Download Chapter 3 THE CELL

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What is Biology?
Biology is the study of living things, including microscopic life,
plants, and animals
WHAT IS LIFE?
All living things share certain characteristics:
 Organized: Atoms ---> molecules ---> cells ---> community
 Genetic Code: DNA
 Homeostasis: Maintain a stable internal environment
(temperature) as outside environment changes (hot/ cold)
 Metabolism: Take in energy from environment, transform it
and use it
 Movement: Respond to the environment (search for food,
evade predators)
 Growth: develop and mature
 Reproduce: cell division or mating
 Adapt to environment: must change to survive as
environment changes.
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THE CELL
Introduction
 The 3 rules of The Cell Theory:
1. The cell is the basics unit of life.
2. All living things are made of one or more cells.
3. All cells are produced from other cells by cell division.
 The cell is the smallest unit that can carry out activities needed for
life (the functional unit of life).
 Cells have an outer surface called a cell membrane that shields the
inside of the cell.
o Cell membranes have “gates” that allow materials in and out of cell.
Cell Types
 Two major types of cells evolved:
1. Prokaryotic Cells
o Small simple cells that lack a nucleus and have been around for
billions of years.
o Prokaryotic cells’ DNA is in a single circular DNA molecule that
is not surrounded by a membrane.
o Organisms that are made up of a single prokaryotic cell are called
prokaryotes
o Prokaryotes are made up of only one cell- bacteria are the only
kind of prokaryotes around today.
2. Eukaryotic cells
o Large complex cells that contain internal parts called organelles
that have their own membrane.
o Eukaryotic cells also have a nucleus which contains DNA and
acts as the control center of the cell.
o Organisms with eukaryotic cells are called eukaryotes.
o Eukaryotes are usually made up of many cells, like people, dogs,
fish, plants, etc.
o Sometimes though they are living one cell organisms like fungi or
protist.
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 Similarities: Eukaryotes and prokaryotes both have a mostly fluid
internal environment called the cytoplasm and both make proteins
with small internal structures call ribosomes. (Also both have DNA
and a cell membrane.) One major difference is size:
Eukaryotic Cells Have Compartments
 These internal structures are called organelles that carry out necessary
functions for the cell to survive.
o This is just like your body contains different specialized organs that
perform necessary functions for you to survive. (Examples?)
o Organelles are specialized compartments inside a cell that perform
specialized functions such as supplying energy, packaging and
delivery products, etc. so the cell and/ or organism can survive.
o Organelles are contained in the cytosol which is the liquid part of
the cytoplasm in the cell.
Organelles: A Cell’s Laborers
 The nucleus directs cell activities: control “brain” center of the cello The nucleus stores the cells DNA in structures called chromosomes.
o The nucleus is encased in a double membrane called the nuclear
envelope.
o The nucleus contains a nucleolus which makes ribosomes.
 The mitochondria is the “powerhouse” of the cello Converts food into energy in a process called cellular respiration.
o The cell uses this energy to “power” its activities.
 The endoplasmic reticulum (ER) looks like many folded sheets.
o Sometimes ribosomes that make protein appear as little round
specks on the ER: the ER then looks rough (R) and is called
the Rough Endoplasmic Reticulum RER.
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o When there are no ribosomes on the ER, the ER appears
smooth(S) and is called the Smooth Endoplasmic Reticulum
SER which provides a location for lipids (fats) to be made.
 The Golgi apparatus is the “post office” of the cell.
o The Golgi apparatus labels molecules such as proteins.
o The Golgi apparatus then packages theses molecules for transport
around or out of the cell.
 Ribosomes are the site of protein synthesis (proteins being made).
 Lysosomes are organelles that digest material such as nutrients, waste
and disease causing bacteria.
 Vacuoles- saclike structures that store materials such as water, food
and waste products.
Plant Cells Differ From Animal Cells in 4 major ways:
1. Plants have bigger and stronger vacuoles - so they can store more
water that creates pressure which helps plants stand upright
(when there is less water, plants wilt).
2. Plant cells contain chloroplasts - Chloroplasts convert energy from
the sun into energy for the plant in a process called photosynthesis.
3. Plants have rigid cell walls - These cell walls provide a thick outer
layer made of protein and cellulose for protection and support.
4. Animals, but not plants, have centrioles - cylinder looking structures
which are help cells divide and multiply so we can grow.