Topic 3 Gas exchange, digestion and mass transport

What is the trend in (Surface are to volume ratio) as an organism gets larger

It decreases due to the decrease in SA

Why do small organisms have a higher metabolic rate?

Because they have a very large surface area for the exchange of substances and a smaller diffusion distance from the outside. And do not have a specialised transport system

Why do large organisms have a low metabolic rate compared to small organisms

They have a small surface area to volume ratio,

therefore less surface area available for gas exchange.

Therefore they need a specialised transport system

What adaptations do large organisms have to increase the SA:Vol ratio?

Villi and microvilli in digestion absorption

Alveoli and bronchi-gas exchange

Spiracles and tracheoles- gas exchange

Gill filaments and lamellae- gas exchange

Thin and wide leaves-gas exchange

Definition of ventilation

The movement of air in and out of the lungs

Definition of respiration

The chemical reaction to release energy in the form of ATP

Definition of gaseous exchange

Diffusion of oxygen from the air into the alveoli into the blood

And carbon dioxide from the blood into the alveoli into the air

Describe what occurs for inspiration to occur in ventilation

External intercostal muscles- contract pulling the ribs up and out

Internal intercostal muscles- relax

Diaphragm- contracts and moves down

Air pressure in the lungs- decreases so air can move in

Lung volume- increases

What occurs for expiration to occur in ventilation?

External intercostal muscles-relax

Internal intercostal muscles- contract to pull the ribs down and in

Diaphragm- relaxes and moves up and expands

Air pressure- increases above the atmospheric pressure, so air can move out

Lung volume- decreases

What is the definition and equation for pulmonary ventilation?

Describe how Oxygen diffuses across the alveolar epithelium

1. Oxygen diffuses out of the alveolus lining (one cell thick)

2. Then across the lining of the blood capillary (one cell thick)

3. Into the blood

4. Where it can bind with haemaglobin to form oxyhaemaglobin

5. Oxyhaemaglobin is carried away

6. Maintaining the concentration of oxygen

Describe three features of the lungs that make it gas exchange efficient

Large SA-Alveoli are air sacs

Short diffusion path-the alveolar epithelium and capillary wall is one cell thick

Moist lining-So gases can dissolve and then diffuse

Constant supply of blood- maintain concentration gradient

Constant supply of air-maintain oxygen concentration gradient

Red blood cells are pushed against the capillary wall- short diffusion distance

Describe three features of fish gills for efficient gas exchange

Movement of water over the gills- maintain the Counter current flow

Large surface area- gills are made up of gill filament stacks. Gill filaments are covered in gill lamellae

Short diffusion path- due to capillary network and thin gill lamellae

Describe how the current counter flow is set up

The flow of water above the gills is in the opposite flow of blood in the capillaries

The ensures that the diffusion gradient is maintained across the length of the gill lamellae

And equilibrium is not reached

How are insects adapted to reduce water loss?

They have an exoskeleton for protection and a lipid layer to prevent water loss

How is the tracheal system of an insect adapted for gas exchange?

Gas exchange in insects involves the tracheal system which consists of trachea, tracheoles and spiracles

Spiracles-openings along the abdomen where oxygen and co2 enter and leave.

Trachea- network of tubes, the have chitin rings to give structural support so it won’t collapse.

Tracheoles-thin tubules which deliver oxygen directly to respiring tissues

Tracheal fluid- allows gases to dissolve and then diffuse into cells

Explain why the trachea has chitin rings

The chitin rings provide the trachea structural support, stopping it from collapsing

Describe the movement of gases/ventilation in the tracheal system WHEN THE INSECT IS AT REST

At rest, the cells respire they use up oxygen and produce more co2 creating a Steep conc. Gradient

From atmosphere to tracheoles.

Describe the movement of gases/ventilation in the tracheal system WHEN THE INSECT IS ACTIVE

During periods of high activity (movement or flying) mass transport occurs.

The insects abdominal muscles contract and relax which actively moves air in and out of the tracheal system. Maintaining the diffusion gradient of (O2 and CO2)

Describe the movement of gases/ventilation in the tracheal system WHEN THE INSECT IS VERY ACTIVE

When the insect is very active(flying) it RESPIRES ANAEROBICALLY and LACTATE is produced. Which lowers the water potential of muscle cells. This causes water at the ends if the tracheoles to move into cells by osmosis. Reducing fluid volume in the tracheoles, so gases diffuse faster through air than liquid. So faster diffusion to tissues

What adaptations do insects have to limit water loss

1. Waterproof exoskeleton- reduces evaporation

2. Spiracles- which can open and close to reduce water loss

3. Spiracles have hairs around them to trap HUMID air, reducing the water potential gradient reducing evaporation

Label the structure of the leaf

Describe gas exchange in plants

Photosynthesis occurs in the chloroplasts in the palisade mesophyll

So CO2 is used up and O2 is produced-creating a conc. gradient

So oxygen travels through air spaces in the spongy mesophyll and diffuse out of the stomata.

And CO2 diffuses in through the stomata

Name one adaptations of plants that reduce water loss

Stomata close at night when photosynthesis does not occur

What are Xerophytic plants?

Plants adapted to living in environments where water is scarce

What adaptations do Xerophytic plants have?

Curled leaves- trap moisture to increase the humidity-reduce water evaporation

Sunken stomatas- increase humidity

Thicker waxy cuticle- reduce evaporation

Longer root network- reach more water in the ground

Definition of digestion

Large biological molecules are hydrolysed into smaller molecules that can be absorbed across cell membranes

Where is amylase produced?

Salivary glands

Pancreas

Describe how carbohydrates are digested by the body

Carbohydrates are digested by Amylase in the Mouth, Duodenum and Ileum

Sucrose is hydrolysed by Sucrase into fructose and glucose

Lactose is hydrolysed by lactase into glucose and galactose

Polysaccharides are broken down by amylase and hydrolysed into maltose

What are the word equations for the the hydrolysis of maltose, sucrose and lactose?

Describe the digestion path of proteins

Stomach

duodenum

ileum-Membrane bound dipeptidases

What three enzymes are proteins hydrolysed by?

Endopeptidases-hydrolyses peptide bonds between amino acids in the MIDDLE of the polymer chain

Exopeptidases-Hydrolyse peptide bonds between between amino acids at the END of the polymer chain

Membrane bound Dipeptidases- hydrolyse peptide bonds in Dipeptides

Where are Bile salts produced and what are their function and importance

Produced in the liver.

Emulsify lipids into tiny droplets called Micelles.

This increases the surface area for Lipase to act

Where is lipase produced and what is its function?

Lipase is produced in the pancreas

Hydrolyses ester bonds in triglycerides to form monoglycerides

Where are lipids be digested in?

Duodenum

Then ileum

What are the products of lipase?

Fatty acids

Glycerol

And monoglycerides

What are the adaptations of the ileum to maximise absorption?

What are micelles?

Water soluble vesicles

Which contain fatty acids, glycerol, monoglycerides

Combined with bile salts

How do Micelles help with lipid absorption

Micelles are water soluble vesicles

That contain fatty acids, glycerol, monoglycerides with bile salts.

It allows the micelles to transport them from the lumen of the intestine and release them to the cell surface membrane of the epithelial cells in the ileum.

It helps to maintain the high conc. gradient of fatty acids near the epithelial cells

So fatty acids are absorbed into the epithelial cells by simple diffusion, down the conc. gradient

Describe what happens to the fatty acids, glycerol and monoglycerides once they are absorbed by the epithelial cells

Inside the cells, they reform into triglycerides in the Golgi apparatus

And packaged into vesicles, allowing them to move to the cell membrane for further transport

In the lymphatic system

Describe the loading and unloading of oxygen in terms of partial pressures

Oxygen is loaded in areas if high partial pressures

And unloaded in areas of low partial pressures

Oxygen dissociation curve

Describe the structure of haemogkobin and how it relates to its function

Haemaglobin is a quarternary protein with 4 polypeptide chains and 4 haem groups which each have a Fe2+ ion. So when one oxygen molecule binds, it changes the shape of the haemogkobin. Making it easier for more oxygen to bind.

So oxygen has a higher affinity to oxygen in areas of high partial pressure

Why is it more unlikely for an oxygen to bind with the 4th haem group?

Because if three of the binding sites are already saturated, there is a ¼ chance of the 4th oxygen to bind.

What is The Bohr effect? And why is it important?

When CO2 dissolves and forms carbonic acid, DECREASING the pH. Changing the shape of the haemoglobin,

decreasing the affinity of oxygen at respiring tissues

Allowing haemoglobin to deliver oxygen at respiring cells

Which it’s important So aerobic respiration to continue

Why do babies in the mothers womb have myoglobin instead of haemoglobin

Myoglobin has a higher affinity to oxygen than haemoglobin. This is because it needs to be able take oxygen from the mother’s red blood cells through the placenta and umbilical cord. Because it is unable to breath.

Why do animals that have a high metabolism (e,g cheetahs) have red bloddcells in with a lower affinity than haemoglobin?

Because they need to be able to dissociate oxygen more readily to respiring tissues.

Why is the human circulatory described as being a closed double circulatory system?

Closed- blood is kept in blood vessels

Double circulatory system- the blood passes through the heart TWICE.

One circuit delivering blood to the lungs

One circuit delivering blood to the rest of the body,

Why is there lower blood pressure in the lungs?

To prevent damage to the capillaries in the alveoli

Reduce the speed of blood flow, to enable time for gas exchange

Why is there a high blood pressure when blood is pumped out of the heart?

To ensure blood reaches all respiring cells in the body

Label the blood vessels

What is the function of the arteries?

Carry blood away from the heart to arterioles

What is the function of the capillaries?

Site of gas exchange

and connect articles to veins

What is the function of the arterioles

Smaller tubules that Connect the artsy to the capillaries

What is the function of the veins?

Carry blood back from the capillary to the heart

Describe the adaptions of the Aorta and how it relates to its function

The largest artery

Carries blood at very high pressure from the heart

Lots of elastic tissue for stretch and recoil in contraction-To maintain blood flow and pressure

Thick muscular wall-to withstand high pressure.

Smooth endothelium-to reduce friction

Describe the adaptations of the Arteries and how it relates to its function

Thick muscular and elastic walls and narrow lumen

Helping them maintain high pressure to direct blood efficiently around the body

Arterioles

Branch from arteries

Regulates blood flow

Thick muscular wall

Which can contract to narrow the lumen. Reducing the blood flowing to capillaries

Describe the adaptations of the Vein and how it relates to its function

Carry blood back to the heart under low pressure

Have thinner walls (less muscle and elastic tissue) and a wider lumen to reduce resistance To blood flow

It has valves to prevent the back flow of blood

Compare the differences between the arteries and veins

How are capillaries adapted for efficient gas exchange?

The lumen is one cell thick- pushes red blood cells against the capillary wall to reduce diffusion distance

Capillary walls also one cell thick

How are capillary networks adapted for efficient gas exchange?

Large surface area for exchange

Highly branched- cells are close to capillaries- reduces diffusion distance

Slow blood flow- increase time available for exchange

What is tissue fluid?

Fluid containing water, glucose, amino acids, fatty acids, ions and oxygen

Bathes tissues

How is tissue fluid formed? (Tissue fluid formation)

Capillaries have small gaps in the walls so liquids and small molecules are forced out

Due to its small lumen there is high hydrostatic pressure. Causing water, amino acids, fatty acids, ions and oxygen to be FILTERED out

This is ultrafiltration

How is water from tissue fluid absorbed by the capillaries?

The capillary will only contain red blood cells, platelets and proteins.

Low water potential at the venule end of the capillary, so water can be re absorbed by osmosis

Describe the structure of the cardiac muscle

It is myogenic it can contract and relax by itself without any stimulation

It never fatigues as long as oxygen is supplied

Label the structure of the heart

What are the three stagesin the cardiac cycle

Atrial systole

Ventricular systole

Diastole

Describe what happens in atrial systole

Blood fills atria

Muscle walls in Atria contracts

Pressure in atria increases

Causing AV valves to open

Describe what happens in ventricular systole

Ventricles contract

Pressure increases in ventricles

AV valves close

SL valves open

Blood enters SL valves to artery

Describe what happens in Diastole

Atrial and ventricular Chambers relax

Pressure decreases

SL close

Blood fills the atria again through the vena cava and the pulmonary vein

What is the formula for cardiac output?

Cardiac output= heart rate x stroke volume

Heart rate is (beats per minute^-1 )

Stroke volume is the volume of blood that leaves the heart per beat in (dm³)

What are the 4 factors that affect transpiration

Light- causes stomata to open-more evaporation

Temperature- more KE,p for water molecules and therefore more evaporation

Humidity- air is more saturated with water. Higher water potential outside the lead. Reduces the water potential gradient

Wind- will blow away humid air, decreases the water potential outside the leaf. Maintains the water potential gradient.

Describe the structure of water that is important in cohesion tension theory

Water can form hydrogen bonds between other water molecules, so water can move up the xylem as a continuous column of water,

The adhesion of water allows water to adhere to the xylem walls

How does a narrower xylem lumen affect water transport?

More surface area for the water column to adhere to. So water can move up faster

Describe the movement of water up the xylem

Water evaporates from the surface of mesophyll cells into air spaces, then diffuse out of the stomata through transpiration

As water is evaporates it decreases the water potential in the cells. So water is drawn up from neighbouring cells. Creating a pull on the water column in xylem vessels. Creating tension in the xylem

The due to the hydrogen binding in water molecules, it causes them to adhere together and move as one continuous column

Describe the structure of the phloem

It has companion cells that have lots of mitochondria to provide ATP

Sieve tube elements- living cells that don’t have a nucleus, and few organelles

Describe the mass flow hypothesis in the phloem from source to sink

Sucrose lowers the water potential of the source cells (photosynthesising) . This causes water to enter by osmosis

Increasing the hydrostatic pressure in the cells

The (respiring)cells us up sucrose, therefore devs reading the waterpotential causing water to leave sink cells by osmosis

Decreasing the hydrostatic pressure in sink cells

Describe the 1. Step of translocation

Sucrose is actively tranported from photosynthesising cells into sieve tube elements

using ATP to move it against the conc. gradient

from the companion cells

Describe the 2. part of translocation

The sucrose lowers the water potential in the sieve tube elements

So water enters by osmosis from the xylem vessel

Increasing hydrostatic pressure at the source end

At the sink end sucrose is used up in respiration

Increasing water potential

So water moves out of the phloem by osmosis

Lowering the pressure

Describe the 3. Part of translocation

The resulting pressure gradient from source to sink

Causes mass flow of phloem sap

Through the sieve tube

Investigating translocation with experiments

Tracers- radioactive labelling carbon and then taking thin slices of the stem and detecting for radioactive carbon

Ringing experiment-removing a ring of tree bark and phloem is removed.

Resulting in the truck swelling of liquid containing sugars.

Showing that with the phloem removed sugars cannot be transported

Proving that the phloem transports sugars.