5.10Chapter 5: Respiration and the Respiratory System

Transport in the blood — Alhussan Biology - Stage 8 Revision Notes & Topical Questions

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📚 Alhussan Biology - Stage 8 Hub / Topical Revision

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Biology 5.10 Transport in the blood — Red Blood Cells, Plasma and White Blood Cells — Alhussan International Academy — Biology (Stages 7–9) notes: Describe the components of blood and explain how each is adapted to its function.Humans — big, active multicellular animals whose cel…

Other substances
Need for blood
Haemoglobin
Adaptations
Phagocytes
Lymphocytes

Part 1 of 7Why blood is needed

Humans

Humans big, active multicellular animals whose cells need lots of digested food and oxygen and produce many waste products to be removed.

Blood

Blood it transports these substances around the body and protects against many diseases.

Volume

Volume an adult has about 5 litres of blood, which is not a simple red liquid.

Part 2 of 7The parts of blood

Component	Description	Function
Plasma	Yellow, straw-coloured liquid, about 55% of blood volume, mostly water	Carries blood cells, platelets, dissolved food, carbon dioxide, urea, hormones, antibodies and heat
Red blood cells	About 44% of blood volume, disc-shaped, no nucleus	Carry oxygen
White blood cells	About 1% of blood volume, large, with a nucleus	Defend against pathogens
Platelets	Tiny pieces of cells, less than 1% of blood volume	Help the blood to clot

Part 3 of 7Plasma

Transport

Transport plasma carries dissolved food and other substances to cells, and toxic carbon dioxide away from cells to the lungs.

Urea

Urea this waste product is carried from the liver to the kidneys, where it is removed in urine.

Other substances

Other substances hormones from glands to target organs and heat from the muscles and liver to the skin.

Need for blood

Need for blood diffusion alone is too slow over long distances, so blood supplies all the cells of large organisms.

Substance	Carried in	From → to
Oxygen	Red blood cells	Lungs → body cells
Carbon dioxide	Plasma	Cells → lungs
Digested food	Plasma	Small intestine → cells
Urea	Plasma	Liver → kidneys

Part 4 of 7Red blood cells

Number

Number you have more red blood cells than any other type of cell, and they are the smallest cells in the body.

Haemoglobin

Haemoglobin the red molecule that carries oxygen from the alveoli of the lungs to body cells for aerobic respiration.
It combines with oxygen in the lungs and releases it in the tissues where oxygen is low.

Adaptations

Adaptations their disc shape and lack of a nucleus leave lots of room for haemoglobin.
The biconcave shape gives a large surface area for rapid diffusion.
Their small, flexible shape lets them squeeze through very small blood vessels one at a time.

Life

Life they live about 120 days and are made in the bone marrow.

Anaemia

Anaemia too few red blood cells or too little iron for haemoglobin causes tiredness and pale skin.

Part 5 of 7White blood cells

White blood cells

Structure

Structure all white blood cells are big and have a nucleus.

Role

Role they protect the body against pathogens, which are microorganisms that get into the body and cause infectious diseases.

Phagocytes

Phagocytes some flow round and digest microorganisms, which is phagocytosis.

Lymphocytes

Lymphocytes others make antibodies, special proteins that stick to microorganisms so they cannot cause disease.
Some lymphocytes become memory cells that give immunity.

Part 6 of 7Platelets

Platelets

Structure

Structure tiny pieces of cells, less than 1% of blood volume.

Clotting

Clotting they make blood clot if you cut yourself, so you do not bleed to death.
They release chemicals that form a mesh of fibrin fibres, trapping blood cells.
Clots form scabs, which cover damaged tissue, protect the wound and stop microorganisms getting in, so the body can repair itself.

Protection

Protection platelets and white blood cells both help to protect against disease.

Part 7 of 7Functions of blood

Functions of blood

Transporting oxygen, digested food and other nutrients.

Removing wastes such as carbon dioxide and urea.

Defending against disease, clotting to seal wounds and spreading heat.

Key terms

Term	Meaning
Plasma	The liquid part of blood.
Haemoglobin	A protein in red blood cells that binds oxygen.
Phagocyte	A white blood cell that engulfs pathogens.
Lymphocyte	A white blood cell that makes antibodies.
Platelet	A cell fragment that helps blood to clot.
Antibody	A protein that targets a specific pathogen.