OCR Gateway GCSE Biology: B2 Scaling Up

What is diffusion?

The net movement of molecules from an area of high concentration to an area of low concentration down their concentration gradient.

How does temperature affect diffusion?

As the temperature increases, the rate of diffusion increases as the particles have more kinetic energy and move faster.

How does the concentration gradient affect diffusion?

The greater the concentration gradient, the faster the rate of diffusion.

How does the surface area of the membrane affect diffusion?

If the surface area increases, so does the rate of diffusion as there is more space for the particles to move through.

What is osmosis?

The net movement of water molecules from a higher water potential to a lower water potential down a concentration gradient across a selectively permeable membrane.

What is active transport?

The movement of molecules from a low concentration to a high concentration against their concentration gradient using energy.

What are the stages of mitosis?

1) The chromosomes are replicated. 2) The chromosomes line up in the middle. 3) The chromosomes are pulled apart. 4) Membranes form around the chromosomes and the cytoplasm divides. 5) The two cells then continue growing.

What is cell differentiation?

Differentiation is where cells become specialised for a particular function.

How are sperm cells specialised to their function?

They have a large tail for movement, an acrosome to digest the egg membrane, lots of mitochondria for energy, and a haploid nucleus.

How are nerve cells specialised to carry impulses?

They have a long axon to transport the impulse long distances, extensions to connect to other nerve cells, and contain neurotransmitters to transmit the impulse.

How are root hair cells specialised to take up water and minerals?

They have lots of mitochondria to generate energy and a large surface area for faster diffusion.

What are stem cells?

Stem cells are undifferentiated cells that can develop into lots of different types of cells.

Where are animal stem cells found?

Animal stem cells are found in embryos and in the bone marrow.

What is the difference between adult and embryonic stem cells?

Embryonic stem cells can differentiate into any type of cell, whereas adult stem cells can only differentiate into cell types from the tissue the stem cells are in.

Where are plant stem cells found?

Plant stem cells are found in meristematic tissue.

What are stem cells used for?

Stem cells are naturally used for growth and repair. They can also be used in treatments for Parkinson's disease and burns.

Why do large multicellular organisms need transport systems?

They have a small surface area to volume ratio, so diffusion alone is not fast enough to transport substances.

Give 4 examples of substances transported within organisms.

Oxygen, CO2, dissolved food molecules, urea and waste products.

Why do mammals need a double circulatory system?

It allows blood to flow at a higher pressure, moving substances quickly around the body.

Describe the double circulatory system in mammals.

The heart pumps blood to the lungs, oxygenated blood returns to the heart, and is then pumped around the body.

What is the difference in function between veins, arteries, and capillaries?

Arteries carry blood away from the heart, veins carry blood towards the heart, and capillaries allow for exchange close to tissues.

Describe the structure of arteries.

They have thick walls made of muscle and elastic tissue and a small lumen for high-pressure blood transport.

Describe the structure of capillaries.

They have thin walls about one cell thick for easy exchange of substances.

Describe the structure of veins.

Veins have less muscle and elastic tissue than arteries, a larger lumen, and valves to prevent backflow.

Describe the structure of the lungs.

The trachea branches into bronchi, which branch into bronchioles, ending in alveoli lined with capillaries for exchange.

Describe the blood flow through the right side of the heart.

Deoxygenated blood flows into the right atrium from the vena cava, passes through the right AV valve into the right ventricle, and is pumped to the lungs through the right SL valve into the pulmonary artery.

Describe the blood flow through the left side of the heart.

Blood enters the left atrium from the pulmonary vein, passes through the left AV valve into the left ventricle, and is pumped out through the left SL valve into the aorta.

What is the name of the wall that separates the right and left sides of the heart?

The septum.

What is the name of the artery that supplies the heart tissue with blood?

The coronary artery.

What type of muscle is the heart made of?

Cardiac muscle.

Why is the wall of the left ventricle thicker than the wall of the right ventricle?

It pumps blood a further distance around the body, requiring higher pressure.

How is plasma adapted as a transport medium?

Plasma is the liquid part of blood, allowing most molecules to be dissolved in water.

Give 3 adaptations of red blood cells to their function.

Biconcave shape for large surface area, no nucleus for more space for hemoglobin, and flexibility to fit through capillaries.

How are root hair cells adapted to their function?

Long extensions increase surface area for uptake, and thin membranes decrease diffusion distance.

What does the xylem transport?

Water and minerals.

State 3 benefits of transpiration.

Cools the plant, supports the plant by creating turgor pressure, and provides a constant water supply for photosynthesis.

How is the xylem adapted to transport water?

It is waterproofed with lignin, and the cells are dead with no organelles for more space for water.

Describe the process of transpiration.

Water is lost through the stomata, and more water is drawn up to replace it.

What is the transpiration stream?

The flow of water through a plant.

How does temperature affect the rate of transpiration?

As temperature increases, transpiration rate increases due to higher kinetic energy and faster evaporation.

How does light intensity affect the rate of transpiration?

Brighter light opens more stomata and increases photosynthesis, leading to increased transpiration.

How does wind speed affect the rate of transpiration?

Faster wind moves water away from the plant, creating a steeper gradient and increasing transpiration.

Describe how to use a potometer to measure transpiration.

Place the plant in an airtight tube with water, introduce an air bubble, and measure the bubble's movement over time.

What does the phloem transport?

Sugars like sucrose.

Describe translocation.

The movement of sugars up or down the phloem from source to sink, using energy.