Transcript Cells and cell structure

Cells
Discovery of the Cell
In 1665, Robert Hooke was one of the first
people to see and identify cells.
• He used a microscope to look at thin slices of
cork. The cork was made of thousands of tiny
chambers.
• He called the chambers “cells” b/c they
reminded him of a monastery’s tiny rooms,
called cells.
Robert Hooke
The Cell Theory
Proposed by 3 scientists in
the mid-1800’s
• All living things are
made of cells.
• Cells are the basic unit
of structure and
function in living things.
• New cells are produced
from existing cells.
The cell theory applies to
ALL living things!
Prokaryotes and Eukaryotes
Prokaryote
• Do not have a nucleus
• Small and simple
• Bacteria are prokaryotic
Eukaryotes
• Have a nucleus
• Larger and complex
• Cells of protists, fungi,
plants, and animals are
eukaryotic
Prokaryotes and Eukaryotes
Prokaryotic Cell
Eukaryotic Cell
Cell Structure
Eukaryotic cells are
divided into two major
parts – the nucleus
and the cytoplasm.
• The cytoplasm is the
portion of the cell
outside the nucleus,
but inside the cell
membrane.
Cell Structure
• Eukaryotic cells
contain many
structures, each
with specialized
functions. These
specialized
structures are
called organelles.
Cell Structure - Nucleus
• Contains almost all of the
cell’s DNA; the DNA
contains genetic info and
instructions for making
proteins
• Controls the cell’s
processes/activities
• The DNA exists as
chromatin when the cell
isn’t dividing. Chromatin
consists of DNA and
protein.
• Double membrane
Cell Structure - Nucleolus
• Inside the nucleus is a
structure called the
nucleolus.
• The nucleolus
manufactures
ribosomes.
Cell Structure - Ribosomes
• Ribosomes are tiny
organelles that
manufacture proteins.
• Ribosomes are located
on rough endoplasmic
reticulum and
throughout the
cytoplasm.
Cell Structure – Endoplasmic
Reticulum
• ER transports
substances throughout
the cell.
• Rough ER has
ribosomes on it, so it
produces proteins.
• Smooth ER lacks
ribosomes
Cell Structure – Golgi Apparatus
• Closely-stacked
membranes
• Modify, sort, and
package proteins
and other materials
from the
endoplasmic
reticulum for
storage in the cell,
or secretion outside
the cell.
Cell Structure - Lysosomes
• Lysomes are small sacs
filled with digestive
enzymes.
• These enzymes break
down macromolecules
into small molecules .
• They also break down
old, worn-out
organelles. They “clean
up” the cell.
Cell Structure - Vacuole
• Large sac-like
organelle in plant
cells
• Stores water, carbs,
proteins, and salts
• Is usually the largest
organelle in plant
cells
Cell Structure - Mitochondria
• Convert the
chemical energy
stored in food into
compounds that
are more
convenient for the
cell to use.
• “Powerhouse” of
the cell
• Double membrane
Cell Structure - Chloroplasts
• Not found in animal or
fungi cells
• Capture energy from
sunlight and convert it
into chemical energy in
a process called
photosynthesis.
• Double membrane
Cell Structure - Cytoskeleton
• In all cells, the
cytoskeleton maintains
the shape of the cell
• Cilia and flagella
(extensions of the
cytoskeleton) help
some cells swim
through water.
Cell Structure - Cytoskeleton
Cilia
• Numerous
• Short and hair-like
• Help unicellular organisms
• Help multicellular
organisms rid organs of dust
and move mucous
Flagella
• Usually a cell only has one
• Long and whip-like
• Help unicellular organisms
swim in liquids
Cell Structure – cell membrane
• Regulates what
enters and
leaves the cell
• Double layer of
phospholipids
• Fluid mosaic
model (not rigid)
• Selectively
permeable
Cell Structure – Cell Wall
• Not present on animal
cells
• Rigid; made of cellulose
and protein
• Support and protect the
cell
Plant vs. Animal Cells
Plant cells
• “boxy”
• Often green
• Contain chloroplasts,
vacuole, and cell wall
Animal Cells
• Variety of shapes depending
on function
• May contain structures for
movement (cilia and
flagella)
Plant Cells
Animal Cells
Transport Across Cell Membrane
• Passive transport requires no energy input
from cell (Ex. Osmosis, diffusion, facilitated
diffusion)
• Active transport requires energy input to
move molecules across the cell membrane
Moving Across the Cell Membrane
(Passive)
Diffusion is the movement • When equilibrium is
of particles (solutes)
reached, solute
from an area of greater
particles still continue
concentration to an
to move across the
area of lesser
membrane in both
concentration.
directions.
When the concentration
of solutes on both sides
of the cell membrane is
the same, equilibrium
exists.
Moving Across the Cell Membrane
Moving Across the Cell Membrane
Osmosis is
the
diffusion of
water
across a
membrane.
• Isotonic if
concentration of
dissolved
particles is the
same outside of
cell compared
to inside
•Hypotonic if
concentration of
dissolved particles is
lower outside of cell
compared to inside
• Hypertonic if
concentration
of dissolved
particles is
higher outside
of cell
compared to
inside
Moving Across the Cell Membrane
Osmotic Pressure
• What would happen to a cell if it were placed
in an isotonic solution?
• What would happen to a cell if it were placed
in a hypertonic solution?
• What would happen to a cell if it were placed
in a hypotonic solution?
Moving Across the Cell Membrane
Movement Across the Cell Membrane
During facilitated
diffusion, molecules
that cannot cross the
cell membrane by
themselves b/c they are
too big, get help from
protein channels in the
membrane.
Uses transport protein
Endocytosis and Exocytosis
• Endocytosis
• Exocytosis
Movement Across the Cell Membrane
Sometimes, cells must
move substances in the
opposite direction of
diffusion against the
concentration gradient
To move substances
from a low
concentration to a
higher concentration
requires energy. This
requires active
transport.
Uses transport protein
Cell Diversity
Unicellular Organisms
• Made of only one cell
Multicellular Organisms
• Made of many cells
Cell Diversity
Multicellular organisms are made of many, many
specialized cells. In cell specialization, the
cells of a multicellular organism develop in
different ways to perform different tasks in the
organism.
Levels of Organization
In multicellular organisms, the levels of organization
of the body are (from simplest to most complex):
• Cells
• Tissues - a group of similar cells that perform a particular
function (ex: nervous, connective, epithelial, and muscle)
• Organs - a group of tissues working together to perform a
specific function (ex: heart, pelvis, uterus)
• Organ systems – group of organs working together to perform
a specific function (ex: cardiovascular system, reproductive
system)`