Ix - MRS. PUCKETT'S COMPUTER CLASS
Chapter 3 Teaching Notes
Table of Contents
Introduction to Cells – Cytology Part I 2
Cytology – cell biology; the study of cells 2
Cell Theory: 2
Unicellular vs. multicellular organisms. 3
Three types of cell junctions (Siegfried) (Goldberg) 3
Cellular Anatomy 4
Two types of cells – based on the structure of the nucleus. 4
Cell Boundaries 4
Cytoplasm 4
Mitochondria 4
Ribosomes and Endoplasmic Reticulum (E.R.) 4
Golgi Apparatus 4
Lysosomes 4
Cytoskeleton 4
Flagella and Cilia 4
Vacuoles and Vesicles 4
The Nucleus 4
3B – Cells and Their Environment 4
The Solutions Around Cells 4
3B-2 – Transportation Across the Membrane 4
Endocytosis and Exocytosis 4
Phagocytosis 4
Pinocytosis 4
Bibliography 4
Chapter 3
Introduction to Cells – Cytology Part I
Cytology – cell biology; the study of cells
The term ‘cell’ comes from Robert Hooke’s observations of a cork. The cells had already died so there was no liquid, but he observed the outer membranes, which looked like rows of rooms in a monastery – so he’s the first person to call them ‘cells’.
Protoplasm – refers to the entire contents of the cell.
In 1838 and 1839 two startling discoveries were made – both plants and animals are made out of cells!
Cell Theory:
▪ The cell is the basic unit of all living things
o The quantity (not the size) of cells determines the size of an organism
o Some parts of an organism are composed of materials that a cell manufactures, i.e., an insect’s body covering.
▪ Cells perform all the functions of living things
o Cells are responsible for the functions of any living thing
▪ Cells come from the reproduction of existing cells.[1]
o Cells reproduce by dividing
Build table 3A using diagrams – all living organisms must carry out each of these functions – however, not every cell will perform every function.
Why can a cell only grow to a certain size? Discuss box on the box of page 72.
BTW – a cell is three-dimensional, not two-dimensional like all the drawings that we see.
Unicellular vs. multicellular organisms.
Most multicellular organisms are organized into tissues – a group of similar cells that work together to carry out a specific function.
Closer look – page 74 (they skip – pulls on info from ch 2) – WOW NEED TO UNDERSTAND THIS – Will not be on test
I need to cover briefly – discuss cell membranes. Made up of lipid protein molecules – shaped like….see page 60 for diagram. Held together chemically.
Three types of cell junctions (Siegfried) (Goldberg)
▪ Tight (for a sealed barrier) – form stomach linings
▪ Anchoring – joins cytoskeleton of one cell to the cytoskeleton of another. (Cytoskeleton - It is a dynamic structure that maintains cell shape, often protects the cell, enables cellular motion (using structures such as flagella, cilia and lamellipodia), and plays important roles in both intracellular transport (the movement of vesicles and organelles, for example) and cellular division.)
o Adherens junction
o Desmosome
o Hemidesmosome
▪ Gap – provides a narrow passageway between cells to allow small molecules and ions to move from the cytoplasm of one cell to the cytoplasm of another.
Protein complexes in one cell (connexions) align with protein complexes in another cell to form the passageways.
Plants do not have these types of cell junctions – they have tiny passageways called plasmodesmata – that span the cell walls between the cells and are lined by the plasma membrane so that it is continuous from one cell to another.
Plasmo – to mold
Desmata – Gk. bond
Look at the diagram at the bottom of page 74.
Cellular Anatomy
▪ A boundary that encloses the cell (3-D)
▪ The cytoplasm containing various kinds of structures and molecules
▪ The nucleus that contains DNA and other materials
Two types of cells – based on the structure of the nucleus.
1) Eukaryotic (Gk. eu – well defined; karyon – kernel)
a. Membrane-bound nucleus
b. Membrane-bound organelles in the cytoplasm
2) Prokaryotic (Gk. pro – before; karyon – kernel – evolutionistic)
a. Non-membrane-bound nucleus
b. Non-membrane-bound organelles
Draw the diagrams on page 75 – students copy – leave room to add. See Margin Notes – page 77 – start with a shell and ask students to suggest what goes in based on their reading.
Students bring sharpened colored pencils to class – I bring three-hole punched blank paper
Compare your drawings from page 75 to the 3-D drawings on page 76 – add any new features we see
Review everything in the chart on page 77 – be sure it is in the drawing. Practice this..
Cell Boundaries
Technically – the outer boundary is the plasma membrane, but many cells have structures outside of this – cell walls, capsules, and sheathers.
Plasma Membrane (cell membrane) – separates the cells from its environment; yet allows nutrients in and waste, etc. out.
Membranes contain lipids (define aqueous – containing water)
REVIEW LIPID STRUCTURE WITH THE CLASS – hydrophilic ends (water loving); hydrophobic ends (water fearing)
Do demonstration in margin on page 77 – set up three or four small observation stations; ready to go quickly.
Could be a cool phospholipid demonstration --
Because membranes are made up of molecule combinations – not all membranes are alike. Membranes are custom built for the job they need to do.
Cell Walls – found in plant cells in addition to the membrane. Outside of the membrane.
A rigid or nearly-rigid structure – made of cellulose.
Primary cell wall – formed early in the cell’s life; 20% to 30% cellulose
Secondary cell wall – formed between the primary and the membrane. Formed as the cell matures – much more cellulose. Several layers – and in each layer the cellulose flows in a different direction.
When the cell dies, the secondary cell wall remains – this is the work structure Robert Hooke saw – good place to look under microscope
See cell wall discussion in the TE margin – page 79
Capsules (sheathes)–
Define polysaccharides (many moleculed sugar) – from ch 2
Sometimes called the slime coat – made of cellular secretions designed to add protection to the cell
Cytoplasm
All of the structures and materials inside the plasma membrane – except for the nucleus.
Need colloid description from Ch 2.
Cytoplasmic matrix
Cytoplasmic streaming – the way of moving organelles around the inside of the cell.
Mitochondria
the powerhouse of the cell; transforms chemical energy stored in sugars to usable energy for the cell – cellular respiration. Smooth outer membrane and an inner membrane with many folds surround the mitochondria.
Mitochondrial matrix – the fluid inside the mitochondria – contains many enzymes needed for respiration.
Motochondria contain their own DNA
Ribosomes and Endoplasmic Reticulum (E.R.)
Ribosome – a non-membrane-bound organelle found in both prokaryotic and eukaryoic cells – composed of proteins and multiple strands of RNA. Primary function – protein synthesis
E.R. – a system of interconnected folded membranes inside the cell. Provides a transportation network and helps maintain the cell’s shape.
Rough E.R. (dotted with ribosomes) – found in cells that produce proteins to be secreted by the cell.
Smooth E.R. (no ribosomes) – found in cells that secrete sterols and in liver cells where toxic substances are broken down.
Golgi Apparatus
Flattened membrane-covered sacs; important in the final processing and packaging of many complex polysaccharides, proteins and lipids produced by the cell.
Works in close association with the E.R.
Processing centers – taking the product of the ER and putting it in small transportable, exportable packets.
Lysosomes
Organelles filled with digestive enzymes. Can digest good and bad materials. Also break down old or nonfunctional cellular structures.
Cytoskeleton
Fibers that control the cell’s shape, give it strength and move structures around inside the cell.
Centrosome – a region located near the nucleus that is important in the production of microtubules in the cytoskeleton
Flagella and Cilia
Flagellum – a long tubular extension of the plasma membrane – often longer than the cell. Usually just one, but can have up to five .
Cilia – like flagellum, except short and frequently cover the entire cell (or an entire section of a cell). Can be used to move the cell – or to move the environment past a cell.
Basal body (kinetosome) – found at the ‘base’ of the flagellum or cilia – used to coordinate and control the movement
Need to show video here. Work on video player…..
Skip reading the facet on pages 82 and 83?
Plastids – found in plant cells and algae – but not in animals or humans
Surrounded by two membranes (like mitochondria)
Classified as leucoplasts (colorless and used as storehouses) or chromoplasts (containing pigment and used in synthesis processes – give the plant its color.)
Best known chromoplast is chloroplast – a green organelle in which light energy is converted into organic compounds.. Chloroplast contains its own DNA.
Vacuoles and Vesicles
Multi-purposes membrane-bound organelles
Vacuoles – contains food, water, wastes or other materials. Tend to be stationary or move very slowly.
Vesicles – usually smaller and move mobile than vacuoles.
Food vacuole – formed when the cell takes in food (ingestion). Lysosomes release a digestive enzyme into the vacuole to break down the food.
Waste vacuole – the indigestible materials remain the vacuole – now termed a waste vacuole. The vacuole is moved to the plasma membrane and attaches, then pushes the waste out (egestion).
See pic on page 85
Contractile vacuole – used in water environments to push unwanted water out of the cell. (Once thought to be hearts by scientists who observed their pumping motion)
Secretion vesicle – usually formed around the E.R. or Golgi apparatus. Transport the materials made by these structures to the plasma membrane where they are secreted.
Peroxisome – small vesicle that contains enzymes that break down amino acids and fatty acids (also breaks down the hydrogen peroxide - H2O2 - that is formed in the process because it is hazardous to the cell)
Central vacuole – quite large; found in plant cells – pushes the cytoplasm and other organelles out to the plasma membrane (see pic on page 85). Full central vacuoles produces turgor pressure – making a plant stem rigid rather than wilted. (See demonstration of turgor pressure – TE margin, page 90 – see continuation at bottom)
The Nucleus
The control center of the cell.
DNA replication and RNA transcription happen here.
Double membrane surrounds it – called the nuclear envelope. Nuclear pores permit the passage of material between the cytoplasm and the nuclear sap within the nuclear envelope.
Chromatin material within the nucleus. All the hereditary information of the cell is stored in the DNA. The nucleolus (may be more than one in a nucleus) contains large concentrations of RNA and is the site in the nucleus where ribosomes are partially assembled beore passing through the nuclear pores into the cytoplasm.
3B – Cells and Their Environment[2]
Cells interact with their environment
Homeostasis – steady state; in reality a dynamic equilibrium as the organism interacts with the surrounding environment to resist change.
Optimal point – the point at which something functions best
Optimal range – the range in which something functions best
Cells walk a tightrope to maintain their living condition. It can be work just to stand still on a tightrope.
Use family example in TE margin – page 87
A thermostat is used to regulate your AC temperature (maintain equilibrium)
Range of tolerance – an organism will remain alive but will not function properly
Limit of tolerance – death occurs
The Solutions Around Cells
The plasma membrane stands between the surrounding environment and the cell and works to maintain homeostasis.
Diffusion – the movement of molecules from an area of higher concentration to an area of lower concentration.
Osmosis – a process in which water molecules diffuse across a semi-permeable membrane from higher to lower concentration until equilibrium is established.
Isotonic – when the concentration of solutes outside the cell is the same as the concentration side the cell. (like red blood cells)
Hypotonic – the solution outside the cell has a higher concentration of water molecules and a lower concentration of solutes than the solution inside the cell. Water molecules move into the cell, causing the cell to swell and perhaps burst (cytolysis)
Hypertonic – the solution inside the cell has more water and less solutes than the solution outside the cell. Water flows out of the cell; collapsing the cell (plasmolysis)
Many cells that live in aquatic environments have rigid cell walls that prevent cytolysis. The central vacuole swells, pushing the cytoplasm, etc to the membrane – equalizing the pressure inside the cell with that outside the cell.
Another way of dealing with the infusion of water is through contractile vacuoles.
Seawater sets up a hypertonic situation. Why is it bad to drink sea water when you are thirsty?
Most fish if transported from fresh to salt water (or vice versa) will die from cytolysis or plasmolysis but salmon are equipped to move back and forth between salt and fresh water.
3B-2 – Transportation Across the Membrane
Passive transport – movement of molecules across the membrane without the expenditure of chemical energy. Diffusion and osmosis are both passive transport.
Factors affecting passage of molecules through a membrane:
▪ Concentration of the molecule (diffusion pressure)
▪ Size and weight of the molecule
▪ Shape of the molecule
▪ Charge of the molecule
▪ Fat-solubility of the molecule (fat-soluble molecules appear to dissolve the phospholipids of a membrane and penetrate more quickly than molecules that are not fat-soluble.
▪ Composition of the membrane
Small molecules (monosaccharides, amino acids, fatty acids and glycerols) penetrate slowly through plasma membranes.
Larger molecules such as disaccharides and proteins penetrate even more slowly.
Lipids barely penetrate membranes at all.
Passive Mediated Transport – membrane transport proteins aid in the transfer of certain molecules across the membrane.
Protein channel – tiny pores in the membrane through which very specific substances pass. (gated channels)
Carrier protein – has a specific receptor site that binds to the molecule it is designed to carry. As it binds – the carrier protein changes shape and the molecule passes through the membrane.
Active Transport Across Membranes – transport against the concentration gradient, so requires energy. (pumps) Uses a carrier protein.
Endocytosis and Exocytosis
Endocytosis – used to transport substances in bulk across the membrane. The plasma membrane folds inward until it completely surrounds the substance – the membrane is then pinched off into the inside of the cell.
Phagocytosis
the movement of any bulk material across the membrane. The resulting vacuole is called the phagocytic vacuole. (cellular eating)
Pinocytosis
the movement of bulk fluids or solutes across the membrane. Results in a pinocytic vesicle (cellular drinking)
Exocytosis – vesicles or vacuoles in the cytoplasm fuse with the plasma membrane and release their contents into the solution outside the cell. (hormones, proteins, waste, etc.)
C
cell 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17
E
energy 8, 11, 15, 16
M
membrane 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17
molecule 4, 5, 7, 14, 15, 16
O
organelles 4, 5, 6, 8, 12
P
protein 4, 5, 9, 16, 17
Bibliography
Goldberg, Deborah T. AP Biology. Cedarhurst: Barron's, 2007.
Porch, Thomas E., Brad R. Batdorf and Jeff S. Foster. Biology Teacher's Edition. Third. Vol. 1. Greenville: BJU Press, 2004. 2 vols.
Siegfried, Donna Rae. Biology for Dummies. New York: Wiley Publishing, Inc, 2001.
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[1]Pg. 70. (Porch, Batdorf and Foster).
[2] (Porch, Batdorf and Foster)
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Fluid Mosaic Model
Fluid because the bilayer can ride on top of the cytoplasmic interior just like oil rides on top of water – moving with the wave.
Mosaic because it is built of many different proteins and each one is built differently. Each protein is put in place depending upon the job that needs done:
Transport
Enzyme – speed chemical reactions
Linking – link to the cytoskeleton
Receptor (linked with a carbohydrate) – links to environment
Recognition (linked with a carbohydrate) – sends out ‘identity’ signals to other cells – friend or foe
Junctional – joins the membranes of cells
Quick review of box on bottom of page 78
Sterols, or steroid alcohols are a subgroup of steroids Sterols of plants are called phytosterols and sterols of animals are called zoosterols. Important zoosterols are cholesterol and some steroid hormones Sterols and related compounds play essential roles in the physiology of eukaryotic organisms. For example, cholesterol forms part of the cellular membrane in animals, where it affects the cell membrane's fluidity and serves as secondary messenger in developmental signaling. In humans and other animals, corticosteroids, such as cortisol act as signaling compounds in cellular communication and general metabolism. Phytosterols may block cholesterol absorption sites in the human intestine thus helping to reduce cholesterol in humans.
TEM – Transmission Electron Microscope
SEM – Scanning
Electron Microscope
Facet – Cytoskeleton – Cellular support and Movement
Cytoskeleton – gives shape, provides a movement structure within the cell, help move the cell
Three major cytoplasm components: (see pic in center of page 82)
1) Microtubules – important in organization of the cell, in cell division and in cell movement. Stiff tubular structures that can be assembled, disassembled and reassembled as needed by the cell. Give shape to the cell – provide tracks to transport organelles inside the cell (see cart picture on page 82) and forms spindle structures important in cell division.
a. Also an important part of flagella and cilia (see pic on right of page 82)
b. Ciliary dynein – a special motor protein that causes a cilium to bend
2) Intermediate Filaments – ropelike structures that provide strength to the cell (not present in plant cells)
3) Microfilaments – thinnest of the three; composed of two molecules of the protein actin – wrapped around each other. Can be assembled and disassembled as needed for the job to be done. Many different types of protein can adhere to it, depending upon the function to be performed
a. Used in cell division
b. Used to contract muscle cells and move body parts
c. Used in movement for “crawling” cells like amoeba – VIDEO
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