Chapter 7 - Tour of the Cell. Cells vary in size but are typically very small. The more complex the internal components the larger the cell can be. prokaryote->eukaryote

Chapter 7 - Tour of the Cell

Cells vary in size but are typically very small. The more complex the internal components the larger the cell can be .

prokaryote->eukaryote cell->protozoan

The small size is a consequence of the cell volume requiring adequate surface area to support nutrient demands

1cm sides: SA=? Vol=? Ratio=?



Prokaryotes:

Eukaryotic Animal Cell: The basic eukaryotic cell contains the following: 1.plasma membrane 2.cytoplasm (semifluid) 3.cytoskeleton - microfilaments and microtubules that suspend organelles, give shape, and allow motion 4.presence of characteristic membrane enclosed subcellular organelles

Plasma Membrane & Internal Membranes: Selectively permeable barriers

Basic structure & makeup is the same. The specific proteins that are present and in what concentration will allow different cell types to respond differently to stimuli and nutrient/waste identification. Glycocalyx identifies cell type. (transplant rejection, hashimoto’s)

Nucleus - control center

Double membrane surrounding the chromosomes and the nucleolus.

Pores allow specific communication with the cytoplasm.

The nucleolus is a site for synthesis of RNA used to make up ribosomes.

Constant chemical communication between the cytoplasm and the nucleus.

Initiation and cessation of life sustaining chemical reactions is ordered by the DNA in the nucleus

Endoplasmic Reticulum - assembly line

Attached to the nuclear envelope for immediate response to the orders of the DNA. A network of interconnected membranes

forming channels and pockets (cisternae) within the cytoplasm.

Rough ERCovered with ribosomes (causing the "rough” appearance) which are in the process of synthesizing proteins for secretion or localization in membranes.

Smooth ER

Ribosome: protein RNA complex that is needed for the synthesis of protein. (free & attached)

•assembly of lipids & carbohydrate•detoxifies toxic chemicals (add OH for solubility)•may store, release & recover cell stimulants

What determines amount & type of ER in cells?

The Golgi - Some manufacture & packaging for exportChemicals assembled and acquired from the ER are placed in a vesicle whose membrane contains target (docking) chemicals identifying the final location of its contents (outside cell or inside organelles)

Lysosome - digests & recyclesMade by the golgi, contains powerful hydrolytic enzymes that digests organic compounds

Cells deprived of O2 or infected by viruses can trigger lysosomes to rupture & release hydrolytic enzymes into cytosol (immune system, tadpole tail, fetal fingers)

H+ pump in membrane enables the lysosome to lower pH and digestion started,

Formation of Lysosomes

The modification and packaging of glycoproteins & glycolipids can establish the glycocalyx on the plasma membrane

Endomembrane systemA series of closed membranes within eucaryotic cells that are either continuous with each other or communicate with one another via vesicles which are formed at one surface and move to a second where they are incorporated.

Vacuoles: Membrane surrounded "bags" that contain water and storage materials in plants.

•Contractile Vacuole•Food Vacuole•Structural Vacuole•Storage Vacuole

URL for Contractile Vacuole

http://www.microscopy-uk.org.uk/mag/artjun99/vidjuna.html

The Mitochondrion - Power generator (Respiration)

Organelle that contains its own DNA and ribosomes. It makes its own proteins. EndoSymbiotic Theory. It converts a non-readily available chemical energy (PGAL) into a usable form - ATP as long as O2 is readily available

Cytoskeleton - cell structure

Cytoskeleton is composed of three main types of protein fibers, Microtubules, Microfilaments, and Intermdiate filaments.

Cytoskeleton revealed by staining with a fluorescent labeled actin antibody

QuickTime™ and aSorenson Video decompressorare needed to see this picture.

The pigment granules move on fixed pathways inside the chromatophore cytoplasm, following radially arranged bundles of microtubules. The process is shown at 24 times the real speed. Movement is caused by light stimulus to he eye or emotion. Nerve fibers discharge transmitters that initiates the movement of the pigment in the microtubules.

Microtubules and Microfilaments also aid in cellular transport:

Motor proteins (kinesin and myosin) can attach to the microtubules or microfilaments and with the use of ATP glide along the surface. As the motor protein moves along the surface it can drags organelles through the cytoplasm

Cytoplasmic streaming

Chrmatophores



The microtubules can be arranged in elaborate bundles creating specialized transport structures (cilia, flagella, centriole)


Cell Surfaces and Junctions OccludingTight Junctions - keratin proteins fuse the adjoining membranes in direct contact (no intracellular space). WeldAnchoring Desmosomes & Adhesion Belts - intermediate filaments penetrate & are shared through the membranes of both cells. (collagen, keratin) Intracellular space still presentCommunicationGap Junctions - pore like conections that allows cytoplasm to flow easily between connected cells (plasmodesmata in plant cells)

Plant Cells are structurally very similar to animal cells:Differences?

Chloroplast - energy transformer (Photosynthesis)In the presence of light and with the use of chlorophyl, the chloroplast converts CO2 and H2O into carbohydrate. This may be used for the production of ATP, storage, or structural material.

Chloroplasts have their own DNA and ribosomes (endosymbiotic theory) and make their own proteins. They develop from an undifferentiated organelle called a Protoplast. Depending on location in the plant and or the presence or absence of light, the protoplast may develop into one of three organelles: •Chloroplast

•Chromoplast•Leucoplast

CellWall

Membrane Structure & Transport Functions?

Cell growth will require formation of additional membrane and deposition of essential membrane chemicals. This is accomplished by the endomembrane system.

The Golgi & ER work together to create the key membrane chemicals which are then concentrated on the inner surface of vessicles that are released.

Vessicle membranes and the plasma membrane fuse much in the same way as soap bubbles can

fuse.

QuickTime™ and aCinepak decompressorare needed to see this picture.

Passive Transport:

All cells require nutrients and produce waste. Movement of these substances into and out of the cell at the optimum rate is essential. What mechanisms insures the proper exchange (nutrients in and wastes out)?

Molecules own kinetic energy insures movement from an area of high concentration to an area of low concentration. The rate at which this movement will occur depends on?

This type of transport is referred to as Passive. Why? Organisms without transport systems depend heavily on this type of movement. What physical characteristics are typical of those organisms lacking transport systems?

Methods of Passive Transport

Water moves freely between the shifting lipid molecules. Water will also move from an area of higher concentration to an area of lower concentration -

Osmosis - diffusion of water through a selectively permeable barrier


Active Transport: MicrotubulesTransport containers filled with basolateral cargo move along microtubules to the cell periphery

http://www.mpi-cbg.de/research/simons/Movie.html

Microtubules responsible for internal cellular transport were tagged with fluro dyes. Th area that is brightly colored is the golgi. Small packets moving to the cell periphery are vessicles containing golgi or ER products.

Sequence of 100 images. Rate was two images per second

QuickTime™ and aVideo decompressorare needed to see this picture.

Carrier Proteins can actively transport substance in or out of cells

Endocytosis•Receptor Mediated Endocytosis (example?)•Pinocytosis (no receptor - example?)•Phagocytosis (example?)

Exocytosis (example?)

QuickTime™ and aCinepak®Pro

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Chapter 7 - Tour of the Cell. Cells vary in size but are typically very small. The more complex the internal components the larger the cell can be. prokaryote->eukaryote