Chapter 6 a tour of the cell
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Chapter 6: A Tour of the Cell. Technology to study cells. light microscopes – pass visible light through specimen and lenses. magnification – ratio of image size to actual size. resolution – clarity of image; minimum distance between two distinguishable points.

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Chapter 6 a tour of the cell

Chapter 6:A Tour of the Cell



Light microscopes pass visible light through specimen and lenses
light microscopes – pass visible light through specimen and lenses


Magnification ratio of image size to actual size
magnification – ratio of image size to actual size


Resolution clarity of image minimum distance between two distinguishable points
resolution – clarity of image; minimum distance between two distinguishable points


electron microscopes – focus beams of electrons through or onto specimen– resolution 100x better than light microscopes


Scanning electron microscope sem studying external structures
scanning electron microscope (SEM) – studying external structures


Transmission electron microscope tem studying internal structures
transmission electron microscope (TEM) – studying internal structures


Cell fractionation take cells apart and isolate organelles
Cell Fractionation – take cells apart and isolate organelles



Surface are to volume ratio: cell components by size and density– limits cell size because as cells get bigger, their volume increases faster than their surface area


Surface area important for transport of substances through the membrane
– surface area important for transport of substances through the membrane

microvilli in intestine

increases surface area for absorption


All cells have
All cells have: through the membrane

  • cytosol– semifluid substance containing organelles and dissolved nutrients

  • plasma membrane – selective barrier

  • chromosomes – packaged DNA

  • ribosomes – make proteins


Prokaryotic cells
Prokaryotic Cells through the membrane


Prokaryotic cells1
Prokaryotic Cells through the membrane

  • smaller than eukaryotic cells

  • no membrane-bound organelles

  • no nucleus (nucleoid – region containing prokaryotic DNA)

  • small ribosomes

  • circular DNA

  • plasmids


Bacterial conjugation using pili through the membrane


Eukaryotic cells
Eukaryotic Cells through the membrane


Nucleus contains dna
nucleus through the membrane – contains DNA

  • nuclear envelope – double membrane that encloses nucleus

  • nuclear pores – holes in the nuclear envelope. Allow passage of large molecules.


  • chromosomes through the membrane – made of chromatin, a complex of proteins and DNA

  • nucleolus – rRNA synthesized, ribosomes assembled


Ribosomes synthesize proteins
ribosomes through the membrane – synthesize proteins

  • made of ribosomal RNA (rRNA) and protein

  • cells that synthesize many proteins have many ribosomes

  • either free-floating in cytosol (make proteins for cell’s use) or bound to rough ER (make proteins for secretion)


Endomembrane system
endomembrane through the membrane system

  • more than half the total membrane of the cell

  • consists of membranous tubules and sacs (cisternae)

  • lumen – interior cavity of cisternae


Smooth endoplasmic reticulum er
smooth endoplasmic reticulum (ER) through the membrane

  • no bound ribosomes

  • synthesizes lipids (phospholipids, oils, steroids)

  • stores calcium ions, especially in muscles (important to muscle contraction)


Enzymes detoxify drugs and poisons especially in the liver
Enzymes detoxify drugs and poisons, especially in the liver through the membrane

  • add hydroxyl groups to drugs; makes them more soluble

  • drug tolerance due to proliferation of smooth ER in addicts; higher doses required to achieve the same effect


Rough endoplasmic reticulum er
rough endoplasmic reticulum (ER) through the membrane

  • has bound ribosomes

  • continuous with nuclear envelope


  • helps in synthesis of through the membrane secretory proteins (proteins made for secretion), especially glycoproteins – proteins that have carbohydrates on them

  • adds carbohydrates to glycoproteins, sends them in transportvescicles (sacs of membrane) to Golgi



Golgi apparatus products of er modified stored and then shipped
Golgi apparatus itself that becomes vescicles; these eventually become part of cell membrane – products of ER modified, stored and then shipped

  • flattened sacs (cisternae)

  • cis face – receiving side

  • trans face – shipping side


  • vescicles itself that becomes vescicles; these eventually become part of cell membrane from ER fuse with cis face and empy contents into lumen of cisternae

  • products of ER modified in Golgi:

    – modifies carbohydrates

    – alters protein structure


  • Golgi makes some macromolecules itself that becomes vescicles; these eventually become part of cell membrane

  • products transferred from one cisternae to another, eventually arrive at trans face.

  • products sorted and “addressed” for where they will go


  • vescicles bud off itself that becomes vescicles; these eventually become part of cell membranetrans face and carry contents to cell membrane for export or to different parts of the cell


Lysosomes digest
Lysosomes itself that becomes vescicles; these eventually become part of cell membrane – digest

  • membrane sac of hydrolytic enzymes

  • digests molecules and worn-out cell parts (autophagy)


phagocytosis itself that becomes vescicles; these eventually become part of cell membrane – food particle engulfed by cell and contained in vescicle– vescicle merges with lysosome and is digested


Tay sachs disease lysosomal disorder in humans allows lipids to accumulate in cells
Tay itself that becomes vescicles; these eventually become part of cell membrane-Sachs disease – lysosomal disorder in humans, allows lipids to accumulate in cells.


Tay sachs
Tay-Sachs itself that becomes vescicles; these eventually become part of cell membrane

  • Lipids accumulate in nervous tissue

  • Degeneration of mental and physical abilities

  • Seizures, paralysis

  • Death before age 4

Cherry-red spot on retina identifies Tay-Sachs


Vacuoles
Vacuoles itself that becomes vescicles; these eventually become part of cell membrane

  • membrane-bound sacs

  • central vacuole – in plants, storage for nutrients and wastes, water

    – membrane: tonoplast


  • food vacuoles itself that becomes vescicles; these eventually become part of cell membrane – formed by phagocytosis

  • contractile vacuoles – in protists, pump excess water out of cell


Mitochondria make cell energy
Mitochondria itself that becomes vescicles; these eventually become part of cell membrane – make cell energy

  • change molecular energy to cellular energy; cell respiration


  • double membrane itself that becomes vescicles; these eventually become part of cell membrane

  • outer membrane is smooth

  • Inner membrane has folds called cristae

  • intermembrane space – between outer and inner membrane

  • mitochondrial matrix – lumen within the inner membrane


Chloroplasts make carbohydrates
Chloroplasts – make carbohydrates itself that becomes vescicles; these eventually become part of cell membrane

  • a plastid (other plastids are amyloplasts (store starch in plants) and chromoplasts (contain pigments that color fruit and flowers)

  • contain pigment chlorophyll


  • double membrane itself that becomes vescicles; these eventually become part of cell membrane

    – outer membrane smooth

    – inner membrane is stacks of sacs called

    thylakoids

  • a stack of thylakoids is a granum

  • fluid between granum and outer membrame is stroma


Peroxisomes
Peroxisomes itself that becomes vescicles; these eventually become part of cell membrane

  • sac containing enzymes that transfer hydrogen to oxygen, producing H2O2

  • digestion of fats, detoxification of alcohol

  • not part of endomembrane system (lysosomes are)


Cytoskeleton
Cytoskeleton itself that becomes vescicles; these eventually become part of cell membrane

  • support, maintain cell shape

  • cell motility (movement): both movement of whole cell and parts of cell within.

  • motor proteins – help cytoskeleton accomplish movement


Microtubules
Microtubules itself that becomes vescicles; these eventually become part of cell membrane

  • hollow tubes of 13 columns of tubulindimers

  • 25 nm

  • -tubulin and -tubulin

  • cell shape (reists compression), cilia and flagella, move chromosomes during cell division, organelle movement


Microfilaments actin filaments
Microfilaments ( itself that becomes vescicles; these eventually become part of cell membraneactin filaments)

  • 2 intertwined strands of actin

  • 7 nm

  • cell shape (resist force), muscle contraction, cytoplasmic streaming, pseudopodia in amoeboid movement


Intermediate filaments
Intermediate filaments itself that becomes vescicles; these eventually become part of cell membrane

  • thick cables of fibrous protein

  • 8-12 nm

  • fibrous Keratin protein

  • cell shape (resist force), anchorage of nucleus and organelles


Centosomes and centrioles
Centosomes itself that becomes vescicles; these eventually become part of cell membrane and centrioles

  • centrosome – region near nucleus where microtubules grow out from

  • centrioles – in animals, 9 sets of triplet microtubules that help organize mitotic spindle during cell division


Cillia and flagella
Cillia itself that becomes vescicles; these eventually become part of cell membrane and flagella

  • 9 + 2 arrangement of microtubules

  • dynein arms are motor proteins


flagella itself that becomes vescicles; these eventually become part of cell membrane – a tail-like structure for cellular locomotion or moving liquid past cell– made of microtubules


Cilia a hair like structure for locomotion or moving liquid past cell
cilia itself that becomes vescicles; these eventually become part of cell membrane – a hair-like structure, for locomotion or moving liquid past cell


  • Dynein arms bend cilia and flagella itself that becomes vescicles; these eventually become part of cell membrane

  • Dynein “walking”: arms of one microtubule grip adjacent doublet, push it up, release, then repeat


Basal body where cilium or flagellum is anchored to cell
basal body itself that becomes vescicles; these eventually become part of cell membrane – where cilium or flagellum is anchored to cell

  • – 9 sets of triplet microtubules (9 x 3)

  • – a basal body of a sperm flagellum enters egg and becomes a centriole


Extracellular components of plants
Extracellular components of plants itself that becomes vescicles; these eventually become part of cell membrane


Cell wall
cell wall itself that becomes vescicles; these eventually become part of cell membrane

  • made of cellulose microfibrils and proteins. Protects, maintains shape, prevents too much water

  • also in prokaryotes, fungi and some protists

  • primary cell wall – young cell wall. Thin and flexible

  • secondary cell well – in woody plants. Grown between membrane and primary wall.


  • middle lamella itself that becomes vescicles; these eventually become part of cell membrane – between primary cell walls of adjacent cells. Rich in pectins (sticky polysaccharides). Glues cells together.

  • plasmodesmata


Animal extracellular matrix ecm
Animal Extracellular Matrix (ECM) itself that becomes vescicles; these eventually become part of cell membrane

  • Mostly glycoproteins; mainly collagen fibers

  • Collagen embedded in a network of proteoglycans


fibronectin itself that becomes vescicles; these eventually become part of cell membrane – another glycoprotein in the ECM that binds integrins on cell membraneintegrins – proteins that span the cell membrane and transmit info on changes outside the cell to the cytoplasm


  • Changes in ECM my trigger changes in cells. itself that becomes vescicles; these eventually become part of cell membrane

  • Integrins help relay signals to and from cells

  • Play role in coordinating behavior of all cells in a tissue.


Intercellular junctions
Intercellular junctions itself that becomes vescicles; these eventually become part of cell membrane

  • Plasmodesmata (plants) – channels made by perforation in cell walls. Cytosol, water and nutrients passes through them, linking cells

  • tight junctions (animals) – membranes of cells tightly pressed together, bound by proteins. Prevents leakage.


tight itself that becomes vescicles; these eventually become part of cell membranejuction


  • desmosomes itself that becomes vescicles; these eventually become part of cell membrane(animals) – fasten cells together into a strong sheet. Like rivets.

  • gap junctions (animals) – channels between cells through which flow ions, sugars, other molecules. Useful in cell communication.


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