IGCSE Biology

Eukaryotic

Organisms with a nucleus and membrane-bound organelles in their cells, can be multicellular or unicellular.

Plants

Multicellular organisms that carry out photosynthesis, store energy as starch, and have cell walls made of cellulose.

Animals

Multicellular organisms without cell walls or chloroplasts, store energy as glycogen, and have nervous coordination.

Fungi

Multicellular or unicellular organisms with chitin cell walls, feed through saprotrophic nutrition, and store energy as glycogen.

Protoctists

Diverse single-celled or microscopic organisms with features of animal cells or plant cells, examples include Amoeba and Chlorella.

Prokaryotic

Unicellular organisms without a nucleus, found in bacteria, contain cell walls made of peptidoglycan, and lack membrane-bound organelles.

Pathogens

Microorganisms causing diseases, including fungi, bacteria, protoctista, and viruses, which reproduce in living cells of other organisms.

Virus

Non-living microscopic particles with a protein coat, containing DNA or RNA, and infecting various living organisms, e.g., HIV and Influenza.

Population

Group of organisms of the same species in the same place, while community includes all populations in an area, and habitat is where an organism lives.

Ecosystem

Interactions of biotic (living) and abiotic (non-living) factors in a community, varying in size, e.g., a garden pond or Antarctica.

Producers

Organisms that produce their own organic nutrients through sunlight energy

Primary Consumer

Organisms that feed on producers

Secondary Consumer

Organisms that feed on primary consumers

Tertiary, Quaternary, etc.

Apex predators or top carnivores in the food chain

Decomposers

Organisms that break down dead materials to recycle nutrients

Carbon Cycle

The process of carbon movement through photosynthesis, respiration, decomposition, and combustion

Bioaccumulation

Concentration of substances in organisms over time without breaking down

Biomagnification

Increase in toxic substance concentration through the food chain

Eutrophication

Excess nutrients entering water bodies causing algal blooms and oxygen depletion

Levels of Organization

Organelle, cell, tissue, organ, organ systems in multicellular organisms

Cell Structures

Nucleus, cytoplasm, cell membrane, cell wall, mitochondria, ribosomes, vacuole

Biological Molecules

Carbohydrates, proteins, and lipids containing carbon, hydrogen, and oxygen

Structure of Molecules

Carbohydrates from simple sugars, proteins from amino acids, lipids from fatty acids and glycerol

Food Tests

Detecting glucose, starch, protein, and fat in food samples using specific chemical tests

Enzymes

Proteins acting as biological catalysts to speed up metabolic reactions without being consumed.

Activation energy

The amount of energy required for a reaction to occur.

Active Site

The part of the enzyme that matches the shape of the substrate.

Denaturation

The process where an enzyme loses its shape and function due to high temperatures or extreme pH levels.

Optimum temperature

The temperature at which enzymes work at their maximum efficiency.

Enzyme-substrate complex

Formed when the substrate binds to the enzyme's active site.

Osmosis

The movement of water from a dilute to a concentrated solution across a partially permeable membrane.

Active Transport

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

Concentration gradient

The difference in concentration of a substance between two areas.

Surface area to volume ratio

The ratio that affects the rate of diffusion in and out of cells.

pH

A measure of the acidity or alkalinity of a solution that can affect enzyme function.

Surface Area to Volume Ratio

The ratio between the surface area of a cell or structure and its volume, affecting the rate of substance movement across the surface.

Adaptations for Diffusion

Modifications in cells to increase surface area, facilitating processes like absorption, e.g., root hair cells in plants and cells lining the ileum in animals.

Diffusion Distance

The shorter the distance molecules travel, the faster transport occurs, seen in structures like blood capillaries and alveoli.

Temperature and Diffusion

Higher temperatures increase molecular movement, leading to faster diffusion rates.

Concentration Gradient

The difference in concentration across a membrane affects the speed of movement, influencing overall diffusion.

Osmosis Experiment

Investigating the effect of concentration on osmosis using potatoes and sucrose solutions.

Photosynthesis

The process in chloroplasts where light energy converts water and carbon dioxide into glucose, releasing oxygen.

Leaf Structure

The complex structure of leaves with specialized cells adapted for photosynthesis, including the palisade and spongy mesophyll.

Factors Affecting Photosynthesis

Temperature, light intensity, and carbon dioxide concentration influence the rate of photosynthesis.

Mineral Ions for Plants

Plants require mineral ions like magnesium for chlorophyll and nitrate for amino acids to support growth and functions.

Carbohydrates

Substances plants make for energy, containing carbon, hydrogen, and oxygen

Proteins

Contain nitrogen, essential for enzymes and amino acids

Mineral Ions

Essential for plant growth and photosynthesis, actively absorbed from soil

Minerals

Naturally occurring inorganic substances, vital for plant functions

Magnesium

Needed for chlorophyll, enzyme function, and nucleic acid production

Nitrate

Source of nitrogen for amino acids, enzymes, DNA, and hormones

Photosynthesis

Process where plants make glucose, requiring light, CO2, and chlorophyll

Starch Production

Demonstrates photosynthesis, starch presence in leaves

Balanced Diet

Includes carbohydrates, proteins, lipids, vitamins, minerals, water, and dietary fiber

Malnutrition

Results from an unbalanced diet, leading to health issues

Dietary Elements

Sources and functions of carbohydrates, proteins, lipids, vitamins, minerals, water, and fiber

Vitamins & Minerals

Functions, sources, and deficiencies of vitamin A, D, C, calcium, and iron

Energy Requirements

Vary with age, activity levels, pregnancy, and sex

Digestion

Breakdown of food into smaller molecules for absorption and energy provision

Alimentary Canal

The channel through which food flows in the body, starting at the mouth and ending at the anus.

Digestion

The process that occurs within the alimentary canal to break down food into smaller molecules for absorption.

Accessory Organs

Organs that produce substances like enzymes and bile needed for digestion but do not have food passing directly through them.

Peristalsis

Rhythmic contractions of circular and longitudinal muscles in the alimentary canal that move food along in a wave-like action.

Digestive Enzymes

Biological catalysts that break down large molecules into smaller ones for absorption.

Amylase

Enzyme that breaks down starch into maltose, produced in salivary glands, pancreas, and small intestine.

Proteases

Enzymes that break down proteins into amino acids, like pepsin in the stomach and trypsin in the pancreas and small intestine.

Lipases

Enzymes that break down lipids into glycerol and fatty acids, produced in the pancreas.

Bile

Alkaline substance produced by the liver, stored in the gallbladder, neutralizes stomach acid, and emulsifies lipids.

Villi

Finger-like projections in the small intestine that increase surface area for absorption, with adaptations like microvilli and a network of blood capillaries.