(2.59-2.64B) Blood and Immune System

What are the components of blood?

Red blood cells

White blood cells

Plasma

Platelets

Describe the structure of red blood cells.

Biconcave discs with no nucleus but plenty of haemoglobin

Describe the structure of white blood cells.

Large cells with a large nucleus. Different types differ slightly in structure and function.

Describe the structure of platelets.

Fragments of cells.

Describe the structure of plasma.

Yellow liquid

What is the role of plasma?

Plasma is key in the transport of:

Carbon Dioxide- waste product of respiration

Digested food and mineral ions- delivered to cells

Urea- waste product of protein breakdown, delivered to kidneys

Hormones- chemical messengers released from glands

Heat energy- created in respiration

What is the role of red blood cells?

Carrying oxygen to respiring cells

How are red blood cells adapted for their purpose?

Full of haemoglobin

Lack of nucleus

Biconcave shape

How does haemoglobin benefit red blood cells?

Haemoglobin is a protein that binds to oxygen.

How does having no nucleus benefit red blood cells?

Allows for more space for haemoglobin to be packed into the cell.

How does a biconcave shape benefit red blood cells?

Gives the cell a large SA:V ratio to maximise diffusion of oxygen.

What is the purpose of white blood cells?

They are part of the immune system, defending against pathogenic microorganisms.

What are the two main types of white blood cell?

Phagocytes

Lymphocytes

How can phagocytes be recognised under a microscope?

• Multi-lobed nucleus

• Granular cytoplasm

How do phagocytes carry out phagocytosis?

• Sensitive cell membrane detects pathogenic chemicals.

• Once encountered, they engulf the pathogen and release digestive enzymes to digest it.

• Non-specific immune response.

How can lymphocytes be recognised under a microscope?

• Large, round nucleus

• clear, non-granular cytoplasm

How do lymphocytes protect against pathogens?

• Produce antibodies and antitoxins which neutralise toxins.

• Antibodies are Y-shaped proteins with a complementary shape to the antigens on the surface of the pathogen.

• Specific type of immune response as one type of antibody will only fit one type of antigen on a pathogen.

• They attach, stopping pathogenic cell movement, and chemicals are released signalling the presence of a pathogen to the phagocytes.

When does an organism have immunity?

When it has sufficient levels of antibodies to protect it from a specific disease.

What is an antigen?

A molecule found on the surface of a cell.

What is an antibody?

A protein made by lymphocytes that is complementary to an antigen.

What is an antitoxin?

A protein that neutralises the toxins produced by the bacteria.

What is a vaccine?

A substance containing harmless/weaker/inactive versions of a pathogen that is used to induce immunity to infectious diseases.

How can scientists ensure that the pathogen in a vaccine is harmless?

Kill it

Make it unable to grow or divide

Use fragments rather than whole cells.

How can a vaccine be administered?

orally, nasally or via injection

How do vaccines work within the body?

Antigens in the vaccine trigger:

• Lymphocytes recognise the antigens in the blood stream

• Activated lymphocytes produce targeted antibodies.

• Memory cells, which last years, and antibodies subsequently remain circulating in the bloodstream- long term immunity.

How does the effects of vaccination affect the body’s response to future infection by the same pathogen?

The response will be much faster and larger than before, so the pathogen cannot cause disease.

How do platelets help clot blood?

Platelets release chemicals that cause

soluble fibrinogen proteins to convert into

insoluble fibrin and form an insoluble mesh across the wound

trapping red blood cells

and forming a clot which

dries and develops into a scab.

Why is blood clotting so important?

• Prevents continued blood loss

• Prevents entry of microorganisms that could cause infection