more about cell Bio.

more about cell Bio.

What is the role of golgi apparatus and endoplasmic reticulum in the secretion of proteins?

Stacks of flattened membrane sacs make up the organelles called Golgi Bodies. They serve as processing, packaging and storage centers for the products released from the cell. In some studies scientists found connections between Golgi body and Endoplasmic Reticulum. Proteins synthesized on the ribosomes attached to the Endoplasmic Reticulum pass through the canals of the endoplasmic reticulum into the golgi bodies. The vesicals migrate to the cell surface, where their membranes fuse with the cell membrane. The materials in the vesicle are then released outside the cell. The process in which materials made by the cell are released to the outside of the cell is called secretion.Cell products other than protiens also may be packaged in the golgi body.

The endoplasmic reticulum is a system of fluid-filled canals, or channels , enclosed by membranes. These canals usually form a continuous network throughout the cytoplasm. The canals of the endoplasmic reticulum serve as paths for the transport of materials through the cell. eg proteins.

Rough endoplasmic reticulum bears the ribosomes during protein synthesis. The newly synthesized proteins are sequestered in sacs, called cisternae . The system then sends the proteins via small vesicles to the Golgi Complex , or, in the case of membrane proteins, it inserts them into the membrane. Rough endoplasmic reticulum may either be vesicular or tubular. Or it may consist of stacks of flattened cisternae (like sheets) that may have bridging areas connecting the individual sheets. The Ribosomes sit on the outer surfaces of the sacs (or cisternae). They resemble small beads sitting in rosettes or in a linear pattern.

Smooth endoplasmic reticulum is found in a variety of cell types and it serves different functions in each. It consists of tubules and vesicles that branch forming a network. In some cells there are dilated areas like the sacs of rough endoplasmic reticulum. The network of smooth endoplasmic reticulum allows increased surface area for the action or storage of key enzymes and the products of these enzymes. In the case of smooth endoplasmic reticulum in muscle cells, the vesicles and tubules serve as a store of calcium which is released as one step in the contraction process. Calcium pumps serve to move the calcium.

Chloroplasts are the green colored pigment and they help in the following process. The main reaction that takes place in chloroplasts is known as the process of Photosynthesis. In this process carbondioxide, water and the energy obtained from sunlight react together to form glucose and oxgen. Chloroplasts are found in plant cells only and in protists. The Many Reactions that occur during the photosynthesis in plants can be grouped into two broad categories.

1. Light reactions (photosynthetic reactions): in this step, energy derived from light energizes an electron in the green organic pigment chlorophyll, enabling electron to move along an electron-transport chain in the thylakoid membrane. The chlorophyll obtains its electrons from water by producing oxygen as a by products. During the electron transport process H+ is pumped across the thylakoid membrane, and resulting electrochemical proton gradient drives the synthesis of ATP in the stroma. In final step high energy loaded onto NADP+.

2. Dark reactions (carbon fixation reactions). ATP and NADPH that are produced in first step are going to be utilized for fixing CO2 into sugar.

The Calvin Cycle :

The cycle spends ATP as an energy source and consumes NADPH₂ as reducing power for adding high energy electrons to make the sugar. There are three phases of the cycle. In phase 1 (Carbon Fixation), CO₂ is incorporated into a five-carbon sugar named ribulose bisphosphate (RuBP). The enzyme which catalyzes this first step is RuBP carboxylase or rubisco. It is the most abundant protein in chloroplasts and probably the most abundant protein on Earth. The product of the reaction is a six-carbon intermediate which immediately splits in half to form two molecules of 3-phosphoglycerate. In phase 2 ( Reduction), ATP and NADPH₂ from the light reactions are used to convert 3-phosphoglycerate to glyceraldehyde 3-phosphate, the three-carbon carbohydrate precursor to glucose and other sugars. In phase 3 (Regeneration), more ATP is used to convert some of the of the pool of glyceraldehyde 3-phosphate back to RuBP, the acceptor for CO₂, thereby completing the cycle. For every three molecules of CO₂ that enter the cycle, the net output is one molecule of glyceraldehyde 3-phosphate (G3P). For each G3P synthesized, the cycle spends nine molecules of ATP and six molecules of NADPH₂. The light reactions sustain the Calvin cycle by regenerating the ATP and NADPH₂.

The Calvin Cycle
The cycle spends ATP as an energy source and consumes NADPH₂ as reducing power for adding high energy electrons to make the sugar. There are three phases of the cycle. In phase 1 (Carbon Fixation), CO₂ is incorporated into a five-carbon sugar named ribulose bisphosphate (RuBP). The enzyme which catalyzes this first step is RuBP carboxylase or rubisco. It is the most abundant protein in chloroplasts and probably the most abundant protein on Earth. The product of the reaction is a six-carbon intermediate which immediately splits in half to form two molecules of 3-phosphoglycerate. In phase 2 ( Reduction), ATP and NADPH₂ from the light reactions are used to convert 3-phosphoglycerate to glyceraldehyde 3-phosphate, the three-carbon carbohydrate precursor to glucose and other sugars. In phase 3 (Regeneration), more ATP is used to convert some of the of the pool of glyceraldehyde 3-phosphate back to RuBP, the acceptor for CO₂, thereby completing the cycle. For every three molecules of CO₂ that enter the cycle, the net output is one molecule of glyceraldehyde 3-phosphate (G3P). For each G3P synthesized, the cycle spends nine molecules of ATP and six molecules of NADPH₂. The light reactions sustain the Calvin cycle by regenerating the ATP and NADPH₂.

The Calvin Cycle
The cycle spends ATP as an energy source and consumes NADPH₂ as reducing power for adding high energy electrons to make the sugar. There are three phases of the cycle. In phase 1 (Carbon Fixation), CO₂ is incorporated into a five-carbon sugar named ribulose bisphosphate (RuBP). The enzyme which catalyzes this first step is RuBP carboxylase or rubisco. It is the most abundant protein in chloroplasts and probably the most abundant protein on Earth. The product of the reaction is a six-carbon intermediate which immediately splits in half to form two molecules of 3-phosphoglycerate. In phase 2 ( Reduction), ATP and NADPH₂ from the light reactions are used to convert 3-phosphoglycerate to glyceraldehyde 3-phosphate, the three-carbon carbohydrate precursor to glucose and other sugars. In phase 3 (Regeneration), more ATP is used to convert some of the of the pool of glyceraldehyde 3-phosphate back to RuBP, the acceptor for CO₂, thereby completing the cycle. For every three molecules of CO₂ that enter the cycle, the net output is one molecule of glyceraldehyde 3-phosphate (G3P). For each G3P synthesized, the cycle spends nine molecules of ATP and six molecules of NADPH₂. The light reactions sustain the Calvin cycle by regenerating the ATP and NADPH₂.

PHOTOSYNTHESIS CHEMICAL REACTION:

CO2 + H2O + Energy = C6H12O6 + O2

(carbon

dioxide) (water) (sunlight) (glucose) (oxygen)

what is the role of mitochondria in making stored chemical-bond energy available to cells by completing the breakdownof glucoseto carbon dioxide?

The chemical energy generated by chloroplasts is stored in the bonds of sugar molecules untill they are broken down by mitochondria. Mitochondria are memebrane-bound organelles in plant and animal cells that transform energy for the cell. This energy is then in the bonds of other molecules that cell organelles can access easily and quickly when energy is needed. The energy for storing these molecules is obtained from completing the breaking down of glucose to carbon dioxide. The main job of mitochondria is the cellular respiration.It reacts totally opposite to that in chloroplast. It combines with glucose and oxygen to give carbon dioxide, water and energy in the ATP ( adenosine triphosphate ) form. C6H12O6 + O2 = CO2 + H2O + Energy . Mitochondria are usually found in all eukaryotic cell eg. protists, fungi, animal cell and in plant cells.

The process occurs in two phases:

Protons are translocated across the membrane, from the matrix to the intermembrane space
Electrons are transported along the membrane, through a series of protein carriers
Oxygen is the terminal electron acceptor, combining with electrons and H⁺ ions to produce water
As NADH delivers more H⁺ and electrons into the ETS, the proton gradient increases, with H⁺ building up outside the inner mitochondrial membrane, and OH^- inside the membrane.

A connection between d,e,f and g

Firts of all, all teh substances described in d,e,f and g are all teh members of a cell. In all the descriptions, these membranes have been described very minutely along with their roles and funcitons, which they carry out. Proteins is the main connection between all these points. Bullet d refers to the path of transfer for proteins to the cytoplasm with the help of ribosomes and RNA. Bullet e refers to the help provided by the endoplasmic reticulum and golgi bodies in the secretion of proteins to the nucleus. Bullet f indirectly states how protein is obtained by chloroplasts. In this process, chloroplasts capture the energy form the sunlight, which is a protein to them for their sustainance. Bullet g too indirectly states how protein is provided to other cells by mitochondria. Mitochondria is known as, "The Powerhouse of Energy". It stores the chemical bond energy within itself and when needed provides this energy(proteins) to other cells

h. types of macromolecules

Polysaccharides (sometimes called glycans) are relatively complex carbohydrates. They are polymers made up of many monosacchrides joined together by glycosidic linkages. They are therefore very large, often branched, molecules. They tend to be amorphous, insolubile in water, and have no sweet taste. When all the constituent monosaccharides are of the same type they are termed homopolysaccharides; when more than one type of monosaccharide is present they are termed heteropolysaccharides.

Examples include storage polysaccharides such as starch and glycogen and structural polysaccharides such as cellulose

proteins are compounds that contain nitrogen as well as carbon, hydrogen, and oxygen. Some proteins also contain sulfur and phosphorus. The number of possible proteins is virtually unlimited. Proteins have an astonishing range of properties. Proteins make life possible in its present degree of complexity. There are proteins in the structural parts of cells and body tissues, such as cartilage, bones, and muscles. There are proteins in the hormones, the chemical messengers that regulate body functions in plants and animals. There are proteins in antibodies, the substance that protects animals against disease organisms.

The Nucleus and the Nucleic Acids: RNA and DNA

Nucliec acids are compounds that contain phosphorous and nitrogen in addition to carbon,hydrogen,and oxygen. There are two kinds of nucleic acids. One is called DNA and RNA. These substances were first found in the nucleus. DNA is the heriditary material that is passed on from one generation to the next during reproduction.

A nucleotide is a monomer or the structural unit of nucleotide chains forming nucleic acids as RNA and DNA. A nucleotide consists of a heterocyclic nucleobase, a pentose sugar (ribose or deoxiribose), and a phosphate or polyphosphate group. Nucleotides also play important roles in cellular energy transport and transformations (notably ATP and NAD+/NADH), and in enzyme regulation (see for example, protein kinase).

PRECURSOR: In biological processes especially metabolism, a precursor is a substance from which another, usually more active or mature substance is formed.

For instance, certain liver enzymes are precursors to insulin. Or, this is the opposite of the body breaking down a more complex substance, like protein into individual chemicals for use within the body.

Lipids are a part of cell structures and serve as a reserve energy supply in an organism. Lipids furnish about twice as much energy as the same ammount of carbohydrates. They include the substances commonly called fats, oils and waxes. Like carbohydrates, lipids are made of crabon,hydrogen and oxygen. However there is less oxygen in lipids than in carbohydrates. Fats and oils are chemically similar.Unlike fats, however, oils remain liquid at room temperature. Plants store oils in seeds. Some familiar oils are peanut oil, corn oil, and castor oil.

Ribo Nucliec Acid (RNA)

Deoxyribose Nucleic Acid (DNA)

How does cytoskeleton and cell wall give shape and internal organisation to a eukaryotic cell?

Eukaryotic cells make up organisims from the Protist, Fungi, Plant, and Animal Kingdoms (That's Mostly All). Eukaryotic cells have large diameters, 10 micrometers and up, which is large in comparison to Prokaryotic cells which range from 5 through 2 micrometers. The size of Eukaryotic cells is small compared to the size of humans but is large in the microbial world.

The largest difference of a Eukaryotic cell from a Prokaryotic cell other than size is the presence of a Nucleus. A Nuclus is a membrane which protects DNA against the elements of the cell. This "Nuclear Envelope" lets Transfer RNA through and keeps ribosomes out. Ribosomes change Transfer RNA into proteins which perform functions in the cell.

Other important objects in a Eukaryotic cell are Mitochondria. Mitochondria produce energy through the burning of Glucose, a sugar. These mitochondria are roughly the size of a Prokaryotic cell. Scientists believe that the first Eukaryotic cells ingested a Mitochondria and formed a symbiosis with it. Another important organelle is found in Plant and Protist cells is the chloroplast, a organelle which produces glucose from sunlight.

The cytoskeleton is another feature unique to the eukaryotes. It is a network of protein filaments, mostly actin and tubulin, which are anchored to the cell membrane, and criss-cross the periphery of the cell. The network provides a structural framework which gives the cell its shape, and stabilizes the membrane systems. It also permits the cell to selectively exert tension on the membrane, making movement of the cell possible. The contractibility of these protein filaments are also responsible for muscle function, and the operation of the spindle apparatus, which separates the chromosomes during mitosis. Thus we see that there are six structures which put together form the cytoskeleton, which in turn supports and gives shape to a cell. These six structures are as follows:Tight junctions, Gap junctions, Desmosomes, Microfilaments, Extraceller Matrix, Cell Wall.

Tight Junctions: Permeation of intercellular tight junctions in epithelia may be altered bymaneuvers that affect the cytoskeleton. Conversely, agents that altertight-junction permeability also often produce alterations in cytoskeletalstructure. We explore the anatomy of theperijunctional cytoskeleton by applying electron microscopy to cytoskeletalpreparations of whole intestinal absorptive cells using detergentextraction techniques. Individual elements of the perijunctionalcytoskeleton, including actin microfilaments as determined by S1 labeling,appear to associate with the tight junction by means of plaque-likedensities that intimately associate with the lateral membrane at the siteof the tight junction. Furthermore, such associations are not diffusewithin the tight junction, but occur only at sites of fusions between lateral membranes that are thought to represent the specificintrajunctional sites at which the barriers to transjunctional permeationreside. These data provide evidence of intimate cytoskeletal-tight-junctionassociations, which may represent the anatomical basis for cytoskeletalcontrol of tight-junction permeability. The cytoskeleton is another feature unique to the eukaryotes. It is a network of protein filaments, mostly actin and tubulin, which are anchored to the cell membrane, and criss-cross the periphery of the cell. The network provides a structural framework which gives the cell its shape, and stabilizes the membrane systems. It also permits the cell to selectively exert tension on the membrane, making movement of the cell possible. The contractibility of these protein filament.

Gap Junctions: Gap junctions are intercellular channels some 1.5–2 nm in diameter. These permit the free passage between the cells of ions and small molecules (up to a molecular weight of about 1000 daltons). They are constructed from 4 (sometimes 6) copies of one of a family of a transmembrane proteins called connexins. Because ions can flow through them, gap junctions permit changes in membrane potential to pass from cell to cell.

Microfilaments: Monomers of the protein actin polymerize to form long, thin fibers. These are about 8 nm in diameter and, being the thinnest of the cytoskeletal filaments, are also called microfilaments. (In skeletal muscle fibers they are called thin filaments. Some functions of actin filaments:

i. How do chemiosmotic gradients store energy in mitochondria and chloroplast?

chemiosmotic gradients are substances or organelles which supports other organelles by providing suitable atmospheric conditions.eg.In plants,chloroplasts are cell organelles that capture sunlight and convert it into chemical energy. They belong to a group of plant organelles called plastids(chemiosmotic gradients), which are used for storage. Some plastids store starches or lipids, where as others contain pigments, molecules that give color. For mitochondria , which are membrane-bound organelles in plant and animal cells that transform energy for the cell. A mitochondrian has an outer membrane and a highly folded inner membrane. As with the endoplasmic reticulum and chloroplasts, the folds of the inner membrane provide a large surface area taht fits in a small space. Energy-storing molecules are produced on the inner folds. These are the chemiosmotic gradients fro mitochondria.

ATP is adenosine triphosphate. It is energy produced by certain chemical reactions. In this case, for mitochondria, glucose and oxygen combine(main reaction), to give carbon dioxide, water and ATP(energy production). In chloroplast, the main process is performing photosynthesis, taht is capturing of sunlight and synthesizing food for its self. In this reaction carbon dioxide, water adn energy from sunlight combine to form glucose and oxygen!

Enter supporting content here

The Citric Acid Cycle