Cell Structure

A comprehensive set of vocabulary flashcards covering IB Biology Higher Level content on cell organelles, structures, and specialized adaptations.

Organelles

Sub-cellular structures adapted to carry out specific functions, often membrane-bound to maintain an internal chemistry different from the cytosol.

Nucleus

The control centre of the cell that stores genetic material as chromatin and coordinates the expression of genes.

Nuclear envelope

A double membrane embedded with pores that acts as a barrier to separate the processes of transcription and translation.

Ribosome

The site of protein synthesis consisting of protein for stability and rRNA for catalytic activity, composed of a small subunit that binds mRNA and a large subunit that binds tRNA.

Free ribosomes

Ribosomes located within the cytosol that synthesise intracellular proteins used within the cytosol.

Rough endoplasmic reticulum (rough ER)

An organelle embedded with ribosomes that produces proteins to be packaged into vesicles for transport and secretion.

Mitochondria

The site of aerobic respiration in eukaryotic cells, adapted with specific compartments for energy production.

Outer membrane (mitochondrion)

Contains transport proteins that enable the shuttling of pyruvate from the cytosol.

Inner membrane (mitochondrion)

Contains the electron transport chain and ATP synthase for oxidative phosphorylation.

Cristae

Folds of the inner mitochondrial membrane that increase the available surface area.

Intermembrane space

A small space between the mitochondrial membranes that exists to maximise the proton gradient.

Matrix

The central cavity of the mitochondrion containing appropriate enzymes and a suitable $pH$ for the Krebs cycle to occur.

Chloroplasts

The site of photosynthesis where photosynthetic pigments convert light energy into chemical energy.

Thylakoid

A flat disc within the chloroplast with a small internal volume to maximise the gradient upon proton accumulation.

Grana

Stacks of thylakoids arranged to increase the $SA:Vol$ ratio of the thylakoid membrane.

Stroma

The central cavity of the chloroplast containing appropriate enzymes and a suitable $pH$ for the Calvin cycle to occur.

Lamellae

Structures that connect and separate thylakoid stacks (grana), maximising photosynthetic efficiency.

Golgi apparatus

An organelle composed of flat sacs called cisternae, responsible for sorting, storing, modifying, and exporting cellular material.

Cisternae

Series of flat sacs in the Golgi apparatus located between the ER (cis facing) and the cell membrane (trans facing).

Lysosome

A type of vesicle that breaks down cellular waste and debris.

Peroxisome

A type of vesicle that digests toxic metabolites.

Clathrin

A triskelion-shaped coat protein recruited to a membrane by adaptor proteins to form a rounded lattice that pulls the membrane into a bud.

Dynamin

A protein that cleaves the membrane bud during vesicle formation to form a complete vesicle.

Type I pneumocytes

Squamous cells that are extremely thin to minimise gas diffusion distances in the alveoli.

Type II pneumocytes

Cuboidal cells in the alveoli containing granules (lamellar bodies) that store and secrete surfactant.

Sarcolemma

The single, continuous plasma membrane found in multinucleate skeletal muscle fibres.

Intercalated discs

Regions connecting individual cardiac muscle cells containing gap junctions for electrical conduction.

Acrosome cap

A structure in the head of a sperm cell containing hydrolytic enzymes used to penetrate an egg.

Axoneme

A microtubule structure within the sperm tail (flagellum) that bends to facilitate movement.

Zona pellucida

The jelly coat surrounding the egg cell that acts as a barrier to sperm entry.

Corona radiata

A layer of follicular cells that support the egg and provide it with nourishment.

Cortical granules

Granules in the egg cytosol that release chemicals upon fertilisation to prevent polyspermy.