6.3 Defence Against Infectious Disease

What is thought of as the primary defenses against pathogens in the human body?

• Lymphocytes and phagocytes

• Antibodies and lymphocytes

• The skin and mucous membranes

• The circulatory system

If the skin is broken then a blood clot forms to seal this cut.

What is the first step in the process of blood clotting?

• Fibrinogen turns into fibrin

• Platelets release clotting factors

• Fibrinogen is converted into thrombin

• Thrombin is converted into prothrombin

What is the effect which thrombin has on the process of blood clotting?

• Fibrinogen is converted to fibrin

• Prothrombin is converted to thrombin

• Platelets are caused to release clotting factors.

• Clotting factors are taken up by red blood cells.

Which type of blood cells are capable of ingesting pathogens?

• Erythrocytes

• Antibodies

• Lymphocyte cells

• Phagocyte cells

Anitigens on pathogens which have got into the human body can lead to the development of specific immunity.

That is an immunity which responds only to this antigen.

Which of the following cells causes the specific immunity?

• Erythrocytes

• Platelets

• Lymphocytes

• Phagocytes

Why do antibiotics have little or no effect on human cells, yet they can cause the death of bacteria?

• Antibiotics block prokaryote cell processes, but not the processes in eukaryote cells.

• Antibiotics can only affect cells below a certain size.

• Human cells have a protective plasma membrane which prokaryote cells don't have.

• Antibiotics are made of proteins which cannot pass through the plasma membrane.

There are limits to the effectiveness of antibiotics.

Why is this?

• Some bacteria have evolved resistance.

• Bacteria are not affected by antibiotics, only viruses.

• Only one species of bacteria is affected by a single antibiotic.

• Only some types of virus and bacteria are affected by antibiotics, because of the evolution of resistance.

Which of the following best describes the effect of HIV on the immune system.

• HIV infection causes a reduction in the number of active blood cells resulting in a high fever.

• HIV reduces the number of active lymphocytes limiting the body's ability to produce antibodies.

• HIV reduces the number of active erythrocytes limiting the production of antibodies.

• HIV reduces the number of phagocytes which in turn limits the production of antibodies.

Florey and Chain shared a Nobel Prize with Alexander Fleming for their work on penicilin.

Which of the following statements best describes their experiment which tested penecillin on mice?

• Four mice injected with a bacterial disease and four injected with penicillin to test toxicity and effectiveness.

• Two mice injected with penicillin and a bacterial disease to test both toxicity and effectiveness against bacteria.

• Toxicity test on two mice, then eight mice injected with a lethal dose of disease bacteria, four of which were also given penicillin to test its effectiveness against bacteria.

• Hundreds of mice injected with penicillin and their lives monitored to measure how many of the mice developed infections during their lives.

What is non-specific immunity to disease?

• Blocking prokaryotic metabolism with antibiotics

• Production of antibodies by lymphocytes

• Phagocytosis of pathogens by white blood cells

• Production of cloned plasma cells