UNIT II – CELL STRUCTURE & FUNCTION

Chpts 6-8 & 11

I. DISCOVERY OF CELLS

• History of Microscopes _____________________________________

First to try stacking several lenseslenses together to view tiny objects. Looked at pond waterpond water First scientist to describedescribe living cells as seen through a microscope.

_____________________________________ Used the microscope to examine thin slices of corkcork. He called the tiny boxes he saw cellscells. He chose the name "cells" because

the chambers he saw reminded him of rooms in a monasterymonastery which were called cells..

• Cell Theory

I. DISCOVERY OF CELLS, cont.• Types of Microscopes

Compound Light Microscope ___________________

Ratio of an objects image to its real size __________________

Measure of clarity of an image

Electron Microscope __________________ Electron Microscope (SEM)

Used to study the surface of the specimen

__________________ Electron Microscope (TEM) Used to study the internal structure of cells

TEM SEM

II. CELL TYPES

• _________________ Cells Typically smaller than

eukaryotes

BacteriaKingdom Archaebacteria Kingdom Eubacteria

No true nucleus – DNA found as a single chromosome in region called ________________

II. CELL TYPES

• Structure found in all prokaryotic cells _____________________ _____________________ _____________________ _____________________ _____________________

• Additional structures that may be present _____________________ _____________________ _____________________

II. CELL TYPES

• ___________________ Cells Larger, more complex Contain true nucleus and membrane-

bound organelles suspended in cytosol Composed of

Nucleus Ribosomes Endomembrane System

o ERo Golgi Apparatuso Lysosomeso Vacuoles

Mitochondria/Chloroplasts Peroxisomes Cytoskeleton

III. EUKARYOTIC CELL STRUCTURES

• _____________________Control center of eukaryotic cell Made up of

________________________Double membrane that protects nucleus; continuous

with ER Contains _____________ to allow RNA to leave nucleus

________________________Site of ribosome and rRNA production

________________________DNA wrapped in proteinWill condense during cell division to form chromosomes

III. EUKARYOTIC CELL STRUCTURES, cont• Endomembrane System – membranes are related either through

physical continuity or by the transfer of membrane segments as vesicles Endoplasmic Reticulum (“within the cytoplasm”; “little net”)

Interconnected network continuous with nuclear envelope Rough ER

Site of __________________________ Smooth ER

Synthesis of _______________ Metabolism of _________________ ____________________ of drugs & poisons

_________________________________ “Cell postmaster” Receives transport vesicles from ER; modifies, stores, and ships products Receiving side is known as the ________ face; shipping side is known as

the __________ face

III. EUKARYOTIC CELL STRUCTURES, cont

• Endomembrane System, cont ______________________________

Sacs containing hydrolytic enzymes Used for recycling cellular materials, destroying

pathogens ______________________________

Storage sac Plants typically have large, central vacuole surrounded

by membrane called ___________________. Absorbs water and helps plant cell to grow larger

Some protists have contractile vacuole to pump out excess water

Endomembrane System The endomembrane system plays a key role in the synthesis (and hydrolysis)

of macromolecules in the cell.

III. EUKARYOTIC CELL STRUCTURES, cont• ____________________________

Suspended in cytosol or found on rough ER Site of protein production in a cell

• _____________________________ Site of ________________________________ (making of ATP) Contain their own DNA, ribosomes Found in virtually all eukaryotes cells Enclosed by 2 membranes; inner membrane has folds called _____________

to increase surface area

III. EUKARYOTIC CELL STRUCTURES, cont• _____________________________

Type of plastid that carries out _____________________ by converting solar energy to chemical energy (glucose)

Contain membranous system of flattened sacs called _______________ – stack is called a _____________

Fluid surrounding thylakoids is called ___________ Contains its own DNA, ribosomes

III. EUKARYOTIC CELL STRUCTURES, cont• ____________________________________

Membrane-bound compartments that use O2 to carry out metabolism

H2O2 is produced; broken down by enzymes to produce ______ & ______

• ____________________________________ Provides structural support to cell More extensive in animal cells Composed of three types of proteins

• ___________________________ – Thinnest filaments …….AKA………. ____________ filaments. – Bundles of them form microvilli - extensions of the cell membrane found in some cells

to increase surface area. – Interact with myosin in muscle cells to create movement

• _________________________________– In between in thickness; more permanent than microtubules/microfilaments.

• _________________________________ – Hollow rods that support cell, serve as tracks for movement within cell. – Help separate chromosomes during cell division - occurs in a region called

centrosome, which is the location of centrioles in animal cells. – Cilia, flagella are constructed from bundles of microtubules covered by extensions of

the cell membrane.

IV. CELL BOUNDARIES• Cell Wall

Found in ___________, _______, ________________, and some _________________

Functions Rigid structure; protects cell Maintains shape of cells Prevents excess water uptake

Plant cell wall _________ - primary component Pectin - Sticky polysaccharide

found between cell walls of adjacent cells; found in middle lamella

Plasmodesmata - Perforations between adjacent cell walls that allow for movement of materials from one cell to another

IV. CELL BOUNDARIES, cont• Extracellular Matrix

Found in animal cells Holds cells together, protects & supports cells Allows for communication between cells Composed primarily of ______________________ – proteins with

carbohydrate chains that are covalently-bonded Must abundant glycoprotein in most animals is _____________

• Intracellular Junctions Tight Junctions – Fuses membranes together tightly; prevents leakage

of fluid Desmosomes (Anchoring Junctions) – Fasten cells together in sheets Gap Junctions – Allow for movement of cytoplasm from one cell to

another; important in communication between cells

IV. CELL BOUNDARIES, cont• ____________________________

Selectively-permeable barrier found in all cells Composed primarily of _______________________ bilayer Fluid Mosaic Model

“Fluid” – Not a rigid structure. Organization due to high concentration of water inside & outside cell

IV. CELL BOUNDARIES, cont Proteins - “Mosaic” – Assortment of different proteins embedded in bilayer;

determine most of membrane’s specific functions. Act as channels, pumps, enzymes in metabolism, binding sites, etc

o _____________ Proteins – Embedded in phospholipid layero _____________ Proteins – Bound to surface of membrane

Carbohydrates – “ID tags” that identify cell. Enable cells to recognize each other and foreign cells. May be bonded to lipids (glycolipids) or proteins (glycoproteins)

____________________ – Found in animal cells for stability

V. CELL TRANSPORT

V. CELL TRANSPORT, cont• ________________ Transport – Movement of materials

from _______ to ______ concentration. No energy output required. ___________________ - Random movement of a substance across

membrane down concentration gradient until equilibrium is reached.

________________________________________ – Passive transport of molecules across cell membrane with the help of transport proteins.

Water is polar – requires protein channels called aquaporins to move in and out of cell.

Glucose also requires protein channels due to size.

V. CELL TRANSPORT, cont• Passive Transport, cont

______________ – Diffusion of water across a membrane. ______________ refers to tendency of cell to gain or lose water.

If the solution is Isotonic to the cell – Solute concentration is same on both sides of membrane. No net

movement of water. Hypertonic to the cell – Concentration of solute is greater outside cell → water moves in

until equilibrium is reached. Cell may shrivel. Hypotonic to the cell – Concentration of solute is lower outside cell → water moves into

cell until equilibrium is reached. Cell may swell to bursting point.

Water moves towards the high solute concentration!!!!!

V. CELL TRANSPORT, cont

• Passive Transport/Osmosis, cont Osmoregulation

Cells must have mechanism to prevent excess loss, uptake of waterCell wall, contractile vacuole_______________________ – Seen in plants; excessive water loss

causes cell membrane to pull away from cell wall

V. CELL TRANSPORT, cont

V. CELL TRANSPORT, cont• ____________ Transport – Movement of materials against

concentration gradient. Requires energy output by cell Carrier Proteins – Na+ / K+ Pump

V. CELL TRANSPORT, cont• Active Transport, cont

_________________ – Secretion of biomolecules by fusion of vesicles with cell membrane. Biomolecules “spit out”.

_________________ – “Sucking In”. Cell membrane surrounds, engulfs particle or biomolecule, pinches in to form vesicle. ______________________ –

“Sucking in” food particles ______________________ –

“Sucking in” fluid droplets Receptor-mediated

Endocytosis – Very specific

VII. CELL SIGNALING• Coordinates cell activities, development• Initiates series of responses known as signal

transduction pathway. Typically involves 3 steps: ________________ – Target cell’s detection of signal

molecule due to binding of signal molecule to receptor protein in cell membrane

________________– Binding of signaling molecule changes receptor protein; triggers a sequence of events within cell

________________– Results in specific cellular response; for example, activation of genes, enzyme catalysis, etc.

• Cyclic AMP – Intracellular compound often involved in signal transduction pathways.

VII. CELL SIGNALING, cont

VIII. THE WORKING CELL• Metabolism

_____________________ Pathway – Breaks down molecules; releases energy

_____________________ Pathway – Pathway that synthesizes larger molecules from smaller ones; requires energy

• Energy Kinetic Energy – Associated with relative motion of objects Potential Energy – Energy that matter possesses; stored energy

Chemical Energy – Potential energy of molecules

• Thermodynamics ________ Law of Thermodynamics states that total amount of

energy in universe is constant – can be transferred or transformed, but it cannot be created or destroyed

________ Law of Thermodynamics states that energy is lost to the environment as heat; that is, some energy becomes unusable

VIII. THE WORKING CELL, cont• Chemical Reactions are classified according to whether they

require or produce energy _____________________ – Requires net input of energy. Energy is then

stored in products as potential energy. _____________________ - Release energy. _____________________– Often used in cellular metabolism. Energy

released in exergonic rxn is used to drive endergonic rxn.

VIII. THE WORKING CELL, cont• ATP – Adenosine triphosphate. Nucleotide that stores &

provides usable energy to the cell Structure of ATP

Adenine – nitrogen baseRibose – pentose3 Phosphate groups

VIII. THE WORKING CELL, cont• ATP, cont

PhosphorylationATP contains potential energy, especially between 2nd and 3rd

phosphate groups. P – P bond is unstable and easily broken by hydrolysis. Exergonic.

Coupled with endergonic rxn – specifically, by transferring phosphate group from ATP to another molecule. Known as phosphorylation.