in solution
Metabolic waste example and how are thye produced?
CO2- from DECARBOXYLATION of respiratory substrates
Nitrogenous waste - ammonia,urea,uric acid
- ammonia from deamination of excess amino acids
Bile pigments - from breakdown of haemoglobin
Urea - ornithine cycle in liver cells
Uric acid - break down of adenine/guanine (purines) in liver
LIVER PRODUCES ALL THESE EXCRETORY SUBSTANCES EXCEPT CO2
Why is excretion important?
Key process in homeostasis
Important in maintaining metabolism - metabolic waste can have bad consequences if accumilates
Effect on body if metabolic waste products accumulate?
CO2 - cell damage if blood pH falls below normal range (acidosis)
Ammonia- increase cytoplasm pH/interfere with metabolic processes (respiration) /receptors for neurotransmitters in brain
Urea - diffuses into cells DECREASING THEIR WP- can burst
URIC ACID: form crystals in joints- cause GOUT (painful form of arthritis)
BILE PIGEMNTS: turn skin yellow - jaundice
Liver external structure?
Good blood supply :
HEPATIC ARTERY - carry OX BLOOD from heart—> liver
(oxygen used for aerobic respiration, fuel metabolic activity in liver cells)
HEPATIC PORTAL VEIN - blood from digestive system —> liver via this vein
(allows liver to absorb/metabolise nutrients absorbed into blood in SI)
HEPATIC VEIN - deoxygenated blood exits liver via this vein /flow back to HEART
What is the liver connected to and what is its role?
Gall bladder
Role:
Store bile - bile contains bile salts for lipid digestion/bile pigments
Release bile - into duodenum via bile duct
Internal liver structure?
Liver consist of cells = HEPATOCYTES
Liver cells arranged into LOBULES - each one is supplied with blood by BRANCHES OF HEPATIC ARTERY/HEPATIC PORTAL VEIN
- blood from hepatic artery/portal vein MIXES in each lobule in wide capillaries (SINUSOIDS)
- each lobule connected to branch of HEPATIC VEIN that drains blood away/into main hepatic vein
What is the role of sinusoids?
Blood flowing through sinusoids can exchange substances with nearby hepatocytes
- allows hepatocytes to performs all functions of liver
liver fucntions?
Storage of glycogen
Formation of urea
Detoxification
How does the liver store glycogen?
- Plays a role in GLYCOGENESIS : convert glucose —> glycogen
- glycogen produced from GLYCOGENOLYSIS is stored IN HEPATOCYTES
How does the liver form UREA?
Amino acids in blood transported to liver via hepatic portal vein
Excess amino acids processed in hepatocytes during 2 step process involving :
- deamination
- ornithine cycle
How does the liver form UREA?
Amino acids in blood transported to liver via hepatic portal vein
Excess amino acids processed in hepatocytes during 2 step process involving :
- deamination
- ornithine cycle
What happens in deamination?
Amino group (NH2) removed from each amino acid , with an extra H+ atom
NH2 + H+ —> NH3 (ammonia)
Part of amino acid remaining after deamination = KETO ACID which can:
Enter Krebs cycle to be respired
Be converted to glucose
Be converted to glycogen/fat for storage
What happens in deamination?
Amino group (NH2) removed from each amino acid , with an extra H+ atom
NH2 + H+ —> NH3 (ammonia)
Part of amino acid remaining after deamination = KETO ACID which can:
Enter Krebs cycle to be respired
Be converted to glucose
Be converted to glycogen/fat for storage
