The Life of a CellThe Life of a Cell

Chemistry

• Element - A substance that can not be broken down into simpler substance.

• Trace elements are found in living things in very small amounts.– Ex. Iron, Zinc, Flourine, Iodine

• Atom - the smallest particle of an element that has the characteristics of that element.

• Proton – (+) in nucleus

Neutron – (no charge) in nucleus

Electron – Forms cloud around nucleus

Electron energy levels

• The electron travels around the nucleus in certain regions called energy levels.

• 1st level – holds two electrons

2nd level – holds eight electrons

3rd level – holds eighteen electrons

Definitions• Element name – How do the get them?

• Chemical symbol - The one or two letter symbol.

• Atomic number - The whole number in every square.

• Mass number: The number with a decimal fraction in most squares

• Number of protons in atom: Always equal to the atomic number.

• Number of electrons in atom: Equal to the atomic number in a normal atom.

• Number of neutrons in atom: Subtract the atomic number from the mass number to find the number of neutrons.

Isotopes• Atoms of the same element that have

different numbers of neutrons are called isotopes– Ex. Carbon-12, Carbon-13, Carbon-14

• Radiation can kill cells, and are used by scientists to kill rapidly growing cancer

Compounds and Bonding• A compound is a substance that is

composed of atoms of two or more different elements that are chemically combined.

• Two types of bonds are:– Ionic Bonds– Covalent Bonds

Chemical Reactions• When chemicals reactions occur, bonds

between atoms are broken or formed, causing substances to recombine as different molecules.

• All the chemical reactions that occur within an organism are referred to as the organism’s metabolism.

Writing Chemical Equations2C12H22O11

• The subscript number in a formula indicate the number of atoms of each element in molecule of the substance.

• The number in front of the chemical formula tells us the number of molecules of each substance.

Mixture

• A mixture is a combination of substances in which the individual components retain their own properties.

• Ex. Sand and sugar

Solution

• A solution is a mixture in which one or more substances (solutes) are distributed evenly in another substance (solvent).

• Ex. Kool-Aid

Acids and Bases• pH is a measure of how acidic or basic a

solution is.

• A scale with values of 0-14 are used.

• Acid - Forms H+ ions and has a pH below 7

• Base - Forms OH- ions has a pH above a 7

Water and Diffusion

Water and Its Importance• 1. Water is polar • 2. It resists temperature changes• 3. It expands when it freezes.

• Polar Molecule – A molecule with an unequal distribution of charge, resulting in the molecule having a pos. end and a neg. end

• Brownian Motion - 1827 Robert Brown used a microscope to observe pollen grains suspended in water

Diffusion• Diffusion is the net movement of particles from

an area of high concentration to an area of lower concentration.

• Three key factors, concentration, temperature, and pressure affect the rate of diffusion.

• Dynamic Equilibrium – result of diffusion where there is continuous movement of particles but no overall change in concentration.

Life Substances• Role of Carbon - A carbon atom has four

electrons available for bonding in its outer energy level.

• Molecular chains - Cells build macromolecules in organisms by bonding small molecules together to form chains called polymers.

Main organic substances• Carbohydrates - The simplest Carbo is simple sugar –

Monosaccharide

• Lipids - Lipids are commonly known as FATS and OILS.

• Proteins - The basic building blocks of proteins is AMINO ACIDS.

• Nucleic Acids - A nucleic acid is a complex macromolecule that stores cellular information in the form of a code.

The Discovery of Cells

Development of Light Microscope

• Anton van Leeuwenhoek was the first scientist to describe living cells as seen through a simple microscope.

• Simple Light Microscope - One lens and uses natural light

• Compound Light Microscope - More than one lens to magnify.– Magnifies up to 1500 times.

Cell Theory

• Robert Hooke used a Compound Light Microscope to study CORK.

• Cells are the basic building blocks of all living things.

The Cell Theory - Three main ideas

1. All organisms are composed of one or more cells

2. The cell is the basic unit of organization of organisms.

3. All cells come from preexisting cells.

Types of Electron Microscopes

• Scanning Electron Microscopes (SEM) - Used to scan the surface of cells to learn their 3-dimensional shape

• Transmission Electron Microscope (TEM) - Used to study the structures contained within the cell.

Two Basic Cell Types• Prokaryotes - Cells Lacking internal

membrane-bound organelles– Contains the following

• Plasma membrane• Ribosomes• Chromosome

• Eukaryotes - Cells containing membrane-bound organelles– Includes all of the organelles.

Prokaryotes • Prokaryotic cells are small, simple and

primitive. They were the first type of cells to appear on Earth. Fossil evidence shows ancient prokaryotes 3.5 billion years old.

• Eukaryotic cells evolved from the prokaryotes about 1.5 billion years ago. They are larger in size and more advanced and complex.

Functions of the Plasma Membrane• Selective Permeability – feature of the

plasma membrane that maintains homeostasis within a cell by allowing some molecules into the cell while keeping other out.

• Plasma Membrane – Controls materials such as water and nutrients in and out of a cell.

Plasma membrane (also called the cell membrane)

Structure

• The plasma membrane is composed of Phosolipid Bilayer, biological molecules that have a phosphate group at the head and two fatty acid chains hanging down as tails.

• Heads – Hydrophilic

• Fatty acid chain tail - Hydophobic

Fluid Mosaic Model

Population Size

Proteins• Integral Proteins are located in membrane

interior, associated with lipids, insoluble, released only by agents which disrupt the membrane bilayer.

• Peripherial Proteins are located on membrane surfaces; soluble, not associated with lipids, released by treatments which leave the bilayer completely intact

Transportation

Cell Structures• Nucleus - Within the nucleus is the DNA

(Chromatin) responsible for providing the cell with its unique characteristics.

• Nucleolus - the prominent structure in the nucleus which produces ribosomes.

• Ribosomes - produce protein and take the RNA message from the ER and turn it into protein

• Cytoplasm - supports the organelles and provides a solvent in which chemical reactions can proceed and consists of the cellular contents held inside the plasma membrane.– The cytoplasm is the "guts" of a cell.

• Cell Wall - A fairly rigid structure located outside the plasma membrane and provides additional support and protection to the cell.

• Endoplasmic Reticulum (ER) - transport materials from the nucleus to other organelles within the cytoplasm. – connecting tunnels for the transportation of cellular

molecules– RNA messages

• There are two kinds of ER, distinguished by the presence or absence of ribosomes– Smooth ER - transports non-protein materials, such

as lipids (no ribosomes)– Rough ER - is dotted with ribosomes, the site of

protein translation

• Golgi Bodies (Function) - It lies serves to receive, modify, and transport the newly synthesized proteins (Structure) - the Golgi is a continuation of the membrane structure of the ER. Consists of a stack of flat membrane disk

• Vacuole - simply an empty space that is surrounded by a single membrane. Some store water, other food, still others store waste.

• Lysosomes - (common in animal cells but rare in plant cells) contain digestive enzymes.

• Peroxisomes - responsible for protecting the cell from its own production of toxic hydrogen peroxide

• Chloroplasts - specialized organelles found in all higher plant cells. These organelles contain the plant cell's chlorophyll, hence provide the green color.

• Mitochondria -provide the energy a cell needs to move, divide, produce secretory products, contract - in short, they are the power centers of the cell

• Cytoskeleton - composed of tiny rods and filaments that form the framework for the cell (like the skeleton in our bodies)

The cytoskeleton is divided into two components:

1. The microfilaments are a network of protein strands anchored to the plasma membrane.

2. The microtubules play several roles within the cell, including forming the mitotic spindle (about which we'll learn more about later), cilia, and flagella.

• Cilia - Are short, hairlike projections that move like WAVE.

• Flagella - Are long projections that move with a whip-like motion.

Cellular Transport• Osmosis: the movement of water molecules

from an area of high concentration to an area of low concentration through a selectively permeable membrane.

• Three types of solutions:

Hypotonic, Hypertonic, and Isotonic

Hypertonic Solutions(Animal cells)

• The concentration of dissolved substances outside the cell is higher than the concentration inside the cell

• More water inside the cell than outside

• Water diffuses out; shrinking of the cell

Hypotonic Solutions(Animal cells)

• The concentration of dissolved substances inside the cell is higher than the concentration outside the cell

• More water outside the cell than inside

• Water diffuses in; exploding of the cell

Plant cells• Hypertonic environment - lose water, mainly

from the central vacuole. The plasma membrane and cytoplasm shrink away from the cell wall.

Hypotonic environment - Do not burst because of rigid cell wall that supports the cell. The plasma membrane is pressed against the cell wall. Instead of bursting, it becomes firm

Isotonic Solutions• contain the same concentration of

dissolved substances inside the cell as it does outside the cell.

• 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.

Active and Passive Transport in Cells

Passive transport• The movement of particles across the cell

membrane by diffusion or osmosis; the cell uses NO energy to move particles across the membrane

• The passive transport of materials across the plasma membrane with the aid of transport proteins is called - Facilitated Diffusion

Active Transport• Movement of materials through a membrane

against a concentration gradient is called - Active Transport (Requires energy)

• Two types of Active transport:

1. Endocytosis – process by which a cell surrounds and takes in material from the environment

2. Exocytosis – the expulsion or secretion of materials from a cell.

• Because endocytosis and exocytosis both move masses of material, they both require energy and are, therefore, both forms of Active Transport.

Cell Growth and ReproductionCell Size Limitations

1. Diffusion limits cell size - Diffusion is fast and efficient process over short distances

2. DNA limits cell size - But there is a limit as to how quickly the blueprints for these proteins can be copied in the nucleus and made into proteins in the cytoplasm.

3. Surface area-to-volume ratio - As a cell’s size increases, its volume increases much faster than its surface area.

Cell Reproduction

• Remember that the Cell Theory states that cells come from preexisting cells.

• Cell Division is the process by which new cells are produced from one cell.

• Old cells are shedding and be replaced, New cells are produced in millions just in seconds.

Chromosomes

• Chromosomes – are structures which contain DNA and become darkly colored when stained.

• Scientist have learned that chromosomes are the carriers of the genetic material that is copied and passed on from generation to generation of cells.

• For most of the cell’s lifetime, chromosomes exist as Chromatin, long strands of DNA wrapped around proteins.

• Under the Electron microscope, chromatin looks like a plate of tangled-up spaghetti

- However before the cell can divide the long stands of chromatin must be reorganized.

The Cell Cycle

• The cell cycle is the sequence of growth and division of a cell.

• There are two basic stages in the life cycle of a cell: Interphase (I), during which the cell grows, and Mitosis (M), during which the cell reproduces. The cell cycle alternates between interphase and mitosis

Interphase• During interphase, the cell grows and does not

divide. The DNA is separated from the cytoplasm inside the nucleus.

• Interphase accounts for about 90% of the time of the cell cycle.

• Interphase is divided into three parts;

- G1, S, G2

G1, S, G2 Phases

• G1 Phase – Rapid Growth and metabolic activities (Protein production is high)

• S Phase – DNA synthesis and replication

• G2 Phase – Cell prepares for division. Also other organelles are manufactured such as mitochondria.

The Phases of MITOSIS

Prophase

Metaphase

Anaphase

Telophase

Prophase – Longest Phase• During prophase the nucleus begins to disappear.

The chromatin pulls together and forms pairs of rope-like structures called chromatid pairs.

• These chromatid pairs are actually identical chromosomes that developed during the S phase of interphase. The chromatid pairs are held together by a structure called the centromere.

• Spindle fibers also begin to appear and along with the centrioles they migrate to the poles of the cell

Prophase

Metaphase• Metaphase begins when the chromatid pairs line up

along the center of the cell. This makes it possible for the chromatids to position themselves so that they can migrate to the opposite poles of the cell

• Anaphase is the stage where this process occurs. The chromatid pairs split and the spindle fibers contract pulling each chromosome toward their pole. This process continues until the chromosomes arrive at each pole. The nucleus reappears and the spindle fibers disappear .

Metaphase

Anaphase

Telophase• Telophase begins as the chromatids reach the

opposite poles and spit into 2 daughter cells, each identical in the number and type of chromosomes. They are smaller than the mother cell and will begin to develop starting interphase again.

• When the cytoplasm splits this is called cytokinesis.

Telophase

Results of Mitosis• In multicellular organisms cell growth and

reproduction result in groups of cells that work together as TISSUE to perform a specific function.

• Tissue organize in various combinations to form ORGANS.

• Multiple organs work together to form an ORGAN SYSTEM.

Control of Cell Cycle• Enzymes are necessary to begin and drive the

cell cycle.

• Cancer is the result of uncontrolled cell division

• A Gene is a segment of DNA that controls the production of a protein.

Cell Energy

ATP• The main energy molecule used by living

things is ATP: (Adenosine triphosphate)

• ATP Structure (Draw below)

Energy is stored in the bonds between the phosphates – they are special high energy

bonds

ATP – ADP cycleThis cycle happens all of the time in the cells of

living things. (Finish the drawing)

ATP

+P -P

ADP(adenosine diphosphate)

• Using new energy to add a phosphate group to ADP to make ATP is called phosphorylation of ADP. Enzymes catalyze these reactions (ATPase breaks down ATP and ATP synthetase makes ATP from ADP)

• It takes millions of ATP-ADP cycles to keep a human alive each day.

• The ATP and ADP molecules get reused over and over again. Energy does NOT get reused.

Sources of New Energy• Sun

• Chlorophyll – containing autotrophs (plants and algae through photosynthesis)

• Heterotrophs that have eaten autotrophs (animals, protozoa, fungi, and bacteria)

• Some produce energy from chemicals instead of sun. These autotrophs use a process known as Chemosynthesis.

Energy Transfer Processes

• Electron transport chain (ETC) – High energy electrons can be transferred from molecule to molecule –as they move, they give off tiny bits of energy with each transfer

• Chemiosmosis – When H+ ions move across membranes in chloroplasts, stored electrochemical energy is released.

• Coenzymes – Large energy carrier molecules. These are able to transfer energy within the cell bycarring high energy H from place to place

Common Coenzymes

• NAD ----- picks up H to become NADH

• NADP ----- picks up H to become NADPH

• FAD ------ picks up H to become FADH

• These coenzymes often carry hydrogens and their electrons to ETC

Photosynthesis• Meaning “making with light”• Photosynthesis is the process of converting

sun energy into usable biological energy (the sugar glucose)

• Photosynthesis takes place in the _________ and ___________ of chloroplasts.

• The green pigment _____________ is required for photosynthesis.

• Write the basic equation for photosynthesis below:

• The speed at which photosynthesis occurs is affected by:A.

B.

C.

Photosynthesis – 1st Step

• LIGHT REACTION – Occurs only in the light. Occurs in membranes of thylakoid disks in chloroplasts.

1. Photons of light strike chlorophyll on the leaf.2. Energy from the light is transferred to electrons

in chlorophyll. These “excited” electrons enter an ETC in the chloroplast membrane.

3. Some of these excited electrons in the energized chlorophyll is transferred to the coenzyme NADP+ to make NADPH

4. Water is split and the oxygen part is released from the leaves as a waste product we breathe.

Photosynthesis – 2nd Step

• Dark Reaction (aka Calvin cycle)– can occur in the light OR in the dark. Since the energy from the light has already been transferred to NADPH and ATP, the dark reaction can take place an time AFTER the light reaction occurs. This process takes place in the stroma of chloroplasts.

1. CO2 enters the plant through holes in the leaves (stomates).

2. The energy from ATP and NADPH is used to put carbon (from ____) and sugar together to make a 6 carbon sugar called ___________.

• The glucose made by the green plants is used in several ways:

1. Directly as energy for the plant – through cell respiration. This occurs in the mitochondria.

2. Stored in long strings as starch – usually roots.

3. used to make cellulose for cell walls

4. Stored as oils in seeds, stems, leaves

Summary of Photosynthesis

Sun Light Dark

Alternative pathways

• Alternative pathways – instead of Calvin cycle

• C3 pathway is used by most plants

• C4 =

• CAM =

Wavelengths of Light• Several different wavelengths of light are used in

photosynthesis.

• Sunlight many because all wavelengths are mixed together, making light appear “white” or clear.

• Wavelengths of light separate in the following order (according to the length of the light wave)

(long) R O Y G B I V (Short)

When light hits an objects, one of three things can happen: (draw)

• The color that objects appear to us is the color of light reflected from the object.

• Green plants reflect green light—they do not use it for energy. They absorb large amounts of Red and Blue light

Cell Respiration • Energy stored in glucose is released through a

process called Cell respiration. This occurs in all living organisms.

Two types of Cell Respiration:

1. Aerobic – requires O2

Glycolysis Kreb’s cycle (CAC)ETC

2. Anaerobic – Does not require O2

Glycolysis Fermentation

Basic Steps of Aerobic Cell Respiration

A. Glycolysis (splitting glucose)

1 glucose (6 carbons) 2 pyruvic acid molecules

(3 carbons each)

Where: __________________________

Type:____________________________

Reactants:_________________________

Products:_________________________

B. Kreb’s Cycle (Citric Acid Cycle) – p. 239

Where: __________________________

Type:____________________________

Reactants:_________________________

Products:_________________________

B. Electon Transport Chain (ETC)

Where: __________________________

Type:____________________________

Reactants:_________________________

Products:_________________________(FADH2 and NADH2 supply energy to convert ADP to ATP)

Electron Transport Chain (draw)

Basic Steps of Anaerobic Cell Respiration

(Occurs after glycolysis if O2 is not present)

1. Cells must perform glycolysis to live. Glycolysis will stop if its products cannot go on to aerobic respiration.

2. The products of glycolysis can be recycled through fermentation.

3. Fermentation allows glycolysis to continue in absence of O2

4. Even though there is no net gain of ATP from fermentation, cells must do it in anaerobic conditions in order to keep functioning.

Fermentation - 2 Types

• Lactic Acid Fermentation (in animals and some bacteria)

Pyruvic Acid + NADH2 lactic acid + NAD (recycled back to glycolysis)

• Alcoholic Fermentation (yeasts, plants)

Pyruvic Acid + NADH2 alcohol + CO2 + NAD

Practical ApplicationsLactic Acid fermentation

1. Bacteria in a closed container of milk are in anaerobic conditions. Forced into fermentation they produce lactic acid. Lactic acid curdles milk. It also produces cheese, yogurt, sour cream, and cottage cheese.

Alcoholic Fermentation

1. Yeasts in bread dough = anaerobic conditions. CO2 gas makes dough rise. Alcohol evaporates out of bread during baking.

Energy Summary(number of ATP molecules formed in each

step of respiration)

Glycolysis 4 (net = 2)

ATP

Kreb’s cycle

2 ATP

Electron Transport

32 ATP

Total: Aerobic

Respiration

38 ATP (net = 36)

Glycolysis 4 (net = 2)

ATP

Fermentation 0 ATP

Total: Anaerobic Respiration

2 ATP