BIOLOGY- AS Level- 3- exchange and transport

Why do organisms need exchange?

Organisms must take in food, oxygen and water, and other essential substances, from the environment as well as the need to remove waste substances.

What is the difference between exchange in multi and single cellular organisms?

In single-celled organisms, substances diffuse directly across the cell membrane while in multi-celled organisms they need exchange surfaces to get the essential nutrients they need

Why do multi-celled organisms need exchange surfaces?

• Cells are not in direct contact with the external environment.

• Diffusion distances between cells and their environment are large.

• Larger organisms have higher metabolic rates, so they need more oxygen and glucose.

What are features of specialised exchange surfaces?

• A large surface area - This provides a larger area across which substances can be exchanged

• Thin walls - These minimise the diffusion distance

• An extensive blood supply and/or ventilation - This maintains steep concentration gradients

• Being surrounded by selectively permeable plasma membranes - This controls what substances are exchanged

What are 3 examples of specialised cells?

Root hair cells- large surface area

Alveoli- thin layer

Gills- good blood supply/ ventalation to maintain a good gradient

What is the order in which air passes through the human respiratory system?

Nasal passage/ Mouth cavity, Trachea, Bronchi, Bronchioles, Alveoli

What is the ciliated epithelium?

A layer of cells which have cilia

What is the function of cilia on the ciliated epithelium?

These waft the mucus, containing dust and micro organisms upward to the mouth so it can be swallowed and destroyed by the stomach acid

Where are goblet cells found?

In the ciliated epithelium

What are the function of goblet cells?

Cells that secrete mucus

What is the function of mucus?

To trap dust and microorganisms

What is the trachea?

A large tube that carries air from the throat down to the lungs

What are the adaptations of the trachea?

• Rings of cartilage- to keep the airway open

• Smooth muscle- which can contract or relax to constrict or dilate the airway and change airflow

• Elastic tissue- which contains elastic fibres with elastin that allows stretching and recoiling

• Lined with ciliated epithelial cells and goblet cells

What is the bronchi?

Two main branches extending from the trachea that carry air into each lung

What are the adaptations of the bronchi?

• Reinforced with cartilage- which keeps the airways open

• Smooth muscle- which can contract or relax to constrict or dilate the airway and change airflow

• Elastic tissue- which contains elastic fibres with elastin that allows stretching and recoiling

• Lined with ciliated epithelial cells and goblet cells

What are the bronchioles?

Smaller airways branching from the bronchi that carry air to the alveoli

What are the adaptations of the bronchioles?

• No cartilage- so they can change shape

• Smooth muscle- which can contract or relax to constrict or dilate the airway and change airflow

• Elastic tissue- which contains elastic fibres with elastin that allows stretching and recoiling

• Simple squamous epithelium (only larger bronchioles have a ciliated epithelium)

What are alveoli?

Tiny air sacs clustered at the ends of the bronchioles, they are folded to increase surface area

What is the structure of alveoli?

Alveoli are tiny air sacs which are clustered at the end of bronchioles, their walls are made of squamous epithelial cells and are surrounded by a network of capillaries so gases can be exchanged efficiently

How do alveoli carry out gas exchange?

1. Oxygen diffuses from the alveoli into the pulmonary capillaries where it binds to haemoglobin in red blood cells

2. Carbon dioxide dissociates from haemoglobin and diffuses from the blood into the alveoli

What are the the three pulmonary blood vessels involved in the circulation of the lungs and hat are their functions?

• The pulmonary artery - This delivers deoxygenated blood from heart to pulmonary capillaries.

• The pulmonary vein - This delivers oxygenated blood from capillaries to heart.

• The pulmonary capillaries - These are the site of gas exchange between blood and alveoli.

What are the adaptations of the pulmonary capillaries for gas exchange?

1. Thin walls (one endothelial cell thick) - This maintains a short diffusion distance

2. Red blood cells pressed against capillary walls - This reduces diffusion distance

3. Large surface area - This increases diffusion speed

4. Movement of blood - This maintains steep diffusion gradient

5. Slow blood movement - This allows more time for diffusion

What is ventilation?

The constant movement of air into and out of the lungs. It consists of inspiration (breathing in) and expiration (breathing out).

What is the structure of the ribcage?

The ribcage is made up of bones called ribs which enclose the thorax and the thoracic cavity, where the lungs are located. There are three different muscles attached to the ribcage which control ventilation- the diaphragm and the internal and external intercostal muscles.

what are the three muscles which act on the ribcage?

• The diaphragm - This is a sheet of muscle that moves the ribcage up and out when it contracts

• The external intercostal muscles - These are found between the ribs and pull the ribcage up and out when they contract

• The internal intercostal muscles - These are found between the ribs but pull the ribcage down and in when they contract

How do the internal and external intercostal muscles work during respiration?

They have opposite effects on the ribcage.

The external muscles expand the ribcage during inspiration, while the internal muscles shrink it during expiration.

What is inspiration?

It is breathing in and it is an active process requiring energy for muscle contraction

What happens during inspiration?

1. The external intercostal muscles contract while the internal intercostal muscles relax, moving the ribcage up and out.

2. The volume of the thoracic cavity increases.

3. The diaphragm contracts and flattens, further increasing the volume of the thoracic cavity.

4. The lung pressure decreases below atmospheric pressure.

5. Air flows into the lungs down the pressure gradient.

What is expiration?

It is breathing out and it is at rest is a passive process so it does not require energy

What is the process of expiration?

1. The external intercostal muscles relax, moving the ribcage down and in.

2. The volume of the thoracic cavity decreases.

3. The diaphragm relaxes and unflattens, further decreasing the volume of the thoracic cavity.

4. The lung pressure increases above atmospheric pressure.

5. Air is forced out of the lungs down the pressure gradient.

What is the tool used to measure ventilation?

Spirometer

What can a spirometer measure?

• Breathing rate

• Title volume

• Vital capacity

• Inspiratory reserve volume

• Expiratory reserve volume

• Residual volume

• Total lung capacity

How to measure breathing rate?

Counting the number of peaks per minute on a spirometer

What is tidal volume?

The volume of air breathes in or out in an average breath during rest measured from the height of each peak at rest.

What is vital capacity?

The maximum volume of air that can be inhaled or exhaled in one deep breath

What is the inspiratory reserve volume?

The max volume of air that can be inhaled above a normal inhalation.

What is the expiratory reserve volume?

The max volume of air that can be exhaled above a normal exhalation

What is the residual volume?

The volume of air that remains in the lungs after the longest possible exhalation

What is the total lung capacity?

The vital capacity added to the residue volume

Why do insects need gas exchange?

• To deliver oxygen to cells

• To remove CO2 from cell

What structures are in an insect gas exchange system?

• Tracheae

• Tracheoles

• Spiracles

What are tracheae and their adaptations?

Air filled tubes branching through the body

• Reinforce with spirals of chitin to prevent collapsing

• Multiple tracheae to increase surface area

What are tracheoles and their adaptations?

Find branches of tracheae that deliver gases to cells

• Penetrate directly into tissues which reduces gas diffusion

• Thin walls which reduces gas diffusion distance

• Highly branched which maximise the surface area

• Not reinforced with chitin which allows gas exchange to occur

• Tracheal fluid at the end of the tracheoles allows oxygen to dissolve to aid diffusion and reduce water loss

What are spiracles and their adaptations?

External openings of the tracheal system on the exoskeleton along the abdomen and thorax

• The open and close which allows control gas exchange within the atmosphere and minimise water loss

How does gas exchange work in insects?

• Air enters the tracheal system through open spiricals

• Air moves into larger tracheae and diffuses into smaller tracheoles

• Oxygen dissolves in water and tracheal fluid and diffuses down its concentration gradient from tracheoles into body cells

• Carbon dioxide diffusers down its concentration gradient out of the body cells and into tracheoles

• This carbon dioxide is carried back through the spiracles via the tracheoles and out of the body

What are the challenges of gas exchange in Bony fish?

• Water is denser and more viscous than air resulting in slower diffusion of oxygen

• Water has less oxygen than air

• Bony fish are very active so have high oxygen demands

Why is the structure of gills in bony fish?

• Covered by an a operculum flap

• Consist of stack filaments containing gill lamellae

• Surrounded by extensive blood vessels

Why are the adaptations of the gills and bony fish?

• The lamellae provide a large surface area

• The lamellae membranes are thin to minimise diffusion distance

• The girls have a rich blood supply to maintain steep diffusion gradient

• The counter current flow of blood and water creates an even steeper concentration gradient

• Overlapping filaments tips increases resistance, slowing water flow over gills and allowing more time for gas exchange

What is the system of countercurrent flow?

• Blood and water flow over the lamellae in opposite directions

• This means oxygen rich blood makes water that is at It’s most oxygen rich when it first moves across the gills this maximise diffusion of oxygen into blood

• Oxygen Poor blood returning from body tissues meet oxygen poor water still allowing diffusion of oxygen into the blood

• This maintains a steep concentration gradient

How does ventilation in bony fish work?

• When fish open their mouth, it increases the volume of the buccal cavity

• This increases the pressure which pulls water into the buccal cavity

• Water flows over the gills and the opperculum