GCSE Biology: Cell Biology, Transport Mechanisms, and Food Chemistry

Comprehensive vocabulary flashcards covering cell structure and specialisations, biomolecules and nutrition, passive and active transport mechanisms, the cell cycle and stem cells, and digestive organ anatomy and enzymes.

Lipids

Large molecules composed of carbon, hydrogen, and oxygen that exist as fats (solids) and oils (liquids); they act as the most efficient energy store in the body, are insoluble in water, and form vital components of cell membranes, hormones, and the nervous system.

Structure of a lipid

A biological molecule formed by three molecules of fatty acids joined to a single molecule of glycerol.

Carbohydrates

Biological molecules containing carbon, hydrogen, and oxygen that provide the primary fuel for the metabolic reactions of life.

Simple sugars

Small carbohydrate units containing either a single sugar unit such as glucose ($C_6H_{12}O_6$) or two sugar units joined together such as sucrose.

Complex carbohydrates

Long chains of simple sugar units bonded together, such as starch and cellulose.

Cellulose

A complex carbohydrate composed of long chains of simple sugar units that acts as an important structural support material in plant cell walls.

Proteins

Molecules made up of carbon, hydrogen, oxygen, and nitrogen that constitute between $15\text{--}16\%$ of human body mass and are used for building cells, tissues, and enzymes.

Amino acids

The building blocks of proteins, comprising approximately $20$ different types that join in long chains via special bonds in various arrangements.

Eukaryotic cells

Complex cells that contain a distinct nucleus and membrane-bound subcellular organelles, with animal and plant cells being key examples.

Prokaryotic cells

Much smaller and structurally simpler single-celled organisms, such as bacteria, that lack a membrane-bound nucleus.

Ribosomes

Subcellular structures responsible for carrying out protein synthesis.

Mitochondria

Organelles in eukaryotic cells that carry out aerobic respiration to release energy for cellular activities.

Chloroplasts

Plant cell organelles containing the green pigment chlorophyll, serving as the site of photosynthesis.

Vacuole

A permanent internal plant organelle that contains cell sap and stores cellular waste products.

Magnification formula

The mathematical calculation defined as $\text{Magnification} = \frac{\text{Image Size}}{\text{Actual Size}}$.

Sperm cell

A specialised male gamete adapted to travel to and fertilise an egg cell, featuring a rotating flagellum, a midpiece packed with mitochondria, a haploid nucleus, and an acrosome.

Acrosome

The anterior tip of a sperm cell's head containing digestive enzymes designed to break down the outer protective layer of an egg cell.

Myelin sheath

A specialised covering around the axon of a neurone that prevents electrical impulses from leaking out and significantly speeds up signal transmission.

Dendrites

Branched extensions of a nerve cell that enable communication and electrical connection with numerous other neurones.

Synapse

The microscopic junction or gap between two neurones across which signals are transferred chemically.

Root hair cell

A specialised epidermal cell found in plant roots that features a long, thin extension to maximise surface area for the absorption of water and mineral ions from soil.

Glycogen

A carbohydrate storage polymer in muscle cells that is rapidly broken down into glucose to fuel aerobic respiration during intensive exercise.

Xylem

A continuous, hollow plant transport tissue composed of dead cells without end walls or cytoplasm, reinforced with lignin, which moves water and dissolved mineral ions upward from roots to leaves.

Lignin

A rigid chemical polymer that thickens and reinforces the cell walls of xylem vessels, providing structural support to keep the plant upright and preventing the vessels from collapsing under tension.

Phloem

Plant vascular tissue constructed from columns of living cells separated by porous sieve plates that transports dissolved sugars and amino acids throughout the plant.

Companion cells

Cells located adjacent to phloem sieve tube elements that contain abundant mitochondria to supply the energy required for the active transport of sugars.

Red blood cells

Specialised blood cells possessing a biconcave disc shape, no nucleus, and packed with haemoglobin to achieve a high surface-area-to-volume ratio for efficient oxygen transport.

Osmosis

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

Partially permeable membrane

A biological membrane that allows only certain small molecules, like water, to pass through while restricting larger solute molecules.

Hypotonic solution

A dilute or pure water solution with a higher water potential than cell cytoplasm, causing water to enter cells by osmosis.

Hypertonic solution

A concentrated or salty solution with a lower water potential than cell cytoplasm, causing water to exit cells by osmosis.

Isotonic solution

A solution with an identical solute concentration to the cell's interior, resulting in no net movement of water across the membrane.

Lysis

The bursting of an animal cell caused by excessive intake of water when immersed in a hypotonic solution.

Crenation

The shrinking and wrinkling of an animal cell resulting from water loss when placed in a hypertonic solution.

Turgid

The swollen, firm condition of a plant cell when its vacuole fills with water in a hypotonic solution, pressing against the rigid cell wall to keep the plant upright.

Plasmolysis

The detachment of the cell membrane from the rigid cell wall in a plant cell as its cytoplasm shrinks due to severe water loss in a hypertonic solution.

Flaccid

The limp state of a plant cell that occurs when it is placed in an isotonic solution because water moves equally into and out of the cell.

Diffusion

The net movement of particles from an area of higher concentration to an area of lower concentration down a concentration gradient.

Surface Area to Volume (SA:V) ratio rule

The biological rule stating that as an organism increases in size, its surface-area-to-volume ratio decreases.

Counter-current flow

An anatomical adaptation in fish gills where blood and water flow in opposite directions across lamellae, maintaining a steep concentration gradient along the entire length of the capillary to maximise oxygen diffusion.

Alveoli

Millions of microscopic air sacs inside the lungs providing an immense surface area and a thin boundary for respiratory gas exchange.

Villi

Finger-like projections extending from the inner lining of the small intestine that drastically expand surface area to maximise nutrient absorption.

Microvilli

Microscopic foldings of the cell membranes on individual intestinal epithelial cells that further amplify the surface area for diffusion and active transport.

Stomata

Microscopic openings situated predominantly on the lower surface of leaves that regulate the exchange of carbon dioxide and oxygen, as well as water loss.

Guard cells

Specialised pairs of cells flanking each plant stoma that alter their shape to open or close the pore to control gas exchange and limit transpiration.

Interphase

The stage of the cell cycle where the cell increases in size, multiplies its sub-cellular structures, and duplicates its DNA.

Mitosis

The phase of the cell cycle during which one set of duplicated chromosomes is pulled to each pole of the cell and the nucleus divides.

Cytokinesis

The final stage of cell division during which the cytoplasm and plasma membrane divide to produce two genetically identical daughter cells.

Purposes of mitosis

The essential biological roles of mitotic cell division: facilitating organismal growth, replacing worn-out cells, and repairing damaged tissues.

Stem cells

Basic, unspecialised precursor cells capable of indefinite self-renewal through cell division and differentiation into specialised mature cell types.

Embryonic stem cells

Pluripotent unspecialised cells derived from an early embryo that possess the potential to differentiate into almost any cell type in the body.

Adult stem cells

Partially differentiated stem cells found in specific tissues (such as bone marrow) that can only differentiate into a limited range of cell types related to that tissue.

Induced pluripotent stem cells (iPSCs)

Mature adult cells that have been genetically or chemically reprogrammed in a laboratory to regain the properties of embryonic stem cells.

Meristem tissue

Regions of rapidly dividing unspecialised plant tissue that retain the ability to differentiate into any specialised plant cell throughout the life of the plant.

Therapeutic cloning

A technique where a patient's nucleus is transferred into an enucleated donor egg to create an embryo, allowing patient-matched stem cells to be harvested for medical therapy.

Peristalsis

Rhythmic waves of involuntary smooth muscle contractions in the walls of the digestive tract, such as the oesophagus, that move food toward the stomach.

Bile

An alkaline fluid synthesised by the liver and stored in the gallbladder that neutralises stomach acid and emulsifies fats into small droplets.

Amylase

A carbohydrase enzyme made in the salivary glands and pancreas that catalyses the hydrolysis of insoluble starch into soluble glucose simple sugars within the mouth and small intestine.

Protease

An enzyme produced by the stomach and pancreas that breaks down proteins into their constituent amino acids within the stomach and small intestine.

Lipase

An enzyme secreted by the pancreas into the small intestine that catalyses the breakdown of lipids into glycerol and fatty acids.

Active transport

An energy-requiring transport process that moves substances across a cell membrane against their concentration gradient, from an area of lower concentration to an area of higher concentration.