Biology

Chapter 5

Animal Cells

Concepts/Ideas/Facts:

cells consist of the same chemicals found in non-living objects.
the source of energy for the body is the chemical energy stored in the carbon bonds of ingested food.
adenosine triphosphate (ATP) is the universal energy carrier – the common energy “currency” of the body.
no usable energy is released during digestion of food.
generally a person has enough glycogen stored to provide sufficient energy for about a day of normal activities and enough stored fat to provide energy for two months.
White blood cells move by amoeboid movement to areas of infection. Collectively they move the equivalent of twice around the Earth within your body everyday.
there are over 200 kinds of cells
the more you exercise the more mitochondria you have
50% of energy in food is released as heat
Chlorophyll loses an electron when energized by light.
Main job of cells is to produce proteins
Surface-to-volume-ratio of cells constrains the cells ability to metabolize and survive.
each organelle has its specific purpose in the life of a cell
prokaryotic cells originated before cells with a nucleus evolved

Cell Theory:

Organisms consist of one or more cells
Cells are the basic units of function and structure in organisms
Only living cells beget living cells
All cells are basically the same in chemical composition

Definitions:

Prokaryotes – smallest and simplest known cells having rigid or semi-rigid cell wall that surrounds the plasma membrane. The cell wall shape and supports the cell. The cell wall is permeable. Sticky, jelly-like polysaccharides often surround the cell wall which help the cell to attach to various surfaces. In prokaryotes a single circular strand of DNA is not housed in a nucleus but is located in a specific area in the cytoplasm called the nucleoid. Prokaryotes move by the movement of one or more flagellum (flagella, plural) that project out from the cell. Prokaryote flagellum do not have orderly inner arrays of microtubules. Prokaryotes do not have all the organelles an eukaryote has.
Eukaryotes – start life with a nucleus and contain many organelles that specialize in producing energy and in breaking apart, building, modifying, and distributing molecules. Organelles physically separate chemical reactions, many of which are incompatible.
Plasma Membrane (Cell Membrane) – very thin, oily membranous structure that encloses each cell. It keeps the cell’s contents separated from its surroundings and keeps the intra-cellular fluid (ICF) within the cell, from mingling with the extra-cellular fluid (ECF)outside the cell. It also selectively controls the movement of molecules in and out of the cell (between ICF and ECF). Primarily made of lipids.
Selectively Permeable Membrane (semipermeable membrane) – cell membrane which allows sselective substance through but not others.
Deoxyribonucleic Acid (DNA) – contains the code for inheritance (instructions) within the nucleus. It directs protein synthesis and serves as a genetic blueprint during cell replication passing on genetic characteristics to future generations and seeing that cells replicated are identical.
Cytoplasm (protoplasm) – portion of the cell interior not occupied by the nucleus containing a number of organelles dispersed in the cytosol.
Cytoplasmic Streaming – the constant motion of the cytoplasm as particles and organelles move around.
Organelles – distinct, highly organized, membrane-enclosed structures within the cytosol. Half the volume of a cell is occupied by organelles. Each organelle type is a separate internal compartment that contains a specific set of chemicals for carrying out a particular cellular function. This separation allows for chemical reactions that would not be compatible with the rest of the cell or organelles to occur simultaneously with other organelles within the same cell.
Lysosomes – destroy unwanted proteins within a cell.
Cytosol – remainder of the cytoplasm not occupied by organelles or nucleus made up of a semi-liquid, gel-like mass laced with an elaborate protein network (cytoskeleton). Compatible chemical reactions occur here.
Cytoskeleton – network of proteins that give the cell shape, proved for a cells internal organization (where things are located), and regulates its various movements.
Intracellular Fluids – includes all the fluids inside the cell, including that within the cytosol, the organelles, and the nucleus.
ER Lumen – fluid filled space enclosed by the ER membrane
Lumin – the inside of an organ
Vesicle – fluid-filled membrane enclosed intracellular cargo container
Sarcoplasmic Reticulum – modified smooth ER in muscle cells that stores calcium that plays a role in muscle contraction.
Exocytosis – the mechanism of extrusion to the exterior of a substance originating in the cell. It is the process where molecules collected in the cell are “dumped” to the outside of the cell.
Secretion – release of the contents of a secretory vesicle by means of exocytosis
Golgi sacs – sacs at the edges of the Golgi stacks
Docking Marker – protein “address” that signals where certain vesicles are allowed to “dock” or drop-off their cargo. (analogous to the address on an envelope)
Docking Marker Acceptor – protein located only at the appropriate destination within the cell (like a house address)
Pinocytosis(“cell drinking”) – extra-cellular fluid is internalized. It is the non-selective up-take of ECF.
Endocytosis – internalization of extra-cellular material within a cell
Receptor-Mediated Endocytosis – selective up-take of a large molecule.
Phagocytosis (“cell eating”) – selective up-take of a multi-molecular particle
Apoptosis – the built in mortality or programmed cell death or cell suicide.
Tay-Sachs Disease – occurs when lysosomes, due to the lack of specific enzymes, are unable to digest or recycle particles and become engorged and interfere with normal cell processes, causing the progressive degeneration of the nervous system.
Oxidative Enzyme – use Oxygen (O₂) to strip Hydrogen from certain molecules.
Adenosine triphosphate (ATP) – is the universal energy carrier – the common energy “currency” of the body – which consists of adenosine with three phosphate groups attached. When the terminal, high-energy bond is split from the adenosine group, a substantial amount of energy is released and adenosine diphosphate (ADP) is created along with inorganic phosphate (P_i). ATP à ADP + P_i + energy
Hydrolytic Enzyme - One of a class of enzymes catalyzing hydrolysis of a variety of bonds, such as esters, glycosides peptides. An enzyme capable of catalyzing (hydrolysis).
Nicotinamide adenine dinucleotide (NAD) – derivative of the B vitamin niacin
Flavine adenine dinucleotide (FAD) – a derivative of the B vitamin riboflavin
Intermediary Metabolism – the chemical reactions inside the cell in the cytoplasm that involves the degredation, synthesis, and transformation of small organic molecules such as simple sugars, amino acids, and fatty acids.
Inclusions – nonpermanent masses of stored material in the cytosol not surrounded by membrane. Fat is the largest and most important stored material. Glycogen granules are stored mostly in the liver.
Adipose Tissue – tissue specialized for storing fat
Glycogen – the storage form of glucose. Liver and muscle cells store the most.
Actin – protein molecule that is assembled into two strands twisted around each other to form a microfilament.
Cilia – plasma membrane covered, numerous tiny, hair-like protrusions, which beat or stroke in the same direction. Cilia project from the surface of the cell and are used to move things about.
Myosin – protein found in muscle cells
Flagellum – plasma membrane covered single whip-like appendage projecting from the surface of a cell used for movement. Sperm cells are the only human cells with a flagellum.
Amoeboid Movement – cell-crawling process that depends on the activity of actin filaments. During amoeboid movement, actin filaments continuously grow at the cell’s leading edge through the addition of actin molecules at the front of the actin chain pushing that portion of the cell forward while at the same time actin is being disassembled at the rear of the filament and transferred to the front of the filament. Thus a cell moves forward through repeated cycles of pseudopod formation by continuously disassembling, moving, and reassembling actin.
Pseudopod (“false feet”)– flexible, temporary irregular lobe of membrane made of microfilaments enclosed cytoplasm that cells use for motility or for engulfing food or capturing prey.
Microvilli – microscopic, nonmotile, hair-like projections from the surface of epithelial cells lining the small intestine and kidney tubules. They greatly increase the surface area facilitating increase absorption of materials across the plasma membrane.
Microtubular Lattice – throughout the cytoplasm, a meshwork of exceeding fine, inter-linked filaments connecting to the inner layer of the plasma membrane that my also constitute interconnections between the cytoskeleton and the various organelles.
Aerobic – with oxygen
Anaerobic – without oxygen
Cellular Respiration –refers to the intracellular oxidation of nutrient derivatives. The complete breakdown of glucose in the presence of oxygen.
Cellular Respiration Formula – C₆H₁₂O₆ + O₂ à CO₂ + H₂O + ATP (refined fuel) + Heat
Oxidative Phosphorylation – the use of O₂ in the final steps of energy conversion when phosphate is added to form ATP.
Oxidation – the addition of an oxygen molecule to a substance or the removal of a hydrogen (dehydrogenation). Any reaction involving the loss of electrons from an atom.
Photosynthesis – 6CO₂ + 6 H₂O à C₆H₁₂O₆ + 6 O₂

(inorganic) (organic)

Pyruvic Acid – (CH₃COCO₂H)
Chemiosmosis – process which drives ADP and phosphate molecules together to produce ATP.
Oncogenes – genes that are directly involved in the development of cancer
Homogenate – ground up cells in a solution
Lyse – to digest substances
Zellweger’s Syndrome – rare, fatal genetic disorder that is the result of malformed peroxisomes.
Hurler’s Syndrome – lysosomal storage disease caused by the inability of the lysosome to break down large molecules of sugar compounds (glycosaminoglycans) because of the lack of the enzyme iduronidase. Storage of these sugar compounds without breaking down then down causes the lysosome to swell jeopardizing the functioning of the entire cell.
I-cell Disease – lysosomal enzymes are produced but are “dumped” outside the cell causing materials to accumulate in the lysosome forming dark clumps or “inclusion bodies.” Children before they reach puberty of heart failure or pneumonia.
Endosymbiosis – symbiotic relationships between tiny organisms allowed for the close interactions of some species within another until both species were unable to live without the other. Essentially one species became an organelle within another species.
Cell Typing – the use of specific intermediate filaments to identify certain animal cells
Hydrolitic Enzyme – an enzyme that catalyzes the hydrolysis of a chemical bond

3 Major Parts of a Cell:

Plasma Membrane – encloses the cell
Nucleus – houses the cell’s genetic material
Cytoplasm – It is the portion of the cell’s interior made up of specialized organelles dispersed in a gel-like liquid called the cytosol and not occupied by the nucleus.

Ribonucleic Acid (RNA) and Protein Synthesis

messenger RNA (mRNA) – after DNA is transcribed into the mRNA within the nucleus, it exits the nucleus through the nuclear pores and within the cytoplasm delivers the coded genetic message to ribosomal RNA. mRNA carries the genetic message from the nucleus to the ribosomes, where protein synthesis takes place.
ribosomal (rRNA) – rRNA reads the delivered code from the mRNA and translates it into the appropriate amino acid sequence for the designated protein being synthesized.
Transfer RNA (tRNA) – tRNA transfers the appropriate amino acids within the cytoplasm to their designated site in the protein under construction. It puts the amino acids in their proper places next to one another.

Main Types of Organelles:

Endoplasmic Reticulum (ER) – elaborate fluid-filled membranous system distributed extensively throughout the cytosol. It a primarily a protein and lipid manufacturing factory.

Smooth Endoplasmic Reticulum – meshwork of tiny interconnected tubules which serves primarily as a central packaging and discharge site for molecules (proteins and lipids). It is involved in the synthesis of fatty acids and membrane components. It is not studded with ribosomes and is not involved in protein synthesis but an area for packaging proteins and lipids in transport vesicles. They are prevalent in liver cells.
Rough Endoplasmic Reticulum – communicates with the nucleus and extends out from the smooth ER as stacks of relatively flattened sacs. It is studded with dark-staining particles called ribosomes. Proteins and lipids are produced by the rough ER and pass to the smooth ER where portions of the smooth ER “bud off” (concentrate proteins and lipids, encircle and enclose them, and then “pinch off” creating or forming transport vesicles that contain proteins and lipids that float free to the Golgi complex for further processing). White blood cells have highly developed rough ER.

Ribosomes – particles of rRNA protein complexes that synthesize proteins under the direction of nuclear DNA. Unattached or “free” ribosomes are also dispersed throughout the cytosol. Attached ribosomes are attached to the rough ER. Some proteins are destined for export to the cell’s exterior as secretory products, such as protein hormones or enzymes. Other proteins are transported to sites within the cell for use in constructing new cellular membrane (either new plasma membrane or new organelle membrane) or other protein components or organelles. Ribosomes are the most numerous of the cell’s organelles.
Nucleus –spherical or oval shaped, largest and densest single organized cell component that houses the cell’s genetic material (DNA). It is constantly active.

a. Nuclear Pores – pores in the nuclear membrane that allow movement between the nucleus and the cytoplasm.

b. Nucleolus – structure found in the nuclei in which ribosomes are synthesized and partially assembled

c. Nuclear Membrane – double membrane that surrounds the nucleolus and separates it from the rest of the cell.

Golgi Complex – associated with the endoplasmic reticulum, the Golgi Body are enzyme containing organelles that modify proteins to their finished state, sorts out, and package proteins in vesicles for transport to a final destination. Each Golgi complex consists of a stack of flattened slightly curved, membrane-enclosed sacs. The Golgi stacks are not physically attached to each other and are organized into separate compartments, which prevents the mixing of enzymes. Cells highly specialized for protein secretion have hundreds of Golgi stacks while others may only have one. Transport vesicles full of proteins and /or lipids (made in the rough ER) are processed and packaged in the Golgi bodies. The Golgi complex packages secretory vesicles for release by exocytosis.
Lysosomes – variable size and shaped, membrane-enclosed sacs containing powerful hydrolytic enzymes (digestive enzymes) that break-down organic molecules that make up cell debris and foreign material, such as bacteria. They also fuse with aged or damaged organelles and remove these useless parts of the cell. Lysosomes are the intracellular digestive system and may contain 40 different enzymes that can digest almost anything in the cell.. There are about 88 per cell in some cells. Lysosomes full of indigestible material are called residual bodies and they often will migrate to the cell surface and eject the material into the external environment.
Peroxisomes – membrane-enclosed organelle about 1/3 to ½ the size of a lysosome, which house very powerful oxidative enzymes (catalase) that detoxify various wastes. Oxygen, which strips hydrogen from certain organic compounds, is used to help detoxify various waste compounds including consumed alcohol that has entered the cell. Harmful hydrogen peroxide (H₂O₂) is generated and peroxisomes break it down into water and oxygen,

(H₂O₂ à H₂O + O₂). Liver cells contain lots of peroxisomes (catalase).

Mitochondria – double membraned, rod shaped or oval structures that are the power- houses of the cell that extract energy from the nutrients in food and transform it into a usable form for the cell activities. Mitochondrial DNA can reproduce itself. Mitochondria generate 90% of all the energy in a cell. The number of mitochondria in a cell depends on the cell type. Heart cells are packed with mitochondria. Mitochondria are the second largest organelle in the cell.

Structure of Mitochondria:

Outer Membrane – smooth outer membrane that encloses the mitochondria.
Cristae – inner membrane that forms a series of in-foldings or shelves within the mitochondria which greater increase the surface area for housing proteins crucial for converting food into energy
Matrix – gel-like solution in the cavity of the mitochondria consisting of concentrated mixtures of hundreds of different dissolved enzymes that prepare nutrient molecules for the final extraction of usable energy by the cristae.
Mitochondrial DNA – DNA within the mitochondria separate from the cells DNA. Less than 1% of the cells DNA, mitochondrial DNA is a circular molecule and is inherited only from the mother.

Vaults – octagonally barrel shaped, hollow interior organelles, three times as large as ribosomes that act as cellular “trucks” in nucleus-to-cytoplasm transport. They may transport mRNA from the nucleus to the ribosomes as they have the same shape and size as nuclear pores.
Cytosol – semi-liquid, gel-like portion of the cytoplasm (55% of the total cell volume) that surrounds the organelles. It is not uniform throughout the cell. Three general categories of activities are associated with the cytosol:

enzymatic regulation of intermediary metabolism – the chemical reactions inside the cell that involves the degredation, synthesis, and transformation of small organic molecules such as simple sugars, amino acids, and fatty acids. Fuels metabolism and is envolved in protein synthesis, the storage of fats, and the storage of glycogen.
ribosomal protein synthesis – free ribosomes which synthesis proteins for use in the cytosol only.
storage of fat, carbohydrate, and secretory vesicles.

Cytoskeleton – intra-cellular protein scaffolding that supports and organizes the cell components into an appropriate arrangement and also controls their movements. The different parts of the cytoskeleton are structurally linked and functionally coordinated to provide certain integrated functions for the cell such as rigidity and special geometry. There are three distinct elements of the cytoskeleton as well as others:

*Microtubules – largest of the cytoskeletal elements made of tubulin, a small, globular, protein molecule. Microtubules are slender, long, hollow, unbranched tubes essential for maintaining an asymmetric cell shape (as in a nerve cell). They are important in the transport of secretory vesicles or other materials from one region of the cell to another by forming microtubular “highways,” for the distribution of chromosomes during cell division, and for the movement of specialized cell projections such as cilia and flagella. Vesicles travel on microtubular highways. Free ribosomes are held by cytoskeleton. Some proteins are used as medicines to prevent microtubules from forming thus destroying the cell (Taxol for cancers).
*Microfilaments – smallest of the cytoskeletal elements made up of two chains of actin molecules wrapped around each other. Microfilaments play a vital role in various cell contractile systems and they act as mechanical stiffeners for several specific cell projections such s the microvilli of the small intestine.
*Intermediate Filaments – intermediate threadlike protein filament made of keratin that hold nucleus in position. They are tough, durable fibers that play a central role in maintaining the structural integrity of a cell and in resisting mechanical stresses externally applied to a cell. Skin cells contain irregular networks of intermediate filaments.
Microtubular Lattice – interlinked filaments attached to the inside of the cell membrane which hold the cell shape and the organelles and other components in position.
Cell Cortex – cross-linked and bundled gel-like microfilaments that reinforce the cell membrane and act in mitosis.
Motor Proteins – act on microfilaments moving cell parts in a sustained directional way when energized repeatedly by ATP.
Centriole – the barrel shaped center that produces an organizes microtubules and is below the microtubule unit as a basal array

MOTOR PROTEINS - proteins that act as engines moving microtubules and microfilaments around.

1. Kinesin – drags chloroplasts into new light-sensitive positions as the sun’s angle changes

2. Myosins – move structures on microfilaments or move one microfilament over another

3. Dyneins – move chromosomes and spindle fibers

Great Cell Illustrations and information click below http://www.cellsalive.com/cells/plntcell.htm Click on the link below to see all of the different organelles http://library.thinkquest.org/C004535/lysosomes.html Great interactive site for cells and organelles! http://www.wiley.com/legacy/college/boyer/0470003790/animations/cell_structure/cell_structure.htm