Biological structures & organs

Animal cell structure

Animal cell structure, the organelles, their functions and how to label an animal cell for SPM Biology.

Plant cell structure

Plant cell structure, the organelles including the cell wall, chloroplasts and vacuole, and how to label a plant cell.

Structure of a bacterium

Structure of a bacterium, cell wall, plasma membrane, nucleoid and plasmid, and how a prokaryotic cell differs from plant and animal cells.

Mitochondrion structure and function

Mitochondrion structure, double membrane, cristae and matrix, and why active cells contain more mitochondria.

Chloroplast structure and function

Chloroplast structure, double membrane, grana, thylakoids and stroma, and how it is adapted for photosynthesis.

Nucleus structure and function

Nucleus structure, nuclear membrane, chromatin and nucleolus, and how the nucleus controls cell activities and division.

Plasma membrane structure (fluid mosaic model)

Plasma membrane structure, the fluid mosaic model of a phospholipid bilayer and proteins, and why the membrane is partially permeable.

The human heart

The human heart structure, its four chambers, valves and blood vessels, and how to label a heart diagram.

The nephron

The nephron structure, the kidney's filtering unit, its parts and how ultrafiltration and reabsorption happen.

The alveolus

The alveolus structure, the tiny air sac where gas exchange happens, and its adaptations for efficient diffusion.

The villus

The villus structure, the finger-like projection in the small intestine, and its adaptations for absorbing food.

The neuron

The neuron (nerve cell) structure, its parts and how sensory, motor and relay neurones differ.

Lung structure and function

Lung structure, trachea, bronchi, bronchioles and alveoli, and how the alveoli are adapted for efficient gaseous exchange.

Small intestine structure and function

Small intestine structure, the duodenum and ileum, and how villi and microvilli are adapted for the absorption of digested food.

Stomach structure and function

Stomach structure, gastric juice, hydrochloric acid and pepsin, and how the muscular wall and acidic pH aid protein digestion.

Blood vessels, arteries, veins and capillaries

Blood vessel structure, comparing arteries, veins and capillaries, and how each is adapted to its role in circulation.

Red blood cell structure and function

Red blood cell structure, biconcave shape, absence of a nucleus and haemoglobin, and how these adaptations suit oxygen transport.

Brain structure and function

Brain structure, the cerebrum, cerebellum and medulla oblongata, and the different functions of each region.

Eye structure and function

Eye structure, cornea, lens, iris, pupil, retina and optic nerve, and how the eye focuses light and adjusts to light intensity.

Kidney structure and function

Kidney structure, cortex, medulla and renal pelvis, and how the nephrons inside carry out excretion and osmoregulation.

Skeleton and joints, structure and movement

Skeleton and joints, functions of the skeleton, hinge and ball-and-socket joints, and how antagonistic muscles, tendons and ligaments produce movement.

Human reproductive organs and their functions

Male and female reproductive organs, testis, sperm duct, penis, ovary, oviduct, uterus, cervix and vagina, and the function of each.

Leaf structure

Leaf structure, the layers of a leaf and how each is adapted for photosynthesis, gas exchange and transpiration.

Root hair cell structure and function

Root hair cell structure, its long projection, thin wall and many mitochondria, and how it absorbs water and mineral ions.

Xylem vessel structure and function

Xylem vessel structure, dead, hollow, lignified tubes with no cross-walls, and how they transport water and give support.

Phloem tissue structure and function

Phloem tissue structure, sieve tube elements and companion cells, and how they translocate sugars in both directions.

Stoma structure and function

Stoma structure, the pore mainly on the lower epidermis of a leaf, its role in gas exchange and transpiration, and how it opens and closes.

Guard cell structure and function

Guard cell structure, unevenly thickened walls and chloroplasts, and how turgor pressure opens and closes the stoma.

Flower structure and function

Flower structure, sepal, petal, stamen and carpel, and how each part is adapted for pollination.

Seed structure and function

Seed structure, testa, radicle, plumule and cotyledon, and how each part supports germination.