YR2-CH5&6-LSN3

• Biologie
• Middelbare school
• havo, vwo
• Leerjaar 2

HAVE READY:

GOOGLE CLASSROOM

KERBOODLE PAGE 67-71

TODAY:

- instruction on theory for today

- work on in class assignments.

Lesson 3: Gass exchange

- I understand what gas exchange is and which gasses need to be exchanged;

- I have a basic understanding of diffusion and how diffusion drives gas exchange;

- I can explain how are organs adapted for optimal gas exchange

- I can explain the differences between organs for gas exchange in different animals.

 GAS EXCHANGE

- To move O2 from the (inhaled) air to the blood

- To move CO2 from the blood to the (exhaled) air

HOW does gas exchange happen?

Diffusion

Explain how diffusion drives gas exchange in the alveoli in the lungs

Diffusion in the alveoli

diffusion

displacement of small molecules 

from high concentration 

to low concentration (with the concentration gradient)

Why does O2 go into the blood?

Why does CO2 go into the air?

DISPLACEMENT from high to low

But there is more to it...

Remember the membrane?

for diffusion to occur the membrane must be passable, therefore thin! There needs to be a short diffusion distance.

But there is more to it...

You need a lot of O2!

In order to get enough oxygen to your cells, you need a lot of alveoli

 There is a high surface area for gas exchange

So diffusion is optimized by...

1. Large concentration gradient (high oxygen in the alveoli by ventilating, low oxygen in the blood by transporting it away).
2. Small diffusion distance (very thin wall between the alveolus and capillary)
3. Large surface area (a lot of alveoli present)

But then it goes wrong.

Animals become short of breath when there is not enough uptake of oxygen in the blood

Diffusion is NOT optimal

On the next slide, a pulmonary disease is briefly described. 

Asthma (example I-question)

Asthma is a common condition in children, with the most common symptom of being regularly short of breath. The muscles around their bronchioles constrict, making the airway narrower, impairing the gas exchange in the alveoli. As a result, less oxygen is diffusing into the blood, causing the shortness of breath

Discuss in your table group:

- Which of the criteria for optimal diffusion is negatively impacted here? Choose between: concentration gradient, diffusion distance or surface area.

- Explain as a result of this oxygen uptake is therefore lower.

- Write your definitive group answer in your note book

Less ventilation in case of asthma

muscle tissue in bronchiole walls contract >

airways become narrower>

less ventilation > 

less O2 in alveoli

the O2 concentration gradient is diminished!

Gas exchange in other animals

Put google to good use: Find information on gas exchange in the following animals:

- fish (gills)

- insects (tracheae / spiracles)

- amphibians 

- worms

- unicellular organisms (amoeba)

Describe in no more than 4 sentences:

- Describe the differences in organs between these animals and lungs of mammals

- Describe how diffusion is optimized in those animals

FISH use gills

• use mouth to press water past gills
• arches filled with filaments
• filaments lined with lamella
• counter current: water flow is AGAINST the blood flow for optimal diffusion

WORMS use their skin

AMFIBIANS use skin AND lungs

• skin is very thin and covered with mucus
• oxygen from air dissolves in mucus
• oxygen then passes through skin
• oxygen can only travel short distances

Insects use tracheae

•  = spiracles
• air tubes through entire body
• completely separated from blood flow
• blood does not carry oxygen (that is why it is not red)

AMOEBA is unicellular

• so small it doesn't require any adaptations for gas exchange
• O2 and CO2 simply pass through the cell membrane

WHAT TO DO NOW:

- work on HW for lesson 3

- work on HW for lesson 4

Have them both completed next week