IB Biology - Cell Theory and Structure

This set of vocabulary flashcards covers the fundamental concepts of cell biology, including cell theory, microscopy techniques, prokaryotic and eukaryotic structures, stem cell potency, and membrane transport mechanisms as presented in the lecture notes.

Cells

The basic structural unit of all living organisms.

Metabolism

Essential chemical reactions undertaken by living things.

Reproduction

The process by which living things produce offspring, either sexually or asexually.

Sensitivity

The property of living things being responsive to internal and external stimuli.

Homeostasis

The maintenance of a stable internal environment in living things.

Excretion

The removal of waste products from living things.

Nutrition

The exchange of materials and gases with the environment.

Growth / Movement

The ability of living things to move and change shape or size.

Cell Theory

A theory consisting of three tenets: the cell is the smallest unit of life, cells only arise from pre-existing cells, and all living things are composed of cells (or cell products).

Total magnification formula

$$\text{total magnification} = \text{magnification of eyepiece} \times \text{magnification of objective lens}$$

Resolution

The smallest increment that an instrument can measure to, or the ability to distinguish between 2 points in microscopy.

Artefacts

Structures produced due to the preparation process that are not actually a feature of the specimen.

Transmission electron microscopes (TEMs)

Microscopes that pass electrons through a specimen to generate a cross-section image.

Scanning electron microscopes (SEMs)

Microscopes that scatter electrons over a surface to differentiate depth and map in 3D.

Cryogenic electron microscopy

A technique involving freezing samples prior to viewing to determine molecular structures at near atomic resolution without requiring crystallisation.

Freeze fracturing

A process where a frozen specimen is cracked along a plane to study internal cellular structures, such as integral membrane proteins.

Magnification formula

$$\text{Magnification} = \frac{\text{Size of the image}}{\text{Size of real object}}$$

Nucleoid

The region in a prokaryotic cell containing the main DNA, which is a single loop of "naked" DNA not enclosed in a membrane.

Plasmid

Extra pieces of small, circular, naked DNA in prokaryotic cells that replicate independently and can be shared between bacteria.

70s ribosomes

Smaller ribosomes found in prokaryotes, where "s" stands for the Svedberg unit.

Aseptic technique

Laboratory procedures carried out to prevent the contamination of pure cultures of microorganisms.

Eukaryotes

Organisms whose cells contain a nucleus and are compartmentalised by numerous membrane-bound organelles.

Endosymbiosis

The process by which eukaryotes are believed to have evolved from prokaryotic cells.

Transcription

The process in the nucleus where DNA instructions (genes) are converted into RNA transcripts (mRNA).

Translation

The synthesis of polypeptide chains (proteins) from RNA transcripts by ribosomes in the cytoplasm.

Lysosomes

Membrane-enclosed organelles containing acid hydrolases active at pH $\approx 5$ used to digest material and obsolete cell components.

Phagocytosis

A type of endocytosis where a cell uses its plasma membrane to engulf a large particle, creating a phagocytic vacuole (phagosome).

Aseptate Fungal Hyphae

Filamentous fungal structures that are not partitioned by septa and have a continuous cytoplasm with multiple nuclei.

Sieve tube elements

Specialized phloem cells that lack a nucleus and organelles to maximize space for sap transport, relying on companion cells for survival.

Stem cell

An undifferentiated cell that can divide indefinitely and differentiate into specialized cell types.

Totipotent stem cells

Cells that can form any cell type and develop into entirely new organisms, such as zygotes.

Pluripotent stem cells

Cells that can form any cell type arising from the three germ layers.

Multipotent stem cells

Adult stem cells that can only form a number of closely related cell types, such as those in bone marrow.

Stem cell niches

Specific areas within tissues where adult stem cells live and receive signals that influence their fate.

Differentiation

The process during development where newly formed cells become more specialised and distinct as they activate different genes.

Morphogens

Gene regulating chemicals (transcription factors) whose concentration gradients control differential gene expression in early embryos.

Amphipathic

A term for molecules, like phospholipids, that possess both hydrophobic and hydrophilic properties.

Integral Proteins

Transmembrane proteins that penetrate the phospholipid bilayer and are permanently attached.

Peripheral Proteins

Proteins temporarily associated with one side of a membrane, often attached to integral proteins or polar heads.

Fluid-mosaic model

A representation of cell membranes as fluid (viscous phospholipid movement) and mosaic (embedded with various proteins).

Glycosylation

The process of attaching carbohydrate chains to phospholipids (forming glycolipids) or proteins (forming glycoproteins).

Simple diffusion

The passive movement of small or lipophilic molecules along a concentration gradient without energy expenditure.

Facilitated diffusion

The passive movement of large or charged molecules across a membrane via transmembrane channel or carrier proteins.

Primary active transport

The movement of a molecule against its concentration gradient using energy from the direct hydrolysis of ATP.

Osmosis

The net movement of water molecules across a semi-permeable membrane from a region of low solute concentration to high solute concentration.

Aquaporins

Integral proteins that function as water channels to facilitate faster water transport across the bilayer.

Osmolarity

A measure of solute concentration defined as the number of osmoles of a solute per litre of solution ($osmol/L$).

Hypovolemia

Low blood plasma levels that can occur due to dehydration or excessive blood loss.