the structure & function of cells the cell is the basic functional unit of all living things....

The Structure & Function of Cells

The Cell is the basic functional unit of ALL living things.

There are 2 basic categories of cells:

1. Eukaryotic Cells= contain plasma membrane (cell membrane), organelles, nucleus, cytoplasmMost cells are of this type (body cells, plant cells, Protists, etc.)

Evolutionarily this is a recent advancement

2. Prokaryotic Cells = contain plasma membrane (cell membrane) and cytoplasm but NO ORGANELLES, NO NUCLEUS

• Bacteria cells are of this type• Ribosomes are the only other real internal

structure• The oldest of cell types are prokaryotic

Question #1

Animal Cell

Plant Cell

Polysome

On Endoplasmic Reticulum = Rough

IMPORTANT PARTS OF THE CELL

Cell Cell OROR Plasma Membrane Plasma Membrane: separates the internal metabolic events from the external environment surrounding the cell

FunctionFunction= control the movement of materials into and out of the cell

StructureStructure= a double phospholipid membrane (Lipid Bilayer), Polar hydrophilic “water loving” heads pointing toward outside and inside of the cell; Nonpolar hydrophobic “water fearing” tails point toward the inside of the membrane.

Question #2

“Fluid Mosaic Model” of the Cell Membrane

Fluid Mosaic Model= describes the structure of the cell membrane. PROTEINS are scattered throughout the flexible lipid bilayer. These proteins can be of 3 different types:

1. Peripheral Proteins: attached loosely to the inner or outer surface of the membrane

2. Integral Proteins: extend into the membrane

3. Transmembrane Proteins: an integral protein that spans across the membrane and appears at both surfaces

Question # 8

Phospholipid Bilayer with Embedded Proteins

Proteins in the plasma membrane provide a wide range of functions

including: Question #9●Channel Proteins: provide passageways through the membrane for certain water soluble substances (i.e. polar & charged molecules)

● Transport Protein: use energy to transport materials across the membrane against a concentration gradient

● Recognition Proteins(Glycoproteins): used to distinguish the identity of neighboring cells

● Adhesion Proteins: attach cells to neighboring cells, provide stability

● Receptor Proteins: provide a binding site for hormones or other chemical triggers

● Electron Transfer Proteins: transfer electrons from one molecule to another during chemical reactions

Features of the Plasma Membrane

It is Semi-Permeable = only small, uncharged, polar, hydrophobic molecules pass freely across the membrane

Permeable = H2O , CO

2 , O

2 , lipid soluble

hydrocarbons

NON-Permeable = large molecules, glucose, all ions

Lets water flow freely, restricts the flow of glucose molecules

Water passes freely raising the water level on side 2

Types of Membrane Proteins


Cholesterol= provide some rigidity to the fluid nature of the membrane in animal cells. Act as a “Cellular Antifreeze” to keep a cell from freezing in cold temps. or melting in warm temps.

Question #11


4. Glycocalyx= carbohydrate coat covering the outer surface of the cell membrane. Used for cell to cell recognition.

ORGANELLES OF THE CELL

Organelle = a structure in the cytoplasm (semi-fluid medium between nucleus and cell membrane) of the cell that serves a specific function related to the metabolism of the cell

Nucleus: contains DNA, the hereditary information of the cell.●Surrounded by a nuclear envelope●Normal DNA = Chromatin: spread out in a threadlike matrix●Chromosomes: visible when the cell begins to divide

The Pores in the Nuclear Envelope:

● Nuclear Envelope = Nuclear Membrane● Provide for the movement of:

Proteins into the nucleus mRNA out of the nucleus Ribosome subunits out of the nucleus

● Endomembrane System: Connects the nucleus to the cell membrane Nuclear Envelope (Pores) --> Rough ER --> Golgi

--> Smooth ER --> Lysosomes --> Cell Membrane

NEW SLIDE!!!!!

Question # 3

Question # 6


Nucleolus: produces rRNA & multiple copies of genes ; concentrations of DNA in the process of manufacturing the components of Ribosomes

Synthesis & Storage of Ribosomes

Question # 4


Ribosomes: assemble amino acids into proteins in the cytoplasm

Cells producing secretory products have many ribosomes

Question # 14

Has large and small subunits

ORGANELLES OF THE CELL Endoplasmic Reticulum (ER): stacks of flattened sacs involved in the production of various membranes & products (#13), looks like a maze when viewed in cross-section, often connected to the nucleus●Rough ER: has ribosomes on it, specializes in protein synthesis; manufacture membranes and other secretory products (#14)●Smooth ER: NO ribosomes, specializes in the production of lipids, detoxification, storage & release of ions etc. (depends on the cell type) (#14)

ORGANELLES OF THE CELL Golgi Apparatus(Complex or Body): a group of flattened sacs arranged like a stack of bowlsᙵhas a Cis and Trans face (opposite fat vs thin ends)●Function to modify and package proteins and lipids, products of Rough ER●Puts the products into Vesicles●Contents of vesicles get released outside the cell

Question # 14

ORGANELLES OF THE CELL Lysosomes: Acidic pH; vesicles that contain hydrolytic digestive enzymes to digest macromolecules . NOT FOUND IN PLANT CELLS


Peroxisomes: breakdown various substances●O

2 + H

2 H

2O

2●Common in liver and kidney cells


Mitochondria: carry out cellular respiration ●Energy in the form of ATP is obtained from carbohydrates Double membrane sac with Cristae

(folding inner membraene)


Chloroplasts: carry out photosynthesis in plants; this is where plants incorporate energy from the sun to make carbohydrates

Thylakoids (Grana): System of flattened sacs inside chloroplast

ORGANELLES OF THE CELL Cytoskeleton: internal structure of the cytoplasmMAINTAIN CELL SHAPE & Anchors Organelles● Microtubules = provide support and motility, made of protein tubulin (spindle fibers during cell division; cilia & flagella) (#10)● Intermediate Filaments = support, maintain cell shape● Microfilaments = made of protein actin, involved in cell motility

Internal Anatomy of a cell

ORGANELLES OF THE CELL Flagella and Cilia: protrude from the cell membrane, used for movement● Flagella = long and few● Cilia = short and many● Both arranged in “9+2” arrangement


Centrioles and Basal Bodies: Microtubule organizing centers


Cell Wall: found only in plants; outside of plasma membrane, provides support, made of Cellulose


Vacuoles and Vesicles: fluid filled, single membrane bound bodies

● Transport Vesicles= move materials between organelles● Food Vacuoles= temporary food storage● Storage Vacuoles= store starch, pigments, and toxins● Central Vacuole= fill up most of the interior in plant cells,

maintain rigidity of the cell (Plant)● Contractile Vacuoles= collect and pump excess water out

of a cell (Plant or Animal)


Cell Junctions: serve to anchor cells to one another● Desmosomes= act as “spot welds” to hold adjacent animal cells together in high stress tissues (skin, heart muscle)● Tight Junctions= “stitched seams” between animal cells, prevent movement of material between the cells (cells lining the digestive tract).● Gap Junctions= narrow tunnels between animal cells, allow passage of small ions and molecules, communication through electrical impulses● Plasmodesmata= narrow channels between plant cell

Types of Cell Junctions

Desmosome

Tight Junction

Gap J unction

Plant vs. Animal Cells

Plants = cell walls, large vacuole, chloroplastsAnimal = lysosomes, centrioles

Animal Cell Plant Cell

Prokaryotes vs. EukaryotesProkaryotes: No nucleus, No Organelles,

Single stranded “naked” DNA, Only Bacteria

Eukaryotes: Have a nucleus, Lots of Organelles, DNA in chromosomes, All other cells

The Movement of Substances

The cell membrane and the membrane of other organelles are Semi-permeable = only certain substances can cross the membrane● Selective Permeability= allowing only specific substances to pass● Water = solvent; dissolved particles = solute● Movement of substances may be from higher to lower concentrations (down or with the concentration gradient) or the reverse (up or against the gradient)● The movement of substances may be active or passive

Selective Permeability

Solute concentrations may be compared:

Hypertonic= higher concentration of solutes

Hypotonic= lower concentration of solutes

Isotonic= equal concentration of solutes

………relative to another region.

Other Types of Movement

Bulk Flow= collective movement of substances in the same direction in response to some force or pressure (blood moving through a vessel)

Passive vs. Active Transport

Passive Transport= Movement of molecules down a concentration gradient (high low)

Does not require the cell to expend any energy!

1. Diffusion: due to the random nature of molecules in motion (dye in a beaker of water)Rates of diffusion are determined by:● Concentration gradient● Shape and size of the molecules● Temperature (higher temp. = faster diffusion time)● Liquid vs. gas (slower in liquids)

Passive Transport

2. Osmosis: the diffusion of water molecules across a semi-permeable membrane● Osmotic Pressure = force water exerts against the inside of a cell● Turgor Pressure = pressure water exerts against the inside of a plant cell, used for structural support

Passive Transport

3. Dialysis: diffusion of solutes across a semi-permeable membrane

4. Plasmolysis: movement of water out of a cell, results in the collapse of the cell

5. Facilitated Diffusion: use channel proteins embedded in the membrane to transport solutes

Active Transport

Active Transport= requires the cell to expend energy to move substances against the concentration gradient (low high)

Usually utilizes transport proteins to move: small ions (Na+, K+, Cl-, H+), amino acids, simple sugars

Active Transport

Exocytosis: Large particles are released from the cell by vesicles forming and fusing with the cell membraneEndocytosis: Large particles enter the cell by vesicles forming and fusing with the cell membrane● Phagocytosis = cell eating (white blood cells attacking bacteria)● Pinocytosis = cell drinking ● Receptor Mediated Endocytosis = special receptors attract certain molecules (cholesterol transport in the blood, hormones)

the structure & function of cells the cell is the basic functional unit of all living things....

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