Topic 2 Summary (Genes and Health) - A-Level Biology A (2015) Salters-Nuffield
19 views 0 purchase
Course
Genes and Health
Institution
PEARSON (PEARSON)
Book
Salters-Nuffield Advanced Biology
This document offers a selection of summary notes on the chapter: Genes and Health. This is based on textbook A-Level Biology A (2015) Salters-Nuffield
→ SA:V ratio determines whether a substance can reach cells be diffusion alone
→ The larger the organism, the smaller the SA:V ratio (diffusion takes longer)
→ Larger SA:V = optimum diffusion rate
Alveoli adapted for gas exchange and diffusion by:
- Large surface area
- Constant blood supply via many capillaries (maintains high conc. difference)
- Thin walls (short diffusion distance between blood and air)
Emphysema (caused by smoking) decreases SA:V of alveoli in lungs (larger diffusion distance). Explain why a person with
emphysema has problems with gas exchange. (4 marks)
✓ Tar from smoking cigarettes sits in alveoli walls which thickens the wall – this increases diffusion distance and
lowers the rate of diffusion
✓ This also increases the SA:V ratio which means it would take longer for the gas exchange of oxygen and carbon
dioxide between the blood capillary and alveoli air
✓ Less blood flow due to destruction of capillaries; less oxygen carried by blood which means there is less surface
area of capillaries
Why can’t large organisms rely on diffusion for the transport of oxygen and glucose? (3 marks)
✓ Large organisms have a lower SA:V ratio which means there is also a larger diffusion distance (diffusion longer)
✓ Large organisms also have a higher metabolic rate which means they require more energy – this cannot be
supplied via diffusion
✓ Therefore, diffusion is ineffective
Explain how rapid gaseous exchange takes place in a mammal. (5 marks)
1) Large surface area provided by alveoli
2) Large surface area provided by capillary network
3) Concentration gradient maintained by {ventilation of / air flow in} the lungs
4) Concentration gradient maintained by {circulation / mass flow} of blood
5) Diffusion pathway is small because alveoli have a thin wall
6) Diffusion pathway is small because capillaries {have a thin wall / are in contact with alveoli / are only one cell thick}
7) Air is warmed because lungs are in core of body
8) Warmer air enables faster {movement / diffusion of gases
9) Reference to {respiratory pigment / haemoglobin / red blood cells} to carry oxygen
, A Level Notes GAH: Cystic Fibrosis Biology
Ciliated cells
✓ Move mucus up trachea
✓ Removes pathogens from airways
Mucus
✓ Protects epithelial cells in respiratory, digestive and
urogenital systems against fungi, bacteria and viruses
✓ Most of the mucus produced us found in the stomach
• Epithelium; the outer layer/surface of an organ
→ Squamous epithelium found in alveoli
→ Columnar epithelium found in intestine + trachea
• Goblet cells in trachea produce mucus
• Mucus is thick and sticky
→ Cilia can’t eject the mucus from the bronchioles
1) A healthy CFTR channel protein transports chloride ions out of cell and into mucus
2) Thus more water moves from cell into mucus by osmosis (Cl- affect osmotic balance)
3) The mucus becomes diluted and is easily removed
CF is caused by a defective CFTR protein
Less chloride ions will enter mucus
Therefore less water moves into mucus
The mucus remains thick and sticky
CFTR; cystic fibrosis transmembrane conductance regulator
Lungs
- Surface area of alveoli reduced
- Pathogens remain in body
Digestive system
- Food in intestine not dissolved/digested
- Poor digestion leads to weight loss + lack of nutrients
Pancreas (exocrine gland which produces enzymes (then released into
pancreatic duct) and produces insulin + glucagon for glucose regulation
- Mucus blocks pancreatic duct
- Digestive enzymes are trapped in pancreas (cysts form)
- Pancreas may be damaged
Intestine
- Reduced digestion in intestine
- Thick mucus lining intestinal wall reduces absorption of nutrients as it is harder for nutrients to diffuse out
Respiratory system
- Cilia can’t move mucus towards throat
- Bronchioles and alveoli blocked (reduced gas exchange)
- Pathogens trapped in mucus may cause infection
Reproductive system
- Sperm duct blocked or absent
- Thick cervical mucus blocks sperm entry
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 justkarima. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $4.66. You're not tied to anything after your purchase.
