Biology Keystone

The Cell

The Cell Theory

• All living things are made up of cells

• All living things function through the activities of their cells (metabolism)

• Cells come only from pre-existing cells

“Cell People”

• Schleiden: Plants are made of cells

• Schwann: Animals are made of cells

• Virchow: Cells come only from cells

• Hooke: Named the cell

• van Leeuwenhoek: Invented a crude microscope; first to see living cells

• Brown: Discovered the nucleus

Structure and Function

• Nerve cells have long processes to transmit information over long distances

Epithelial Cells (Skin)

• Epithelial cells are flat and platelike in order to form a protective covering over the organism

Prokaryotic Cells

• Lack an organized nucleus

• Lack membrane-bound organelles

• Usually have a cell wall

Plant Cells

• Have a cell wall

• Contain a large central vacuole

• Usually contain chloroplasts

Animal Cells

• Do not have a cell wall

• Have centrioles

• Have smaller vacuoles

• Have lysosomes

The Cell Wall

• Made of cellulose

• Gives support to the plant cell

• Gives strength to the plant cell

• Is permeable

Plasma Membrane

• Controls what enters and leaves the cell

• Made of a phospholipid bilayer

• Found in all types of cells

Cytosol

• The area of the cytoplasm outside of the individual organelles is called the cytosol

• The cytosol contains thousands of enzymes

• The cytosol takes molecules and breaks them down, so that the individual organelles can use them

The Nucleus

• Contains the cell’s DNA

• Is surrounded by its own nuclear envelope

• Often referred to as the “control center” of the cell

DNA

• The genetic material in the nucleus

• Double helix

• Forms chromatin (working DNA) and chromosomes (nonworking DNA)

Nucleolus

• The nucleolus is an approximately spherical region within the nucleus of eukaryotic cells

• It stores RNA and ribosomal subunits

Mitochondria

• Mitochondria generate the cell’s energy through cellular respiration

• Usually they are rod-shaped, however, they can be round

• The inner membrane is thrown into folds or shelves called cristae

• Mitochondria have their own DNA and ribosomes

• They are capable of reproducing themselves

• Humans inherit mitochondrial DNA only from the mother

• Powerhouses of the cell

• Site of cellular respiration

• Breakdown of food to release energy and generate ATP

Chloroplasts

• Chloroplasts are the site of photosynthesis, the process by which autotrophs make food

• Chlorophyll is the light-trapping pigment in the chloroplast

• Stroma is the semi-fluid filled space that contains enzymes

• Thylakoids are hollow sacs that provide membrane for photosynthetic reactions

• Grana are stacks of thylakoids

• Lamellae connect the grana

• Like mitochondria, chloroplasts have a double membrane, their own DNA, and ribosomes

• Chloroplasts can reproduce themselves

Ribosomes

• Granular organelles

• Site of protein synthesis

• Attached to the rough ER or located in the cytoplasm

• Manufactured in the nucleolus

• Made of RNA and protein subunits

Rough Endoplasmic Reticulum

• A complex network of membranes

• Bears the ribosomes during protein synthesis

• Processes and transports polypeptides to the Golgi complex

• Hollow interior is known as the “lumen”

Smooth Endoplasmic Reticulum

• Smooth ER is associated with the production and storage of lipids, especially steroids

• Releases calcium in cardiac and skeletal muscle cells so that contraction can occur

• Detoxifies alcohol and poisons in the liver and kidney cells

Golgi Apparatus

• Receives proteins from the rough ER

• Processes, packages, and delivers the proteins

• Packaging occurs via vesicles

• Responsible for packaging proteins for the cell

• Proteins produced by the rough ER pass into the Golgi cisternae

• These proteins are then squeezed off into vesicles (small vacuoles) for transport out of the cell

Lysosomes

• Found in animal cells

• Contains hydrolytic enzymes to digest almost everything in the cell

• Manufactured by the Golgi Apparatus

• Autophagy

  • Digestion of worn organelles

• Autolysis

  • Digestion of damaged or extra cells

Peroxisomes

• Not from the Golgi apparatus

• Neutralize free radicals (Oxygen ions that damage cells) in the liver and kidneys

• Detoxify alcohol and drugs

• Break down fatty acids for the mitochondria to use for energy

Glyoxysomes

• Found in some seeds

• Break down stored fats to provide energy for the developing plant embryo

Vacuole

• Large fluid-filled vesicle surrounded by a membrane

• Can store water, nutrients, wastes, and pigments

• Larger in plant cells

• Help plant cells create turgor, internal water pressure

Contractile Vacuoles

• Membrane-bound sac

• Plays roles in release of excess water from protists that live in watery environments

Other Vacuoles

• Amyloplasts

  • Store starch in plant cells

• Chromoplasts

  • Store pigments other than chlorophyll; give color to petals and leaves

Cytoskeleton

• For mobility and stability

• Primary types of fibers comprising the cytoskeleton are microfilaments, microtubules, and intermediate filaments

Centrioles

• In animal cells only

• Two cylinders at right angles to one another

• Close to the nucleus

• Help to form the spindle fibers for cell division

Flagella and Cilia

• Flagella are long and whiplike

• Cilia are short and hairlike

• Both are used for locomotion

• Cilia are also used internally to sweep cells or particles

Animal Cell

Plant Cell

Organic Compounds

Organic Compounds

• The Molecules of Life

• Made of

  • Carbon

  • Hydrogen

  • Usually Oxygen

    • Sometimes:

      • Nitrogen

      • Phosphorus

      • Sulfur

The Carbon Atom

• Has four valence electrons

• Forms strong covalent bonds

• Can form single, double, and triple bonds

• Likes to bond to itself

• Carbon compounds take many shapes such as:

  Chains

Branched Chains

Rings

Functional Groups

• Groups of atoms sometimes bond to carbon chains

• These “functional” groups give the carbon compound unique properties

  • Hydroxyl: OH

    

    Carbonyl: CO

    • 

  • Carboxyl: CO2H

    • (R is a placeholder)

      

  • Amino: NH2

    • 

  • Methyl: CH3

    • 

  • Phosphate: PO4H2

Building Organic Compounds

• Monomers are single units of an organic compound that have all the properties of the compound

• Polymers are large organic compounds consisting of several monomers bonded together

• Macromolecules refer to extremely large polymers

• Glucose is the monomer of starch, glycogen, chitin, and cellulose

Organic Compounds

• The four categories of Organic Compounds found in living things

  • Carbohydrates

  • Lipids

  • Proteins

  • Nucleic Acids

Carbohydrates

• Sugars

  • Used for energy

  • Produced by plants through photosynthesis

  • Simple sugars

• Made of Carbon, Hydrogen, and Oxygen

• The ratio of C:H:O is 1:2:1

• Monosaccharides are the monomers of carbohydrates

  • C6H12O6 is the formula for a monosaccharide

    • Glucose: blood sugar

    • Fructose: fruit sugar

    • Galactose: found in milk

• Disaccharides

  • Are built from two monosaccharides

  • C12H22O11 is the general formula

    • Sucrose: table sugar; sweet

    • Lactose: milk sugar; nourishment for young mammals

    • Maltose: sugar in seeds; nourishment for embryo plants

      • Glucose + Glucose = Maltose + H2O

      • Glucose + Fructose = Sucrose + H2O

      • Glucose + Galactose = Lactose + H2O

• Polysaccharides

  • Large molecules (polymers)

  • Made of many monosaccharides bonded together

    • Starch: energy storage in plants

    • Glycogen: energy storage in animals

    • Cellulose: cell wall construction

    • Chitin: cell walls in fungi and exoskeletons in arthropods

• Isomers

  • Compounds that have the same molecular formula but different structures are called isomers

  • Each isomer has its own properties because the shape of the molecule determines its characteristics

  • Shape determines properties

• Condensation Reaction (Dehydration Synthesis)

  • Building a large organic molecule from two smaller organic molecules by removing a molecule of H2O through a process called condensation reaction

  • The water is produced by removing an OH group from one molecule and a H from a hydroxide group in the other molecule

• Hydrolysis

  • The breaking of polymers into monomers through the addition of water

Lipids

• Made of Carbon, Hydrogen, and Oxygen

• Monomers are glycerol and fatty acids

• The high Carbon:Hydrogen ratio enables the molecules to store more energy than carbohydrates

  • Fatty Acids

    • Made of long hydrocarbon chains

    • Attached to a carboxyl functional group

    • Saturated Fatty Acids

      • Have only single Carbon to Carbon bonds

      • Fatty acid tails are straight

      • Can cause Cardiovascular disease

      • The bad fat

    • Unsaturated Fatty acids

      • Have one or more double Carbon to Carbon bonds

      • Fatty acid tails are “kinked”

      • Less likely to cause cardiovascular problems

      • The good fat

    • Unsaturated fats are liquid at room temperature

    • Olive oil and corn oil are unsaturated fats

    • Most saturated fats are solid at room temperature

    • Butter and lard are saturated fats

      • Coconut oil is an exception

    • Trans Fat

      • The new health threat

Types of Lipids

• Triglycerides

  • 3 fatty acids:1 glycerol

  • Used for insulation under the skin and around organs

  • Store energy for future use

• Phospholipids

  • Composed of

    • Two fatty acids

    • One glycerol

    • One phosphate group

  • Phospholipid Structure

    • Hydrophilic head

    • Hydrophobic tails

    • The unsaturated fatty acid tails create kinks that enable the phospholipid to spin freely

  • Allow our membranes to be fluid

• Steroids

  • Chemical messengers

  • Composed of four fused Carbon rings

  • Cholesterol

    • Keeps membrane’s fluid at low temperatures

    • Stabilizes membranes at high temperatures (keeps them together)

  • Estrogen and Testosterone

    • Responsible for the development of secondary sexual characteristics

• Waxes

  • Waterproof

    • Form a protective coating on plants

    • Form protective layers in animals

      • Earwax prevents bacteria from entering the ear

Proteins

• Made of Carbon, Hydrogen, Oxygen, and Nitrogen

• Monomers are called amino acids

• Amino acids are help together by peptide bonds

• Amino Acids

  • Essential

    • Cannot be made by the body

    • Must be supplied in the diet

  • Nonessential

    • Can be made by the body

  • Ex:

    • 
      

      

  • The alpha carbon is in the center

  • A hydrogen atom, a carboxyl group (acid group), and an amino group are bonded to the alpha carbon in all amino acids

  • The rest of the amino acid referred to as the “R” group is unique to each of the 20 amino acids

• Condensation Reaction

  • Polypeptide is the name given to protein polymers

  • They can be built by removing a molecule of water from every two amino acids bonded together

  • Peptide Bonds

    • H is removed from the amino group of one amino acid, and the OH is removed from the carboxyl group of the other amino acid

• Hydrolysis

  • Polypeptides can be broken down into amino acids by adding back the H2O

• Structural Proteins

  • Uniquely made in each person

  • Used for skin, hair, nails, muscles, bones

    • Examples: collagen and keratin

• Transport Proteins

  • Found in the cell membrane to bring molecules in and out

  • Some are unique to particular cells

    • Example: Hemoglobin- carries oxygen

• Messenger Proteins

  • Hormones are chemical messengers

    • Example: Insulin- regulates blood sugar

• Motile Proteins (Mobility)

  • Found in cytoskeleton and muscles

    • Examples: actin and myosin

• Storage Proteins

  • Proteins that remain in supply for growth and development

    • Example: egg white

• Defense Proteins

  • Antibodies fight specific infections

• Enzymes

  • Controls every activity in the cell

  • Speed up reactions at least one-million times

  • Examples: lactase and sucrase

• Heat can change protein structure

• Other agents that denature proteins are:

  • Extreme pH

  • Exposure to Lead (Pb) and Mercury (Hg)

Nucleic Acids

• Made of monomers called nucleotides

  • One 5-Carbon sugar

  • One phosphate group

  • One Nitrogen base

• DNA

  • Transmits genetic information from one generation to the next

  • Contains the information necessary to tell the cell how to make proteins

  • The genetic material in the nucleus

  • Double Helix

  • Forms chromatin and chromosomes

  • Sugar in DNA is deoxyribose

  • Always in a double strand called a helix

  • Has four bases:

    • Adenine

    • Thymine

    • Guanine

    • Cytosine

• Watson and Crick

  • Used the research of many people

  • Put together the double helix model of DNA

  • Won the Nobel Prize with Wilkins for the model

• Rosalind Franklin

  • Took the x-ray pictures of DNA that enabled Watson and Crick to figure out the double helix model

  • Died before the Nobel Prize was awarded

• RNA

  • Copies the DNA genetic code

  • Controls protein synthesis according to directions from DNA

  • Sugar in RNA is ribose

  • Exists as a single strand

  • Has four bases:

    • Adenine

    • Uracil

    • Guanine

    • Cytosine

• ATP

  • Adenosine Triphosphate

  • Composed of

    • Adenine- a nitrogen base

    • Ribose- a five carbon sugar

    • Three phosphate groups

  • The molecule is the energy storage mechanism for all living things

  • Recycling ATP

    • When energy is needed, the cell breaks down ATP molecules

    • ATP → Energy + ADP + Phosphate

    • During cellular respiration, energy is released and used to replace the phosphate

    • ADP + Energy + Phosphate → ATP

Enzymes