Mitochondria and chloroplasts (article) | Khan Academy
Start studying Cristae, Thylakoids, & Grana. Learn vocabulary, terms, and more with flashcards, games, and other study tools. To a superficial extent (division in grana and stroma lamellae), this difference is .. We also tested this (not shown) and found this illumination region to allow. The existence of grana thylakoid membranes sets special structural constraints to the relation between the width of the stromal gap in grana stacks and the stromal . A method that promises to test its existence is EM tomography that has the.
Cytochrome b6f complex[ edit ] Main article: Cytochrome b6f complex The cytochrome b6f complex is part of the thylakoid electron transport chain and couples electron transfer to the pumping of protons into the thylakoid lumen. Energetically, it is situated between the two photosystems and transfers electrons from photosystem II-plastoquinone to plastocyanin-photosystem I.
Mitochondria and chloroplasts
It is integrated into the thylakoid membrane with the CF1-part sticking into stroma. Thus, ATP synthesis occurs on the stromal side of the thylakoids where the ATP is needed for the light-independent reactions of photosynthesis.
Lumen proteins[ edit ] The electron transport protein plastocyanin is present in the lumen and shuttles electrons from the cytochrome b6f protein complex to photosystem I. While plastoquinones are lipid-soluble and therefore move within the thylakoid membrane, plastocyanin moves through the thylakoid lumen. The lumen of the thylakoids is also the site of water oxidation by the oxygen evolving complex associated with the lumenal side of photosystem II.
Lumenal proteins can be predicted computationally based on their targeting signals. However, during the course of plastid evolution from their cyanobacterial endosymbiotic ancestors, extensive gene transfer from the chloroplast genome to the cell nucleus took place. This results in the four major thylakoid protein complexes being encoded in part by the chloroplast genome and in part by the nuclear genome.
Plants have developed several mechanisms to co-regulate the expression of the different subunits encoded in the two different organelles to assure the proper stoichiometry and assembly of these protein complexes.
For example, transcription of nuclear genes encoding parts of the photosynthetic apparatus is regulated by light. Biogenesis, stability and turnover of thylakoid protein complexes are regulated by phosphorylation via redox-sensitive kinases in the thylakoid membranes.
The redox state of the electron carrier plastoquinone in the thylakoid membrane directly affects the transcription of chloroplast genes encoding proteins of the reaction centers of the photosystems, thus counteracting imbalances in the electron transfer chain.
Most thylakoid proteins encoded by a plant's nuclear genome need two targeting signals for proper localization: An N-terminal chloroplast targeting peptide shown in yellow in the figurefollowed by a thylakoid targeting peptide shown in blue.
Difference Between Grana and Thylakoid | Definition, Function, Relationship
Proteins are imported through the translocon of outer and inner membrane Toc and Tic complexes. After entering the chloroplast, the first targeting peptide is cleaved off by a protease processing imported proteins.
This unmasks the second targeting signal and the protein is exported from the stroma into the thylakoid in a second targeting step. This second step requires the action of protein translocation components of the thylakoids and is energy-dependent.
Proteins are inserted into the membrane via the SRP-dependent pathway 1the Tat-dependent pathway 2or spontaneously via their transmembrane domains not shown in figure. Let's take a closer look at these two very important organelles. Chloroplasts Chloroplasts are found only in plants and photosynthetic algae.
Difference Between Grana and Thylakoid
Humans and other animals do not have chloroplasts. The chloroplast's job is to carry out a process called photosynthesis. In photosynthesis, light energy is collected and used to build sugars from carbon dioxide.
The sugars produced in photosynthesis may be used by the plant cell, or may be consumed by animals that eat the plant, such as humans. The energy contained in these sugars is harvested through a process called cellular respiration, which happens in the mitochondria of both plant and animal cells. Chloroplasts are disc-shaped organelles found in the cytosol of a cell.
They have outer and inner membranes with an intermembrane space between them. Diagram of a chloroplast, showing the outer membrane, inner membrane, intermembrane space, stroma, and thylakoids arranged in stacks called grana.
Thylakoid discs are hollow, and the space inside a disc is called the thylakoid space or lumen, while the fluid-filled space surrounding the thylakoids is called the stroma.
You can learn more about chloroplasts, chlorophyll, and photosynthesis in the photosynthesis topic section. Mitochondria Mitochondria singular, mitochondrion are often called the powerhouses or energy factories of the cell. The process of making ATP using chemical energy from fuels such as sugars is called cellular respirationand many of its steps happen inside the mitochondria.Chloroplasts - Structure
The mitochondria are suspended in the jelly-like cytosol of the cell. They are oval-shaped and have two membranes: Electron micrograph of a mitochondrion, showing matrix, cristae, outer membrane, and inner membrane.
Modification of work by Matthew Britton; scale-bar data from Matt Russell. The matrix contains mitochondrial DNA and ribosomes. We'll talk shortly about why mitochondria and chloroplasts have their own DNA and ribosomes. The multi-compartment structure of the mitochondrion may seem complicated to us.
That's true, but it turns out to be very useful for cellular respirationallowing reactions to be kept separate and different concentrations of molecules to be maintained in different "rooms.
Dark reaction of the photosynthesis occurs in the stroma of chloroplast. A single chloroplast contains 10 to grana. Granum inside the chloroplast is shown in figure 1. Granum in Chloroplast What is Thylakoid Thylakoid is the little, round, flat, pillow-shaped things inside the chloroplast.
Thylakoid is a membrane-bound structure. The space between thylakoid membrane is called thylakoid lumen. The functional parts of the chloroplast are its membrane and the lumen. The light-trapping green pigment, chlorophyll is found in the thylakoid membrane, held by the membrane proteins. Chlorophylls are organized into photosystem 1 and photosystem 2 on the thylakoid membrane.
The light energy of the sunlight is converted into electrical energy by chlorophyll.