Hurst Biology Department - Combined Shell, Remove and Fifth Form Topics

Comprehensive practice flashcards covering iGCSE Biology topics including cell biology, human physiology, plant biology, ecology, and inheritance.

What is the key difference between movement and respiration in living organisms?

Movement is the ability of an organism to change its position, whereas respiration is a chemical reaction occurring in cells that releases energy from glucose.

Which cell structures are unique to plant cells according to the notes?

Cell wall (made of cellulose), chloroplasts (site of photosynthesis), and a vacuole containing cell sap.

What are the five levels of biological organisation in order from smallest to largest?

Organelle, cell, tissue, organ, and organ system.

How do you convert a measurement from millimeters (mm) to micrometers ($\mu m$)?

Multiply the value by $1000$.

What chemical and starting colour are used to test for the presence of glucose?

Benedict's solution, which starts as blue.

In the Biuret test for protein, what is the positive result colour?

Lilac.

What is the definition of a biological catalyst (enzyme)?

An enzyme speeds up the rate of reaction without being used up by having an active site with a specific shape that fits a complementary substrate to form an enzyme-substrate complex.

Why does enzyme activity decrease above $40\,^{\circ}\text{C}$?

The enzyme starts to denature, causing the active site to change shape so the substrate no longer fits and enzyme-substrate complexes cannot be formed.

How do diffusion and active transport differ in terms of energy and concentration gradients?

Diffusion is passive (no energy) and moves particles from high to low concentration, whereas active transport requires energy (ATP) to move particles from low to high concentration.

What is the model answer for the definition of osmosis?

The movement of water from an area of high water potential to an area of low water potential through a partially permeable membrane.

Why do animal cells burst in high water potential solutions while plant cells do not?

Animal cells have no cell walls to provide pressure, while plant cells possess cell walls that allow them to become turgid rather than bursting.

What is the balanced chemical equation for aerobic respiration?

$$C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$$

What is the word equation for anaerobic respiration in plants and fungi?

$$\text{Glucose} \rightarrow \text{Ethanol} + \text{Carbon Dioxide}$$

Which indicator turns from red to yellow in the presence of Carbon Dioxide?

Hydrogen Carbonate Indicator.

Explain the actions of the intercostal muscles and diaphragm during inhalation.

The intercostal muscles contract (moving ribs up and out) and the diaphragm contracts (lowers/flattens).

What are the structural adaptations of alveoli for gas exchange?

Thin walls (one-cell thick), large surface area, moist walls to dissolve gases, and a dense network of capillaries to maintain a steep concentration gradient.

How does Carbon Monoxide in cigarette smoke affect red blood cells?

It binds easily to haemoglobin, which reduces the blood’s capacity to carry oxygen.

What are the two main differences between Eukaryotic and Prokaryotic organisms?

Eukaryotic organisms have a nucleus and membrane-bound organelles (like mitochondria), while Prokaryotic organisms have no nucleus (DNA is free) and contain plasmids.

How do fungi obtain nutrition?

Through saprotrophic nutrition, where they secrete enzymes to digest large molecules outside the cells into small molecules for absorption by the hyphae.

What is the specific role of a Lymphocyte in the immune response?

It detects pathogens and produces specific antibodies that match the antigens on the pathogen's surface to mark them for phagocytosis.

Which bacteria is used in the production of yoghurt to break down lactose into lactic acid?

Lactobacillus.

What is meant by a 'limiting factor' in photosynthesis?

An environmental factor that, if in short supply, restricts or prevents the process of photosynthesis.

What are the functions and deficiency symptoms of Nitrates and Magnesium in plants?

Nitrates are for amino acids/growth (deficiency = stunted growth); Magnesium is for chlorophyll (deficiency = yellow leaves).

Match the following vitamins to their deficiency diseases: Vitamin A, Vitamin C, and Vitamin D.

Vitamin A: Night Blindness; Vitamin C: Scurvy; Vitamin D: Rickets.

Where is the enzyme Trypsin made and what is its specific substrate?

It is made in the pancreas and its substrate is protein.

What are the two primary roles of bile in digestion?

1) It neutralises stomach acid to create an optimum pH for enzymes. 2) It emulsifies fats, converting large droplets into small droplets to increase surface area for lipase.

What is the definition of peristalsis?

The wave-like contraction of muscles used to move food along the alimentary canal.

Contrast the genetic traits and parent requirements of sexual and asexual reproduction.

Sexual reproduction requires two parents and produces genetically unique offspring; asexual reproduction requires one parent and produces genetically identical offspring (clones).

What are the functions of the placenta during development?

It allows the exchange of glucose, oxygen, and antibodies from mother to baby, and carbon dioxide and urea from baby to mother, via diffusion without the blood mixing.

How do insect-pollinated and wind-pollinated flowers differ in stigma and anther placement?

In insect-pollinated flowers, the stigma and anther are inside the flower; in wind-pollinated flowers, the stigma is large/feathery/exposed and the anther is exposed/hangs outside.

What are the three factors required for seed germination (WOW)?

Water (to activate enzymes), Oxygen (for aerobic respiration), and Warm temperature (for enzyme activity).

Define Homeostasis.

The maintenance of a constant internal environment.

Outline the neural pathway from stimulus to response.

$$\text{Stimulus} \rightarrow \text{Receptor} \rightarrow \text{Sensory Neurone} \rightarrow \text{Coordinator (CNS)} \rightarrow \text{Motor Neurone} \rightarrow \text{Effector} \rightarrow \text{Response}$$

How does the eye focus on a distant object (accommodation)?

The ciliary muscles relax, the suspensory ligaments tighten, and the lens becomes thin/flat.

What happens to the iris and pupil in bright light (CCRR)?

Circular muscles contract and radial muscles relax, causing the pupil to constrict (diameter decreases).

Compare the response speed and duration of the endocrine and nervous systems.

The nervous system is quick acting with short acting responses; the endocrine system is slow acting with long lasting responses.

Explain the difference between vasoconstriction and vasodilation.

Vasoconstriction is the narrowing of blood vessels in the cold to reduce blood flow and heat radiation; vasodilation is the widening of blood vessels in the heat to increase blood flow and radiation.

What is the role of Plasma in the blood?

It is a straw-coloured liquid that transports carbon dioxide, glucose, hormones, heat energy, and urea.

Compare the structure of arteries, veins, and capillaries.

Arteries have thick muscular/elastic walls; veins have thinner walls and valves; capillaries are one-cell thick for gas exchange.

How does Coronary Heart Disease lead to a heart attack?

Blocked coronary arteries limit oxygen/glucose to heart muscle, leading to anaerobic respiration and lactic acid build-up, which denatures enzymes and stops muscle contraction.

What is the structural difference between Xylem and Phloem?

Xylem is dead, made of lignin, and transports water/minerals in one direction; Phloem is alive and transports sucrose/amino acids in both directions.

Define Eutrophication.

An increase in nitrates or phosphates in waterways resulting in an algal bloom, which reduces oxygen availability and leads to the death of aerobic organisms.

Explain the Greenhouse Gas Effect model answer.

Short wave radiation strikes Earth; some is re-emitted as long wave radiation which is reflected back by greenhouse gases (CO2, methane, etc.), trapping heat and contributing to global warming.

What is the difference between population and community?

A population is the number of organisms of one species; a community is all organisms of different species interacting in an ecosystem.

Why is energy lost between trophic levels in a food chain?

Energy is lost through respiration (as heat), movement, incomplete ingestion, egestion of undigested material, and excretion.

Contrast Mitosis and Meiosis by daughter cell count and genetic outcome.

Mitosis produces 2 genetically identical diploid daughter cells; Meiosis produces 4 genetically unique haploid daughter cells.

Define Polygenic and Transgenic.

Polygenic refers to a phenotype controlled by more than one gene; Transgenic refers to an organism that has gained a gene from a different species.

What is the model answer for Natural Selection?

1) Genetic variation exists due to mutations. 2) Individuals with beneficial characteristics are better adapted and survive. 3) Survivors reproduce and pass on the alleles. 4) The process repeats over generations.

What is the formula for percentage change?

$$\text{Percentage change} = \frac{\text{Final number} - \text{Original number}}{\text{Original number}} \times 100$$

How do precision and reliability differ in practical work?

Precision involves using equipment with finer graduations (e.g., mm vs cm); reliability is improved by repeating the experiment and calculating a mean after removing anomalies.