Animal cells, surroundings

Animal cells, surroundings of 431-443 Animal tissue, composition of 31 Ankyrin 405... 

Each cell consists primarily of a membrane, which separates it from the environment, preserves its structural integrity, and keeps it apart from other cells or from the surrounding environment. Plant cells, unlike animal cells, also have, in addition to a cell membrane, a cell wall, composed of cellulose and lignin. The cell wall provides structural strength not only to the vegetable cell itself but to all plant tissues as well. Inside the membrane, the interior of the cell, known as the protoplasm, includes two main... 

Unlike other Eukarya, animal cells lack cell walls, though they tend to be surrounded by a highly developed glycocalyx of up to 140 nm in thickness [108]. This diffuse layer of densely packed oligosaccharides has a heterogeneous composition and is connected to the membrane via lipids or integral proteins. The boundary of the cell usually extends beyond the mere lipid bilayer with its embedded proteins, and the extracellular structures provide initial sites of interaction or are themselves targets for MAPs such as antimicrobial peptides [115]. 

In virtually every animal cell type, the concentration of Na+ is lower in the cell than in the surrounding medium, and the concentration of K+ is higher (Fig. 11-36). This imbalance is maintained by a primary active transport system in the plasma membrane. The enzyme Na+K+ ATPase, discovered by Jens Slcou in 1957, couples breakdown of ATP to the simultaneous movement of both Na+ and K+ against their electrochemical gradients. For each molecule of ATP converted to ADP and I , the transporter moves two K+ ions inward and three Na+ ions outward across the plasma membrane. The Na+K+ ATPase is an integral protein with two subunits (Mr -50,000 and -110,000), both of which span the membrane. 

BLASTULA A form of embryo found in the early development of many animals, which is typically composed of a single spherical layer of cells surrounding a completely closed central cavity. 

Many cells contain centrioles,53 little cylinders about 0.15 pm in diameter and 0.5 pm long, which are not enclosed by membranes. Each centriole contains a series of fine microtubules of 25 nm diameter. A pair of centrioles are present near the nucleus in most animal cells and play an important role in cell division. Together with surrounding materials they form the centrosome. However, centrioles have never been observed in plant cells. 

Plants are able to maintain their form because the cells are surrounded by thick walls that cement the cells together. However, animal cells lack rigid walls and must be held together by specialized contacts.138 139 Contacts between cells of both plants and animals are... 

A eukaryotic cell is surrounded by a plasma membrane, has a membrane-bound nucleus and contains a number of other distinct subcellular organelles (Fig. 1). These organelles are membrane-bounded structures, each having a unique role and each containing a specific complement of proteins and other molecules. Animal and plant cells have the same basic structure, although some organelles and structures are found in one and not the other (e.g. chloroplasts, vacuoles and cell wall in plant cells, lysosomes in animal cells). 

Animal cells are bounded by a cell membrane or PM and within the interior cytosol are various membrane-bound organelles, namely the nucleus (containing the genome and surrounded by a double membrane having elaborate pore structures) the ER network the cis- and trans-Go g network of membranes (involved in processing, folding and glycosylation of... 

Plant cells are surrounded by rigid cellulose walls, (unlike animal cells), but plant cells still take in water by osmosis when placed in pure water. However, plant cells do not burst because their cellulose cell walls limit how much water can move in. The cell walls exert pressure, called turgor pressure, as the cells take up water. Turgor... 

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