Cell Structure and Function

These flashcards provide definitions and essential characteristics of cell structures, organelles, and membrane transport processes as described in the lecture notes.

Cell

The basic unit of structure and function in the body, which is a highly organized molecular factory consisting of the plasma membrane, cytoplasm, and nucleus.

Plasma Membrane

A selectively permeable double layer of phospholipids that surrounds the cell, gives it form, and restricts the passage of polar compounds.

Glycoproteins and Glycolipids

Carbohydrates on the outer surface of the plasma membrane that impart a negative charge and can serve as cell surface markers (antigens).

Bulk Transport

The process by which cells move large molecules and particles across the plasma membrane.

Phagocytosis

A type of bulk transport used by cells, such as white blood cells and macrophages, to take in particulate matter.

Endocytosis

A process where the plasma membrane invaginates to take in a vesicle of extracellular substance.

Pinocytosis

The non-specific intake of fluid particles into the cell.

Receptor-mediated endocytosis

A specific process that uses receptors to take in compounds, including some viruses, into the cell.

Exocytosis

The process cells use to export products into the extracellular fluid via secretory vesicles involving $SNARE$ proteins.

Cilia

Hair-like structures that beat in unison, line the respiratory and reproductive tracts, and contain microtubules in a $9 + 2$ arrangement.

Microvilli

Finger-like structures on the surface of some epithelial cells that expand the surface area for absorption.

Cytoplasm

The jellylike matrix within a cell consisting of fluidlike cytosol and organelles.

Cytoskeleton

A latticework of microfilaments and microtubules that gives the cell its shape and serves as tracks for internal transport.

Organelles

Cytoplasmic structures that perform specialized functions for the cell.

Lysosomes

Vesicle-like organelles containing digestive enzymes involved in recycling cell components and programmed cell death ($\text{apoptosis}$).

Apoptosis

The process of programmed cell death.

Peroxisomes

Membrane-walled sacs containing oxidase enzymes that neutralize free radicals, break down poisons and long chains of fatty acids, and are numerous in the liver and kidneys.

Catalase

An enzyme found in peroxisomes that neutralizes the hydrogen peroxide produced by the organelles.

Mitochondria

Energy-producing organelles believed to have originated from symbiotic bacteria that make $ATP$ and contain an inner membrane, outer membrane, matrix, and cristae.

Ribosomes

The cell's protein factories where proteins are synthesized, composed of $2$ $rRNA$ subunits and proteins.

Endoplasmic Reticulum (ER)

A system of membranes specialized for the synthesis or degradation of molecules, consisting of rough $ER$ for protein synthesis and smooth $ER$ for steroid synthesis and inactivation.

Golgi Complex

A stack of flattened sacs where vesicles from the $ER$ are modified and from which lysosomes and secretory vesicles are formed.

Nucleus

The organelle containing the cell's $DNA$, enclosed by a double membrane nuclear envelope.

Nuclear Pore Complexes

Structures that fuse the inner and outer nuclear membranes, allowing small molecules to diffuse while requiring active transport for proteins and $RNA$.

Transcription

The first stage of gene expression where a $DNA$ sequence in a gene is turned into an $mRNA$ sequence.

Translation

The second stage of gene expression where an $mRNA$ sequence is used to make a protein at the ribosomes.

Nucleoli

Dark areas within the nucleus containing genes that are actively making $rRNA$.