Paper 1 content

• Journey of blood around the body

  Body tissues ➔ vena cava ➔ right atrium ➔ right ventricle ➔ pulmonary artery ➔ lungs ➔ pulmonary vein ➔ left atrium ➔ left ventricle ➔ aorta ➔ body tissues
• The movement of blood between the ventricles and atria

  1. The walls of the atria contract, pushing blood into the relaxed ventricles.
  2. The walls of the ventricles contract, pushing blood out of the heart. At the same time, more blood will enter the now-relaxed atria.
  3. The cycle repeats.
• The coronary arteries supply the heart muscle with oxygen and nutrients.
• Capillaries carry blood through the body tissues, allowing oxygen, nutrients, and waste products, to be exchanged between tissues and the blood.
• Structure and function of arteries

  1. Arteries are large and carry blood at a very high pressure.
  2. Artery walls have a thick middle layer, containing both muscle and elastic tissue.
  3. The muscle tissue provides strength, and allows the arteries to direct blood flow.
  4. The elastic tissue allows the arteries to stretch and recoil.
  5. Compared to their walls, arteries have a relatively narrow lumen, which keeps the blood pressure high.
• Structure and function of capillaries:

  Capillaries are the smallest of the three blood vessels.

  • The role of capillaries is to exchange nutrients and waste products with the tissues.
  • Capillary walls are permeable, meaning substances are able to move through them.
  • Their walls are also only one cell thick which means a short distance for diffusion.
  • Capillaries carry blood at a low pressure and have a lower rate of flow than arteries.
• Structure and function of veins:

  1. The role of veins is to carry blood from the body (or lungs) back to the heart.
  2. Veins are a similar size to arteries, but they have relatively thin walls and a relatively wide lumen
  3. This is because they carry blood at a much lower pressure.
  4. Veins also contain valves to prevent the blood from flowing backwards.
• rate= volume/time

  
  

  is measured in ml/min
• If you consider all the blood vessels inside of a human body, which type of blood vessel accounts for the majority of the cross-sectional area?

  Capillaries
• How are red blood cells adapted for their function?

  They have a biconcave shape to increase their surface area

  They have no nucleus to fit in more haemoglobin 
• How do antibodies help defend against pathogens? 

  They bind to pathogens and help immune cells destroy them
• Give two reasons why it is so important that our blood clots when we are cut.

  Blood clotting is important because it prevents us from losing blood from the blood vessels, and it also prevents pathogens from entering the blood, which could cause infection. 
• Do platelets have a nucleus? 

  No

  Platelets are only fragments of cells, so they don't have a nucleus like complete cells do. 
• Coronary heart disease 

  1. Coronary arteries branch out of the aorta and supply oxygenated blood to the heart muscle.
  2. In coronary heart disease, layers of fatty material build up inside the coronary arteries, causing the lumen to get narrower.
  3. This reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen and nutrients for the heart muscle.
  4. This can cause chest pain as the heart muscle is starved of oxygen, and in severe cases, can cause a heart attack. 
• How does a stent help treat coronary heart disease?

  It expands within the artery to widen the lumen 
• What are the benefits of stents when treating coronary artery disease?

  The stents can last a long time 

  The stents have an almost immediate effect

  Surgery is quick
• How do statins help treat coronary heart disease?

  They decrease the amount of LDL cholesterol in the blood 

  They increase the amount of HDL cholesterol in the blood 
• What are the disadvantages of statins when treating coronary artery disease?

  It can take months to see the positive effects 

  The pills have to be taken every day

  They have side effects such as kidney failure and headaches
• What are two problems that may be caused by faulty heart valves?

  Not enough blood can pass though the valve

  Blood can pass backwards through the valve
• Faulty heart valves can be replaced. Biological valves come from other animals such as pigs or cows. Meanwhile mechanical valves are man-made, often from metal.  
• Which of the following are treatments for heart failure?

  Replacement with artificial heart

  Replacement with biological heart 
• What are two characteristics of malignant tumours?

  They can lead to secondary tumours

  The tumour cells can spread around the body in the blood

  Is classified as 'cancer'
• Benign tumours:

  They don't invade neighbouring tissues

  They are usually contained within a membrane
• The upper epidermis is transparent so that light can pass through it. This means that as much light as possible can reach the palisade mesophyll cells below, and be used in photosynthesis. 
• What is meristem tissue and where is it found? 

  Meristem tissue is made up of plant stems cells. It's found in the growing parts of the plant such as the tips of shoots and roots. 
• Which substance are xylem cells reinforced with to make them stronger? 

  Lignin
• What is transpiration?

  The evaporation of water from the leaves
• Why does water loss slow down if a plant is put into a plastic bag?

  The humidity of the air in the bag increases at the plant loses water. This means there is a lower concentration gradient between the inside and outside of the leaves, reducing the rate of water loss. 
• rate= no. of breaths/time

  is measured in breaths/min
• One way to increase the rate of chemical reactions is to increase the temperature, this is partly why our bodies are a relatively warm 37°C.

  Give two reasons why we can't just make our cells even warmer to increase the rate of reactions?  

  Heating our cells more would require a lot of energy

  Higher temperatures could damage our cells

  Higher temperatures would also speed up non-useful reactions 
• Explain how increasing the temperature can cause an enzyme to denature

  High temperatures start to break the bonds holding the enzyme together 

  This causes the enzyme and it's active site to change shape

  This means the enzymes active site will no longer be complementary to the substrate 
• Explain why it is important that we get enough iron in our diet. 

  
  

  Iron is an important component of haemoglobin 

  Haemoglobin is the protein in red blood cells that allows them to transport oxygen around the body

  A lack of iron (and hence haemoglobin), can lead to anaemia, where we can't transport enough oxygen to our tissues. 
• Starch is broken down by the enzyme amylase into maltose molecules. These are then broken down further by maltase into glucose. 
• How does bile help with the digestion of lipids?

  It emulsifies the lipids which increases the surface area for lipase enzymes to break them down
• Villi are finger-like protrusions of the small intestine that are responsible for absorbing nutrients into the body.

  Give three ways in which villi are adapted for this role.

  There are many villi, which gives them a large total surface area over which to absorb nutrients

  They have a single layer of cells on their surface, which means nutrients only have to diffuse a short distance.

  They have a good blood supply which maintains a strong concentration gradient between the lumen and the blood 

  The cells lining the villi have microvilli on their surface, which further increases the surface area