Topic 1: Lifestyle and risk

• where do most cells get energy from?

  aerobic respiration
• what are the raw materials for aerobic respiration?

  glucose and oxygen
• why can single cell organisms use diffusion to exchange substances?

  in single-celled organisms, these materials can diffuse directly into the cell across the cell membrane. This is as the materials diffuse across a very short distance and therefore the rate of diffusion is faster.
• why are multi-cellular organisms unable to use diffusion to exchange substances?

  multi-cellular organisms have a larger sa:v. therefore diffusion across the outer membrane would be too slow because of the large distance the substances would have to travel to supply ALL the cells.
• what do multi-cellular organisms rely on to exchange substances? using what process?

  a mass transport system to move substances efficiently over long distances by mass flow
• what is mass flow?

  the bulk movement of substances from one area to another due to differences in pressure.
• mass transport systems are used...


  to carry raw materials from specialised exchange organs (e.g. lungs and digestive system) to the body cells and to remove metabollic waste e.g. carbon dioxide
• what is the mass transport system in mammals?

  the circulatory system
• how is the circulatory system a mass transport system?

  >> the flowing fluid (blood) and all the particles carried in it are transported in one direction due to a difference in pressure in a process known as mass flow

  >> the heart is used to pump the blood around the body so it is able to reach body cells
• single celled organisms do not have...

  a bloodstream; they rely on diffusion to exchange substances
• what are the two types of circulatory system?

  open and closed
• what is an open circulatory system?

  a simpleheart pumps blood outinto cavities surrounding the animal's organs. substances can diffuse between the blood and cells. when the heart muscle relaxes, blood is drawnfrom the cavity back into the heartthrough small, valved openings along its length.

  
• what is a closed circulatory system?

  the blood is enclosed within tubes, known as blood vessels. this generates higher blood pressure as the blood is forces along fairly narrow channels instead of flowing into large cavities. this means blood travels faster and so the blood system is more efficient at delivering substances around the body.

  
• what are the two types of closed circulatory system?


  single & double
• what is a single circulatory system?

  Blood flows through the heart once for each complete circuit of the body.
• explain the circulatory system of a fish:

  a fish has a single circulatory system.

  the heart pumps deoxygenated blood to the gills where gaseous exchange occurs. carbon dioxide diffuses from the blood to the water and oxygen from the water diffuses into the gills. the blood then leaves the gills and flows round the rest of the body before returning to the heart

  
• what is a double circulatory system?

  blood flows through the heart twice for each complete circuit of the body
• explain the circulatory system of a human (basic):

  the circulatory system of a human is a double circuit.

  in the first circuit, the heart pumps deoxygenated blood to the lungs to take in oxygen. the oxygenated blood then flows back to the heart. in the second circuit, the heart pumps oxygenated blood around all the organs of the body to deliver oxygen to the body cells. deoxygenated blood returns back to the heart.

  
• what are the advantages of having a double circulatory system?

  - prevents mixing of oxygenated and deoxygenated blood

  - enables high pressure so is faster

  >> therefore oxygen supply is highly efficient
• describe the flow of blood through the heart:

  • superior / inferior vena cava

  • right atrium

  • atrioventricular / tricuspid valve

  • right ventricle

  • semi lunar valve

  • pulmonary artery

  • lungs

  • pulmonary vein

  • left atrium

  • atrioventricular / bicuspid valve

  • left ventricle

  • semi lunar valve

  • aorta

  • body
• state the four vessels that enter and exit the heart

  • aorta

  • vena cava

  • pulmonary artery

  • pulmonary vein
• state the four chambers of the heart

  • Left atria

  • Left ventricle

  • Right Atria

  • Right ventricle
• what is special about the pulmonary artery?

  it is the only artery that carries deoxygenated blood
• what are the differences between the atria and ventricles?

  the atria are receivers of blood from the body/lungs whereas the ventricles receive blood from the atria.

  the ventricles muscle is thicker than the atria. this is because the ventricles push out blood at a higher pressure in order to reach all parts of the body. the atria, on the other hand. only need to generate enough pressure to open the valves which is ashorter distance
• what are the differences between the right and left sides of the heart?

  the left side is thicker as it needs to pump oxygenated blood all around the body and therefore must be strong enough to withstand the pressure. the left side, on the other hand, only needs to pump deoxygenated blood to the lungs in order to intake oxygen. blood towards the lungs should not be pumped at a high pressure as it may burst the lungs and less blood will become oxygenated
• what are the atrioventricular valves for?

  the AV valves link the atria to the ventricles and stop the backflow of bloodto the atriawhen theventricles contract. cords attach the AV valves to the ventricles to stop them beingforced upinto the atria when the ventricles contract
• explain the importance of the heart and circulation to a large mammal:

  - as a large mammal has a small SA:V, it cannot rely on diffusion to supply the entire volume of its cells, therefore it has its own transport system

  - the heart has to pump blood along wayaround the body throughmass flowtherefore the blood must bepumped at a high pressure

  - to do this, blood vessels are needed to contain the blood so it can be pumped at a high pressure, thus they have a closed double circulatory system

  - circulation is needed in a large mammal to provide oxygen and glucose for respiration as larger mammals have high metabollic rates

  - the circulatory system helps theregulation of body temperature
• what type of molecule is water?

  polar molecule
• define "polar molecule"


  a molecule with an uneven distribution of electrical charge
• how is water polar?

  - a molecule of water consists of one atom of oxygen joined to two atoms of hydrogen by shared electrons.

  - because the shared hydrogen electrons, which are negative, are pulled towards the oxygen atom, the other side of each hydrogen atom is left with a slight positive charge

  - the unshared negative electrons on the oxygen atom give it a slight negative charge

  - this makes water a dipolar molecule- it has a partial negative charge on one side and a partial positive charge on the other.

  
• what is responsible for the properties of water?

  - the slightly negatively charged oxygen atoms attract the slightly positively charged hydrogen atoms of other water molecules.

  - this attraction is calledhydrogen bondingwhich gives water its useful properties.

  
• name some of the properties of water:

  - liquid at room temperature

  - cohesive

  - good solvent

  - high specific heat capacity

  - high boiling point
• why is water liquid at room temperature?

  the slightly positive charged end of a water molecule is attracted to the negative ends of surrounding water molecules. hydrogen bonding holds the water molecules together. these bonds require alot of energy and heat to break them.
• why is the fact that water is liquid at room temperature important to blood?

  this means the blood will not change state
• why is water a good solvent?

  since water is polar, it is able to dissolve ionic substances. the slightly positive end of a water molecule will be attracted to the negative ion and the slightly negative end of a water molecule will be attracted to the positive ion. this means the ions become totally surrounded by water molecules (hydrated.)

  
• why is water being a good solvent an important role in the blood?

  water's dipole nature means ions can dissolve in the water in blood and then be transported around the body
• polar molecules dissolve...


  polar molecules easily and ionic compounds
• polar molecules which dissolve easily in water are said to be...

  hydrophillic
• non-polar (e.g. fats) molecules do not...

  dissolve in water
• non-polar molecules are said to be...

  hydrophobic