Transport systems: GCSE questions with answers

Answer: D Spreading of particles from high to low concentration

Diffusion is the net movement of particles from where they are more concentrated to where they are less concentrated. It needs no energy from the cell. Oxygen diffuses into cells, while carbon dioxide and urea diffuse out.

Checked against OpenStax Biology 2e, 5.2 Passive Transport

Answer: A A steeper concentration gradient

Diffusion is faster when the concentration gradient is steeper, the temperature is higher, the surface area is larger and the distance is shorter.

Checked against OpenStax Biology 2e, 5.2 Passive Transport

Answer: A Diffusion of water through a partially permeable membrane

Osmosis is the diffusion of water across a partially permeable membrane, from a dilute solution (more water) to a more concentrated one (less water). It is the water that moves, not the dissolved sugar or salt.

Checked against OpenStax Biology 2e, 5.2 Passive Transport

Answer: B Water moves in and the cell becomes firm

In pure water, water enters cells by osmosis. A plant cell swells and becomes firm (turgid), but its strong cell wall stops it bursting. An animal cell such as a red blood cell has no wall, so it can burst.

Checked against OpenStax Biology 2e, 5.2 Passive Transport

Answer: C Movement against a concentration gradient using energy

Active transport moves substances from a more dilute solution to a more concentrated one, against the concentration gradient. This needs energy, which comes from respiration.

Checked against OpenStax Biology 2e, 5.3 Active Transport

Answer: C Mineral ions into root hair cells

Active transport lets cells take in substances that are scarce outside. Root hairs take in mineral ions from very dilute soil water, and the small intestine absorbs glucose into blood that already has more glucose.

Checked against OpenStax Biology 2e, 5.3 Active Transport

Answer: D Active transport

Diffusion and osmosis are passive: substances move down a concentration gradient with no energy from respiration. Osmosis is only about water. Active transport moves substances against a gradient and needs energy from respiration.

Checked against OpenStax Biology 2e, 5.3 Active Transport

Answer: B Its surface area is large compared with its volume

A tiny organism has a large surface area compared with its volume, and short distances, so diffusion across its surface is enough. As size increases, the surface area to volume ratio gets smaller.

Checked against OpenStax Biology 2e, 4.2 Prokaryotic Cells

Answer: C Diffusion alone is too slow for inner cells

A large organism has a small surface area to volume ratio and many cells far from the surface. Diffusion alone would be too slow, so it needs specialised exchange surfaces and a transport system to carry substances to every cell.

Checked against OpenStax Biology 2e, 40.1 Overview of the Circulatory System

Answer: D A very thin surface

Good exchange surfaces have a large surface area, a thin surface for a short diffusion path, a rich blood supply and, for gases, ventilation. Millions of alveoli with thin walls and dense capillaries do all of this.

Checked against OpenStax Biology 2e, 39.1 Systems of Gas Exchange

Answer: A They give a large surface area

The small intestine is lined with millions of tiny finger-like villi. They give a huge surface area, have a thin lining and a good blood supply, so digested food is absorbed quickly.

Checked against OpenStax Biology 2e, 34.3 Digestive System Processes

Answer: B Urea

When the body has more amino acids than it needs, they are broken down and urea is made. Urea is carried in the plasma to the kidneys, which remove it from the body in urine.

Checked against AQA GCSE Biology (8461) specification, 4.4.2.3 Metabolism, page 40

Answer: D To make amino acids for proteins

Plants take in mineral ions dissolved in soil water through their roots. Nitrate ions are used, with sugars from photosynthesis, to make amino acids and then proteins. Mineral ions are not a source of energy.

Checked against AQA GCSE Biology (8461) specification, 4.4.1.3 Uses of glucose from photosynthesis, page 38

Answer: B It is a waste product of respiration

Animal cells need oxygen for aerobic respiration, which releases energy from glucose. Respiration makes carbon dioxide as a waste product, which must be carried away and breathed out.

Checked against OpenStax Biology 2e, 39.1 Systems of Gas Exchange

Answer: D Carbon dioxide

In bright light, photosynthesis is faster than respiration, so a leaf takes in carbon dioxide and gives out oxygen overall. The gases move in and out through the stomata by diffusion.

Checked against OpenStax Biology 2e, 30.4 Leaves

Answer: A Dissolved in the blood plasma

Dissolved food molecules such as glucose and amino acids are absorbed into the blood and carried in solution in the plasma to cells all over the body.

Checked against OpenStax Biology 2e, 40.2 Components of the Blood

Answer: D Blood passes through the heart twice per circuit

Humans have a double circulatory system. The right ventricle pumps blood to the lungs to collect oxygen, and the left ventricle pumps it round the rest of the body, so blood goes through the heart twice on each full circuit.

Checked against OpenStax Biology 2e, 40.1 Overview of the Circulatory System

The right order:

1. Vena cava
2. Right atrium
3. Right ventricle
4. Pulmonary artery
5. Lungs

Blood from the body enters the right atrium through the vena cava, then the right ventricle pumps it to the lungs in the pulmonary artery. Oxygenated blood returns in the pulmonary vein to the left atrium, and the left ventricle pumps it out through the aorta.

Checked against OpenStax Biology 2e, 40.3 Mammalian Heart and Blood Vessels

Answer: B Pulmonary artery

Arteries carry blood away from the heart and veins carry it back. So the pulmonary artery takes deoxygenated blood to the lungs, the pulmonary vein brings oxygenated blood back, the aorta leaves for the body, and the vena cava returns from it.

Checked against OpenStax Biology 2e, 40.3 Mammalian Heart and Blood Vessels

Answer: C It pumps blood all round the body

The left ventricle has the thickest muscle wall because it must pump blood at high pressure all round the body; the right ventricle only pumps to the nearby lungs. Valves let blood flow one way through the heart and stop it flowing back.

Checked against OpenStax Biology 2e, 40.3 Mammalian Heart and Blood Vessels

Answer: A To withstand blood at high pressure

Arteries carry blood away from the heart at high pressure. Their thick muscular and elastic walls withstand the pressure and stretch and recoil with each heartbeat.

Checked against OpenStax Biology 2e, 40.3 Mammalian Heart and Blood Vessels

Answer: B Veins

Veins carry blood back to the heart at low pressure. They have thinner walls and a wider space inside than arteries, and valves that stop the blood flowing backwards.

Checked against OpenStax Biology 2e, 40.3 Mammalian Heart and Blood Vessels

Answer: A To give a short distance for diffusion

Capillaries are tiny vessels that reach almost every cell. Their walls are one cell thick, so substances such as oxygen, glucose and carbon dioxide only have a short distance to diffuse.

Checked against OpenStax Biology 2e, 40.3 Mammalian Heart and Blood Vessels

Answer: C From the alveoli into the blood

Air travels down the trachea and bronchi to the alveoli. Oxygen diffuses from the alveoli into the blood in the capillaries, and carbon dioxide diffuses the other way. The oxygenated blood returns to the heart to be pumped round the body.

Checked against OpenStax Biology 2e, 39.1 Systems of Gas Exchange

Answer: C Haemoglobin

Red blood cells carry oxygen. They are packed with haemoglobin, which joins with oxygen, and have no nucleus so there is more room for it. Their biconcave shape gives a large surface area for oxygen to diffuse in and out.

Checked against OpenStax Biology 2e, 40.2 Components of the Blood

Answer: B Defending the body against pathogens

White blood cells defend the body against pathogens. Some, called phagocytes, change shape to engulf and digest pathogens; others, lymphocytes, make antibodies. Unlike red blood cells, white blood cells have a nucleus.

Checked against OpenStax Biology 2e, 40.2 Components of the Blood

Answer: B Help the blood to clot

Platelets are tiny fragments of cells with no nucleus. At a wound they help form a clot, which stops bleeding and helps keep pathogens out.

Checked against OpenStax Biology 2e, 40.2 Components of the Blood

Answer: C Plasma

Plasma is the pale yellow liquid part of the blood. Blood cells and platelets are suspended in it, and it carries dissolved substances such as glucose, amino acids, carbon dioxide, urea and hormones around the body.

Checked against OpenStax Biology 2e, 40.2 Components of the Blood

Answer: D Water and mineral ions

Xylem carries water and mineral ions up from the roots to the stems and leaves. It is made of dead cells that form hollow tubes with no end walls, strengthened by lignin so they do not collapse.

Checked against OpenStax Biology 2e, 30.5 Transport of Water and Solutes in Plants

Answer: A Dissolved sugars

Phloem carries dissolved sugars, such as sucrose, from the leaves to where they are used or stored, which can be up or down the plant. It is made of living cells joined end to end, with pores in the end walls so the sap can pass through.

Checked against OpenStax Biology 2e, 30.5 Transport of Water and Solutes in Plants

Answer: C It has a large surface area

A root hair cell has a long thin extension that gives a large surface area for absorbing water. Water enters by osmosis, because the soil water is more dilute than the cell sap.

Checked against OpenStax Biology 2e, 30.3 Roots

Answer: A To take in mineral ions by active transport

Mineral ions are often more concentrated inside root hair cells than in the soil, so they must be taken in by active transport. This needs energy, which the cell releases by respiration in its mitochondria.

Checked against AQA GCSE Biology (8461) specification, 4.1.3.3 Active transport, page 23

Answer: A Loss of water vapour from the leaves

Transpiration is the loss of water vapour from the leaves, mostly through the stomata. As water evaporates and diffuses out, more water is pulled up the xylem from the roots. This flow is the transpiration stream.

Checked against OpenStax Biology 2e, 30.5 Transport of Water and Solutes in Plants

The right order:

1. Water enters a root hair cell by osmosis
2. Water passes through the root to the xylem
3. Water moves up the xylem in the stem
4. Water evaporates inside the leaf
5. Water vapour diffuses out through the stomata

Water enters root hair cells by osmosis, crosses the root to the xylem and is pulled up the stem in the transpiration stream. In the leaf it evaporates, and the water vapour diffuses out through the stomata.

Checked against OpenStax Biology 2e, 30.5 Transport of Water and Solutes in Plants

Answer: A Moving dissolved sugars through the phloem

Translocation is the movement of dissolved sugars made in the leaves through the phloem to other parts of the plant, such as growing tips, roots and fruits, for use or storage.

Checked against OpenStax Biology 2e, 30.5 Transport of Water and Solutes in Plants

Answer: D Guard cells

Stomata are tiny pores in the leaf surface. Each is surrounded by two guard cells that open and close it, controlling gas exchange and water loss. When water is short the stomata close to save water.

Checked against OpenStax Biology 2e, 30.4 Leaves

Answer: D More stomata open

In brighter light more stomata open, so more water vapour escapes and the plant takes up water faster. A potometer measures how quickly a cut shoot takes up water, which is close to the rate of transpiration.

Checked against OpenStax Biology 2e, 30.5 Transport of Water and Solutes in Plants

Answer: D It blows water vapour away from the leaf

Wind carries water vapour away from around the leaf, which keeps the concentration of water vapour outside low. The concentration gradient stays steep, so water vapour diffuses out faster.

Checked against OpenStax Biology 2e, 30.5 Transport of Water and Solutes in Plants

Answer: C Water evaporates and diffuses faster

When it is warmer, water molecules have more kinetic energy, so water evaporates and diffuses out of the leaf faster. The plant then takes up water more quickly.

Checked against OpenStax Biology 2e, 30.5 Transport of Water and Solutes in Plants

Answer: B A raw material for photosynthesis

Plants take in water through their roots. They use it as a raw material for photosynthesis, to keep their cells firm and to carry dissolved mineral ions. Water is not a source of energy, and most of it is lost by transpiration.

Checked against OpenStax Biology 2e, 31.1 Nutritional Requirements of Plants