Key difference - chloroplast vs. mitochondria
Chloroplasts and mitochondria are two organelles found in the cell. The chloroplast is a membrane-bound organelle that only occurs in algae and plant cells . Mitochondria occur in fungi, plants and animal and eukaryotic cells . The main difference between chloroplasts and mitochondria is their function; Chloroplasts are responsible for producing sugar using sunlight in a process called photosynthesis, while mitochondria are the cells' powerhouses, breaking down sugars for energy in a process called cell respiration.
This article is about,
1. What is chloroplast - structure and function 2. What are mitochondria - structure and function 3. What is the difference between chloroplast and mitochondria
What is chloroplast?
Chloroplasts are a type of plastid found in algae and plant cells. They contain chlorophyll pigments to carry out photosynthesis. Chloroplast consists of its own DNA . The main function of chloroplasts is the production of organic molecules, glucose from CO 2 and H 2 O with the help of sunlight.
structure
Chloroplasts are identified as lenticular, green color pigments in plants. They have a diameter of 3-10 µm and a thickness of about 1-3 µm. Plant cells process 10-100 chloroplasts per cell. Various forms of chloroplast are found in algae. The algae cell contains a single chloroplast that can be in the shape of a net, cup, or ribbon-like spiral.
Figure 1: Chloroplast structure in plants
Three membrane systems can be identified in a chloroplast. They are outer chloroplast membrane, inner chloroplast membrane, and thylakoids.
Outer chloroplast membrane
The outer membrane of the chloroplast is semi-porous so that small molecules can easily diffuse. But large proteins cannot diffuse. Therefore, the proteins required by the chloroplasts are transported from the cytoplasm through the TOC complex into the outer membrane.
Inner chloroplast membrane
The inner chloroplast membrane maintains a constant environment in the stroma by regulating the passage of substances. After proteins have passed the TOC complex, they are transported through the TIC complex in the inner membrane. Stromules are the protrusions of the chloroplast membranes into the cytoplasm.
Chloroplast stroma is the fluid that is surrounded by two membranes of the chloroplast. Thylakoids, chloroplast DNA, ribosomes, starch granules, and many proteins swim around in the stroma. Ribosomes in the chloroplasts are 70S and are responsible for the translation of proteins encoded by the chloroplast DNA. Chloroplast DNA is referred to as ctDNA or cpDNA. It is a single circular DNA that resides in the nucleoid of the chloroplast. The size of the chloroplast DNA is approximately 120-170 kb and contains 4-150 genes and inverted repeats. Chloroplast DNA is replicated through the double displacement unit (D-loop). Most of the chloroplast DNA is transferred to the host genome by endosymbiotic gene transfer. A cleavable transit peptide is added to the N-terminus of the proteins translated in the cytoplasm as a targeting system for the chloroplast.
Thylakoids
The thylakoid system consists of thylakoids, a collection of highly dynamic, membrane-like sacs. Thylakoids consist of chlorophyll a , a blue-green pigment that is responsible for the light reaction during photosynthesis. In addition to chlorophylls, two types of photosynthetic pigments can be present in plants: yellow-orange carotenoids and red phycobilins. Grana are piles formed by the arrangement of thylakoids together. Different grana are connected to one another by the stromal thylakoids. Chloroplasts from C 4 plants and some algae consist of free-floating chloroplasts.
function
Chloroplasts are found in leaves, cacti, and stems of plants. A plant cell made up of chlorophyll is called chlorenchyme. Chloroplasts can change their orientation based on the availability of sunlight. Chloroplasts are able to produce glucose by using CO 2 and H 2 O with the help of light energy in a process called photosynthesis. Photosynthesis goes through two steps: the light reaction and the dark reaction.
Light reaction
The light reaction takes place in the thylakoid membrane. During the light reaction, oxygen is created by splitting water. The light energy is also stored in NADPH and ATP through NADP + reduction or photophosphorylation. Thus the two energy carriers for the dark reaction are ATP and NADPH. A detailed diagram of the light response is shown in Figure 2 .
Figure 2: Light reaction
Dark reaction
The dark reaction is also called the Calvin cycle. It occurs in the stroma of chloroplasts. The Calvin cycle goes through three phases: carbon fixation, carbon reduction and ribulose regeneration. The end product of the Calvin cycle is glyceraldehyde-3-phosphate, which can be doubled to glucose or fructose.
Figure 3: Calvin cycle
Chloroplasts are also able to produce all of the amino acids and nitrogenous bases in the cell on their own. This eliminates the need to export them from the cytosol. Chloroplasts are also involved in the plant's immune response to ward off pathogens.
What are Mitochondria?
A mitochondrion is a membrane-bound organelle that is found in all eukaryotic cells . The cell's chemical energy source, ATP, is produced in the mitochondria. Mitochondria also contain their own DNA within the organelle.
structure
A mitochondrion is a bean-like structure 0.75 to 3 µm in diameter. The number of mitochondria present in a particular cell depends on the cell type, tissue and organism. Five different components can be identified in the mitochondrial structure. The structure of a mitochondrion is shown in Figure 4.
Figure 4: Mitochondrion
A mitochondrion is made up of two membranes - the inner and outer membrane.
Outer mitochondrial membrane
The outer mitochondrial membrane contains a large number of integral membrane proteins called porins. Translocase is an outer membrane protein. Translocase-linked N-terminal signal sequence of large proteins enables the protein to invade mitochondria. The association of the mitochondrial outer membrane with the endoplasmic reticulum forms a structure called MAM (mitochondria-associated ER membrane). MAM enables the transport of lipids between mitochondria and the ER through calcium signals.
Inner mitochondrial membrane
The inner mitochondrial membrane is made up of more than 151 different types of proteins that function in a variety of ways. Porins are missing; the type of translocase in the inner membrane is called the TIC complex. The intermembrane space is located between the inner and outer mitochondrial membrane.
The space enclosed by the two mitochondrial membranes is called the matrix. Mitochondrial DNA and ribosomes with numerous enzymes are suspended in the matrix. Mitochondrial DNA is a circular molecule. The DNA is about 16 kb in size and codes for 37 genes. Mitochondria can contain 2-10 copies of their DNA in the organelle. The inner mitochondrial membrane forms folds in the matrix called the cristae. Cristae increase the surface area of the inner membrane.
function
Mitochondria produce chemical energy in the form of ATP, which is used in cellular functions in the process called breathing. The reactions involved in breathing are collectively referred to as the citric acid cycle or the Krebs cycle. The citric acid cycle takes place in the inner membrane of the mitochondria. It oxidizes pyruvate and NADH, which are formed in the cytosol from glucose with the help of oxygen.
Figure 5: Citric Acid Cycle
NADH and FADH 2 are the carriers of the redox energy generated in the citric acid cycle. NADH and FADH 2 transfer their energy to O 2 by traversing the electron transport chain. This process is known as oxidative phosphorylation. Protons released during oxidative phosphorylation are used by ATP synthase to produce ATP from ADP. A diagram of the electron transport chain is shown in Figure 6 . The ATPs produced pass through the membrane with the help of porins.
Figure 6: Electron transport chain
Functions of the mitochondrial inner membrane
- Carrying out oxidative phosphorylation
- ATP synthesis
- Holding transport proteins to regulate the passage of substances
- Holding the TIC complex for transportation
- Participation in mitochondrial splitting and fusion
Other functions of mitochondria
- Regulation of metabolism in the cell
- Synthesis of steroids
- Storage of calcium for signal transmission in the cell
- Membrane potential regulation
- Reactive oxygen species used in signal transmission
- Porphyrin synthesis in the heme synthesis pathway
- Hormonal signaling
- Regulation of apoptosis
Difference Between Chloroplast and Mitochondria
Cell type
Chloroplasts: Chloroplasts are found in plant and algae cells.
Mitochondria: Mitochondria are found in all aerobic eukaryotic cells.
colour
Chloroplast: Chloroplasts are green in color.
Mitochondria: Mitochondria are usually colorless.
shape
Chloroplast: Chloroplasts are disc-shaped.
Mitochondria: Mitochondria are bean-like in shape.
Inner membrane
Chloroplast: folds in the inner membrane form stromules.
Mitochondria: folds in the inner membrane form cristae.
Grana
Chloroplast : Thylakoids form stacks of discs called grana.
Mitochondria: Cristae do not form a grana.
subjects
Chloroplast: Two compartments can be identified: thylakoids and stroma.
Mitochondria: There are two compartments: cristae and the matrix.
Pigments
Chloroplast: Chlorophyll and carotenoids are present as photosynthetic pigments in the thylakoid membrane.
Mitochondria: No pigments can be found in mitochondria .
Energy conversion
Chloroplast: Chloroplast stores solar energy in the chemical bonds of glucose.
Mitochondria: Mitochondria convert sugar into chemical energy, which is ATP.
Raw materials and finished products
Chloroplast: Chloroplasts use CO 2 and H 2 O to build glucose.
Mitochondria: Mitochondria break down glucose into CO 2 and H 2 O.
oxygen
Chloroplast: Chloroplasts release oxygen.
Mitochondria: Mitochondria use up oxygen.
Processes
Chloroplast: Photosynthesis and photorespiration take place in the chloroplast .
Mitochondria: Mitochondria are a site of the electron transport chain, oxidative phosphorylation, beta oxidation and photorespiration.
diploma
Chloroplasts and mitochondria are both membrane-bound organelles that are involved in energy conversion. Chloroplast stores light energy in the chemical bonds of glucose in a process called photosynthesis. Mitochondria convert the light energy stored in glucose into chemical energy in the form of ATP, which can be used for cellular processes. This process is known as cellular respiration. Both organelles use CO 2 and O 2 in their processes. In addition to their main functions, both chloroplasts and mitochondria are involved in cell differentiation, signal transmission and cell death. They also control cell growth and the cell cycle. Both organelles are considered to have arisen through endosymbiosis. They contain their own DNA. However, the main difference between chloroplasts and mitochondria lies in their function in the cell.
Reference: 1. "Chloroplast" . Wikipedia, the free encyclopedia, 2017. Accessed on 02/02/2017 2. “ Mitochondrion ”. Wikipedia, the free encyclopedia, 2017. Retrieved on 02/02/2017
Image courtesy of: 1. “Chloroplast structure” By Kelvinsong - Own work (CC BY-SA 3.0) via Commons Wikimedia 2. “Thylakoid Membrane 3” By Somepics - Own work (CC BY-SA 4.0) via Commons Wikimedia 3 . ": Calvin-cycle4" By Mike Jones - Own work (CC BY-SA 3.0) via Commons Wikimedia 4. "Mitochondrial Structure" By Kelvinsong; modified by Sowlos - Own work based on: Mitochondrion mini.svg, CC BY-SA 3.0) via Commons Wikimedia 5. “Citric acid cycle noi” By Narayanese (talk) - Modified version of Image: Citricacidcycle_ball2.png. (CC BY-SA 3.0) via Commons Wikipedia 6. “Electron Transport Chain” By T-Fork - (Public Domain) via Commons Wikimedia
