GCSE Combined Science: Cell Biology, Organisation, Infection, and Bioenergetics

Practice flashcards covering cell structure, transport mechanisms, organ systems, cardiovascular health, non-communicable and communicable diseases, plant transport, bioenergetics, and metabolism.

Which three sub-cellular structures are found in plant and algal cells but not in animal cells?

A cell wall made of cellulose, a permanent vacuole filled with cell sap, and chloroplasts.

How does the arrangement of genetic material differ between prokaryotic and eukaryotic cells?

In eukaryotic cells, genetic material is enclosed within a nucleus. In prokaryotic cells, the genetic material is not enclosed in a nucleus; it consists of a single DNA loop and may include one or more small rings of DNA called plasmids.

What bacterial species are given as examples of spherical, spiral, rod, and curved rod shapes?

Spherical: Staphylococcus aureus; Spiral: Treponema pallidum; Rod: Streptobacillus moniliformis; Curved Rod: Vibrio cholerae.

What are plasmids and why are they useful in scientific research?

Plasmids are small, circular sections of DNA that can replicate independently of chromosomal DNA and move genes between cells; they allow genes to be inserted into bacteria during genetic engineering.

What are the typical diameters of a plant cell, an animal cell, and a prokaryotic cell?

A typical plant cell is around $0.1\,\text{mm}$ ($100\,\mu\text{m}$), an animal cell is $0.02\,\text{mm}$ ($20\,\mu\text{m}$), and a prokaryotic cell is often about $0.002\,\text{mm}$ ($2\,\mu\text{m}$) long.

How many micrometres (um) and nanometres (nm) are in one metre ($1\,\text{m}$)?

There are $1\times 10^6$ ($1\,000\,000$) micrometres and $1\times 10^9$ ($1\,000\,000\,000$) nanometres in one metre.

What is resolution in microscopy, and when was the electron microscope first used?

Resolution is the ability to see two or more objects as separate objects. The electron microscope was first used in 1933.

What is the formula used to calculate magnification?

$$\text{magnification} = \frac{\text{size of image}}{\text{size of real object}}$$

How many pairs of chromosomes are found in normal human body cells compared to dog body cells?

Humans have $23$ pairs of chromosomes, whereas dogs have $39$ pairs.

What three main events occur during the cell division stage of mitosis?

One set of chromosomes is pulled to each end of the cell, the nucleus divides, and the cytoplasm and cell membranes divide to form two identical cells.

What are embryonic stem cells, adult stem cells, and meristems?

Embryonic stem cells come from human embryos and can differentiate into all types of cells; adult stem cells (such as in bone marrow) can only form certain cell types; meristems are plant tissues located at the tips of roots and shoots that can differentiate into any plant cell throughout the plant's life.

How is therapeutic cloning carried out, and what is its primary advantage?

A nucleus from a patient is transferred into an enucleated egg cell, which is stimulated to divide into an embryo clone; the resulting stem cells share the patient's genes and will not be rejected by the patient's immune system.

What three factors affect the rate of diffusion?

The concentration gradient (difference in concentrations), the temperature, and the surface area of the membrane.

What is the definition of osmosis?

Osmosis is the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.

What is active transport and what does it require?

Active transport is the movement of substances against a concentration gradient, from an area of low concentration to high concentration, requiring energy released from respiration.

What are two examples of active transport in living organisms?

Mineral ions being absorbed from dilute solutions in the soil into plant root hair cells, and sugar molecules being absorbed from lower concentrations in the gut into the blood.

How are sperm cells specialised for their function?

They possess a tail to propel them towards the egg, numerous mitochondria to supply energy via respiration, and an acrosome containing enzymes to penetrate the outer layer of the egg.

How are xylem cells specialised to transport water and minerals?

They are arranged end to end with broken-down end walls to form hollow tubes, and their cell walls are strengthened with lignin.

What three types of tissue make up the stomach, and what are their roles?

Muscle tissue contracts to churn stomach contents; glandular tissue produces digestive juices and acid to sterilise food; epithelial tissue covers the inside and outside of the stomach.

What is the 'lock and key theory' of enzyme action?

A model explaining that the reacting chemical (the substrate, or 'key') has a specific complementary shape that fits into the active site (the 'lock') of the enzyme protein molecule.

Where is amylase produced and what reaction does it catalyse?

Amylase is produced in the salivary glands and pancreas; it is a carbohydrase that catalyses the breakdown of starch into maltose (which is later broken down into glucose).

Where are protease and lipase produced, and what are their digestion products?

Protease is produced in the stomach, pancreas, and small intestine and breaks down proteins into amino acids; lipase is produced in the pancreas and small intestine and breaks down lipids into fatty acids and glycerol.

Where is bile made, where is it stored, and what are its two main functions in digestion?

Bile is made in the liver and stored in the gall bladder; it is alkaline to neutralise stomach hydrochloric acid and emulsifies fats into small droplets to increase their surface area for lipase.

What qualitative reagents and colour changes are used to test for sugars, starch, and protein?

Sugars: Benedict's reagent turns red after heating in a water bath; Starch: iodine solution turns blue-black; Protein: biuret reagent turns purple.

How are red blood cells adapted for their function?

They contain haemoglobin to bind oxygen, lack a nucleus to maximise space for haemoglobin, are small enough to fit through narrow capillaries, and have a biconcave disc shape to provide a large surface area for diffusion.

How do the structural walls of arteries, veins, and capillaries compare?

Arteries have thick walls containing muscle and elastic fibres; veins have thinner walls and contain valves to prevent backflow; capillaries are narrow and thin-walled to permit substance exchange.

Where is the natural pacemaker of the heart located, and what is its role?

It is a group of cells located in the right atrium that controls the natural resting heart rate.

How does blood circulate between the heart and the lungs?

The heart pumps deoxygenated blood to the lungs via the pulmonary artery, and oxygenated blood returns from the lungs to the left atrium via the pulmonary vein.

What proven causal risk factors are linked to cardiovascular disease, Type 2 diabetes, and liver/brain damage?

Cardiovascular disease: lack of exercise, smoking, and high saturated fat intake; Type 2 diabetes: obesity (a BMI of $30$ or over); Liver and brain damage: excessive alcohol intake.

How much does the NHS spend treating diabetes and its complications?

The NHS spends $£1.5\,\text{million}$ every hour, or $£25\,000$ every minute.

What treatments are available for coronary heart disease and heart valve failure?

Coronary heart disease can be treated with stents to keep coronary arteries open and statins to lower cholesterol; faulty valves can be replaced with biological or mechanical valves.

What is the difference between a benign tumour and a malignant tumour?

Benign tumours are non-cancerous, usually contained within a membrane, and do not invade other tissues; malignant tumours are cancerous, invade neighbouring tissues, and spread to form secondary tumours.

What is transpiration and which environmental factors affect its rate?

Transpiration is the evaporation and diffusion of water from plant leaves through the stomata; its rate increases with higher temperature, faster air flow, and higher light intensity, but decreases with increased humidity.

What is translocation in plants?

The movement of dissolved sugars from the leaves to the rest of the plant through phloem tissue.

What pathogen causes measles, how is it spread, and what are its symptoms?

Measles is caused by a virus spread by inhaling droplets from coughs and sneezes; its symptoms include fever and a red skin rash.

How does HIV damage the body if left untreated?

HIV enters the lymph nodes and attacks the body's immune cells, eventually leading to late-stage HIV (AIDS), where the immune system cannot fight off secondary infections or cancers.

What are the symptoms and treatments or preventions for gonorrhoea?

Symptoms include a thick, yellow or green penile/vaginal discharge and pain during urination; it can be prevented using barrier contraception (e.g. condoms) and treated with antibiotics, though resistant strains have emerged.

What causes malaria, how is it transmitted, and how can its spread be controlled?

Malaria is caused by a protist pathogen transmitted by mosquitoes acting as vectors; control methods include killing mosquitoes and using mosquito nets.

What are the symptoms, effects, and treatment of rose black spot?

Caused by a fungus spread by water or wind, it produces purple or black spots on leaves that turn yellow and drop early, reducing photosynthesis and growth; treated with fungicides and by removing/burning infected leaves.

What non-specific chemical and physical defences protect the human body against infection?

The skin acts as a physical barrier; sebaceous glands secrete sebum to kill bacteria and fungi; tears contain antimicrobial enzymes; nasal hairs and mucus trap particles; cilia sweep mucus out of the respiratory tract; stomach hydrochloric acid destroys ingested bacteria.

What three defence mechanisms do white blood cells use against pathogens?

Phagocytosis (surrounding, engulfing, and digesting pathogens), antibody production (targeting specific antigens on pathogens), and antitoxin production (neutralising bacterial toxins).

From which natural sources were the drugs digitalis, aspirin, and penicillin originally extracted?

Digitalis originates from foxgloves, aspirin originates from willow bark, and penicillin was discovered by Alexander Fleming from the Penicillium mould.

What occurs in a double-blind clinical trial?

Patients are randomly allocated to receive either the active drug or a placebo; neither the patients nor the doctors know who is receiving which treatment, preventing bias.

What is the chemical equation for photosynthesis?

$$6\text{CO}_2 + 6\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$$

What is the inverse square law as applied to light intensity during photosynthesis?

Doubling the distance between the light source and the photosynthetic organism reduces the light intensity to one quarter ($\frac{1}{4}$) of its previous value.

What is the balanced equation for aerobic respiration?

$$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O}$$

What are the word equations for anaerobic respiration in animals versus yeast?

In animals: $\text{glucose} \rightarrow \text{lactic acid}$; in yeast (fermentation): $\text{glucose} \rightarrow \text{ethanol} + \text{carbon dioxide}$.

What is oxygen debt and where is lactic acid processed after exercise?

Oxygen debt is the amount of extra oxygen needed after exercise to react with and remove accumulated lactic acid; blood transports lactic acid from muscles to the liver, where it is broken down.

What is metabolism in living organisms?

The sum of all the enzyme-controlled chemical reactions that occur continuously in a cell or in the body.