CELL BIOLOGY AND TRANSPORT

Eukaryotic cell

A type of cell whose genetic material ($\text{DNA}$) is contained within a membrane-bound nucleus (e.g., animal and plant cells).

Cell membrane

The sub-cellular structure that controls the passage of substances into and out of the cell.

Nucleus

The organelle in eukaryotic cells that encloses the genetic material ($\text{DNA}$) organized into chromosomes.

Mitochondria

The cellular sites of aerobic respiration, where energy is released for cellular processes.

Ribosomes

The sub-cellular sites of protein synthesis.

Cytoplasm

A jelly-like fluid inside the cell where most metabolic chemical reactions take place.

Permanent vacuole

A fluid-filled sac in plant cells that contains cell sap and helps support cell rigidity.

Chloroplasts

Plant organelles containing the pigment chlorophyll, which absorbs light energy to drive photosynthesis.

Cell wall

A rigid outer layer made of cellulose found in plant cells that provides structural support and strength.

Timing of cell differentiation in animals vs plants

Most animal cells differentiate early in development, whereas plant cells retain the ability to differentiate throughout their lifespan.

Sperm cell adaptations

Has a long tail for swimming toward the egg and many mitochondria to release the energy required for movement.

Red blood cell adaptations

Has a biconcave disc shape to increase surface area, lacks a nucleus to maximize space, and contains haemoglobin to bind oxygen.

Muscle cell adaptations

Contains protein fibres that contract to shorten the cell and many mitochondria to supply energy for contraction.

Nerve cell adaptations

Has branched dendrites to connect with other neurons and a myelin sheath that insulates the axon to speed up impulse conduction.

Root hair cell adaptations

Has a long extension that increases surface area for water and mineral uptake, along with many mitochondria to provide energy for active transport.

Palisade mesophyll cell adaptations

Packed with chloroplasts and located near the top surface of the leaf to maximize light absorption for photosynthesis.

Prokaryotic cell

A single-celled organism (such as a bacterium) lacking a membrane-bound nucleus, having a single circular loop of $\text{DNA}$ and plasmids.

Plasmid

A small, circular ring of accessory $\text{DNA}$ found in the cytoplasm of bacterial cells.

Flagellum

A whip-like structure that rotates to provide movement in bacterial cells.

Light microscope

An instrument using visible light and lenses to magnify specimens; it can image living material but has relatively low resolution and magnification.

Electron microscope

An instrument that uses a beam of electrons to achieve much higher magnification and resolution than a light microscope, revealing fine cell structures.

Magnification formula

$$\text{Magnification} = \frac{\text{Image size}}{\text{Actual size}}$$

Diffusion

The passive net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient.

Factors affecting diffusion rate

The steepness of the concentration gradient, temperature, and the surface area of the exchange membrane.

Osmosis

The passive diffusion of water molecules from a dilute solution to a concentrated solution across a partially permeable membrane.

Active transport

The movement of dissolved substances against a concentration gradient (from low to high concentration), requiring energy released by cellular respiration.

Active transport in the human digestive system

The uptake of glucose from the small intestine into the bloodstream when glucose concentration in the blood is higher than in the gut.