Download 1.2 * Cells: The Basic Units of Life

1.2 – Cells: The Basic Units of Life
There are many different kinds of cells designed to carry out different
functions
The most common division of cell types is into the categories: ANIMAL
and PLANT.
General Structure of a Cell
Extracellular fluid (ECF) – The watery
environment outside of a cell
Cytosol – The aqueous solution inside a cell in
which all organelles are suspended
Cytoplasm – the cytosol and cell organelles
outside of the nucleus
• The nucleus acts as the control center of the
cell
Cell membrane (CM) – separates the insides of
the cell from the extracellular fluid
• Controls the movement of substances into
and out of the cell
• Has a property known as permeability – most
cells are ‘semi-permeable’ (meaning they
selectively allow certain substances through)
Cell wall – firm, porous structures found outside
of the cell membrane which give plants rigidity
while allowing water and dissolved materials to
pass through; found ONLY in PLANTS
Membranes
Made of a phospholipid bilayer – 2 layers of fat
molecules that have phosphate groups attached
to them
Also have proteins and carbohydrates
Are “fluid” – always moving
Organelles such as the nucleus, mitochondria,
and chloroplasts also have membranes
Nucleus
The control center of the cell that directs all of
the cell’s activities
Contains the genetic material DNA and RNA
Nucleolus – produces ribosomes
Nuclear envelope – porous membrane that
surrounds the nucleus and separates the
nucleus from the cytoplasm
Nuclear Pore – opening that allows things to
pass into and out of the nucleus
Nucleoplasm – the fluid inside the nucleus
Ribosomes
Produce proteins
Found in the cytoplasm or attached to
membranes
• Cytoplasm ribosomes – make proteins that
are used inside the cell
• Membrane ribosomes – make proteins that
are used outside the cell
Endoplasmic Reticulum (ER)
Membranous tubes that connect to the nuclear envelope
There are 2 types of ER:
1. Rough Endoplasmic Reticulum (RER)
• Has ribosomes attached to it
• Many proteins are made on it
2. Smooth Endoplasmic Reticulum (SER)
• Doesn’t have ribosomes
• Used for detox
• Produces molecules of fat
The products of the ER are packed in
membrane-bound structures called vesicles
Vesicles can be formed by the ER or the Golgi
apparatus
• Used for transport
Golgi Apparatus (GA)
The “post office” of the cell
Membranous tubes
Produce lysosomes
Chemically changes the proteins and fats made in the
ER and packages them into vesicles
The vesicles move through the cytoplasm, attach to the
CM, and release their contents into the ECF
Lysosomes
ONLY in ANIMAL cells
Contain proteins that can break down the
molecules that cells are made of into their
individual chemical components(breaks big
compounds into individual chemical
components)
• Used to digest food particles, can destroy
invading organisms (ie. Bacteria, viruses)
• Also used to decompose entire cells when
cells get too old to function properly
Apoptosis – cell suicide
The cell uses the remaining compounds to build
new cells
Mitochondria
The “powerhouse” of the cell
Membranous organelles that float freely in the
cytoplasm
Location of cellular respiration (CR) – a set of
reactions occurring in the mitochondria (in both
plants and animals) that produces energy (ATP)
Has 2 membranes:
1. Outer membrane – smooth
2. Inner membrane – highly folded; folds are
called cristae
• Cristae folds contain the compounds that
carry out the cellular respiration reactions
• The folds increase the surface area of the
membrane so that the mitochondria can produce
a lot of energy
• Cells that require a lot of energy have A LOT of
mitochondira (e.g., muscle cells, nerve cells)
Matrix – the protien-rich fluids that fill the space
inside of the mitochondria (inside the inner
membrane)
Intermembrane space – space between the outer
and inner membranes
Centrioles
Produce spider-web like fibres called spindle
fibres which are used in cell replication/division
(more on these later on in the course )
Plastids
Store useful materials and carries out vital
functions such as photosynthesis
• Photosynthesis – a set of chemical reactions
that converts carbon dioxide (CO2) and water
(H2O) into oxygen (O2) and food molecules
(glucose)
Chloroplast – a plastid that contains chlorophyll
and carries out the reactions of photosynthesis
• Contain 2 membranes: outer and inner
• Thylakoids – membrane-bound compartment
found in chloroplasts
• Granum – stack of thylakoids found in
chloroplasts
• Chlorophyll – the green pigment that begins the
process of photosynthesis; it is found in the
thylakoid membranes
• Stroma – protein-rich fluid that fills the space
between thylakoid membranes and the inner
membrane of the chloroplast
Other plastids include:
• Amyloplasts – white/colourless; store energyrich products of photosynthesis in the form of
starch
• Chromoplasts – colourful; contain the red,
orange, yellow pigments found in flowers,
fruits, and vegetables
Vacuoles
Large membrane-bound sacs filled with a watery
solution (water, dissolved sugars, minerals, and
proteins)
Turgor pressure – pressure, caused by water in the
cytoplasm and 1 or 2 large vacuoles, that helps
keep the cell membrane pressed firmly against the
cell wall of a plant cell
• This is why vegetables are firm and watery
When plant cells lose water, the vacuoles shrink,
turgor pressure decreases, the plant structures wilt
Homework
• Page 15 # 2-7, 9