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Mitochondria are oval-shaped, double membrane organelles ( [link] ) that have their own ribosomes and DNA. Each membrane is a phospholipid bilayer embedded with proteins. The inner layer has folds called cristae. The area surrounded by the folds is called the mitochondrial matrix. The cristae and the matrix have different roles in cellular respiration.

This transmission electron micrograph of a mitochondrion shows an oval outer membrane and an inner membrane with many folds called cristae. Inside the inner membrane is a space called the mitochondrial matrix.
This electron micrograph shows a mitochondrion as viewed with a transmission electron microscope. This organelle has an outer membrane and an inner membrane. The inner membrane contains folds, called cristae, which increase its surface area. The space between the two membranes is called the intermembrane space, and the space inside the inner membrane is called the mitochondrial matrix. ATP synthesis takes place on the inner membrane. (credit: modification of work by Matthew Britton; scale-bar data from Matt Russell)


Peroxisomes are small, round organelles enclosed by single membranes. They carry out oxidation reactions that break down fatty acids and amino acids. They also detoxify many poisons that may enter the body. (Many of these oxidation reactions release hydrogen peroxide, H 2 O 2 , which would be damaging to cells; however, when these reactions are confined to peroxisomes, enzymes safely break down the H 2 O 2 into oxygen and water.) For example, alcohol is detoxified by peroxisomes in liver cells. Glyoxysomes, which are specialized peroxisomes in plants, are responsible for converting stored fats into sugars.

Vesicles and vacuoles

Vesicles and vacuoles are membrane-bound sacs that function in storage and transport. Other than the fact that vacuoles are somewhat larger than vesicles, there is a very subtle distinction between them: The membranes of vesicles can fuse with either the plasma membrane or other membrane systems within the cell. Additionally, some agents such as enzymes within plant vacuoles break down macromolecules. The membrane of a vacuole does not fuse with the membranes of other cellular components.

Animal cells versus plant cells

At this point, you know that each eukaryotic cell has a plasma membrane, cytoplasm, a nucleus, ribosomes, mitochondria, peroxisomes, and in some, vacuoles, but there are some striking differences between animal and plant cells. While both animal and plant cells have microtubule organizing centers (MTOCs), animal cells also have centrioles associated with the MTOC: a complex called the centrosome. Animal cells each have a centrosome and lysosomes, whereas plant cells do not. Plant cells have a cell wall, chloroplasts and other specialized plastids, and a large central vacuole, whereas animal cells do not.

The centrosome

The centrosome    is a microtubule-organizing center found near the nuclei of animal cells. It contains a pair of centrioles, two structures that lie perpendicular to each other ( [link] ). Each centriole is a cylinder of nine triplets of microtubules.

The centrosome consists of two centrioles that lie at right angles to each other. Each centriole is a cylinder made up of nine triplets of microtubules. Nontubulin proteins (indicated by the green lines) hold the microtubule triplets together.

Questions & Answers

A skeleton is any film structure that gives mechanical support to the body and provides protection to the softer parts of the body.
Patrick Reply
A skeleton is a frame or bony part of a body that aid in the movement of different parts of the body.
What is a skeleton?
Chipo Reply
is a bone without meat
what is an electron microscope?
Chr Reply
what is biochemist
Lenard Reply
biochemistry:-is the study of chemical reaction with living organisms
what are the scientific method
Precious Reply
describe the functioning of the Golgi body in animal cells
Naiga Reply
what features does red blood have that allows it to effectively move through the blood and transport oxygen? list at least four features and explain how they help RBC's carry out their functions.
Alice Reply
has nucleus, haemoglobin
what is biology
kenneth Reply
it's the study of living organisms and their interactions with one another and the environment
Biology is the study of life.
describe the structure of DNA
Mafashion Reply
it a double helical structure negatively charged as a results of a phosphate backbone and the two strands are joined together by hydrogen bonds
Bring out clearly the process of clothing
Irene Reply
How is the region of unwinding called
what is hoemositasis
homeostasis is the regulation of a constant internal environment
is an unfavourable conditions cost by capavic bacteria
hashim Reply
no idea
no idea
Describe the following terms used in nutrition, parasitism, saprophytic, symbiosys
Meymo Reply
parasitism involves gaining and losing
a saprophyte does not cause harm to it Host.
in symbiosis the two organisms are benefiting
what is meiosis?
Emmanuel Reply
Meiosis is a two successive cell division with only one duplication of chromosomes
what are types of white cells
Kennedy Reply
phagocytes and lymphocytes
Lymphocytes and phagocytosis
which plant tissue conducts sucrose in solution?
granulocytes and agranulocytes
granulocytes and agranulocyte
types of asexual reproduction
Iradukunda Reply
what is prokaryotic
a bacteria
what is the right medication for heart burn?

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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