Homework

Learning Package 6, BOOK 2•Q1•Q2(b)(ii)•Q3 (d)(iI)•Q4

•If you are unsure of any of these questions, ASK ME FOR HELP

•Due Thursday 25th September

•No homework = Friday afternoon detention with Miss Tagore

Title: Surface Area and Volume Ratios 21 April 2023

Learning question: How does Surface Area to Volume ratio influence gas exchange.

Homework: AS Human Biology Booklet 2 (Year 12) Learning Package 6

Why are babies so well wrapped up in winter?

Large surface area to volume ratio

Small surface area to volume

Nomogram

Surface area Vs Volume

There is an inverse relationship between surface area and volume

As the organism gets larger, the ratio of surface area to volume decreases

This means that larger organisms have to provide a mechanism for providing additional

surface area to meet their needs

Nomgrams• Nomogram : a scale to

estimate human surface area based on height and body mass

• To determine body volume multiply mass in kilograms by 0.9.

• One kilogram of body mass occupies a volume of about 0.9L (remember this is just roughly!).

Key words

•Gas exchange

•Alveolus•Recoil•Surfactant

Aims from specification

(e) relate cell size to cell surface area to volume ratio, in relation to the exchange of materials with the environment;

(f) outline the main features of the gaseous exchange surface of the lungs (only details relating to the cells in contact with blood capillaries, elastic fibres and the role of surfactant are required);

(g) describe the process of gaseous exchange in the alveoli;

(e) relate cell size to cell surface area to volume ratio, in relation to the exchange of materials with the environment;

– The smaller a cell, the larger its surface area to volume ratio.–Cells need to be microscopic in size to maximise

the surface area to volume ratio–A large surface area to volume ratio enables

materials to be adequate diffuse to the centre of the cell in time to maintain the cell processes… keep it alive!!!

Can you relate this to our lesson?

What do all of these exchange surfaces have in common?

(f) outline the main features of the gaseous exchange surface of the lungs (only details relating to the cells in contact with blood capillaries, elastic fibres and the role of surfactant are required);

Read page 50 and 51 and write a description of:1.Cells in contact with blood Capillaries2.Elastic fibres3.Surfactant

Elastic fibres: These allow the alveoli to expand when breathing in and recoil easily when breathing out.Surfactant: A detergent like substance that lowers the surface tension of the alveoli, and therefore reduces the amount of effort needed to breathe in and inflate the lungs. It also has an antibacterial effect, healing to remove any harmful bacteria that reach the alveoli.

Cells in contact with blood capillaries: what do you already know about these cells?

(g) describe the process of gaseous exchange in the alveoli;

There is a concentration gradient between the oxygen in the alveoli and oxygen in the capillaries and oxygen diffuses into the capillary. A concentration gradient is set up so that carbon dioxide diffuses into the alveolus.

Homework

Learning Package 6, BOOK 2•Q1•Q2(b)(ii)•Q3 (d)(iI)•Q4

•If you are unsure of any of these questions, ASK ME FOR HELP

•Due Thursday 25th September

•No homework = Friday afternoon detention with Miss Tagore