MITOCHONDRIA

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Mitochondria The organelle that releases energy

in the cell. (The powerhouse of the cell)

Mitochondria produce ATP using energy stored in

food molecules.

Mitochondria are the primary energy producers in

cells.

Structure

• Mitochondria have a double membrane structure

• There is a single outer membrane and a folded inner membrane

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• Sac with two inner compartments which are separated by the inner membrane.

• The first compartment is between the outer and inner membranes.

• The outer compartment is inside the inner membrane.

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• The outer mitochondrial membrane is composed of about 50% phospholipids by weight and contains a variety of enzymes involved in such diverse activities as the elongation of fatty acids, oxidation of epinephrine (adrenaline), and the degradation of tryptophan.

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• The inner membrane contains proteins with three types of functions [Alberts, 1994]:

• those that carry out the oxidation reactions of the respiratory chain

• ATP synthase, which makes ATP in the matrix • specific transport proteins that regulate the passage

of metabolites into and out of the matrix.

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Function

• Energy production the mitochondria has been called the "powerhouse of the cell".

• They use complex molecules and oxygen to produce a high energy molecule know as ATP (Adenosine Triphosphate)

• process called aerobic respiration• Mitochondria are very abundant in cells that

require lots of energy.• Ex:- Muscle

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Unique

• Mitochondria are very unique in several regards – have their own circular DNA – have their own Ribosomes.

(The DNA in the cell nucleus does not code for the construction of mitochondria. )

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• All the mitochondria in your body came from your mother.

• Mitochondria are not part of the genetic code in the nucleus of your cells.

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• Fathers only give genes to their children. • Mothers give genes and cytoplasm to their

children in their egg cells.

• Since mitochondria are in the cytoplasm and reproduce themselves .

• Geneticists have used this curious feature of mitochondria to study maternal family lines and rates of evolution.

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• Although the primary function of mitochondria is to convert organic materials into cellular energy in the form of ATP, mitochondria play an important role in many metabolic tasks, such as:

• Apoptosis-Programmed cell death • Glutamate-mediated excitotoxic neuronal injury • Cellular proliferation • Regulation of the cellular redox state • Heme synthesis • Steroid synthesis

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• Heat production (enabling the organism to stay warm).

• Some mitochondrial functions are performed only in specific types of cells. For example, mitochondria in liver cells contain enzymes that allow them to detoxify ammonia, a waste product of protein metabolism. A mutation in the genes regulating any of these functions can result in a variety of mitochondrial diseases.

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PlastidsIn most plant cells structures called plastids are found. They are found in the cytoplasmic matrix of plant cells only. These structures are generally spherical or ovoid in shape and they are clearly visible in living cells. We will discuss 3 types of plastids found in plant cells:

Chromoplasts

Chromoplasts are red, yellow or orange in color and are found in petals of flowers and in fruit. Their color is due to two pigments, carotene and xanthophylls.

Functions•the primary function in the cells of flowers is to attract agents of pollination,•and in fruit to attract agents of dispersal.

LeucoplastsLeucoplasts are colourless plastids and occur in plant cells not exposed to light, such as roots and seeds. They are colourless due the absent of pigments.

Functions•leucoplasts are the centers of starch grain formation;•they are also involved in the synthesis of oils and proteins.

PlastidsMembrane-bound organelles found only in plants

Chloroplast performs photosynthesis

Chromoplast stores pigments(little orange circles)

All little green circles are chloroplasts

Cell walls

Chloroplasts

Chloroplasts are probably the most important among the plastids since they are directly involved in photosynthesis. They are usually situated near the surface of the cell and occur in those parts that receive sufficient light, e.g. the palisade cells of leaves. The green colour of chloroplasts is caused by the green pigment chlorophyll.

Functions

•chloroplasts are the sites for photosynthesis;•they contain enzymes and co-enzymes necessary for the process of photosynthesis.

Structure

Chloroplasts are usually disc-shaped and surrounded by a double membrane. Inside the inner membrane there is a watery protein-rich ground substance or stroma in which is embedded a continuous membrane system, the granal network. This network forms a three- dimensional arrangement of membrane-bound vesicles called thylakoids. The thylakoids usually lie in stacks called grana and contain the photosynthetic pigments - green chlorophyll a and b and the yellow to red carotenoids. The grana are interconnected by tubular membranes called the intergranal frets or lamellae.

The endoplasmic reticulum is made out of a lipid membrane. The endoplasmic reticulum is still connected to the nuclear membrane that is wrap around the cell’s DNA. So there is a straight connection between the cells nucleus and the endoplasmic reticulum.

 Endoplasmic reticulum

•The rough endoplasmic reticulum is located around the nucleus in the cells of both plants and animals. It function and transports proteins and lipids throughout the cell.

•The smooth endoplasmic reticulum is connected to the nuclear envelope of cells in plants and animals. It's primary function is to facilitate the metabolism of carbohydrates and steroids in the cell

The endoplasmic reticulum is a eukaryotic organelle that forms an interconnected network of tubules, vesicles, and cisternae within cells.

Rough endoplasmic reticula synthesize proteins, while smooth endoplasmic reticula synthesize lipids and steroids, metabolize carbohydrates and steroids, and regulate calcium concentration, drug detoxification, and attachment of receptors on cell membrane proteins. Sarcoplasmic reticula solely regulate calcium levels.

Golgi Body

Structure• A group of flattened

cavities, is located near the nucleus.

Function• To take enzymes and other

proteins that have been synthesised in the endoplasmic reticulum and to package them into membrane-bound vesicles.

• The appearance of the Golgi Body is constantly changing as material comes in on one side from the ER and is lost from the other as completed vesicles ‘bud off’. Such vesicles transport materials to other parts of the cell, or fuse with the cell surface membrane, releasing their contents outside the cell.

How structure helps function?• The structure of the Golgi apparatus supports its

function. Electron microscopy indicates that the structure resembles interconnected, deflated balls or bags.

• One end serves as a “receiving point,” the other a “shipping center,” and the middle contains molecules that sort products and synthesize vesicles to surround them.

Lysosomes

–-Enzyme-filled sacs•-Generally spherical•-Surrounded by single membrane

How are they structured?

The “garbage disposals” of your cells; they are responsible for digesting and recycling materials that the cell no longer needs or has to get rid of.Lysosomes are very common in white blood cells, where disease and sickness are fought so a lot bacteria needs to be digested.Their shape and size vary depending on what material is digested. They contain about 40 different enzymes (ex. nucleases, proteases, lipases, and carbohydrases).

Main Functions of Lysosomes

1. Digestion of ingested material(by releasing enzymes into the new vacuole)

2. Autophagy & Cell Death(by digesting internal parts of the cell, such as organelles)

VACUOLES

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Vacuoles are organelles found in cells. They store various substances essential to the life of the cell. They also store waste to later remove from the cell.

Vacuoles, like vacuums, remove waste products harmful to the cell. In addition, they store water and essential nutrients for later use. For this reason, they are called “storage bubbles "or “storage bins”.

Microbodies/Peroxisome

Structure• A crystalline structure inside a sac which also contains

amorphous gray material • Bound by a single membrane that separates their contents

from the cytosol (the internal fluid of the cell) and contain membrane proteins critical for various functions