Zoology 100 Notes 2

ZOOLOGY 100 NOTES (2) THE CELLULAR BASIS OF LIFE: STRUCTURAL & FUNCTIONAL UNIT OF LIFE OBJECTIVES 1. State the two tenets of the Cell Theory 2. Describe the structure of a prokaryotic cell, and give a function for each part 3. Describe the structure of a eukaryotic cell, and give a function for each part 4. Name the structures that form the endomembrane system, and explain how they are related to one another 5. Explain the relationship between chloroplasts and mitochondria, and describe the structure and function of each 6. Name the components of the cytoskeleton, and describe the structure and functions of each component 7. Contrast the structures of prokaryotic cells, eukaryotic animal cells, and eukaryotic plant cells THE CELLULAR BASIS OF LIFE TOPICS I. CELL THEORY II. CELL TYPES A. Prokaryotic cells B. Eukaryotic cells III. METHODS OF CELL STUDY (discussed already in MICROSCOPY) IV. CELL STRUCTURE AND FUNCTION A. Biological cell membrane and walls B. Organelles C. Cytoplasm and Cytoskeleton V. TRANSPORT MECHANISM OF SUBSTANCES THROUGH THE CELL MEMBRANE AND WALLS A. Diffusion B. Osmosis C. Dialysis D. Endocytosis E. Exocytosis VI. PLANT MITOSIS CELL THEORY What level of complexity is necessary for life? • Aristotle (384 – 322BC)

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Xavier Bichat (1771-1802): An organ is composed of different tissues and several organs can be grouped together as an organ system (e.g. the digestive system) An idea of hierarchy of structure developed:

THE CELL THEORY • Matthias Schleiden (1838) & Theodor Schwann (1839) “The cell is the basic unit of living tissue” • The cell is an autonomous unit (“a citizen”) grouped together to form an organism (“the society”) • Rudolf Virchow (1858) noted that: “all cells come from pre-existing cells” • All living thing organisms are made up of cells, these cells are the structural and functional unit of life. • Cells are produced spontaneously by their own (De nove). Later they are produced by Cell Division. • Each cell contains certain “Hereditary material” which is responsible for the passage of characters from one generation to the next. THE ORGANISMAL THEORY The counter argument: • Reichert a morphologist: Argued that an organism has a structured plan • Strasberger a cytologist: Cells are connected in an organism sometimes by cytoplasmic bridges (plant cell plasmodesmata)

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Sherrington and Pavlov neurophysiologists: Cells communicate with one another and they are co-ordinated in their actions

SUMMARY

Cell theory or organismal theory? • That the cell is the basic unit of living organisms is accepted • That unicellular organisms carry out all the functions of life is accepted • BUT multicellular organisms are not simply a mass of similar building blocks More is different! • As a multicellular organism grows and develops it follows a structured plan • The cells specialise (differentiate) • The whole organism shows homeostatic control • A developing multicellular organism shows emergent properties • It is not just a the sum of the parts CELL TYPES: A. PROKARYOTIC CELLS B. EUKARYOTIC CELLS

Prokaryotic Cells “The cells in which true or complete nucleus is not present, instead, genetic material is found scattered in the cytoplasm” – pro = before, karyon = kernal (what nuclei looked like to those who first saw them through a microscope) – cells without organized nuclei bounded by a nuclear membrane – Eubacteria (true bacteria), and cyanobacteria (blue-green algae) – cell wall – no membrane bound organelles – nucleoid (main genetic content of the cell) – Plasmids (small circular pieces of DNA that are separate from the DNA of nucleoid Examples of rod-shaped bacteria. Top: Rod-Shaped Bacterium, hemorrhagic E. coli, strain 0157:H7 (division)

Spherical (cocoid) and spiral bacteria. Top: Coccoid-shaped Bacterium (causes skin infections), Enterococcus faecium (SEM x33,370). Bottom: Left, a cross-section of a cell illustrating the location of a flagella inside the cell; Center, Borrelia burgdorferi, the organism that causes Lyme disease; and Right, Treponema pallidum, the spirochete that causes the venereal disease syphilis.

Eukaryotic Cells “The cells having complete nucleus bounded with a nuclear membrane” – eu = true, karyon = kernel (nucleus) – cells with organized nuclei bounded by a nuclear membrane – Examples: Plant cells, Animal cells, fungi, and protists (single celled organisms) – cell wall in some – plasma membrane in all – Membrane bound nucleus – membrane bound organelles • "Endoplasmic Reticulum" (ER) • "Ribosomes" • "Golgi Apparatus and Dictyosomes" or Golgi look alike • "Lysosomes" • "Mitochondria" • Chloroplasts ("Plastids“) – Examples: red and white blood cells

Comparison of Prokaryotes and Eukaryotes Prokaryotes

Eukaryotes

Organisms

Monera: Eubacteria and Archebacteria

Protists, Fungi, Plants and Animals

Level of organization

single celled

single celled (protists mostly) or multicellular usually with tissues and organs

Typical cell size

small (1 -10 microns)

large (10 - 100 microns)

Cell wall

almost all have cell walls (murein)

fungi and plants (cellulose and chitin); none in animals

Organelles

usually none

many different ones with specialized functions

Metabolism

anaerobic and aerobic; diverse

mostly aerobic

Genetic material

single circular double stranded DNA

complex chromosomes usually in pairs; each with a single double stranded DNA molecule and associated proteins contained in a nucleus

Mode of division

binary fission mostly; budding mitosis and meiosis using a spindle; followed by cytokinesis

CELL STRUCTURE AND FUNCTION A. Biological cell membrane and walls B. Organelles C. Cytoplasm and Cytoskeleton

Cell membrane and Cell wall descriptions

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Cholesterol to hold the membrane together like glue. Adds strength to the membrane. Proteins (2 types): 1. Intrinsic Proteins • Extend into or through lipid bilayer • Often are channel proteins allowing large molecules in/out 2. Extrinsic Proteins • Exist only on surfaces of the bilayer • Often serve as receptor molecules • Glycoproteins serve as cellular markers (nametags) •

Similar functions of cell membrane and cell wall

CYTOPLASM and CYTOSKELETON

TYPES OF CYTOSKELETONS 1. INTERMEDIATE FILAMENTS * strong,stable,rope-like * form desmosomes (junctional complex of the cell membrane) and provide internal guy wires to resist pulling forces on the cell 2. MICROFILAMENTS * involved in motility and producing changes in the cell shape. 3. MICROTUBULES * tube-like structures which determine the overall shape of the cell and the distribution of the organelles * important in cell division

Cilia and flagella  Hairlike projections  for locomotion in some cells; also, movement of invading organisms out of the body Flagella are relatively large in size and occur in small numbers Cilia are short and occur in large numbers Summary of the major cell organelles: ORGANELLE

MAIN FUNCTIONS

DIMENSIONS

Nucleus

Cell division, protein synthesis

10 µm diameter

Mitochondrion

Respiration pathways

1.0 to 12.5 µm

Chloroplast

Photosynthetic pathways

5 to 10 µm diameter

Lysosome

Digestion, recycling & isolation

0.5 to 3.0 µm diameter

Golgi apparatus

Secretion, reprocessing, lysosome synthesis

Cisternae: 0.5µm thick, l-3µm diameter

Endoplasmic Reticulum (ER) Support, Golgi apparatus synthesis. 26 to 56 nm thick Ribosome

Protein synthesis

20 nm diameter

ORGANELLE

LOCATION

DESCRIPTION

FUNCTION

cell wall

plant, not animal

*outer layer *rigid, strong, stiff *made of cellulose

*support (grow tall) *protection *allows H2O, O2, CO2 to pass into and out of cell

cell membrane

both plant/animal

*plant - inside cell wall *animal - outer layer; cholesterol *selectively permeable

*support *protection *controls movement of materials in/out of cell *barrier between cell and its environment *maintains homeostasis

nucleus

both plant/animal

*large, oval

*controls cell activities

nuclear membrane

both plant/animal

*surrounds nucleus *selectively permeable

*Controls movement of materials in/out of nucleus

cytoplasm

both plant/animal

*clear, thick, jellylike material and organelles found inside cell membrane

*supports /protects cell organelles

endoplasmic reticulum (E.R.)

both plant/animal

*network of tubes or membranes

*carries materials through cell

ribosome

both plant/animal

*small bodies free or attached to E.R.

*produces proteins

mitochondrion

both plant/animal

*bean-shaped with inner *breaks down sugar membranes molecules into energy

vacuole

plant - few/large animal - small

*fluid-filled sacs

*store food, water, waste (plants need to store large amounts of food)

lysosome

plant - uncommon animal - common

*small, round, with a membrane

*breaks down larger food molecules into smaller molecules *digests old cell parts

chloroplast

plant, not animal

*green, oval usually containing chlorophyll (green pigment)

*uses energy from sun to make food for the plant (photosynthesis)

TRANSPORT MECHANISM OF SUBSTANCES THROUGH THE CELL MEMBRANE AND WALLS: A. Diffusion B. Osmosis C. Dialysis D. Endocytosis E. Exocytosis TRANSPORT MECHANISMS THROUGH THE CELL MEMBRANE AND CELL WALL 1. PASSIVE TRANSPORT (no energy needed): a. Diffusion: Movement of molecules from high to low concentrations. (eg oxygen, carbon dioxide). b. Osmosis: Movement of water from low to high solute (salt) concentrations. a. Facilitated transport: Movement across the membrane via a protein channel 2. ACTIVE TRANSPORT (need to expend energy): Pumping of ions or molecules across the membrane and from low to high concentrations using the energy from ATP (produced by respiration) and carrier proteins PASSIVE TRANSPORT - Does not require energy - Does not require oxygen - flow of materials is from greater to lesser concentration(follows concentration gradient) - flow rate is slower - examples: Diffusion, Osmosis (isotonic, hypotonic and hypertonic solutions), and Facilitated diffusion

ACTIVE TRANSPORT - requires for energy - requires oxygen - flow of materials is from lesser to greater concentration (does not follow concentration gradient) - flow rate is faster - examples: Endocytosis (phagocytosis, pinocytosis), and Exocytosis

SOLUTION, SOLVENT AND SOLUTE • A solution is a homogenous molecular mixture of two or more substances. • The solvent is the substance that has the greatest concentration and that dissolves the other substance/s in the solution. • solutes are substances that are found in lesser concentration in solutions and are the substances dissolved by solvents.

Example: When you put a spoonful of sugar in a cup of water, the result is a solution. The water is the solvent and the sugar is the solute. Situation: Suppose you have a cup of coffee with sugar in it. __________ is the solvent and _________ and __________ are the solutes. DIFFUSION • The principal means of passive transport • It is the random movement of molecules from a area of higher concentration to an area of lower concentration. • the direction is determined by the concentration of specific molecules in the two sides of the membrane and the energy that causes the diffusion It is important to bear in mind that: - the movement is random - the steeper the concentration gradient (ie. the bigger the difference between the higher concentration and lower concentration), the faster will be the movement.

TYPES OF DIFFUSION 1. SOLID OVER a. solid - MASTICATION b. liquid - DIGESTION c. gas - TRANSPIRATION 2. LIQUID OVER a. solid - PERSPIRATION b. liquid -DIGESTION c. gas - EVAPORATION 3. GAS OVER a. solid - SUBLIMATION b. liquid - OXYGENATION c. gas - RESPIRATION DIFFUSION OF SOLID OVER LIQUID

DIFFUSION THROUGH THE LIPID BILAYER - nonpolar, hydrophobic molecules - gases, fatty acids, steroids

DIFFUSION THROUGH MEMBRANE CHANNELS membrane channels – ion channels

-for sodium, potassium, chloride, Ca ions

FACILITATED DIFFUSION - a solute binds to a specific transporter on one side of the membrane and is released on the other side after the transporter undergoes a conformational change.

What • • • • • • • • • •

factors can influence the rate of diffusion? Temperature. The state of the solvent; i.e. whether the solvent is a solid, liquid or gas. The size of the molecules. The steepness of the diffusion gradient. Permeability Size of molecules Size of pores Solubility Electrical charges Membrane structure

Property of Diffusion • The greater the space between these molecules the greater the ability for the molecular particles to spread out from one another. • The more packed the molecules are in the substance the less space to maneuver, and therefore, the more difficult for diffusion to occur. • Requires diffusion pressure OSMOSIS • is the movement of water molecules from a region of their higher concentration to a region of their lower concentration, through a partially permeable membrane

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Water will move by osmosis into and out of cells due to differences in water potential between the cell and its surroundings.

Water potential is the chemical potential of water and is a measure of the energy available for reaction or movement (Bidwell 1974:59). .

Some Basic Principles of Osmosis • Water always moves from high water potential to low water potential. Water potential is a measure of the tendency of water to move from high free energy to lower free energy. • Distilled water in an open beaker has a water potential of 0(zero). - The addition of solute decreases water potential. - The addition of pressure increases water potential. • In cells, water moves by osmosis to areas where water potential is lower. – A hypertonic solution has lower water potential. • A hypotonic solution has higher water potential

TONICITY Hypertonic Solutions: contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel. Hypotonic Solutions: contain a low concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode Isotonic Solutions: contain the same concentration of solute as an another solution (e.g. the cell's cytoplasm). When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic.

Summary of the direction of OSMOSIS CONDITION

CELL SOLU’ N

ENV’T SOLU’N

WATER MOV’T

CELL RXN.

1. solute concentration in the surrounding solution is higher than in the cell, solvent is lower

Hypotonic

Hypertonic Example: 10% salt water solu’n

Away from the cell

Shrink or crenation

2. solute concentration in the surrounding solution is lower then in the cell, solvent is higher

Hypertonic

Hypotonic Towards the cell Swell and burst or Example: lysis distilled water

3. Solute concentration is equal between the surrounding solution and that of the cell

Isotonic

Isotonic In and out of the No change Example: saline cell solu’n

ACTIVE TRANSPORT Endocytosis begins when a particle contacts the plasma membrane of a cell. An invagination of the membrane occurs until the particle is completely wrapped in membrane. The wrapped particle is now inside a vesicle in the interior of the cell. There are two types of endocytosis: phagocytosis and pinocytosis.

Exocytosis is the reverse of endocytosis. In this case material exits from the cell. As with endocytosis, the plasma membrane is actively involved. Material in a sac or vesicle moves to the membrane and when it makes contact the membrane opens and the material inside the vesicle pours out. Note that the plasma membrane and the vesicle membrane fuse to form a new border for the cell.

ACTIVE TRANSPORT a. Primary Active Transport - energy derived from hydrolysis of ATP changes the shape of a transporter protein

b. Secondary Active Transport - energy stored in a Na ion or H ion concentration gradient is used to drive other substances across the membrane against their own conc. gradients. 1. Antiporters – carry 2 substances in opposite directions. 2. Symporters – carry 2 substances in the same direction. VESICULAR TRANSPORT - formation of a vesicle or sac 1. Endocytosis - materials move into the cell in a vesicle formed from the plasma membrane a. Receptor-Mediated - ligands b. Phagocytosis - solid particles c. Pinocytosis - tiny droplets of ECF

2. Exocytosis - movement of materials out of a cell in vesicles that fuse with the plasma membrane. a. Neurotransmitters - neurons b. Hormones and Digestive Enzymes - secretory cells The difference between phagocytosis and pinocytosis has to do with the size of the material ingested. 1. Phagocytosis (cell eating) is shown above and occurs when solid material is involved. A white blood cell phagocytosis bacteria when it ingests them and breaks them down inside the cell. 2. Pinocytosis (cell drinking) occurs when smaller particles, such as large molecules, that are in solution are ingested by a cell. The process is the same as that shown above, but the type of material taken into the cell differs CELLULAR METABOLISM • a major biochemical pathway along which the cells release the chemical bond energy from the food and convert it to usable form (ATP) • the many synthesis or breakdown of material taking place within the cell. METABOLISM AND ENERGY: 1. ENDERGONIC REACTION – the synthesis of compounds which require energy outside the reacting substances Ex. Photosysntesis 2. EXERGONIC REACTION – the life processes accompanied by loss or release of energy

Ex. Maintenace and repair, physiological oxidations

secretion of substances,

CELLULAR RESPIRATION • the series of complex oxidation reactions whereby living • cells obtain energy through breakdown of organic substances and other intermediate materials. • release of energy by the oxidation of fuel molecules by taking oxygen and release carbon dioxide TYPES OF CELLULAR RESPIRATION: 1.ANAEROBIC RESPIRATION /GLYCOLYSIS - the cytoplasmic cellular activity which consists of the enzymatic breakdown of glucose molecules without the use of molecular oxygen • glucose is stable molecule and will not decompose spontaneously to release energy: 1 glucose molecule 2 ATP molecules • involves phosphorylation reaction – phosphates are released from the 2 ATP and become ADP and the other phosphate become attached to glucose and form PHOSPHORYLATED SUGAR (P-C6-p) under the control of the enzyme phosphorylase. • Products: 2 ATP, 2 pyruvic acids (3-carbon sugar),lactic acids 2. AEROBIC RESPIRATION / KREB’S CYCLE/CITRIC ACID CYCLE • a series of oxidation-reduction mitochondrial reactions that complete the breakdown of pyruvic acid produced by glycolysis • pypyruvic acid must enter the mitochondrion so that it can be used as a source of energy • 3-carbon pyruvic acid molecules is reacted upon by acetyl-co-enzyme a, and carbon dioxide is the waste product and is eventually released into the atmosphere • 5 pairs of hydrogen bonds are removed and become attached to the H carriers • involves 3 uses of water and ETS • products: 34 ATP(17 per pyruvic acid), Carbon Dioxide, water COMPARISON OF ANAEROBIC AND AEROBIC RESPIRATION BASIS

GLYCOLYSIS

KREB’S CYCLE

1. Site 2. Oxygen requirement 3. Raw materials/Energy Source 4. Processes involved

Cytoplasm Do not require oxygen 1 Glucose molecule (CHO,CHON, Fats) Breakdown of glucose to pyruvic acid, phosphorylation, lactic acid formation

Mitochondrion Require oxygen 2 Pyruvic acid from glycolysis Breakdown of pyruvic acids

5. Enzymes 6. Products

Phosphorylase, NAD(Nicotinamide Adenine Dinucleotide, 2 ATP, 2 pyruvic acids (3carbon sugar),lactic acids CHO (FATS,CHON)

Coenzyme A (CoA), FAD (Flavin Adenine Dinucleotide) 34 ATP(17 per pyruvic acid), Carbon Dioxide, water PYRUVIC ACID

GLYCOGEN GLUCOSE PYRUVIC ACID , LACTIC ACIDS

OXALOACETIC ACID(CoA) ATP,

ATP, CO2 , H