AQA Biology Trilogy Paper 1 Flashcards

Prokaryotic cells

Small, simple cells lacking a true nucleus and membrane-bound organelles, containing genetic material as a single loop of DNA or plasmids (e.g., bacteria).

Eukaryotic cells

Complex, larger cells containing a nucleus and distinct sub-cellular structures (e.g., plant and animal cells).

Resolution in microscopy

The ability to distinguish between two separate points; higher resolution allows smaller details to be seen clearly.

Unit conversion from millimetres to micrometres

Multiply the millimetre value by $1000$ ($1\,\text{mm} = 1000\,\mu\text{m}$).

Light microscope vs electron microscope

Light microscopes use light rays and have lower magnification and resolution; electron microscopes use electron beams and offer much higher magnification and resolving power.

Nucleus function

Contains genetic material (DNA) and controls the activities of the cell.

Cytoplasm function

Gel-like fluid where chemical reactions take place inside the cell.

Cell membrane function

Partially permeable barrier that controls the movement of substances into and out of the cell.

Mitochondrion function

Site of aerobic cellular respiration, where energy is released for the cell.

Ribosome function

Site of protein synthesis within the cell.

Permanent vacuole function in plant cells

Filled with cell sap to support the cell and keep it turgid (firm).

Cell wall composition and function in plants

Made of cellulose; strengthens and provides rigid structural support to the plant cell.

Chloroplast function

Site of photosynthesis; contains chlorophyll pigments that absorb light energy.

Sperm cell adaptations

Streamlined head with a long tail for swimming, many mitochondria to provide energy, and an acrosome containing digestive enzymes.

Nerve cell adaptations

Long axon to carry electrical impulses across large distances, surrounded by branched dendrites to connect with other cells.

Xylem vessel adaptations

Hollow tubes with no end walls for rapid water flow, reinforced with thick walls of lignin to withstand pressure.

Phloem vessel adaptations

Living elongated cells with perforated end walls (pores) to allow dissolved sugars to move through the plant.

Stem cell

An undifferentiated cell of an organism that can divide to make more cells and differentiate into specialised cell types.

Meristem tissue

Plant stem cell tissue in growing root and shoot tips that can differentiate into any plant cell type throughout the plant's lifetime.

Three stages of the cell cycle

Stage 1 (Growth): cell grows and increases sub-cellular structures; Stage 2 (DNA replication): DNA duplicates to form two copies of each chromosome; Stage 3 (Mitosis): chromosomes are pulled apart, nucleus divides, and cytoplasm and cell membrane divide into two identical daughter cells.

Diffusion

The net movement of particles from an area of higher concentration to an area of lower concentration down a concentration gradient (requires no energy).

Osmosis

The diffusion of water molecules from a dilute solution to a more concentrated solution across a partially permeable membrane (requires no energy).

Active transport

The movement of particles from a dilute solution to a more concentrated solution against a concentration gradient, requiring energy from cellular respiration.

Adaptations of effective exchange surfaces

Large surface area, thin membrane (short diffusion path), and efficient blood supply or ventilation to maintain a steep concentration gradient.

Determining internal potato tissue concentration in the osmosis practical

Locating the point where the line of best fit crosses the horizontal axis ($x$-axis) on a graph of percentage change in mass, where net water exchange is zero.

Structural hierarchy in organisms

Cells aggregate into tissues, tissues group into organs, organs cooperate in organ systems, which together form an organism.

Enzyme active site and 'lock and key' model

The active site has a specific 3D shape complementary to a specific substrate; binding allows catalysis to form products.

Denaturation of enzymes

High temperatures or non-optimum pH alter the active site's shape so the substrate no longer fits, permanently inactivating the enzyme.

Amylase

Carbohydrase enzyme produced by the salivary glands, pancreas, and small intestine that breaks down starch into glucose sugars in the mouth and small intestine.

Protease

Enzyme produced in the stomach, pancreas, and small intestine that breaks down proteins into amino acids.

Lipase

Enzyme produced in the pancreas and small intestine that breaks down lipids into fatty acids and glycerol.

Bile

Alkaline fluid made in the liver and stored in the gall bladder that neutralises hydrochloric stomach acid and emulsifies lipids into smaller droplets.

Biuret test for proteins

Add Biuret reagent to the sample; a positive result changes the solution from pale blue to lilac/purple.

Iodine test for starch

Add iodine solution to the sample; a positive result turns the reagent from orange-brown to blue-black.

Benedict's test for reducing sugars

Mix with Benedict's reagent and heat in a water bath; a positive result shifts from blue to green, yellow, or brick red depending on sugar concentration.

Ethanol emulsion test for lipids

Dissolve the food sample in ethanol, then add water; a positive result produces a cloudy white emulsion.

Double circulatory system

A circulatory system where blood flows through the heart twice per circuit: right side pumps deoxygenated blood to the lungs, while left side pumps oxygenated blood to the body.

Artery vs vein structure

Arteries have thick muscular/elastic walls and narrow lumens to withstand high blood pressure; veins have thinner walls, wide lumens, and valves to prevent backflow.

Capillary structure

Microscopic vessels with walls that are only one cell thick and very narrow lumens to allow efficient diffusion of substances.

Blood components

Red blood cells (transport oxygen via haemoglobin), white blood cells (phagocytes and lymphocytes that defend against disease), platelets (cell fragments that clot blood), and plasma (liquid carrying dissolved solutes).

Coronary Heart Disease (CHD)

Accumulation of fatty deposits inside the coronary arteries, restricting blood flow and oxygen supply to heart muscle, reducing aerobic respiration and leading to heart attacks.

Stents vs statins

Stents are metal mesh tubes surgically inserted to hold narrowed coronary arteries open immediately; statins are daily drugs taken to lower blood cholesterol levels and slow fatty plaque buildup.

Transpiration

The loss of water vapour from the aerial parts of a plant (primarily stomata via evaporation), driving the upward movement of water in the xylem.

Environmental factors increasing transpiration rate

Higher temperatures, lower humidity, increased air movement (wind), and higher light intensity.

Translocation

The transport of dissolved sugars (food molecules) from the leaves to other plant tissues through the phloem for immediate use or storage.

Pathogen

A disease-causing microorganism, which can be a bacterium, virus, fungus, or protist.

Bacterial disease mechanisms vs viral disease mechanisms

Bacteria reproduce rapidly and produce toxins that damage tissues; viruses reproduce inside host cells, causing cellular damage and cell lysis.

Measles

Viral disease spread by airborne droplets causing fever and a red skin rash; prevented by childhood vaccination.

HIV (Human Immunodeficiency Virus)

Viral infection transmitted by bodily fluids or sexual contact that attacks immune cells; controlled with antiretroviral therapy.

Tobacco Mosaic Virus (TMV)

Plant virus causing a characteristic mosaic discolouration on leaves, reducing chlorophyll content and halting photosynthesis and growth.

Salmonella

Bacterial infection caused by ingesting contaminated food, producing toxins that cause fever, abdominal cramps, vomiting, and diarrhoea.

Gonorrhoea

Bacterial sexually transmitted disease causing thick green or yellow discharge and pain when urinating; treated using antibiotics.

Rose black spot

Fungal infection spread by wind and water causing purple or black spots on plant leaves, leading to leaf drop and stunted growth.

Malaria

Disease caused by a parasitic protist spread by mosquito vectors, causing recurrent episodes of severe fever and potential fatality.

White blood cell immune defences

Phagocytosis (engulfing and digesting pathogens), antibody production (neutralising antigens), and antitoxin production (neutralising bacterial poisons).

Mechanism of vaccination

Injecting inactive or dead forms of a pathogen into the body; antigens trigger white blood cells to produce specific antibodies and memory cells for rapid secondary response.

Why antibiotics are ineffective against viruses

Viruses reproduce inside host body cells; antibiotics target bacterial structures and cannot destroy viruses without damaging host body tissues.

Origins of aspirin, digitalis, and penicillin

Aspirin originated from willow trees, digitalis originated from foxgloves, and penicillin was discovered in Penicillium mould by Alexander Fleming.

Preclinical vs clinical drug testing

Preclinical testing uses isolated cells, tissues, and live animals to evaluate toxicity and efficacy; clinical trials test on healthy human volunteers for safety, then on patient volunteers for dosage and efficacy.

Double-blind clinical trials

Clinical drug trials where neither the trial participants nor the doctors know who receives the active drug and who receives a placebo, eliminating psychological bias.

Benign vs malignant tumours

Benign tumours are abnormal cell growths encapsulated within a membrane that do not invade other tissues; malignant tumours are cancerous cells that invade neighbouring tissues and metastasise via blood.

Photosynthesis chemical equation

$6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$ (an endothermic reaction driven by light energy absorbed by chlorophyll).

Uses of glucose in plants

Used in aerobic respiration, converted into insoluble starch for storage, converted to fats or oils for storage, converted to cellulose for cell walls, and combined with nitrates to produce amino acids.

Limiting factors of photosynthesis

Light intensity, carbon dioxide concentration, ambient temperature, and chlorophyll availability.

Inverse square law for light intensity

Light intensity is inversely proportional to the square of the distance from the light source ($\text{Light intensity} \propto \frac{1}{\text{distance}^2}$).

Aerobic respiration chemical equation

$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O}$ (an exothermic reaction releasing energy in mitochondria).

Anaerobic respiration in human muscle cells

$\text{Glucose} \rightarrow \text{Lactic acid}$ (occurs without oxygen, yielding substantially less energy per glucose molecule than aerobic respiration).

Anaerobic respiration in yeast (fermentation)

$\text{Glucose} \rightarrow \text{Ethanol} + \text{Carbon dioxide}$ (used industrially in brewing alcoholic beverages and bread baking).

Oxygen debt

The extra volume of oxygen required after strenuous exercise to break down accumulated lactic acid in the liver and restore normal metabolic state.

Metabolism

The sum total of all the biochemical reactions occurring within a cell or an organism.