Biology: Topic 2.1 - transport and exchange (a + b)

Fick's law equation?

(SA x difference in conc) / thickness of membrane

Surface area of an organism?

The total number of cells in contact with the surrounding environment

Volume of an organism?

the total three dimensional shape occupied by metabolically active tissue

Things which improve diffusion?

> large SA

> short diffusion distance

> high concentration gradient

How to increase surface area?

> flattened shape

> folded external exchange area

> folded internal exchange area

How are lungs adapted to maximise diffusion?

> 600 million alveoli w/ 100m² SA

> alveolus 1 cell thick

> constant ventilation replaces air to maintain conc gradient

What is a erythrocyte?

red blood cell

How are RBC adapted to maximise diffusion?

> biconcave

> no nucleus

> packed w/ haemoglobin

> constant movement through lungs and tissue cause movement of gases in and out of cell

How are root hair cells adapted to maximise diffusion?

> extension of cell wall for large SA

> thin and fully permeable cell wall

> O² enters and is used for respiration

> active transport allows entry of ions

How are capillaries adapted to maximise diffusion?

> long

> thin cell membrane

> constant movement of blood

How are leaves adapted to maximise diffusion?

> large SA of spongy mesophyll

> gases diffuse straight into leaf cells

> wind replaces air around leaves

What is mass flow/mass transport?

Transport systems of large mammals and plants delivering substances in bulk

Main difference between transport system of plants and animals?

Animal's systems will transport gases while plant's systems won't

2 mass transport systems in animals?

Blood system and ventilation system

2 mass transport systems of plants?

Phloem and Xylem

What does the phloem do?

Transport (translocation) of sucrose to roots and growing regions

What does the xylem do?

Transports water and mineral ions from the roots and leaves

How does the movements of substances through these systems come about in plants and animals?

Differences in pressure

How is the pressure difference created in xylem?

water evaporating from the leaf creates tensions that pulls water up the plant in the transpiration stream

How is the pressure difference created in the phloem?

ATP is needed to move the sucrose from the companion cell to the phloem slieve tube

How is the pressure difference created in animal circulatory system?

pumping of the heart

How is the pressure difference created in animal ventilation system?

> Reduction of pressure in the thorax causes air to enter the lungs

> Increased pressure in the thorax causes air to be expelled from the lungs

Function of circulatory system in mammals?

Transport of substances, including oxygen, CO2, amino acids, lipids and urea around the body

Function of ventilation system?

Fresh air enters the lungs which removes air with raised CO₂ levels and low O₂ levels

> ensures diffusion of gases can take place between alveoli and capillaries

Features needed to maximise gas exchange?

> large SA

> moisture

> diffusion gradient

> permeable

> very thin

Why is moisture needed to diffuse gases?

for gases to dissolve

Gas exchange surface in mammals?

Lungs

How do lungs ensure large SA?

approx 700 million alveoli w/ SA of 75m²

How do lungs have thin membrane?

Capillary and alveoli membrane 1 cell thick for shorter diffusion distance

How do the lungs maintain concentration gradient?

> Ventilation in the lungs bring in O₂ and removes CO₂

> Blood flow too

Fick's law equation

diffusion rate is directly proportional to (SA x difference in conc)/thickness of membrane

What can hinder gas exchange in the lungs?

Surface tension

What brings about surface tension?

the inward cohesive force of water molecules lining the alveoli, which creates a tendency for the air sacs to collapse and resists expansion during inhalation.

How can surface tensions cause difficulties?

It can prevent the alveoli from decreasing in volume, it can cause collapse, and it keeps the alveoli stuck together

What is the purpose of surfactant?

It reduces surface tension

Where is surfactant produced?

surfactant secreting cells

Label diagram of the lungs

page 20/ipad

Function of trachea?

> lined w/ columnar epithelial cells

> cells have cilia covered in mucus

> cilia beat upwards to move mucus and bacteria to the mouth

Function of bronchi?

> Each bronchus enters a lung

> Rings of cartilage keep the tube open during pressure changes

Function of bronchioles?

branching tubes carry the air in and out

Function of alveolar ducts?

connect bronchioles to alveoli

Function of alveoli?

Tiny sacs that are the main site of gas exchange

Function of intercostal muscles?

> External contract to move ribs up and out

> Internal contract to move the ribs down and in

Ribcage function?

protects the heart and lungs

Diaphragm function?

> Separates the thorax from the abdomen

> Movements in the diaphragm change the volume and pressure in the thorax to cause breathing or ventilation movements

What happens when you breath in?

> External intercostal muscles contract

> Ribs and sternum move up and out

> Width of thorax increases

> Diaphragm contracts

> Diaphragm moves down, flattening

> Depth of thorax increases

> Volume of thorax increases

> Pressure decreases

> Lungs expand

> Air pressure in alveoli is less than atm

> Air is forced into lungs by external atm pressure

What happens when you breathe out?

> Internal intercostal muscles contract

> Ribs and sternum move down and in

> Width of thorax decreases

> Diaphragm relaxes

> Diaphragm moves up

> Depth of thorax decreases

> Volume of thorax decreases

> Pressure increases

> Lung tissue recoils

> Air pressure in alveoli is morethan atm

> Air is forced out of lungs by external atm pressure

Carcinogen meaning?

Cancer causing

What is the harmful part of cigarettes?

Tar

Negative effects smoking can have on the respiratory system?

> Lung cancer

> Emphysema

> Bronchitis

> Cilia damage

How can lung cancer damage the lungs?

> Cells divide uncontrollably to produce a tumour

> once the tumor reaches a certain size it can block airways or damage lungs

How can emphysema damage the lungs?

> Irritation from tar damages the alveolar lining to the extent that the walls of many alveoli break down

> Fewer alveoli means reduced SA

> Cig smoke also breaks down the elastic lining, reducing their ability to recoil during expiration

How does bronchitis damage the lungs?

> Inflammation of the bronchial tubes

> The narrowed tubes and increased mucus production reduces air flow

How does cilia damage harm the lungs?

Tar paralyses the cilia which prevents them from removing mucus and microbes from respiratory tract

When are the compensation points for CO₂ production in plants?

dawn and dusk

Graph showing CO₂ production in plants

page 25

What is compensation point?

When the rate of CO₂ used in photosynthesis is the same as the rate of CO₂ produced in respiration

How is the leaf adapted for gas exchange?

> Thin

> Large SA (spongy mesophyll)

> Moist (spongy mesophyll)

> Intracellular spaces

> Stomata

Label leaf diagram?

page 26

How is the large SA of a leaf obtained?

Loose arrangement of spongy mesophyll cells creates a large SA

How do stomata control when they open and close?

> They are sensitive to the concentration of CO₂ in the air spaces and when in is high they close

> They also open and close at dawn and dusk

What is used to measure the rate of oxygen intake and carbon dioxide output?

Respirometer

Label respirometer diagram?

page 29

What is the purpose of hydrogen peroxide solution?

It removes carbon dioxide from the test tube

What does it mean in the droplet moves towards the test tube?

Oxygen in being taken in by respiration

How is the rate calculated?

the distance the droplet moves in a given time

What does it suggest if the droplet does not move?

The organism is respiring anaerobically

How do you calculate the rate when the test tubes are filled with water?

use the difference between oxygen intake and carbon dioxide output -> measure the distance the droplet moves in a given time and compare it to the test tubes containing hydrogen peroxide

What does it suggest if the fluid stays the same in tube w/ water?

there are equal volumes of oxygen intake and carbon dioxide output

What does it suggest if the droplet moves towards the test tube?

more oxygen is taken in than carbon dioxide produced