A2 Unit F214 - Communication, Homeostasis and Energy
Summary
Summary OCR A Level Biology A* Excretion Detailed Notes
19 views 0 purchase
Course
A2 Unit F214 - Communication, Homeostasis and Energy
Institution
OCR
These A-Level Biology notes are designed for students aiming for top grades and a future in medicine. They are both aesthetic and detailed, offering comprehensive coverage of the syllabus while being visually engaging.
Comprehensive Coverage: Every topic is fully covered, directly aligned with t...
A2 Unit F214 - Communication, Homeostasis and Energy
All documents for this subject (31)
Seller
Follow
alevelrevisionresources
Content preview
5.2 Excre*on notes
5.2.1 Importance of Excre*on
- Excre'on = process of removing toxic metabolic waste that are in excess of requirement from the body
- Key in homeostasis and in maintaining metabolism as metabolic waste is dangerous if it accumulates
Metabolic waste
- Mammals are ac've, warm-blooded animals so have high metabolic rates and hence produce large
amounts of metabolic waste e.g. CO2 from decarboxyla'on of respiratory substrates, nitrogenous waste
(ammonia from the deamina'on of excess amino acids/urea/uric acid), bile pigments
- If these two waste products are not excreted properly they can accumulate and change the cytoplasm and
body fluid pH -> enzymes work less efficiently
5.2.2 Mammalian Liver Structure
External Structure
- Liver has mul'ple roles inc. breakdown of unwanted/toxic substances AND produc'on of excretory waste
- Requires constant blood supply:
1a. Oxygenated blood from heart via hepa'c artery
1b. Deoxygenated blood from diges've system via hepa'c portal vein -> liver can absorb and metabolise
many nutrients that have been absorbed into the blood via the small intes'ne
2. Deoxygenated blood leaves the liver via the hepa'c vein back to the heart
- Liver is directly connected to the gallbladder where bile salts (help digest fats) and bile pigments (waste
product from breakdown of haemoglobin) are stored as part of the bile -> bile is released into the
duodenum via the bile duct
, Internal Structure
- Mainly made up of hepatocyte cells that carry out almost all required func'ons
- Liver is divided into many lobules separated from one another by connec've 'ssue (consis'ng of cells that
secrete an extracellular matrix)
- Branches of the hepa'c artery and hepa'c portal vein supply each lobule with blood
- Blood is carried in wide capillaries called sinusoids lined with an incomplete layer of endothelial cells
which allows blood to reach hepatocytes, allowing substances to be exchanged between blood and cells
(so hepatocytes are adapted to have a large surface area in contact with blood to maximise exchange)
- Each lobule is also connected to a branch of the hepa'c vein that drains blood away from the lobule
- The lobule is the func'onal unit of the liver as all the func'ons of the liver occur within each lobule
5.2.3 Mammalian Liver Func*on
- 3 main func'ons:
1. Storage of glycogen
2. Forma'on of urea
3. Detoxifica'on
Storage of glycogen
- Liver plays vital role in conver'ng glucose into glycogen (process of glycogenesis) to regulate blood glucose
concentra'on
- Insulin triggers glycogenesis (synthesis of glycogen from glucose molecules) a[er it detects increased
blood glucose conc. -> this removes glucose from the bloodstream and decreases blood glucose conc. to
the normal range
- Glycogen acts as a compact and efficient carbohydrate storage molecule
Forma*on of urea
- Protein is digested into amino acids -> absorbed into the blood -> transported to the liver
- Excess amino acids are deaminated so the rest of the molecule can be used as a good energy source
- Process of deamina'on:
1. Amino group (-NH2) removed with an extra hydrogen atom
2. These combine to form ammonia (NH3) -> forms ammonium ions (NH4+) in the cytoplasm
3. Remaining keto acid may enter the Krebs cycle in mitochondria to be respired/converted to
glucose/converted to glycogen or fat for storage
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller alevelrevisionresources. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $9.07. You're not tied to anything after your purchase.
