Download Surface Area

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
24 May 2017
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!).
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
Capillaries
2. Elastic fibres
3. Surfactant
Elastic
Cells infibres:
contact
These
withallow
blood
capillaries:
alveoli tothat
what
expand
do you
when
Surfactant:
A detergent
likethe
substance
lowers
the
breathing
alreadytension
know
in and
about
easily
cells?
when
breathingreduces
out.
surface
ofrecoil
thethese
alveoli,
and therefore
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.
(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
