Cells as the Basic Units of Life

This set of vocabulary flashcards covers the fundamental concepts of cell biology, including cell types, organelles, their specific functions, stem cells, and the levels of biological organization.

Cell

The basic units of life; all life on Earth is made from them, and without them, there can be no life.

Unicellular Organism

An organism that consists of only one cell, such as bacteria.

Multicellular Organism

An organism that consists of more than one cell (millions or billions), such as trees and blue whales.

Specialised Cells

Different types of cells within a multicellular organism, each with a different function.

Cell Wall

A non-living rigid layer found only in plant cells that consists of cellulose, is permeable, and gives the cell shape and structure.

Middle Lamella

One of the three layers of the plant cell wall, which is made of sticky pectin.

Cell Membrane

A thin double membrane made of a phospholipid bi-layer that surrounds the cytoplasm and is selectively permeable.

Cytoplasm

A jelly-like substance that fills the cell and contains a large amount of water, where organelles are suspended and chemical reactions take place.

Nucleus

An organelle consisting of a double nuclear membrane, nucleoplasm, nucleolus, and chromatin network that contains DNA and controls the cell.

Mitochondrion

The powerhouse of the cell responsible for cellular respiration and providing energy; it contains an inner membrane with folds called cristae.

Chloroplast

An organelle found only in plant cells that contains the green pigment chlorophyll and allows for photosynthesis.

Thylakoids

Structures inside the chloroplast that form stacks called grana.

Vacuole

An organelle used for storage of water, nutrients, and pigments and to provide support; plant cells have one large vacuole while animal cells have very small or none.

Tonoplast

The membrane that surrounds the vacuole.

Cell Sap

The liquid found inside the vacuole that contains dissolved substances and water.

Ribosomes

Organelles responsible for protein synthesis, either attached to the endoplasmic reticulum or floating in the cytoplasm.

Amyloplast

A plant cell organelle used for storing starch grains.

Stem Cells

Cells that have not yet differentiated (become specialized) and have the ability to divide and develop into different types of cells.

Embryonic Stem Cells

A type of stem cell found in the embryo capable of dividing into almost any cell type.

Adult Stem Cells

Stem cells found in specific locations in adults that can only differentiate into a limited number of related cell types, such as bone marrow stem cells.

Meristems

Regions in plants, typically close to the tip of the shoot and the root, where stem cells occur and can produce all types of plant cells.

Muscle Cells

Specialised cells that contract and relax for movement.

Nerve Cells

Specialised cells that transfer electrical impulses along the nervous system.

Red Blood Cells

Specialised cells that transport oxygen throughout the body.

Levels of Organization

The hierarchy of biological complexity: Organelle $\rightarrow$ Cell $\rightarrow$ Tissue $\rightarrow$ Organ $\rightarrow$ Organ system $\rightarrow$ Organism.