Cell Structure & Function

Take-home message 3.1  The most basic unit of any organism is the cell, the smallest unit of life that can function independently and perform all of the necessary functions of life, including reproducing itself.  All living organisms are made up of one or more cells and all cells arise from other pre- existing cells.

1. A prokaryotic cell does not have a nucleus; its DNA simply resides in the middle of the cell Every cell on earth falls into one of two basic categories:

2. A eukaryotic cell has a central control structure called a nucleus which contains the cell’s DNA.

FOUR STRUCTURES IN ALL PROKARYOTES PLASMA MEMBRANE Encloses cell contents: DNA, ribosomes, and cytoplasm CYTOPLASM Jelly-like fluid inside cell RIBOSOMES Granular bodies in the cytoplasm that convert genetic information into protein structure DNA One or more circular loops containing genetic information ADDITIONAL STRUCTURES THE PROKARYOTE: BASIC STRUCTURE CELL WALL Protects and gives shape to the cell PILI Hair-like projections that help cells attach to other surfaces FLAGELLUM Whip-like projection(s) that aids in cellular movement

Cell Structure & Function Prokaryotic Cells = 1 st cells (e.g., bacteria) Characteristics - chromosomes = circular molecule DNA - lack extensive compartmentalization - cell wall = outer layer of cell - plasma membrane: inside cell wall; semi- permeable membrane encloses cytoplasm

Cell Structure & Function Prokaryotic Cells (continued) - cytoplasm: watery medium inside plasma membrane - ribosomes: assemble amino acids into polypeptides

Cell Wall Three Main Functions: 1) maintains shape of cell 2) physical protection 3)

3.3 Eukaryotic cells have compartments with specialized functions.

Eukaryotic cells have organelles.

Eukaryotic Cells Eukaryotes differ from prokaryotes in several ways: 1) separation of nucleus from cytoplasm by double membrane (nuclear envelope) 2) DNA organized into distinct chromosomes (X-shaped) 3) complex membrane-bound organelles (e.g., mitochondria)

Plant Cells Have Them, Animal Cells Do Not: organelles: (“small organ”) structure that plays a specific role in the life of the cell

3-4. All cells are bordered by plasma membranes.

3.5 Molecules embedded within the plasma membrane help it perform its functions.

Simple Diffusion High Low

Take-home message 3.8  Cells must acquire necessary materials, such as food molecules, from outside the cell.  Cells must remove metabolic waste molecules and molecules for use elsewhere in the body.

3.9 Osmosis is the passive diffusion of water across a membrane.

Take-home message 3.8  In passive transport – which includes diffusion and osmosis – the molecular movement occurs spontaneously, without the input of energy.

3.10 In active transport, cells use energy to move small molecules. Molecules can’t always move spontaneously and effortlessly in and out of cells.

Active transport: uses energy directly from ATP

Three Functional Categories of Eukaryotic Organelles 1)Manufacturing Nucleus – genetic control center - DNA & RNA synthesis and ribosome assemble ribosomes: assemble amino acids into polypeptides (proteins/enzymes)

Three Functional Categories of Eukaryotic Organelles 1)Manufacturing Rough Endoplasmic Reticulum (Rough ER) - network of interconnected membrane- bound sacs - “rough” appearance because ribosomes stuck to membrane surface

Three Functional Categories of Eukaryotic Organelles Rough ER Two Functions: 1) make more ER membrane & other organelle membranes 2)

Three Functional Categories of Eukaryotic Organelles 1)Manufacturing Smooth ER - attached to Rough ER - network connected tubules that lack ribosomes - synthesize lipids, metabolize carbohydrates in liver, detoxify liver

Three Functional Categories of Eukaryotic Organelles 1)Manufacturing Golgi Apparatus (GA) “cell’s warehouse/factory” - stacks of membrane-bound sacs - work in close association with ER - receive, store, modify products of ER

Three Functional Categories of Eukaryotic Organelles 2) Breakdown of Material Lysosomes - produced by Rough ER & GA - digest nutrients within cell Vacuoles - plant cells - digest nutrients & storage sac

Three Functional Categories of Eukaryotic Organelles 3) Energy Processing Chloroplasts - plant cells - site of photosynthesis - absorb sun light & transform this energy to food - light absorbed in grana (stacked “solar packs”)

Three Functional Categories of Eukaryotic Organelles 3) Energy Processing Mitochondria – “cell powerhouse” - cellular respiration - double membrane - folds (cristae) of inner membrane - matrix is the inner fluid

Origin of Eukaryotic Cells (Essay Question?) Endosymbiotic Hypothesis Forerunners = symbiotic consortiums of prokaryotic cells Symbiotic cells within larger prokaryotes = origin of mitochondria & chloroplasts????

Endosymbiotic Hypothesis Ancestor of mitochondria = bacteria? Mitochondria: 1)