Transcript Cells

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 preexisting cells.
Every cell on earth falls into one of two
basic categories:
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.
THE PROKARYOTE: BASIC STRUCTURE
FOUR STRUCTURES IN ALL PROKARYOTES
ADDITIONAL STRUCTURES
PLASMA MEMBRANE
CELL WALL
CYTOPLASM
PILI
Encloses cell contents: DNA,
ribosomes, and 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
Protects and gives shape to
the cell
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 = 1st cells (e.g., bacteria)
Characteristics
- chromosomes = circular molecule DNA
- lack extensive compartmentalization
- cell wall = outer layer of cell
- plasma membrane: inside cell wall; semipermeable 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)
organelles: (“small organ”) structure that plays
a specific role in the life of the cell
Plant Cells Have Them, Animal
Cells Do Not:
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 membranebound 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)