A basic overview of the structures and functions of Smooth Endoplasmic Reticulum and Mitochondria.

1. MITOCHONDRIA AND
SMOOTH ENDOPLASMIC
RETICULUM
Sarah, Olivia, Anna and Jonti

2. Where are they located in the cell?
• Mitochondria used to be single-
celled organisms 2 billion years ago
but are now freely suspended in the
cytoplasm of cells often near a cell’s
flagella if the cell is particularly
active. Although most DNA is
within the nucleus, mitochondria
also have a small amount of their
own DNA, known as mitochondrial
DNA or mtDNA.
• Smooth Endoplasmic Reticulum,
SER, unlike RER, is not integrated
into the membrane of the nucleus
but is instead held in the cytoplasm,
but with one end still near to the
nucleus, or sometimes even
connected to the RER.

3. The Structure of a Mitochondrion
• Christae, projections of
the inner membrane,
extend into the matrix of
the cell. Giving the inner
membrane a larger
surface area, the christae
increase the rate of ATP’s
synthesis.
• Mitochondria have a double membrane
structure, each membrane 6nm in thickness.
The outer membrane is much smoother and
has an abundance of ‘porin’ transport
proteins that pass through the outer
membrane, allowing for more passive
diffusion. The inner layer is much more rough
but still highly permeable. A higher
concentration of protons (H+ ions) outside
the inner membrane of the mitochondria
than inside the inner membrane, creating a
gradient, drives the formation of ATP.
• The matrix of the
mitochondria
contains the
enzymes, ATP
synthase, that are
involved in the
synthesis of ATP.
• ATP synthase is an enzyme
that synthesizes the reaction
between ADP and a
phosphate to create ATP. It
uses the movement of H+
ions across the membrane to
carry out the reaction.

4. What is the function of a mitochondrion?
The function of the mitochondria is to create adenosine triphosphate, chemical
energy, from adenosine diphosphate and a phosphate.Through the membranes,
the ATP can then be released to the rest of the cell, where it is needed.
Some functions of ATP in the cell include:
• ActiveTransport- moving substances across cell membranes.
• ‘Mechanical Work’- releasing the energy needed for muscle contraction.
• ‘Chemical Work’- supplying the energy needed to synthesize the molecules that
the cell requires.
• ATP is also used to control chemical reactions and to send messages across the
cell.

5. Which Cells require an abundance of
Mitochondria?
The Heart’s Muscle Cells Sperm Cells Brain Cells

6. The Structure of SER
• Smooth ER is more tubular than RER and is formed of a long network of a folded,
hollow membrane. It can be thought of as a pipe with a lot of twists and turns. Like
in vessels the inside of the SER is called the lumen, which is enclosed by a
phospholipid membrane, just like the membrane around the entire cell.The
number of smooth ER units in a cell depends on the type of cell and also it
purpose.

7. What is the function of SER?
• The main function of SER is to act as a
storage organelle. It’s important in the
creation and storage of lipid molecules
and steroids Most SER in both plant and
animal cells makes lipids, however, and
so cells involved in the manufacture of
lipids contain more SER than others. .
Cells in your body that release oils also
have more SER than most cells, for
example. Additionally, the testes have
lots of SER, as do the ovaries, as they
need to make testosterone (in men and
women) and oestrogen (women).
Steroids are organic compounds that are
made up of four rings of carbon atoms.
Steroids are a type of organic molecule
used for many purposes in an organism.
For example, the hormones testosterone
and oestrogen are steroids.