Eukaryotic Cell Functions

Skeletal Muscle Structure.The cells of skeletal muscles are long fiber-like structures. They contain many nuclei and are subdivided into smaller structures called myofibrils. Myofibrils are composed of 2 kinds of myofilaments. The thin filaments are made of 2 strands of the protein actin and one strand of a regulatory protein coiled together. The thick filaments are staggered arrays of myosin molecules.

-Sarcoplasmic Reticulum (SR) then releases Calcium which binds to troponin in the thin filament, exposing myosin-binding sites;

Cytoplasmic streaming is the organised flow of the cytoplasm and its constituents within a living cell (Shimmen et al., 2004). Organelles and important molecules move through the cytosol along the structure of the cytoskeleton (actin filaments and microtubules) with the aid of myosin I, an actin-binding motor protein that plays a part in various cell functions including cell motility and endocytosis (Flavell et al., 2008). Actin microfilaments (F-actin) are the thinnest filaments of the cytoskeleton,

Serves as the cell 's skeleton. It is an interior protein system that gives the cytoplasm quality and adaptability. The cytoskeleton of all cells is made of microfilaments, halfway fibers, and microtubules. Muscle cells contain these cytoskeletal parts in addition to thick fibers. The fibers and microtubules of the cytoskeleton frame a dynamic system whose ceaseless rearrangement influences cell shape and capacity.

Muscle fibres, as shown in Diagram 1, consist of myofibrils, which contain the proteins, actin and myosin, in specific arrangements . The diagram illustrates how a muscle is made up of many fascicles, which in turn are made up of many endomysiums, and within them, many muscle fibres. Each muscle fibre is made up of many myofibrils that consist of sarcomeres bound end on end . Actin is a thin filament, about 7nm in diameter, and myosin is a thick filament, about 15nm in diameter , both of which reside in the sarcomere. They are held together by transverse bands known as Z lines . Diagram 2 shows actin and myosin filaments within a sarcomere, and the Z lines that connect them.

When a muscle contracts, myosin heads in thick filaments bind to actin in thin filaments and pulls the thin filament, shortening the length of the muscle fiber. However, without Ca++ when troponin binds to actin, the tropomyosin moves into a position that

Actin and myosin filaments can be found in skeletal muscle and are the smallest units that form a sarcomere, which is the smallest contractile unit in muscle (Baechle, 2008). The Sliding Filament Theory states that the actin filaments slide inward on the myosin filaments, pulling on the boundaries of the sarcomere, causing it to shorten the muscle fiber, also known as a concentric muscular contraction (Baechle, 2008). The Sliding Filament Theory is composed of five steps: the “Resting Phase”, the “Excitation-Contraction Coupling Phase”, the “Contraction Phase”, the “Recharge Phase”, and the “Relaxation Phase” (Baechle, 2008). During the Resting Phase, the actin and myosin filaments are lined up with no cross-bridge binding of the two filaments. During the Excitation-Contraction Coupling Phase, Calcium is released from the sarcoplasmic reticulum and binds to troponin, causing a shift in tropomyosin where the binding cites are exposed (Baechle, 2008). When the binding cites are exposed, the myosin cross-bridge head attaches to actin. During the Contraction Phase, ATP bonds break, releasing energy that is used to allow the myosin head to flex, causing the actin filaments to move toward the M-bridge. During the Recharge Phase, there is a continuous repetition of the Excitation-Contraction Coupling Phase and the Contraction Phase in order to produce muscular

Before you buy cilia and flagella it is important to understand their functions and structures. Both cilia and flagella are whip-like columns of microtubules, covered in a membrane. They serve to move liquids across or over the surface of a cell, and can also be used to transport the cell from point A. To point B. There are 3 different types of flagellum, and 2 different types of cilia.

To understand the sliding filament theory, one should first look at the muscles. All movement through the body is created and stopped by muscles. Muscles work in antagonistic pairs, that means that when one muscle relaxes, it antagonistic pair will contract and vice versa. Muscle fibres are found in

1. _Actin__ Th in contractile protein involved in cross-bridge formation, comes in filamentous or globular forms.

P1 – Describe the microstructure of a typical animal cell and the functions of the main cell components. A typical animal cell is seen as a tiny, three dimensional sac which is in fact made up of many components, each as important as the other. The microstructure of an animal cell was in fact uncovered mainly through the use of both cell fractionation and electron microscopy. Each main component has its own, individual function which helps a cell to function and maintains the cell membrane. The components that I will be describing include the cell membrane, nucleus, cytoplasm, mitochondria, lysosomes, Golgi bodies, centrioles, endoplasmic reticulum (both smooth and rough) and ribosomes.

actin “slid” past each other and neither filament changed in length. In 1957 Allan Huxley

The answer is B, lysosomes. The answer cannot be A because chloroplasts are responsible for functions within photosynthesis and do not contain hydrolytic enzymes to break down cellular components. Central vacuole, answer C, cannot be correct either because the central vacuole is responsible for holding substances such as water within plant cells, helping to support the structure of the cell. Peroxisome and glyoxysome (D and E) are also incorrect because peroxisomes are used primarily within oxidative reactions and glyoxysomes are responsible for converting

The cell membrane is made of phospholipids and proteins, like eukaryotic membranes, and controls the entry and exit of substances into and out of the cell. The mesosome is a tightly folded region of the cell membrane containing all the membrane-bound proteins required for respiration and photosynthesis. The flagellum is a rigid rotating helical-shaped tail used for propulsion. The motor is embedded in the cell membrane and is driven by a H+ gradient across the membrane. A clockwise rotation drives the cell forwards, while an anticlockwise rotation causes a chaotic spin.

The cytoplasm is a semifluid in the plasma membrane. It is in all eukaryotic cells. In prokaryotes, this is where the chemical processes of the cell take place. In eukaryotic cells, this is where organelles perform their functions. Cellular respiration also takes place here. One of stages of cellular respiration is glycolysis. Glycolysis is when glucose breaks down to form two pyruvates and 4 ATP. Its net result of 2 ATP is important for another process called the Krebs Cycle. This process is important because it begins cellular respiration. The cytoplasm also gives the cell its shape; without it, the cell would be “deflated” and substances would not be able to move throughout the cell. Organelles would have difficulty functioning too. It has been misunderstood that organelles float freely in the cytoplasm even