Transcript b. Section 1.2 Cells

Unit 1: Cells and Systems
Section 2: Cells
I. Cell Theory
1. All organisms are made up of one or more cells.
2. The cell is the basic unit of life.
3. Cells are reproduced from other cells.
Organelles: smaller structures within cells that
carry on life functions.
• Unicellular: describes a single-celled living
thing.
• Multicellular: describes a living thing made up
of many cells.
• Both unicellular and multicellular things are
called organisms.
• Two main types of cells:
 Plant Cells
 Animal Cells
II. Cell Structures
Three Major Cell Parts
• Cell Membrane – thin flexible structure that
surrounds the cell. Regulates what enters and
exits the cell.
• Nucleus - “brain” of the cell. Controls
functions of the cell. Contains genetic
information – Deoxyribonucleic acid (DNA)
• Cytoplasm – jelly-like fluid in which organelles
are found. This is where many chemical
reactions take place within the cell.
Other Major Organelles:
• Mitochondrion –
converts the energy
stored in food into usable
energy for the cell (the
“powerhouse”) - cellular
respiration
• Ribosome – manufacture
proteins, the building
blocks for structures in
the cell.
• Endoplasmic reticulum – network of flattened tubes
that transport proteins within the cell.
• Golgi Body – sorts and packages proteins in
membrane-wrapped structures called vesicles.
• Vesicles - small packages containing proteins,
nutrients and water into, out of, and around the
cell.
• Vacuole – temporary storage areas; assist in
regulating water (usually bigger in plant cells)
• Lysosomes – contain digestive chemicals that break
down food particles, cell wastes, and worn-out cell
parts.
Additional Plant Cell Structures
• Cell Wall - rigid outer wall that provides protection,
support and shape. Contains pores to allow
substances to pass.
• Chloroplast - captures light to synthesize food
energy. Contains green pigment chlorophyll.
III. Energy for Cells
Photosynthesis
• Process where plants manufacture their own
food
• Occurs in the chloroplast, which contains the
pigment chlorophyll
• chlorophyll absorbs light and converts it into
chemical energy.
Photosynthesis
light energy
carbon dioxide + water
--->
glucose + oxygen
chlorophyll
• The glucose (sugar) is then stored for use later
Cellular Respiration
• cellular respiration takes place in the mitochondria
• occurs in both plants and animals
glucose + oxygen ---> carbon dioxide + water + energy
• the energy released can then be used by the cell
IV. Prokaryotic vs. Eukaryotic Cells
• Prokaryotic cells contain
organelles which are NOT
surrounded by a membrane.
• Eukaryotic cells contain
organelles which ARE
surrounded by a membrane.
• All multicellular organisms (and some unicellular
organisms such as amoeba) are composed of
eukaryotic cells.
V. Bacteria
• smallest and simplest form of life (prokaryotic
- no nucleus)
• single cells range from 1 nm to 20 nm long
• single large DNA strand
• Three main types:
• bacilli (rod-shaped)
• spirilla (spiral-shaped)
• cocci (sphere-shaped)
Bacteria - Harmful vs. Helpful
Harmful
• bacteria cause disease by invading the bodies of other
organisms and interfering with normal cell functions.
• Food spoilage
Helpful
• food production (yogurt, sourdough bread, cheese)
• tanning leather
• cleaning up environmental spills
• aids our digestive system
• Used to produce medicine such as insulin
VI. Viruses
• lack characteristics of living
cells – NON-LIVING!
ie. do not use energy,
move or grow.
• can only be seen by electron microscopes
• consist of a piece of DNA, covered by a protective
protein coat.
• Viruses reproduce by injecting their DNA into a host
cell, tricking it into manufacturing new viruses.
• The viruses accumulate in the cell preventing the cell
from functioning properly (causing disease).
Bacteria
Viruses
Are they considered living?
Yes
No
Composed of…?
A single prokaryotic cell
A piece of DNA
surrounded by protein
How do you treat a disease
caused by this organism?
Antibiotics
Bed rest, drink lots of
fluids, rarely antivirals
Section 1.3 Diffusion, Osmosis, and
the Cell Membrane
I. Membrane Permeability
• Permeable – lets everything through
o Cheesecloth is permeable to water
• Semi or selectively permeable – lets only
some things through
o A sieve is selectively permeable to pasta and water
• Impermeable – lets nothing through
o A plastic bag is impermeable to water
II. Concentration
• amount of substance in a given space.
– The more you have in a given space, the higher
the concentration.
III. Diffusion
• movement of molecules from an area of high
concentration to an area of low concentration.
Movement of Substances In and Out of the Cell
• Nutrients and waste materials must be able to
move into and out of the cell.
• Cell membrane regulates the passage of substances
in and out of the cell.
• “Selectively permeable” – permits only certain
molecules to enter or leave (semi-permeable).
Equilibrium
• reached when there is an equal number of particles on
either side of a membrane
• particles will still move back and forth, but the number
of particles on each side stays the same
IV. Osmosis
• process by which water moves across a membrane.
• Water moves across the cell membrane, depending
on the relative concentration of water inside and
outside the cell.
• Water moves from high water concentration to low
water concentration (special type of diffusion).
Diffusion
What type of
Nutrients and waste
material(s) is/are
products
transported?
How is it used by To bring in food, to
the cell?
export wastes
Which direction High concentration
is the flow of the
to low
material?
concentration
Osmosis
water
To maintain a
balance of water
within the cell
High concentration
to low
concentration