A Tour of the Cell Microscopic view Membrane structure Nucleus and ribosomes The Endomembrane System Chloroplasts, Mitochondria Cytoskeleton Cilia and flagella
A Prokaryote Example? Bacteria Name some structures: Plasma membrane yellow Cell wall green Flagella Capsule orange Pili Ribosomes (blue ‘dots’) Nucleoid region (DNA) Measured in microns ~ 0.5 mm
Functions? Flagella Ribosomes 1. Surface appendages that allow a bacterium to stick to a surface 2. Where are proteins synthesized? Cell wall 3. The sticky, jellylike protective layer outside the cell wall 4. The rigid structure that surrounds, supports, and protects the cell 5. Which structure is a selective barrier, allows passage of oxygen, nutrients, and wastes? Capsule 6. Where is the cell's DNA, containing the genes that control the cell 7. The structure that propels the cell Plasma membrane Nucleoid region Pili
Compare cells A 1. Which is the animal cell? B 2. Which is the plant cell? 3. Which is characteristic of bacteria? 4. Which does not have a nucleus? 5. Which does not have a cell wall? 6. Which does not have organelles? C
Eukaryotic cells Plasma membrane Cytoskeleton The Golgi Apparatus Nucleus Ribosomes DNA Lysosomes Mitochondria Endoplasmic Reticulum (rough, smooth) Cilia, flagella
Plasma membrane Separates living cells from nonliving surroundings It is known as? the fluid mosaic model Extracellular fluid Glycoprotein Lipid bilayer Cholesterol Carb Cytoskeleton Protein Cytoplasm
Phospholipid bilayer Extracellular fluid ? ? What is the function of this component? Hydrophilic ‘head’ Hydrophilic ‘tails’ Hydrophilic ‘head’ ? Cytoplasm
Learning check Which best describes the structure of the plasma membrane? • Proteins sandwiched between 2 layers of phospholipid • Proteins embedded in 2 layers of phospholipid • A layer of protein coating a layer of phospholipid • Phospholipids embedded in 2 layers of protein
The Nucleus Is the ‘manager’ of the cell What does it contain? • DNA (Chromatin; chromosomes) • Nucleolus (Produces parts of ribosomes) It is bordered by a double membrane & has pores
What is chromatin? Long DNA molecules + protein (forms long fibers) What is the nucleolus? Ball like mass (of fibers and granules) Produces part of ribosomes (blue ‘dot’)
What are ribosomes? Organelles responsible for protein synthesis Where do they go? Move from nucleus to cytoplasm Why? Protein synthesis occurs in the cytoplasm
Recall protein synthesis? DNA (cf last talk on molecules of life) Transfers information To mRNA Leaves nucleus Travels to cytoplasm Binds to ribosome Protein synthesized
Learning check In eukaryotic cells, the first step in protein synthesis is the ____. • translation of an RNA nucleotide sequence into a sequence of amino acids • linking of nucleotides to form a polypeptide • translation of a DNA nucleotide sequence into a sequence of amino acids • transferring of information from DNA to messenger RNA
Endoplasmic reticulum RER: Makes membrane and secretory proteins SER: lipid synthesis and detoxification Nuclear membrane RER with ribosomes (blue ‘dots’) SER
Example? Secretory proteins Saliva with enzymes After the RER synthesizes a molecule, it packages the molecule into transport vesicles Secretory vesicle Ribosome with peptide chain Buds off
SER Structure? • No ribosomes • But, membrane has many enzymes What are some of the enzyme functions? Ovaries, testes: Sex hormones enriched Liver cells: Detoxification of drugs
Learning check Proteins destined for secretion are made on _____ bound to the _____. a. lysosomes ... Golgi apparatus b. ribosomes ... Golgi apparatus c. ribosomes ... mitochondria d. mitochondria ... endoplasmic reticulum e. ribosomes ... endoplasmic reticulum
The Golgi Apparatus Refines ER products and packages And packages them in transport vesicles Flattened sacs What do transport vesicles do? transport to organelles vesicles ‘become’ lysosomes export from cells
Lysosomes Membrane enclosed sac of digestive enzymes What do they break down? • Food • Damaged organelles Lysosome Proteins, polysaccharides, fats, nucleic acids Mitochondria
Learning check Lysosomes can form by budding directly off _____.
The Endomembrane System Transport of ? 1. 2. Digestive ? 3. Storage ? 4. Secreted ?
Chloroplasts & Mitochondria Think energy! Site of cell respiration Produces ATP (energy) from food molecules Site of photosynthesis Conversion of light (energy) to chemical energy More to come in Chapter 7 More to come in Chapter 6
Cytoskeleton Its like an infrastructure: ‘Skeleton’ ‘Muscles’ What is it made up of? Its a network of fibers (microtubules, filaments)
Microtubules Are straight, hollow tubes What are they composed of? Globular proteins Tubulin What are some functions? • Anchor organelles • Move organelles • Guide movement of chromosomes • Crawling motion
Crawling motion? • Rapid degeneration and rebuilding of microtubules • Allows ‘crawling’ movement like the amoeba • And some of our white blood cells
Cilia and flagella are motile appendages How do cilia move? • In a coordinated back-and-forth way Example? Paramecium
How do flagella move? • In a whip-like motion Example? Sperm
What happens in our respiratory tract? The human windpipe is lined with cilia on non-motile cells Function to move fluid over the surface of the tissue Sweep mucus with trapped debris out of lungs
Learning check Which one of the following statements about cilia and flagella is true?
Which of these organelles is found within the nucleus? a. nucleolus b. mitochondrion c. SER d. chloroplast e. ribosome Which of these organelles carries out cellular respiration? a. nucleolus b. chromatin c. SER d. mitochondrion e. ribosome Which organelle plays a role in intracellular digestion? a. Lysosome b. ribosome c. chloroplast d. Golgi apparatus
Concept Check The three domains of life described by biologists today include the bacteria, the archaea and the eukarya (all other forms of life). • The prokaryotes do not have a plasma membrane surrounding the cell. • The prokaryotes use RNA and not DNA to pass on the genetic message. • The eukaryotes have the interior of the cell divided by internal membranes into specialized compartments. • The eukaryotes engage in cellular metabolism while the prokaryotes do not.