Cells

Cell Theory• Cells are the fundamental (smallest) units

of life.• All organisms are composed of cells.• All cells come from preexisting cells.

(Proved by Pasteur who disproved spontaneous generation in 1859.)

• Spontaneous Generation

• Formulated in 1838 by Schwann and Schleiden.

Surface area to volume ratio• Cells have a large surface area to volume

ratio.• The cell’s volume determines the rate of

chemical activities over time.• The cell’s surface area determines the

amount of substances a cell can take in an expel.

• Because cells need to transport substances frequently, small size is essential.

• How do you increase cell SA without increasing size?

SA• Increase the folding to increase SA.• The respiratory tract has the SA of a tennis

court due to folding…• The intestines has the SA of a football

field….• The excretory system has large SA for N

removal:• Ammonia in fish• Urea in humans and animals• Uric acid in birds and reptiles

Surface Area of the lungs (alveoli)

Digestive Tract Small Intestine averages 23 feet.

Villi and Microvilli on the interior of the small intestine Key

Nutrientabsorption

Microvilli(brush border)

Epithelial cellsLacteal

Lymphvessel

Villi

Largecircularfolds

Epithelialcells

Bloodcapillaries

Vein carrying bloodto hepatic portalvessel

Muscle layers

Villi

Intestinal wall

Excretory Structures

Nitrogenous Waste filtering

Figure 4.2 Why Cells Are Small (Part 1)

Figure 4.2 Why Cells Are Small (Part 2)

Figure 4.1 The Scale of Life (Part 2)

Figure 4.1 The Scale of Life (Part 1)

Since cells are small we need ocular assistance…

Most cells are < 200 μm in size.Minimum resolution of human eye is 200

μm. Resolution is the distance apart that two

objects must be in order for the eye to view them as distinct not a blur.

Microscopes improve resolution.

Figure 4.3 Looking at Cells (Part 1)

Figure 4.3 Looking at Cells (Part 2)

Figure 4.3 Looking at Cells (Part 3)

Types of Microscopes• Light microscopes- glass lens and visible

light to form a magnified image of an object. Magnifies about 1000x.

• Electron microscopes-uses electromagnets to focus an electron beam. The beam is then directed to a fluorescent screen/photographic film to create a visible image. Magnifies about 1,000,000x. Can see subcellular.

Cell Similarities• 1. All cells have a cell membrane.

(Phospholipid bilayer.)• 2. All cells contain DNA.

Cell Membrane Structure• 1. Phospholipids- are amphipathic. They

line up to form a barrier from the water that is inside/outside the cell. • Remember Phosphate heads are (-)• Phosphates prevent hydration shells around

each phospholipid.• 2. Proteins- are amphipathic.

• A. Integral run through c.m. Function: structure and transport

• B. Peripheral- on one side of c.m. Function: attachment of cytoskeleton and ECM

Cell Membrane

AmphipathicPhospholipids

Hydrophilichead

Hydrophobictail

WATER

WATER

AmphipathicProteins

Hydrophilic regionof protein

Hydrophobic region of protein

Phospholipidbilayer

Cell Membrane

C.M. Proteins Cont.The proteins of the cell membrane can have

several functions. • Molecule transport (Helps move food, water,

or something across the membrane.)• Act as enzymes (To control metabolic

processes.)• Cell to cell communication and recognition

(So that cells can work together in tissues.)• Signal Receptors (To catch hormones or other

molecules circulating in the blood.)

Membrane Protein Functions

EnzymesSignal

ReceptorATP

Transport Enzymatic activity Signal transduction

Membrane Protein Functions

Glyco-protein

Cell-cell recognition Intercellular joining Attachment to thecytoskeleton and extra-cellular matrix (ECM)

C.M. Cont.• 3. Cholesterol- keeps c.m. flexibility. Also

prevents plant cell membranes from freezing

Data Set (U1,D12)

Synthesis Question (U1,D12)• Question: All living cells have to have a cell membrane to remain living and intact. All cells

are mostly water inside the cell. Cells live mainly in a watery environment. Water is a polar molecule. In four sentences or less, how does the presence of water on the inside and outside of a cell contribute to the structure of cell membranes? (5 Points)

•  1pt. Discussion of negative phosphorus atoms, of phospholipids being attracted to water and

forming a barrier in the bi-layer. 1pt. Discussion of the bi-layer needed to prevent water from forming hydration shells • around the phospholipids. 1pt. Discussion of the fatty acid tails being protected sandwiched in-between the

Phosphorus barriers. 1pt. Correct use of scientific terms. 1pt. Answer has no more than three sentences. (Following Directions.)

Prokaryotic Cells• “Kary” means kernel, in this case the

nucleus.• Prokaryotes compose the Domains:

Archaea and Bacteria.• Do not have membrane bound organelles.• Thought to have been the “first cells”

Prokaryotes• Can live in more diverse environments than

eukaryotes.• Can sustain life on more diverse energy

sources than eukaryotes.• Typically smaller than eukaryotes.• Tend to aggregate in chains or clusters.

• 1. Plasma membrane regulating incoming/outgoing substances.

• 2. Nucleiod- contains DNA, not a defined region

• 3. Cytoplasm: (2 parts)• Cytosol-consists mostly of water with ions and

water soluble molecules such as proteins• Insoluble particles including ribosomes.

• Ribosomes are RNA and proteins.

Prokaryote Composition

Specialized Prokaryotic Features• Some prokaryotes developed specialized

features. Why?• 1. Cell Walls- located exterior to the cell

membrane. Dissimilar to plant cell walls• Cell walls typically contain peptidoglycan an

amino sugar • Sometimes have an outer membrane.• Sometimes a capsule:= Slime layer made of

polysaccharides; prevents drying out and aids in attachment to other cells (sickness)

Figure 4.4 A Prokaryotic Cell

Cell Walls, Internal Membranes, & Flagella and Pili

• Plasma membrane will fold in to form specialized compartments for photosynthesis, cell division, or catabolic activities.

• Structures of Movement• Flagella- made of protein flagellin, rotates like

an axel for movement.• Pili- aka cilia, hairlike projections for

movement

Figure 4.5 Prokaryotic Flagella (A)

Figure 4.5 Prokaryotic Flagella (B)

• Cytoskeleton- helical structures just inside the plasma membrane.• Composed of proteins similar to actin. Actin

makes up cytoskeleton in eukaryotes.• Cytoskeleton commonly found in rod shaped

bacteria.

Let’s Practice• Cell Review

Eukaryotic Cells• Eukaryotic cells ~10x bigger than

prokaryotes.• Have membrane bound organelles.• Organelle can be membrane bound or not.• Organelles have a specific functions and

shapes.• The role/function of an organelle is defined

by the chemical reactions that take place

Cell fractionation and microscopy• Cell organelles first detected by light

microscopes.• Cell fractionation-break down plasma

membrane, organelles separate based on size/density.

• Biochemical analysis can then be done to detect for certain macromolecules

• Many organelles identical in plants and animals.

Figure 4.6 Cell Fractionation

Nucleus• Typically the largest organelle in animal

cells.• Site of DNA (chromatin vs. chromosome).

• Nucleolus- site of RNA and ribosome synthesis.

Nuclear Structure• Surrounded by a double membrane called

the nuclear envelope.• ~3500 nuclear pores exist in the envelope• The pores consist of over 100 different

proteins• These proteins will aggregate in pore

complexes of 8 proteins.• Small molecules can get into the pores,

larger molecules need a nuclear localization signal. (chain of amino acids)

Figure 4.8 The Nucleus is Enclosed by a Double Membrane (Part 2)

Figure 4.8 The Nucleus is Enclosed by a Double Membrane (Part 1)

Ribosomes- NOT ORGANELLES• Function: protein synthesis per nucleic acid

instructions• Location:

• Attached to Endoplasmic reticulum-out of cell proteins,

• free-floating in cytoplasm-in cell proteins • inside mitochondria and chloroplasts.

• Composed of two different subunits:• rRNA- ribosomal RNA• Protein molecules (>50 different ones)

Endomembrane System• Made up of Endoplasmic Reticulum and

Golgi Bodies/Apparatus• Vesicles serve as transporters of substances

between the endomembrane structure and within the cell.

Endoplasmic Reticulum• Location: extends from the outer

membrane of the nuclear envelope.• Two Types: RER,SER• Because of its many folds it has a surface

area greater than the cell membrane• The interior of the ER is called the lumen• Tubes are called cisternae

Rough Endoplasmic Reticulum• It is called rough because ribosomes are

temporarily attached .• Site of protein synthesis• Proteins undergo folding within the RER• Proteins can then be shipped to

incorporated endomembranes (GB), other organelles, or extracellular locations.

Smooth Endoplasmic Reticulum• No ribosomes attached• Function:

• Modification of some proteins from RER• Hydrolysis of glycogen• Synthesis of lipids, phospholipids, and steroids• Detoxifies blood• Stores calcium

What does this mean?• Cells that synthesize a lot of proteins have

a lot of ER. • e.g. Gland cells that secrete enzymes and WBC

• Cells that modify molecules that enter the body (food) have a lot of ER• e.g. liver cells have lots of SER

Figure 4.10 Endoplasmic Reticulum

Figure 4.11 The Golgi Apparatus (Part 1)

Golgi Bodies/Apparatus• Flattened membranous sacs called

cisternae, think stacks of pancakes• Functions:

• further modifies proteins by attaching sugars to them so they can leave through the c.m. (glycoproteins)

• Concentrates, packages, and sorts proteins to be shipped extracellular

• Makes cellulose/starch for plant cell walls

Medial Region

Lysosome• Originate from the Golgi bodies• Contain digestive enzymes to hydrolyze all

4 macromolecule types (enzymes=lysozymes)

• When molecules enter through phagocytosis: called the phagosome (vesicle/vacuole with macromolecule)

• Phagosome attaches to primary lysosome forming a secondary lysosome where digestion takes place

Figure 4.12 Lysosomes Isolate Digestive Enzymes from the Cytoplasm (Part 1)

Small particles diffuse through cytoplasm

Figure 4.12 Lysosomes Isolate Digestive Enzymes from the Cytoplasm (Part 2)

Phagocytosis & Pinocytosis

Lysosomes and Autophagy• Autophagy- organelles are ingested,

hydrolyzed, and released into the cytoplasm for reuse.

• Plant cells do not have lysosomes, but their central vacuole contains digestive enzymes.

.

Phagocytosis: lysosome digesting food

1 µm

Plasmamembrane

Food vacuole

Lysosome

Nucleus

Digestiveenzymes

Digestion

Lysosome

Lysosome containsactive hydrolyticenzymes

Food vacuolefuses withlysosome

Hydrolyticenzymes digestfood particles

Mitochondria and Chloroplasts• Prior to the mitochondria and chloroplasts,

breakdown of fuel molecules begins in the cytosol.

• Both organelles transform energy from one form to another

• Chloroplasts take light energy and convert it into chemical energy.

• Mitochondria take molecules such as glucose and convert it into a usable form of energy

Mitochondria and Cellular Respiration• Mitochondria make ATP (adenosine

triphosphate) through cellular respiration.• Cells that require the most energy have the

most mitochondria per volume. (Liver cells have ~1000/cell.)

• Mitochondria can reproduce by binary fission

• Contains its own DNA, ribosomes, and enzymes

• Thought to have been purple bacteria.

Figure 4.13 A Mitochondrion Converts Energy from Fuel Molecules into ATP

Outer Membrane- little resistance to flow of materials.

Inner Membrane- folded (cristae): greater surface area than O.M. Controls flow of substancesEmbedded with proteins to synthesize ATPMatrix- contains enzymes, DNA, and ribosomes

Chloroplast• Type of Plastid (plastid-pigment container)• Located in plants and algae• Have DNA, ribosomes, enzymes• Reproduce by binary fission• Thought to have been blue green algae

Chloroplasts

Lynn Margulis

Endosymbiotic Hypothesis

Peroxisomes• Membrane bound organelles that contain

toxic peroxides.• Peroxides are unavoidable by-products of

chemical reactions, that can be safely broken down within the peroxisome.

Vacuoles• Membrane bound organelle filled with an

aqueous solution and many solutes.• Function:

• Central-Storage• Food vacuoles- in simple eukaryotes, used in

lieu of digestive system. Intake of food cause a vacuole which fuses with a lysosome, and chemical energy is released in to the cell.

• Contractile vacuoles- typically in protists; helps with movement as a result of filling with water because of osmotic pressure differences.

Figure 4.18 Vacuoles in Plant Cells Are Usually Large

Contractile Vacuole

Removes excess water in aquatic single celled organisms

Cytoskeleton• Not a membrane-bound organelle.• Function:

• Supports and maintains cell shape• Provides for some cellular movement• Positions organelles with in the cells• Some fibers can act as tracks that motor

proteins can move organelles intracellularly• Interacts with extracellular structures to anchor

the cell in place.• Types: microfilaments, intermediate filaments,

and microtubules

Microfilaments-smallest cytoskeleton• Can exist alone, in bundles, or networks• Made up of actin (protein). These PULL.• Microfilaments responsible for:

• Cytoplasmic streaming- movement of cytoplasm

• Pinching/Mitotic Movement- formation of daughter cells

• Pseudopodia- “False feet” for movement

Intermediate filaments-medium cytoskeleton

• Fibrous proteins of the keratin family.• Function: stabilize cell structure.

Microtubules-largest cytoskeleton• Function: move organelles or cell.• Composed of the protein microtubulin. • Examples:

• Cilia and flagella• Centrosomes/Centrioles• Spindle Fibers

Cell Walls• Plant cell= cellulose• Fungus= chitin• Bacteria= peptidoglycan

Anticipatory Set 9-8-11

Organic Compound

Monomer Example Function

Amino acid

Fat, oil, wax

carbohydrate

Synthesis Questions U1,D16• Question: The one part of evolution tries to show

unity and diversity exists among all organisms on earth. All living organisms on Earth are either composed of Prokaryotic cells or Eukaryotic cells. In no more than four sentences, justify unity by stating one cellular structure all organisms have in common and for diversity state two structures that all eukaryotic cells possess that Prokaryotic cells do not possess. For each structure state the structures function within the cell. (5 Points)

• 1pt. (Half point for one of the following: DNA, ribosomes, cell membrane, cytoplasm)• (Half point for structures purpose: information, making proteins, Holding cell • together, space to work)• 1pt. Structure 1 with correct function from following list• RER – make proteins• SER – lipids and carb metabolism, detoxification• Mitochondria – Making energy• Chloroplast – Sugar production• Golgi Apparatus – protein modification• Vesicles – Storage• Lysosomes – Digestion• Cytoskeleton – support• Cell Wall or ECM - protection• 1pt. Structure 2 with correct function• 1pt. Correct use of scientific terms.• 1pt. Answer has no more than three sentences. (Following Directions.)

Figure 4.20 The Cytoskeleton (Part 1)

Extracellular Matrix• Area outside of animal cells• Composed of fibrous proteins like collagen

and proteoglycans/glycoproteins (proteins + sugar).

• The extracellular matrix is specific to the tissue type, and is made of proteins and fluids the cells secrete.

Function of Extracellular Matrix• Holds cells together in tissues• Contributes to physical properties of

cartilage, skin, and other tissues.• Helps filter materials passing between

tissues.• Helps orient cell movements during

embryonic development and tissue repair.• Role in chemical signaling.

Figure 5.1 The Fluid Mosaic Model

Figure 3.20 Phospholipids (A)

Repeat Fig 3.20A here

Cell Membrane• All biological membranes consist of lipids,

carbohydrates, and proteins.• The cell membrane is sometimes referred

to as the fluid mosaic model.• This is because it prevents a lot of hydrophillic

substances from rapidly entering, and embeds a lot of floating proteins.

Figure 5.2 A Phospholipid Bilayer Separates Two Aqueous Regions

Cell Membrane Content• Phospholipids can vary with respect to fatty

acid chain length, degree of unsaturation (presence of double bonds), and phosphate groups present.

• 25% of lipid content can be cholesterol.• Most cholesterol in membranes is not

detrimental to your health; maintains membrane integrity.

Cell Membrane Fluidity• Fluidity is affected by:

• Lipid composition• Temperature

• When temp. decreases, membrane fluidity decreases. Therefore cellular function decreases.

• Plants and animals that hibernate may change their lipid content (sat. to unsat. F.A. tails to achieve shorter tails) to survive.

• Fluidity=Function No Fluidity=No Function

Membrane Proteins• All membranes have proteins.• Two Types of Membrane Proteins:

• Integral- hydrophobic and hydrophillic regions, located within the membrane. Include transmembrane proteins.

• Peripheral- only have hydrophillic regions, interact with other hydrophillic regions of other proteins or heads of phospholipids.

Transmembrane Proteins• Transmembrane proteins

are a type of integral protein. Extend out on both sides of the membrane. • R groups from amino acids

determine hydrophobic/hydrophillic location.

• Integral proteins are only on one surface of the cell membrane. (Inside or outside)

Carbohydrates in Cell Membranes• Located on the outer surface of cell

membranes.• Serve as a recognition site for other cells

and molecules.• Sometimes carbohydrates fuse with lipids

and proteins:• Glycoproteins

= carbohydratecovalent bond protein• Glycolipid

= carbohydrate covalent bond lipid

Cell Recognition• Cell recognition- one cell specifically binds

to another cell of a certain type.• An example would be sperm and egg fusing.• Homotypic binding- same glycoprotein sticks

out of both cells, and the exposed similar carbohydrates bind cells together. eg. tissues

• Heterotypic binding- different glycoproteins stick out from cells, but they have an affinity for one another so they bind together. eg. fertilization

Cell Adhesion• Cell Adhesion- the connection between two

cells is strengthened.• Cell Junction- result of cell adhesion; 3 types.

1. Tight Junctions• Link epithelial cells

which line organs and inside of mouth.

• Function of T.J. prevent substances from moving between cells, and dictate the function of each region of the cell.

• Like a quilted pattern• (Controls membrane

proteins)

2. Desmosomes• Connect adjacent cell membranes like a

spot weld. Allow substances to move everywhere but the connection.

• Desmosome attached to intermediate filaments inside each cell

3. Gap Junctions• Function in communication between cells.

(Desmosomes and tight junction have mechanical functions.)

• Connexons are the channel proteins that span between cells and allow for molecules and ions to pass through

Figure 5.1 The Fluid Mosaic Model

Theory of Endosymbiosis1. Prokaryotes first absorbed food through environment.2. Then Photosynthesis evolved.3. Larger cells engulfed smaller cells, but smaller cells

were not digested.4. The smaller cell divided along with the bigger cell.5. The big cell provides protection, the little cell

provides energy.6. 1980s, Margulis suggests endosymbiosis of

chloroplast and mitochondria because they have their own circular DNA, ribosomes, and same size as prokaryotes.

Endosymbiosis• Theory is strengthened by:

• Prokaryotes and eukaryotes share:• Nucleic acids as genetic material• Same 20 amino acids in protein structure• D sugars and L amino acids

2011 Released Essay Prokaryote vs. Eukaryote

• Scoring Guide