OCR GCE Biology - Exchange and Transport
- Created by: Quincy Washington
- Created on: 02-12-10 18:00
Why do cells need to take in oxygen?
-Aerobic respiration
-Nutrient
Name 2 waste products of cells
-Urea
-Carbon dioxide
What does the ease of exchanging substances depend on?
-Surface area to volume ratio
Smaller animal have h***** SA:V ratio
-Higher
How do you calculate SA:V ratio?
-Divide surface area by volume
What sort of SA:V ratio do large organisms have in comparison to small organisms?
-Small
What do large organisms need, due to their small SA:V ratio?
-Exchange organs
Give examples of substances that must be supplied to cells for respiration
-Oxygen, glucose
Why do waste products need to be removed from a cell?
-Stop it damaging itself
In single-celled organisms, substances can ******* directly into or out of the cell across the cell surface membrane
-Diffuse
The diffusion rate is q**** for single-celled organisms
-Quick
Why is the diffusion rate for single-celled organisms quick?
-Substances have to travel small distances only
In what sorts of organisms/animals is the diffusion rate slow? Why?
-Multicellular animals/organisms
-Some cells are deep within the body – there’s a big distance between them and the outside environment
-Larger animals have a low surface area to volume ratio – it’s difficult to exchange enough substances to supply a large volume of animal through a relatively small outer surface
Give an example of a specialised exchange organ?
-Lungs etc.
Describe the route of air in the lungs?
-1-Trachea
-2-Air splits into two bronchi – one bronchus leading to each lung
-3-Bronchus branches off into smaller tubes called bronchioles
-4-Bronchioles end in small ‘air sacs’ called alveoli, where gases are exchanged
-5-Ribcage, intercostal muscles and diaphragm work together to move air in and out
Where does gas exchange happen?
-Alveoli
What is an alveolus made of?
-Single layer of thin, flat cells called the alveolar epithelium
Describe the alveoli
-Arranged in bunches at the end of bronchioles
-Surrounded by a network of capillaries, giving each alveolus its own blood supply
Is it epithelial tissue common in the body? Where is it found?
-Yes
-Exchange surfaces
What is the name of the tissue that makes the capillary?
-Capillary endothelium
Briefly describe deoxygenate blood being oxygenated at the capillary
-O2 diffuses out of the alveoli, across the alveolar epithelium and the capillary endothelium, and into haemoglobin in the blood
-CO2 diffuses into the alveoli from the blood, crossing the capillary endothelium then the alveolar epithelium. After entering the alveolar space, it’s breathed out
Name 2 things most gas exchange surfaces have in common
-Large surface area, which increases the rate of diffusion
-Thin (often just 1 layer of epithelial cells) – provides a short diffusion pathway across the gas exchange surface, which increases the rate of diffusion
Outline how large surface area and thin wall are shown in the lungs
-Alveoli (large surface area)
-Thin wall (alveolar epithelium and capillary endothelium) one cell thick giving…
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