AP Bio - Ch.4: Tour of the Cell

Plasma membrane, cytosol, chromosomes, ribosomes

All Eukaryotic cells have these

Nucleus

houses most of the DNA

Enclosed by the nuclear envelope

Chromosomes

contains genetic material. Sub-unit of DNA

appears as:

• chromatin: DNA + protein complex

• nucleoli: where RNA is synthesized and rRNA + proteins are assembled → ribosomes

Nuclear envelope

Encloses the nucleus and perforated with pores to filter in traffic in cytoplasm

• has inner + outer membrane

• lined by nuclear lamina inside → made of protein filaments → maintain shape

• outer membrane is continuous with endoplasmic reticulum

ribosomes

utilizes DNA to make proteins

primary parts (rRNA and protein) assembled in the nucleoli

• free ribosomes → proteins in cytosol

• bound ribosomes → proteins that are attached to ER

endomembrane system

Involves the entirety of the membranes (including organelles) in and surrounding an eukaryotic cell. In charge of: synthesizing proteins, metabolizing lipids, and detoxifying

Includes:

• nuclear envelope

• endoplasmic reticulum

• Golgi apparatus

• lysosomes ← (not found in plant cells)

• vesicles and vacuoles

• plasma membrane

smooth endoplasmic reticulum

ER that lacks ribosomes. Synthesizes lipids and detoxifies drugs and poisons

(more poisons = higher detoxification rate)

rough endoplasmic reticulum

ER embedded with proteins. Responsible for synthesizing secretory proteins (glycoproteins), and membranes (a membrane factory)

• helps separate and package secretory proteins and their products into vesicles

  • helps expand plasma membrane of the cell itself

Golgi Apparatus

Flattened membranous sacs (cistarnae) that receives, modifies and transfers the products of the ER

Lysosomes

Membranous sac of hydrolytic enzymes that hydrolyze (digest) cell food

Hydrolyzes in two ways:

• phagocytosis — engulfs cell to digest components (food vacuole)

• autophagy — fuses with damaged components to digest them to be reused

  • recycles the cells’ own organelles and macromolecules

Mitochondria

site of cellular respiration: metabolic process that uses oxygen to drive intake of sugars to produce ATP.

“Power house of the cell” : responsible for providing energy for cellular processes

Made up of:

• inner and outer membrane

• cristae — folding in inner membrane → increases SA:V ratio

• matrix — compartment inside inner membrane

Chloroplast

site of photosynthesis: the conversion of solar energy into chemical energy Made up of:

• two membranes

• thylakoids — flattened membranous sacs

  • granum — a stack of thylakoids

• stroma — fluid outside of thylakoids

vacuoles

Membrane bound vesicle derived from Golgi and ER.

In plant cells: central vacuole — contains plant cells sap + responsible for their shape

peroxides

organelles that detoxify by transporting a hydrogen atom form a harmful substance

cytoskeleton

Network of fibers that stretch throughout the cytoplasm of a cell. Transports organelles through motor proteins, helps provide cell shape and alters plasma membrane to form food vacuole

Made up of:

• microtubules: creates dyneins (motor proteins in cillia/flagellum)

  • typically grows out of the centrosome ← only found in animal cells

• microfilaments: creates microvilli of cell and myosin (motor proteins in muscle cells contraction)

• intermediate filaments: related to keratin (found in hair)

Cell wall

Extracellular structure of plant cells that protects a plant cells, helps maintain its shape, and prevents and excessive intake of water

Made up of (2) layers:

• primary cell wall (innermost, thinnest wall)

• middle lamella (thin layer rich with polysaccharides)

extracellular matrix

ECM. Meshwork of proteins and molecules (glycoproteins and carbohydrates) surrounding an eukaryotic cell.

Helps communicate the cell’s environment with the cell through binding at receptor proteins called integrins

Includes:

• collagen — most abundant + forms strong fibers outside of cells

• fibronectin — secreted by eukaryotic cells → binds to integrins

Plasmodesmata

Cell junctions found only in plants

An open channel through the cell wall, connecting the cytoplasm of adjacent plant cells

Tight junctions

Cell junctions found in animal cells

“Seals” and prevents leakage of liquids/water between cells

Desmosomes

Cell junctions found in animal cells.

Fastens the cells together in strong sheets (“rivet”)

Gap junctions

Cell junctions found in animal cells.

Provides cytoplasmic channels for cell (similar to a plant cell’s plasmodesmata) ; necessary for communication between cells in tissues.