1 Cell And Tissue Function Flashcards
What is the cell membrane? What are the three layers?
- it acts as a semipermeable structure that separates the intracellular and extracellular environments. It controls the transport of materials from the extracellular fluids to the interior of the cell, holds and binds receptors for hormones and other biologically active substances, participates in the generation and conduction of electrical currents in nerve and muscle cells, and aids in regulation of cell growth and proliferation. It is a dynamic and fluid structure consisting of organized arrangement of lipids, carbohydrates, and proteins.
Main structural components of the membrane is its lipid bilayer that consists primarily of phospholipids, cholesterol, and glycoproteins. It provides the basic fluid structure of the membrane and serves as a relatively impermeable barrier to all but lipid-soluble substances. Phospholipids molecules along with glycolipids are aligned such that their hydrophilic heads face outward on each side of the membrane and their hydrophobic tails project toward the middle. The reserve of cholesterol makes the membrane regionally less deformable and less permeable to small water soluble molecules.
Proteins carry out most of the specific functions. Integral proteins(transmembrane) span the entire lipid bilayer and are part of the membrane. Peripheral proteins are bound to one or the other side of the membrane and don’t pass into the lipid bilayer. The manner in which proteins are associated with the cell membrane often determines their function. Peripheral proteins are associated with functions involving the inner or outer side of the membrane where they are found. Several serve as receptors or are involved in the intracellular signaling systems. The transmembrane proteins can function on both sides of the membrane or transport molecules across it. Integral transmembrane proteins form the ion channels found on the cell surface.
The cell coat or glycocalyx is a fuzzy looking layer. It consists of long, complex carbohydrates chains attached to protein molecules that penetrate the outside portion of the membrane; outward-facing membrane lipids; and carbohydrate-binding proteins called lectins. It participates in cell to cell recognition due to antigens that label cells as self or no self and are important in tissue transplatataion
What is the nucleus? What are the three types of RNA? What are the two nuclear membranes?
The nucleus of a non dividing cell appears as a rounded or elongated structure situated near the Center of the cell. It is enclosed in a nuclear a envelope and contains chromatin, the genetic material of the nucleus, and a distinct region called the nucleolus. It is regarded as the control Center for the cell. It contains DNA that a is essential to the cell because its genes encode the information necessary for the synthesis of proteins that the cell must produce to stay alive. The genes also represent the individual units of inheritance that transmit information from one generation to another. It is also the site for synthesis of the three types of RNA that move to the cytoplasm and carry out the actual synthesis of proteins.
Messenger RNA copies and carries the DNA instructions for protein synthesis to the cytoplasm. Ribosomal RNA is the site of protein synthesis. Transfer RNA transports amino acids to the site of protein synthesis for incorporation into the protein being synthesized.
The complex structure of DNA and DNA-associated proteins dispersed in the nuclear matrix is called chromatin.
Also contains the darkly stained round body called the nucleolus that is the site of rRNA synthesis and initial ribosomal assembly.
Sorrounding the nucleus is the nuclear envelope formed by the inner and outer nuclear member and containing a perinuclear space between them.
The inner nuclear membrane is supported by a rigid network of protein filaments called nuclear lamina that bind to chromosomes and secure their position in the nucleus.
The outer nuclear membrane resembles and is continuous with the membrane of the endoplasmic reticulum. At the site where the inner and outer membranes fuse, the nuclear envelope is penetrated by pores containing nuclear pore complexes. These acts as barriers and enable selective transportation of RNA, ribosomes, and lipids and proteins with signaling functions between the nucleus and cytoplasm to coordinate events such as gene transcription and metabolic activities.
What is the cytoplasm? What are its Membranebound organelles?
Surrounds the nucleus and it is in the cytoplasm that the work of the cell takes place.
The membrane enclosed organelles are endoplasmic reticulum ER, Golgi apparatus, mitochondria, and lysosomes. Without membranes ribosome and proteasomes.
What are ribosomes, endoplasmic reticulum, and Golgi apparatus?
Ribosomes are small particles of nucleoproteins rRNA and proteins that are held together by a strand of mRNA. Poly ribosomes exist as isolated clusters of free ribosomes within the cytoplasm or attached to the membrane of the ER. Free ribosome are involved in the synthesis of proteins that remain in the cell as cytoplasmic structural or functional elements, whereas those attached to the ER translate mRNAs that code for proteins to be bound in membranes or destined for secretion.
Endoplasmic reticulum ER is an extensive dynamic system of interconnected membranous tubes and sac-like cisternae. Within the lumen of the ER is a matrix that connects the space between the two membranes of the nuclear envelope to the cell periphery. The ER functions as a tubular communication system for transporting various substances from one part of the cell to another. A large surface area and multiple enzyme systems attached to the ER membranes also provide the machinery for many cellular metabolic functions. There are two forms of ER; rough and smooth. Rough ER is studded with ribosomes attached to specific binding sites on the membrane. These ribosomes, with their accompanying strand of mRNA, synthesize proteins destined to be incorporated into cell membranes, used in the generation of lysosomal enzymes, or exported from the cell. Smooth ER is free of ribosomes and is continuous with the rough ER. It does not participate in protein synthesis; instead its enzymes are involved in the synthesis of lipid and steroid hormone molecules, regulation of intracellular calcium and metabolism and detoxification of certain hormones and drugs. The sarcophagi comes reticulum of skeletal and cardiac muscle cells is a form of smooth ER. Calcium ion needed for muscle contraction are stored and released from cisternae of the sarcoplasmic reticulum. The smooth ER of the liver is involved in glycogen storage and metabolism of lipid soluble drugs.
Golgi apparatus consists of stacks of thin flatten vesicles or sacs. These Golgi bodies are found near the nucleus and function in association with the ER. Substances produced in the ER are transported to the Golgi complex in small, membrane bound transport vesicles. Many cells synthesize proteins that are large than the active product. The Golgi complex modifies these substances and packages them into secretory granules or vesicles. Insulin is an example
What are lysosomes? What do small and large particles get digested? What happens to intracellular particles?
They can be viewed as digestive organelles in the cell, are small, membrane. Bound scs filled with hydrologic enzymes. These enzymes can break down excess and worn out cell parts as well as foreign substances that are taken into the cell. All of the lysosomal enzymes are acid hydro lasers, which means that they require an acid environment. The lysosomes provide this environment by maintaining a pH of approximately 5.0 in their interior. The pH of the cytoplasm and other cellular components is approx. 7.2. Lysosomes not only contain a unique collection of enzymes, but also have a unique surrounding membrane that prevents the release of its digestive enzymes into the cytosol. They are formed from digestive vesicles called endoscopes. Lysosomal enzymes are synthesized in the rough ER and then transported to the Golgi apparatus, where they are biochemically modified and packaged for transport to the endoscopes. The late endoscopes mature into lysosomes as they progressively accumulate newly synthesized acid hydro lasers from the Golgi apparatus and attain digestive abilities.
Small particles such as extracellular proteins and plasma membrane proteins form endocytotic vesicles after being internalized by pinocytosis or receptor-mediated endocytosis. These vesicles are converted into early and late endoscopes, after which they mature into lysosomes.
Large extracellular particles such as bacteria, cell debris, and other foreign particles are engulfed in a process called phagocytosis. A phagosome, formed as the material is internalized within the cell, fuses with a lysosome to form a phagolysosome.
Intercellular particles such as entire organelles, cytoplasmic proteins and other cellular components are engulfed in a process called autophagy. These particles are isolated from the cytoplasmic matrix by ER membranes to form an autophagosome, which then fuses with a lysosome to form an autophagolysosome.
What are some genetic disease that affect the Lysosome?
Lysosomal storage diseases, a specific lysosomal enzyme is absent or inactive, in which case the digestion of certain cellular substances (glucocerebrosides, gangliosides) does not occur. As a result these substances accumulate in the cell
In Tay-Sachs disease an autosomal recessive disorder, hexosaminidase A, which is the lysosomal enzyme needed for degrading the GM, gaglioside found in nerve cell membranes, is absent. Although the GM ganglioside accumulates in many tissues, such as the heart, liver, spleen, its accumulation in the nervous system and retina of the eye causes the most damage.
What are peroxisomes?
They are spherical membrane-bound organelles which contain enxymes that are used in oxidative reactions. Reactions occurring in the peroxisomes use oxygen to produce peroxide’s and convert hydrogen peroxide to water. Also contain the enzymes needed for breaking down very-long chain fatty acids, which are in effectively degraded by mitochondrial enzymes. In liver cells peroxisomal enzymes are involved in the formation of the bile acids.
What are proteasomes?
Are cytoplasmic protein complexes that are not bound by membranes. They are responsible for proteolysis of malformed and misfolded proteins and have roles in many cellular responses and events. The process of cytosolic proteolysis is carefully controlled by the cell and requires that the protein be targeted for degradation. This process involves ubiquity nation, a process whereby several small ubiquitin molecules are attached to an amino acid residue of the targeted protein. Once a protein is so tagged, it is degraded by proteasomes. The resultant amino acids join the intracellular pool of free amino acids and the ubiquitin molecules are released and recycled.
What is the mitochondria? It is composed of tow membranes?
Are literally the “power plants” of the cell because they contain the enzymes needed for capturing most of the energy in foodstuffs and converting it into cellular energy. This multi step process requires oxygen and is often referred to as aerobic metabolism. Much of this energy is stored in the high-energy phosphate bonds of adenosine triphosphate (ATP) that serves to power various cell activities. They are found close to the site of energy consumption in the cell. The number of mitochondria in a given ell type is largely determined by the type of activity the cell performs and how much energy is needed to undertake the activity.
The outer membrane that encloses the periphery of the mitochondrion and an inner membrane that forms shelflike projection called Cristal. The narrow space between the outer and inner membranes is called the inter membrane space, whereas the large space enclosed by the inner membrane is termed the matrix space. The outer mitochondrial membrane contains a large number of transmembrane poring, through which inorganic ions and metabolites may pass. The inner membrane contains the respiratory chain enzymes and transport proteins needed for the synthesis of ATP.
They contain their own DNA and ribosomes and are self-replicating. The DNA is found in the mitochondrial matrix and is distinct from the chromosomal DNA found in the nucleus. The DNA is a double-stranded, circular molecule that encodes the rRNA and tRNA required for intramitochondrial synthesis fo the proteins needed for the energy-generating function of the mitochondria. They also function as key regulators of apoptosis or programmed cell death.
What is the cytoskeleton? What do the products do?
They control cell shape and movement, these structures are a major component of the structural elements.
The organelles are microtubules, microfilaments, and intermediate filaments.
Microtubules are slender and rigid tubular structures composed of globular proteins called tubulin. Each consists of parallel protofilaments, each composed of a andB tubulin diners. They function in many ways, including the development and maintenance of cell form; participation in intracellular a transport mechanisms, including axoplasmic transport in neutrons; and formation of the basic structure for several complex cytoplasmic organelles, including the cilia, flagella and centrioles. Cilia and flagella are microtubules-filled cellular extensions extending from the cell membrane that are capable of sweeping movements. Celia are found on the apical surfaces of many epithelial linings, including the nasal sinuses and passages of the upper respiratory system. Flagella form the tail-like structures that provide motility for sperm.
Actin microfilaments and intermediate filaments the first are composed of actin, whereas intermediate filaments are a heterogeneous group of filaments with diameter sizes between those of microtubules and actin filaments. Actin is of central importance to cellular biology. It contributes to cell motility, positioning of organelles in the cell, and cell shape and polarity. Many functions of the actin filaments are performed in association with myosin motor proteins. Contractile activities involving actin microfilaments and associated thick myosin filaments contribute to muscle contraction. Intermediate filaments include the cytokeratins, vixen tin, and neurofilaments. They have structural and maintenance functions that are important in tissue, cellular, developmental, and differentiation processes.
What is cell metabolism and energy storage?
Energy metabolism refers to the chemical processes involved in converting carbohydrates, fats, and proteins from the foods we eat into the energy needed for cell functions. Cells use oxygen to transform the breakdown products of the foods we eat into the energy needed for muscle contraction; the transport of ions and other molecules across cell membranes; and the synthesis of enzymes, hormones and other macromolecules.
The special “unit of currency” for transferring energy in living cells is ATP. Adenosine triphosphate molecules consist of adenosine, a nitrogenous base ribose, a five-carbon sugar; and three phosphate groups. ATP is hydrolyzed to form adenosine diphosphate ADP with the loss of one high energy bond and to adenosine monophosphate AMP with the loss of two such bonds.
What are the two types of energy production? What are the three major pathways ATP is formed?
Anaerobic metabolism is the anaerobic process by which energy is liberated from glucose. It is important energy for cells that lack mitochondria. It also provides a temporary source of energy for cells that are deprived of an adequate supply of oxygen. Glycolysis involves a sequence of reactions that convert glucose to Pyruvic acid, with the concomitant production of ATP from ADP. Net gain is one molecule of glucose to two ATP molecules. Happens during the first few minutes of exercise. 1. Glycolysis requires the presence of nicotine die adenine dinucleotide NAD, a hydrogen carrier. The end products of glycolysis are pyruvate and NADH plus H+.
Aerobic metabolism which supplies 90% of the body’s energy needs, occurs in the cells mitochondria and requires oxygen. It is here that the hydrogen and carbon molecules from dietary fats, proteins, and carbohydrates are broken down and combined with molecular oxygen to form carbon dioxide and water as energy is released. In 24 h period oxidative metabolism produces 150-300 mL of water.
2. Citric acid cycle (kerbs cycle) both of the pyruvic acid molecules formed by the glycolytic patahway enter the mitochondrial where each combines with acetylcoenzyme to form acetyl-coenzyme A. It begins the reactions that occur in the citric acid cycle. This process produces hydrogen atoms and CO2. As hydrogen is generated, it combines with NAD or FAD for transfer to the electron transport system.
3. Electron transport chain. At the completion of the citric acid cycle, each glucose molecule has yielded only four new molecules of ATP. In the principal function of these earlier stages is to make the electrons from glucose and other food substrates available for oxidation. Is accomplished through a series of enzymatically catalyze reactions in the mitochondrial electron transport chain. During these reactions, protons H+ combine with O2 to form H2O and large amounts of energy are released and used to add a high energy phosphate bond to adenosine diphosphate ADP, converting it to ATP. Net yield of 36 molecules of ATP for 1 molecule of glucose = 32 form electron transport chain.
What are the cell signaling and communication mechanisms?
Signaling systems consist of receptors that reside either on the cell membrane or within the cells. Receptors are activated by a variety of chemical messengers including neurotransmitters, hormones, growth factors, and other chemical messengers as well as signaling proteins called cytokines and lipids.
Cell surface receptors. Each cell type in the body contains numerous receptor proteins, which as a set may characterize the cell type, that enable it to respond to a complementary set of ligands or signaling molecules in a specific, preprogrammed way. Three major classes G protein-linked receptors, enzyme linked receptors and ion channel-linked receptors.
G protein-linked receptors mediate cellular responses for numerous types of first messengers through regulatory proteins called G proteins that bind to guanine nucleotides such as GDP or GTP. They all have a ligand-binding extracellular receptor component, which recognizes a specific Ligand.
Enzyme-linked receptors. Are transmembrane proteins with their ligand-binding site on the outer surface of the cell membrane. The binding of the hormone to special transmembrane receptor results in activation of the enzyme adenylyl Cyclades at the intracellular portion of the receeptor This enzyme catalyze the formation of the second messengers cAMP
Ion channel-linked receptors are involved in the rapid synaptic signaling between electrically excitable cells. Neurotransmitters mediate this type of signaling by transiently opening or closing ion channels formed by inter grail proteins in the cell membrane
What are membrane transport mechanisms?
The lipid layer of the cell membrane serves as a barrier against the movement of water, and water-soluble substances betweeen the intracellular and extracellular fluids,
There are three types diffusion, active transport, vesicular transport.
What is diffusion? There are four types what are they and how do they work?
Refers to the passive process by which molecules and other particles in a solution become widely dispersed and reach a uniform concentration because of energy created by their spontaneous kinetic movements. The process of reaching uniform concetration these molecules and particles move “downhill” from an area of higher to an area of lower concentration. If the molecules or particles carry a net charge, both the concentration gradient and the electrical potential difference across the membrane influence transport.
- Simple diffusion means that the kinetic movement of molecules or ions occurs through a membrane opening or through intermolecular spaces without any interaction with a carrier protein. The rate depends on how many particles are available for diffusion, the kinetic movement of the particles, and the number and size of the openings in the membrane.
- Facilitated diffusion. Occurs down a concentration gradient; thus it does not require input of metabolic energy. It does requires a transport protein. Such as glucose, cant pass unassisted through the cell membrane because they are not lipid soluble or they are too large to pass through the membranes pores. These substances combine with special transport proteins at the membranes outer surface are carried across the membrane attached in the transporter, and then are released. Can only move from an area of higher concentration to one of lower concentration. The rate depends on the availability of transport proteins.
- Ion channels and gates. Ion channels are integral proteins that span the width of the membrane and are normally composed of several polypeptides or protein subunits that form a gating system. Contains two basic groups of ion channels; leakage channels and gated channels. Leakage open and close in response to specific stimuli. 3 types of gated channels; voltage-gated channels which have electrically operated channels that open when the membrane potential changes beyond a certain point; ligand-gated channels, which are chemically operated and respond to specific receptor-bound ligands; mechanically gated channels which open or close in response to such mechanical stimulations as vibrations, tissue stretching, or pressure.
- Movement of water across the cell membrane. Water molecules move through adjacent phospholipid molecules in the cell membrane by osmosis without actually dissolving in the region occupied by the fatty acid side of the chains. Osmosis is regulated by the concentration of nondiffusible particles to the side with the higher concentration. Also contain transmembrane proteins called aquaporins that function as water channels.
