The blood
Laura Armstrong & Joe Wolfensohn
Teachers
Recall Questions
This topic requires prior knowledge of basic cell structure and the differences between specialised cells.
What is the function of the nucleus in a cell?
It contains the genetic material and controls the activities of the cell.
What is a specialised cell?
A cell that has adapted features to perform a specific function.
Give one example of a specialised animal cell and describe how it is adapted
E.g., A sperm cell has a tail to help it swim towards the egg.
E.g., Ciliated epithelial cells have cilia to move the egg cell along the oviducts or to move mucus up the trachea.
Topic Explainer Video
Check out this @JoeDoesBiology video that explains the blood, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
Blood: A Specialised Tissue
Blood is a tissue made up of different components, each with a specific function. These components are suspended in a liquid called plasma.
Components of Blood:
|
Component |
Function |
|
Plasma |
Yellow liquid that transports dissolved substances such as; carbon dioxide, urea, hormones, and nutrients. |
|
Red blood cells |
Carry oxygen around the body using haemoglobin. |
|
White blood cells |
Defend the body against infection by destroying pathogens (e.g. by phagocytosis or producing antibodies). |
|
Platelets |
Help blood clot at the site of a wound to prevent bleeding and reduce chances of infection. |
Adaptations of Blood Cells
Red Blood Cells:
-
No nucleus - more space for more haemoglobin (so more oxygen can be transported).
-
Biconcave shape - increases surface area for faster oxygen diffusion.
-
Contain haemoglobin - binds with oxygen to form oxyhaemoglobin.
-
Flexible - to squeeze through narrow capillaries.
White Blood Cells:
-
Lymphocytes - can produce specific antibodies and antitoxins.
-
Phagocytes - can engulf and digest pathogens.
-
Have a large nucleus and a flexible shape.
Platelets:
-
Fragments of cells with no nucleus.
-
Trigger the blood clotting process when blood vessels are damaged.
Key Terms
-
Plasma – the liquid part of blood.
-
Haemoglobin – protein in red blood cells that carries oxygen.
-
Platelets - Fragments of cells that help blood to clot.
No answer provided.
Exam Tip
You may be asked to identify blood cells from microscope images or diagrams. Use size, shape, and presence or absence of a nucleus to help you.
No answer provided.
Practice Question
Some types of cancer can cause the numbers of blood components in a person’s body to fall to a dangerously low level.
A person with one of these types of cancer may experience symptoms such as:
• tiredness
• frequent infections
• bleeding that will not stop after the skin is cut.
Explain how a very low number of blood components in the body can cause these symptoms. (6 marks)
Tiredness
• fewer red blood cells
• so less haemoglobin
• so less oxygen transported around the body so less (aerobic) respiration can take place
• so more anaerobic respiration takes place
• less energy released for metabolic processes or less energy released so organs cannot function as well
• lactic acid produced (during anaerobic respiration) causes muscle fatigue
Frequent infections
• fewer white blood cells / phagocytes / lymphocytes
• so fewer antibodies produced or less phagocytosis
• so fewer pathogens / bacteria / viruses killed
Bleeding
• fewer platelets
• so blood does not clot as easily
Note - to get 5 or 6 marks - all three of the blood components - red blood cells, white blood cells and platelets - must be discussed in the answer.
More Practice
Try to answer these practice questions from the TikTok videos on your own, then watch the videos to see how well you did!