3.1 - Exchange Surfaces and Breathing Flashcards Preview

Biology AS/A Level OCR > 3.1 - Exchange Surfaces and Breathing > Flashcards

Flashcards in 3.1 - Exchange Surfaces and Breathing Deck (38):

What four things need to be interchanged between an organism and its environment?

Respiratory gases (O2 and CO2)
Nutrients (glucose, fatty acids, amino acids, vitamins and minerals)
Waste products (urea and CO2)


In what two ways can exchange occur?

Passively (no energy required) - diffusion and osmosis
Actively (energy required) - active transport


In what way are small organisms able to exchange efficiently?

Large surface area to volume ratio. Surface area is large enough compared to their volume.


How are organisms adapted to exchange if diffusion is the only transport method?

Flat shape so that no cell is ever far from the surface. Specialised exchange surfaces with large surface areas to increase SA:V ratio.


What are the features of a specialised exchange surface?

Large surface area
Short diffusion distance
Steep concentration gradient maintained


Define simple diffusion.

The net movement of molecules from an area of high concentration to an area of low concentration.


What is the equation for Fick's law?

Rate of diffusion = (surface area x concentration gradient) divided by diffusion distance


Describe the changes when you inspire (breathe in).

External intercostal muscles contract, internal intercostal muscles relax.
Ribs move up and out.
Diaphragm contracts (flattens).
Volume of the thorax increases.
Air pressure in the lungs decreases.


Describe the changes when you expire (breathe out).

External intercostal muscles relax, internal intercostal muscles contract.
Ribs move down and in.
Diaphragm relaxes (domed).
Volume of the thorax decreases.
Air pressure in the lungs increases.


Describe the structure and function of the trachea.

Flexible airway made of rings of cartilage.
Cartilage stops collapsing when air pressure changes.
Walls made up of ciliated epithelia and goblet cells.
Goblet cells produce mucus that traps dirt particles and bacteria from air breathed in.
Cilia move dirty mucus up to throat where it passes down oesophagus into stomach.


Describe the structure and function of the bronchi.

Two divisions of the trachea, each leading to one lung.
Similar function to the trachea (mucus moved up).


Describe the structure and function of the bronchioles.

Branching subdivisions of the bronchi, muscle walls lined with epithelial cells.
Muscle allows for constriction to control air flow in and out of the alveoli.


Describe the structure and function of the alveoli.

Minute air sacs at the end of bronchioles, contain elastic fibres and are lined with epithelial cells.
Elastic fibres allow for stretching and recoil when breathing in and out.


Why is diffusion from alveoli to blood rapid?

Walls of alveoli and capillaries are very thin, and red blood cells are squeezed flat against capillary walls - short diffusion pathway.


What are the causes, effects and symptoms of asthma?

Smooth muscle walls of bronchi/bronchioles contract and secrete more mucus.
Constriction and inflammation decreases the diameter of the airways.
Air flow in and out reduced, reducing the amount of oxygen to the alveoli.
Lower concentration gradient so lower rate of diffusion.


What is the function of the squamous epithelium?

Provides short diffusion distance.


What is the function of the ciliated epithelium?

Cilia waft mucus along airway.


What is the function of the glandular tissue?

Produces mucus.


What is the function of the cartilage?

Supports the airway.


What is the function of the smooth muscle?

Constricts the airway.


What is the function of the elastic tissue?

Recoils to dilate airways or to help expel air from the alveoli.


What is the function of the blood?

Transports gases.


What is the function of the nervous tissue?

Carries messages to coordinate action.


What is the function of the connective tissue?

Holds other tissues together.


What machine is used to measure the air into and out of the lungs?

A spirometer.


What does tidal volume mean?

Volume of air inhaled or exhaled in one breath during normal breathing.


What does vital capacity mean?

The maximum volume of air that can be moved by the lungs in one breath.


What does residual volume mean?

Volume of air that remains in the lungs even after forced expiration.


What does total lung capacity mean?

Vital capacity + residual volume.


State the equation for calculating minute ventilation.

Minute ventilation = tidal volume x ventilation rate


How do you calculate oxygen uptake on a spirometer trace?

Exhaled CO2 is absorbed by the soda lime in the spirometer, so the volume of air decreases.
Measure the gradient of the decrease to calculate rate of oxygen uptake.


How do fish ensure a one-way flow of water over their gills?

Mouth opens - opercular valves closed.
Floor of the mouth moves downwards increasing the volume and decreasing the pressure and so water moves into the buccal cavity.
Mouth closes - floor is raised again, decreasing the volume. Opercular valves open to reduce pressure in the opercular cavity, helping water to flow through the gills.


Describe the structure of the gills.

Gills are located behind the head.
Gills are made up of gill filaments, these are stacked up in a pile.
Gill lamellae are at right angles to the gill filaments.


How are the gills adapted for efficient gas exchange?

Gill filaments and lamellae are very thin - providing a short diffusion distance.
Many gill filaments and lamellae provide a large surface area.
Countercurrent exchange system maintains a concentration gradient.


Describe how countercurrent exchange works.

Water and blood flow in opposite directions along the whole length of the gill.
Water is always next to blood with a lower concentration.
In this way the concentration gradient is maintained and hence a fast rate of diffusion.


Describe how oxygen reaches the muscle of the wings in an insect.

Air enters through spiracle.
Respiring cells have a low concentration of O2.
Passes along the tracheae/tracheole along a concentration gradient.
Gases diffuse into tracheole fluid and then directly into the muscle cells.
CO2 moves in the opposite direction (from cells to the atmosphere) along its concentration gradient.
This is a passive process.


How do tracheoles increase the rate of diffusion?

There is a short diffusion pathway between the tracheoles and the tissues.
Extensive network provides a large surface area.


How can insects respond to a high oxygen demand?

Tracheal fluid is withdrawn, increasing the surface area for exchange.
Changing the volume of the thorax and/or the abdomen which forces movements of air in and out of the tracheae along a pressure gradient.