edexcel biology higher

What is the structure of a prokaryotic cell?

Prokaryotic cells lack a nucleus and membrane-bound organelles. They consist of a cell membrane, cell wall, cytoplasm, and genetic material (DNA) that is not enclosed in a nucleus.

What is diffusion?

Diffusion is the movement of particles from an area of high concentration to an area of low concentration, resulting in the equal distribution of substances.

Explain the function of ribosomes in a cell.

Ribosomes are the site of protein synthesis in the cell, where they translate messenger RNA (mRNA) into amino acid sequences to form proteins.

What is the role of enzymes in biological processes?

Enzymes are biological catalysts that speed up chemical reactions in the body without being consumed in the reaction. They lower the activation energy required for reactions to occur.

Define photosynthesis and its equation.

Photosynthesis is the process by which green plants and some organisms convert light energy into chemical energy in the form of glucose, using carbon dioxide and water. The equation is: 6CO2 + 6H2O \xrightarrow{light\, energy} C6H{12}O6 + 6O2.

What are the stages of the cell cycle?

The cell cycle consists of interphase (G1, S, G2) and mitotic phase (M phase), during which the cell grows, duplicates its DNA, and divides.

What is natural selection?

Natural selection is the process whereby organisms better adapted to their environment tend to survive and produce more offspring, leading to evolutionary change.

Explain the importance of genetic variation in a population.

Genetic variation increases the chances that some individuals in a population will survive in changing environments, contributing to the evolution of the species.

What is the function of the pancreas in the human body?

The pancreas produces digestive enzymes and secretes hormones such as insulin and glucagon, which regulate blood sugar levels.

What is the role of the cell membrane?

The cell membrane acts as a barrier that controls the movement of substances in and out of the cell, maintaining homeostasis.

What is the function of a chloroplast?

Chloroplasts are organelles found in plant cells that conduct photosynthesis, converting light energy into chemical energy stored as glucose.

Describe the significance of mitosis.

Mitosis is the process by which a single cell divides to produce two identical daughter cells, important for growth, repair, and asexual reproduction.

What is an antibiotic, and how does it work?

Antibiotics are substances that kill or inhibit the growth of bacteria, often targeting specific bacterial processes or structures.

How do vaccines work?

Vaccines stimulate the immune system to recognize and fight specific pathogens, providing immunity against diseases without causing the illness.

What is homeostasis?

Homeostasis is the maintenance of a stable internal environment in an organism, despite external changes, often regulated by feedback mechanisms.

What is the role of the liver in the body?

The liver plays a crucial role in metabolism, detoxification, and the production of biochemicals necessary for digestion, including bile.

What are enzymes and how do they function?

Enzymes are proteins that catalyze biochemical reactions by lowering the activation energy, allowing reactions to occur more readily.

Explain the importance of cellular respiration.

Cellular respiration is the process by which cells convert glucose and oxygen into energy (ATP), carbon dioxide, and water, essential for cellular functions.

What is the purpose of DNA replication?

DNA replication is the process of copying the DNA prior to cell division, ensuring that each daughter cell receives an identical set of genetic instructions.

What is the relationship between genotype and phenotype?

The genotype is the genetic makeup of an organism, while the phenotype is the observable traits resulting from the expression of the genotype.

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

The cell wall provides structural support and protection to plant cells, maintaining their shape and preventing osmotic lysis.

Define osmosis.

Osmosis is the diffusion of water molecules across a selectively permeable membrane from an area of low solute concentration to an area of high solute concentration.

What is the function of stomata in plants?

Stomata are small openings on the surface of leaves that allow for gas exchange, facilitating the intake of carbon dioxide and the release of oxygen during photosynthesis.

How do organisms obtain energy from glucose?

Organisms obtain energy from glucose through cellular respiration, which converts glucose into ATP, the energy currency of the cell.

What is the difference between aerobic and anaerobic respiration?

Aerobic respiration requires oxygen and produces more ATP, while anaerobic respiration occurs in the absence of oxygen and results in less ATP and byproducts like lactic acid in animals and ethanol in yeast.

Explain the importance of biodiversity.

Biodiversity increases ecosystem resilience, supports food webs, and provides resources for medicine, agriculture, and ecosystem services.

What is a food chain?

A food chain is a linear sequence that shows the feeding relationships between organisms, where each organism is eaten by the next in the chain.

Define trophic levels.

Trophic levels are the hierarchical levels in an ecosystem, typically divided into producers, primary consumers, secondary consumers, and tertiary consumers.

What is the greenhouse effect?

The greenhouse effect is the warming of the Earth caused by the accumulation of greenhouse gases in the atmosphere, trapping heat from the sun.

Explain how the structure of arteries relates to their function.

Arteries have thick, elastic walls that withstand high pressure from the heart and help maintain blood flow, while their narrow lumen keeps the blood flowing quickly.

What is a mutation?

A mutation is a change in the DNA sequence that can lead to changes in protein synthesis and may result in variations in traits among individuals.

Differentiation in cells refers to what?

Differentiation is the process by which a less specialized cell becomes more specialized in structure and function, allowing for the formation of different cell types.

What is the role of hormones in the body?

Hormones are chemical messengers that regulate various physiological processes, including growth, metabolism, and homeostasis.

Describe the structure and function of the heart.

The heart is a muscular organ with four chambers (two atria and two ventricles) that pumps blood throughout the body, delivering oxygen and nutrients while removing waste.

Explain the process of fertilization in plants.

Fertilization in plants occurs when pollen grains (male gametes) land on the stigma of a flower and travel down the style to unite with ovules (female gametes) in the ovary.

What factors affect enzyme activity?

Factors affecting enzyme activity include temperature, pH, enzyme concentration, substrate concentration, and the presence of inhibitors.

Define selective breeding.

Selective breeding is the process of breeding plants or animals for specific traits by selecting parents with desirable characteristics.

Explain the water cycle.

The water cycle describes the movement of water through evaporation, condensation, precipitation, and collection, facilitating the distribution of water on Earth.

What role do decomposers play in an ecosystem?

Decomposers break down dead organic matter, recycling nutrients back into the soil and supporting plant growth, thus maintaining ecosystem balance.

What is the role of producers in an ecosystem?

Producers, such as plants and algae, convert sunlight into chemical energy through photosynthesis, forming the base of the food chain.

What is sympathetic nervous system?

The sympathetic nervous system prepares the body for 'fight or flight' responses during stressful situations by increasing heart rate, blood pressure, and energy availability.