Edexcel IGCSE Biology: Cell Structure, Reproduction, Ecology, and Resources

What does the acronym MRS C GREN stand for?

Movement, Reproduction, Sensitivity, Control, Growth, Respiration, Excretion, Nutrition.

What are eukaryotes?

Organisms that have a nucleus and organelles within a plasma membrane.

What is the function of the nucleus in a cell?

Contains genetic material that codes for proteins and is enclosed in a nuclear membrane.

What is the role of mitochondria in a cell?

Where aerobic respiration occurs, providing energy for the cell.

What is the function of ribosomes?

Where protein synthesis occurs, often found on the rough endoplasmic reticulum.

What do chloroplasts do?

Where photosynthesis takes place, containing chlorophyll that absorbs light.

What is the function of the cell membrane?

Contains receptor molecules to control what enters and leaves the cell.

What is a permanent vacuole?

Stores cell sap and improves the rigidity of plant cells.

What is the primary component of bacterial cell walls?

Peptidoglycan.

What distinguishes prokaryotes from eukaryotes?

Prokaryotes do not have a nucleus or membrane-bound organelles.

What are pathogens?

Disease-causing organisms, which can be fungi, bacteria, protoctists, or viruses.

What is the structure of a virus?

Composed of nucleic acid (DNA or RNA) and a protein coat, not a cellular structure.

How do bacteria reproduce?

Through binary fission.

What is saprotrophic nutrition?

Feeding by extracellular secretion of digestive enzymes to absorb nutrients.

What is the function of the cell wall in plant cells?

Provides strength and support, made from cellulose.

What are specialised cells?

Cells that have developed specific characteristics to perform particular functions.

What is differentiation in cells?

The process by which a cell gains new sub-cellular structures to suit its role.

What is the role of sperm cells?

To carry the male's DNA to the egg cell for reproduction.

What adaptations do nerve cells have?

Long axons for distance signal transmission and many mitochondria for energy.

What is the main function of the cytoplasm?

A liquid substance where chemical reactions occur and organelles are found.

What is the role of enzymes in the cytoplasm?

Biological catalysts that speed up the rate of chemical reactions.

What type of nutrition do fungi typically exhibit?

Saprotrophic nutrition.

What is the function of the acrosome in sperm cells?

Contains digestive enzymes to break down the egg cell's outer membrane.

What is the significance of chlorophyll in chloroplasts?

It absorbs light needed for photosynthesis.

What is the primary storage form of carbohydrates in animals?

Glycogen.

What is the primary storage form of carbohydrates in plants?

Starch or sucrose.

What is a mycelium?

A body structure of fungi organized into thread-like structures called hyphae.

What is the role of the rough endoplasmic reticulum?

Site of protein synthesis, where ribosomes are attached.

What are muscle cells specialized for?

Muscle cells are specialized to contract quickly to move bones (striated muscle) or to squeeze (smooth muscle).

What proteins slide over each other to cause muscle contraction?

Myosin and actin.

What is the role of mitochondria in muscle cells?

Mitochondria provide energy from respiration for muscle contraction.

What do root hair cells specialize in?

Root hair cells specialize in taking up water by osmosis and mineral ions by active transport from the soil.

How do root hair cells increase water absorption?

They have a large surface area due to root hairs.

What is the function of xylem cells?

Xylem cells transport water and mineral ions up the plant from the roots to the shoots.

What happens to xylem cells upon formation?

Lignin is deposited, causing the cells to die and become hollow, forming a continuous tube.

What do phloem cells carry?

Phloem cells carry the products of photosynthesis (food) to all parts of the plant.

What are sieve plates in phloem cells?

Sieve plates are structures formed when the cell walls break down, allowing substance movement from cell to cell.

What is a stem cell?

A stem cell is an undifferentiated cell that can undergo division to produce more similar cells.

What are embryonic stem cells capable of?

Embryonic stem cells can differentiate into any type of cell in the body.

Where are adult stem cells usually found?

Adult stem cells are usually found in bone marrow.

What are meristems in plants?

Meristems are found in root and shoot tips and can differentiate into any type of cell throughout the plant's life.

What is one benefit of using stem cells in medicine?

Stem cells can be used to replace damaged cells in conditions like type 1 diabetes and paralysis.

What is a risk associated with stem cell therapies?

There is no guarantee of success and potential long-term effects are unknown.

What are carbohydrates made of?

Carbohydrates are made of carbon, oxygen, and hydrogen.

What do proteins break down into?

Proteins break down into amino acids.

What is the composition of lipids?

Lipids are made of carbon, oxygen, and hydrogen.

What color indicates the presence of glucose in a test?

Brick red indicates the presence of glucose.

What color change indicates the presence of starch?

Blue-black indicates the presence of starch.

What color indicates the presence of protein in a test?

Purple indicates the presence of protein.

What indicates the presence of fat in a solution?

A milky white emulsion indicates the presence of fat.

What are enzymes?

Enzymes are biological catalysts that increase the rate of reaction without being used up.

What is the Lock and Key Hypothesis?

The Lock and Key Hypothesis states that the shape of the substrate is complementary to the shape of the active site of the enzyme.

What happens to enzymes at high temperatures?

Enzymes can become denatured, changing the shape of the active site and preventing substrate binding.

What is the optimum pH for most enzymes?

The optimum pH for most enzymes is around 7.

How does pH affect enzyme activity?

If the pH is too high or too low, it can denature the enzyme, changing the shape of the active site.

What is the purpose of adding amylase and starch solutions in an experiment?

To investigate the effect of pH on the breakdown of starch by amylase.

How is the temperature controlled in the amylase experiment?

By placing the test tube in a water beaker above a Bunsen burner.

What indicates that starch is still present in the solution during the experiment?

The mixture turns blue-black when iodine is added.

What is the optimum pH for amylase activity according to the experiment?

Around pH 7.0.

Define diffusion.

The spreading out of particles resulting in net movement from an area of higher concentration to an area of lower concentration.

Is diffusion an active or passive process?

Diffusion is a passive process as it does not require energy.

What types of molecules can diffuse through cell membranes?

Small molecules such as oxygen, glucose, amino acids, and water.

What is the effect of a greater concentration gradient on diffusion?

The greater the difference in concentration, the faster the rate of diffusion.

How does temperature affect the rate of diffusion?

Higher temperatures increase particle movement, resulting in more collisions and a faster rate of diffusion.

What is osmosis?

The movement of water from a less concentrated solution to a more concentrated solution through a partially permeable membrane.

What happens to animal cells in a hypertonic solution?

Water moves out, causing the cells to shrivel.

What is the result of placing plant cells in a hypotonic solution?

Water moves into the cells, causing them to swell and become turgid.

What is active transport?

The movement of particles from an area of lower concentration to an area of higher concentration, requiring energy.

Give an example of active transport in root hair cells.

Root hair cells take up water and mineral ions from the soil against their concentration gradient.

What is the equation for photosynthesis?

Carbon dioxide + Water → Glucose + Oxygen (light energy).

How does temperature affect the rate of photosynthesis?

The rate increases with temperature until enzymes denature at high temperatures.

What is the relationship between light intensity and distance from the light source?

Light intensity is inversely proportional to the square of the distance from the light source.

What role does carbon dioxide play in photosynthesis?

Carbon dioxide is a reactant needed to produce glucose.

What is the purpose of using water plants like Elodea in photosynthesis experiments?

To observe the evolution of oxygen bubbles during photosynthesis.

What is the effect of a dilute external solution on animal cells?

Water enters the cells, potentially causing them to burst.

What is plasmolysis in plant cells?

The process where the cell membrane pulls away from the cell wall due to water loss in a hypertonic solution.

What is the effect of surface area to volume ratio on diffusion?

A greater surface area allows for a faster rate of diffusion.

What is the significance of turgor pressure in plants?

Turgor pressure helps keep leaves and stems rigid.

What is the control in the osmosis potato experiment?

Potato strips placed in a 0% sucrose solution.

What is the expected outcome of the potato osmosis experiment?

Changes in mass of potato strips after being placed in different sucrose solutions.

What happens to plant cells in a concentrated external solution?

Water moves out of the cells, leading to wilting and potential death.

What is the purpose of sodium hydrogen carbonate in photosynthesis experiments?

To supply carbon dioxide to the water plant.

What is the first step in investigating the effect of light intensity on pondweed?

Place pondweed in water and set up a desk lamp next to a ruler to measure the distance.

How is the effect of carbon dioxide investigated in the pondweed experiment?

By using different concentrations of sodium hydrogen carbonate solution while keeping other variables the same.

What is the purpose of covering half of a leaf with foil in the starch production experiment?

To determine which half of the leaf can produce starch through photosynthesis.

What color change indicates the presence of starch in the leaf after iodine solution is applied?

The exposed half of the leaf changes to blue-black.

What is the role of the waxy cuticle in leaf structure?

It helps to reduce water loss by evaporation and acts as a protective layer.

What is the function of the palisade mesophyll in leaves?

It contains many chloroplasts for rapid photosynthesis.

What do guard cells do?

They open and close the stomata by absorbing or losing water.

What is the role of magnesium in plants?

It is required for chlorophyll production; deficiency causes leaves to turn yellow.

What is the function of carbohydrates in the human diet?

They serve as a high energy source.

What is the role of dietary fiber in human nutrition?

It provides roughage to keep food moving through the gut; deficiency causes constipation.

How does pregnancy affect energy requirements?

Energy requirements increase to support the growth of the fetus.

What is the function of the pancreas in digestion?

It produces carbohydrase, protease, and lipase enzymes and secretes them into the stomach and small intestine.

What is chyme?

The digested food that is formed in the stomach.

What is the role of bile in the small intestine?

It neutralizes hydrochloric acid and emulsifies fats.

What is the primary function of the ileum in the digestive system?

To maximize absorption of digested soluble molecules into the blood.

What are the products of lipid digestion?

Glycerol and 3 fatty acids.

What is the equation for aerobic respiration?

C6 H12O6 + 6O2 ---> 6CO2 + 6H2O.

What is produced during anaerobic respiration in animals?

Lactic acid.