Mcat Biology The Cell

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The Cell Theory

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-All living things are composed of cells
-The cell is the basic functional unit of life
-Cells arise from pre-existing cells
-Cells carry genetic information (DNA) which is passed from a parent cell to a daughter cell

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Autoradiography

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-uses radioactive molecules to trace and identify cell structures and biochemical activity
-cells are exposed to radioactive compound for a brief, measured period of time, then are incubated, fixed at various intervals, and processed for microscopy
-can be used to study protein synthesis

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Centrifugation

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-used to separate cells or mixtures of cells without destroying them in the process
-cell mixtures separate into layers on the basis of their cell type

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Prokaryotes

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-bacteria and cyanobacteria
-unicellular, no membrane bound organelles
-single, circular DNA in the nucleoid
-might contain plasmids(smaller rings of DNA),
-contain cell walls
-no nucleus
-respiration occurs @ cell membrane
-can survive in adverse conditions

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Eukaryotes

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-protists, fungi, plants, animals
-cell wall only in fungi and plants
-containsorganelles
-contains a nucleus

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Cytosol

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the fluid component of the cytoplasm annd consists of an aqueous solution containing free proteins, nutrients, and other solutes

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Cytoskeleton

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composed of microtubules, microfilaments, intermediate fibers, and other accessory proteins, it is also found in the cytosol
-give cell its shape and anchor the organelles
-aid in cell maintenance and intracellular transport

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Fluid Mosaic Model

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-cell membrane consists of a phospholipid bilayer with proteins embedded throughout
-the lipids and many of the proteins can move freely within the membrane

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Hydrophilic

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-polar
-phosphoric acid
-exterior surfaces

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Hydrophobic

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-nonpolar
-fatty acid
-located on the interior of the membrane
-cholesterol molecules embedded in the hydrophobic interior contribute to the membrane's fluidity

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Transport Proteins

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membrane-spanning molecules that allow certain ions and polar molecules to pass through the lipid bilayer

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Cell Adhesion Molecules

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proteins that contribute to cell recognition and adhesion, and are particularly important during development

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Nuclear Membrane

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-aka envelope
-a double membrane that maintains a nuclear environment distinct from that of the cytoplasm

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Nuclear Pores

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-allow selective two-way exchange of materials between the nucleus and the cytoplasm

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Histones

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-structural proteins that form chromosomes

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Nucleolus

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-a dense structure in the nucleus where ribosomal RNA synthesis occurs

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Ribosomes

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-the sites of protein production
-synthesized by the nucleolus
-free ribosomes are found in the cytoplasm
-bound ribosomes line the outer membrane of the ER

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Endoplasmic Reticulum

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-a network of membrane-enclosed spaces connected at points with the nuclear membrane
-involved in the transport of materials throughout the cell,especially those materials destined to be secreted from the cell

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Smooth ER

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-involved in lipid synthesis and the detox of drugs and poisons

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Rough ER

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protein synthesis

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Golgi Apparatus

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-stack of membrane-enclosed sacs
-receives vesicles and their contents from smooth ER, modifies them, repackages them into vesicles, and distributes them
-distribution of newly synthesized materials to the cell surface

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Secretory Vesicles

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-produced by the Golgi Apparatus
-release their contents to the cells exterior by the process of exocytosis

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Vesicles and Vacuoles

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-membrane bound sacs involved in the transport and storage of materials that are ingested, secreted, processed, or digested by the cell
-vacuoles are larger than vesicles and are more likely to be found in plant cells

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Lysosomes

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-membrane bound vesicles that contain hydrolytic enzymes involved in intracellular digestion
-max effective at a pH of 5
-fuse with endocytotic vacuoles,thereby breaking down the material ingested by the cell
-aid in renewing cells own components by breaking down the old ones and releasing their molecular building blocks into the cystol for reuse

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Microbodies

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-containers for metabolic reactions
-2 types: peroxisomes & glyoxysomes

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Peroxisomes

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-microbodies
-contain oxidative enzymes that catalyze a class of reactions in which hyrogen peroxide is produced by the transfer of hydrogen from a substrate to oxygen
-break fats down into smaller molecules that can be used for fuel, and are also used in the liver to detoxify compounds harmful to the body, such as alcohol

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Glyoxysomes

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-microbodies
-usually found in the fat tissue of germinating seedlings
-convert fats into sugars until photosynthesis can occur

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Mitochondria

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-sites of aerobic respiration and supplier of energy
-bound by an inner and outer phospholipid bilayer membrane
-semiautonomous

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Intermembrane Space

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-mitochondria
-area between the inner and outer membranes
-many convolutions called cristae and a high protein content that includes the proteins of the ETC

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Mitochondrial Matrix

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-the site of many reactions in cell respiration

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Semiautonomous

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-mitochondria
-contain their own DNA(circular) and ribosomes, which enable themt o produce some of their own proteins and to self-replicate by binary fission

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Chloroplasts

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-plastids
-found only in algal and plant cells
-contain chlorophyll and are the site of photosynthesis
-contain their own DNA and ribosomes and exhibit the same semiautonomy as mitochondria

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Cell Wall

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-composed of cellulose (plants)
-composed of chitin (fungi)

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Centrioles

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-specialized type of microtubule involved in spindle organization during cell division and are not bound by a membrane
-only in animals

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Microtubules

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-hollow rods made up of polymerized tubulins that radiate throughout the cell and provide it with support
-provide a framework for organelle movement within a cell
-centrioles are composed of microtubules

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Microfilaments

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-solid rods of actin
-involved in cell movement as well as support
-move materials across the plasma membrane

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Intermediate Filaments

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-collection of fibers involved in maintenance of cytoskeletal integrity

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Simple Diffusion

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-move down the concentration gradient
-higher to lower

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Osmosis

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simple diffusion of water from lower solute concentration to higher solute concentration

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Hypertonic

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when the cytoplasm of the cell has a lower solute concentration than the extracellular medium
-water will flow out causing the cell to shrink

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Hypotonic

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-when cytoplasm has a higher solute concentration than the extracellular medium
-water will flow in causing the cell to swell

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Facilitated Diffusion

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-net movement of dissolved particles down their concentration gradient with the help of carrier molecules
-does not require energy

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Active Transport

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-net movement of dissolved particles against their concentration gradient with the help of transport proteins
-requires energy
-required to maintain membrane potentials in specialized cells such as neurons

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Endocytosis

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-cell membrane invaginates, forming a vesicle that contains extracellular medium

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Pinocytosis

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-ingestion of fluids or small particles
-receptor carries the molecule into the cell

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Phagocytosis

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the engulfing of large particles

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Exocytosis

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-a vessicle within the cell fuses with the cell membrane and releases its contents to the outside

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Epithelial Tissue

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-covers the surfaces of the body and lines the cavities, protecting them from injury, invasion, and desiccation
-also involved in absorption, secretion and sensation

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Connective Tissue

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-involved in body support and other functions
-include: bone, cartilage, tendons, ligaments, adipose tissue, and blood

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Nervous Tissue

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-composed of specialized cells called neurons that are involved in the perception, processing and storage of information concerning the internal and external environments

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Muscle Tissue

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-has great contractile ability and is involved in body movement
-3 types: skeletal, cardiac and smooth

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Viruses

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-composed of nucleic acid enclosed by a protein coat
-nucleic acid can be linear or circular
-4 types nucleic acid: single stranded DNA, double stranded DNA, single stranded RNA, and double stranded RNA
1)attaches itself to a host cell and injects their nucleic acid, taking control of the protein synthesis within the cell
2) viral genome replicates itself many times, produces new protein coats and assembles new virions that leave the host cell in search of new hosts

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Obligate Intracellular Parasites

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-viruses
- they can express their genes and reproduce only within a living host cell since they lack structures necessary for independent activity and reproduction