Cell Structure and Function: A Comprehensive Guide for High School Biology | Schemes and Mind Maps Biochemistry

CELL

Cell Theory

All living things are made of cells

Cells are the basic unit of structure and function in an

organism (basic unit of life)

Cells come from the reproduction of existing cells (cell

division)

Cell Sizes and Cell Types

Cells, the basic units of organisms, can only be observed

under microscope.

Three basic types include:

oAnimal Cell

oPlant Cell

oBacteria Cell

Number of Cells

Although all living things are made of cells, organisms may

be composed of one cell (Unicellular) or composed of many

cells that may organize into tissues (Multicellular).

Cell Structure And Function

Cytoskeleton

oNetwork of protein fibers running throughout the

cytoplasm that give a cell its shape and provide a

basis for movement.

oMicrofilaments – tw o intertwined strands of actin

protein.

oIntermediate Filaments – fibrous proteins

supercoiled into think cables.

oMicrotubules – hollow tubes of tubulin,

chromosome movement during division.

oCentrosome – also called the “microtubule

organizing center”, an area in the cell where

microtubules are produced.

In animal cells, a pair of centriole is

made of nine sets of triplet microtubules.

Cell or Plasma Membrane

oComposed of double layer of phospholipids and

proteins.

oSurrounds outside of ALL cells.

oControls what enters or leaves the cell.

oLiving layer.

Cell Membrane (Plants)

oLies immediately against the cell wall in plant cells.

oPushes out against the cell wall to maintain cell

shape.

Cell Wall

oNonliving layer

oFound in plants, fungi, & bacteria

oMade of cellulose in plants

oMade of peptidoglycan in bacteria

oMade of chitin in fungi

oSupports and protects cell

oFound outside of the cell membrane

Phospholipids

oHeads contain glycerol & phosphate and are

hydrophilic (attract water).

oTails are made of fatty acids and are hydrophobic

(repel water).

oMake up a bilayer where tails point inward toward

oeach other.

oCan m ove laterally to allow small molecules (O2,

CO2, & H2O to enter).

Cytoplasm

oJelly-like substance enclosed by cell membrane.

oProvides a medium for chemical reactions to take

place.

oConsists of cytosol and cellular organelles except

for the cell nucleus. cytosol is made up of water,

salts, organic molecules and many enzymes that

catalyze reactions.

Nucleus

oControls the normal activities of the cell.

oContains the DNA in chromosomes. DNA is

condensed & wr apped around proteins forming as

chromosomes in dividing cells.

oBounded by a nuclear envelope ( membrane) with

pores.

Nuclear Envelope

oDouble membrane surrounding nucleus, also

called nuclear membrane.

oContains nuclear pores for materials to enter &

leave nucleus and is connected to the rough ER.

Nucleolus

oInside the nucleus, cell may have 1 to 3 nucleoli.

oDisappears when cell divides.

oMakes ribosomes that make proteins.

Centrioles

oMade of bundle of microtubules.

oAppear during cell division forming mitotic spindle,

helps pulling chromosome pairs apart to opposite

ends of the cell.

Mitochondrion

oGenerate cellular energy (ATP).

oMore active cells like muscle cells have MORE

mitochondria, both plants & animal cells have

mitochondria.

oSite of cellular respiration.

Endoplasmic Reticulum

oProduction Factory, makes proteins and lipids.

oSystem of membranous channels and vesicles.

oInternal production & delivery system of the cell.

Rough ER is studded with ribosomes,

site of protein synthesis and processing.

Makes membrane proteins and proteins

for export out of cell.

Smooth ER lacks ribosomes. Site of

synthesis of phospholipids and

packaging of proteins into vesicles.

Makes cell products that are used inside

the cell.

Ribosomes

oMade of proteins and rRNA, “Protein factories” for

cell.

oJoin amino acids to make proteins.

Golgi Apparatus

oThe assembly factory. Packages, modifies, and

transports materials to different location

inside/outside of the cell.

oReceives protein and also lipid filled vesicles from

the ER, packages, processes, and distributes

them within the cell or for export out of the cell

(secretion).

Vesicles

oSmall compartments separated from the cytosol

by at least one lipid bilayer.

oStore, transport, or digest cellular products and

waste.

oVesicles form while taking in (endocytosis) or

discharging (exocytosis) materials.

Lysosomes

oBreak down food into particles and also destroy

old cellular components.

oContain hydrolytic enzymes and are involved in

intracellular digestion.

Vacuoles

oFluid filled sacs for storage. Plant cells have a

large central vacuole.

oNo vacuoles in bacterial cells

Chloroplasts

oUse energy from sunlight to make own food

(glucose). Energy from sun stored in the chemical

bonds of sugars.

oOuter membrane smooth. Inner membrane

modified into sacs called thylakoids

oThylakoids in stacks called grana & interconnected

oStroma – gel like material surrounding thylakoids

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CELL

Cell Theory  All living things are made of cells  Cells are the basic unit of structure and function in an organism (basic unit of life)  Cells come from the reproduction of existing cells (cell division) Cell Sizes and Cell Types  Cells, the basic units of organisms, can only be observed under microscope.  Three basic types include: o Animal Cell o Plant Cell o Bacteria Cell Number of Cells  Although all living things are made of cells, organisms may be composed of one cell (Unicellular) or composed of many cells that may organize into tissues (Multicellular). Cell Structure And Function  Cytoskeleton o Network of protein fibers running throughout the cytoplasm that give a cell its shape and provide a basis for movement. o Microfilaments – two intertwined strands of actin protein. o Intermediate Filaments – fibrous proteins supercoiled into think cables. o Microtubules – hollow tubes of tubulin, chromosome movement during division. o Centrosome – also called the “microtubule organizing center”, an area in the cell where microtubules are produced.  In animal cells, a pair of centriole is made of nine sets of triplet microtubules.  Cell or Plasma Membrane o Composed of double layer of phospholipids and proteins. o Surrounds outside of ALL cells. o Controls what enters or leaves the cell. o Living layer.  Cell Membrane (Plants) o Lies immediately against the cell wall in plant cells. o Pushes out against the cell wall to maintain cell shape.  Cell Wall o Nonliving layer o Found in plants, fungi, & bacteria o Made of cellulose in plants o Made of peptidoglycan in bacteria o Made of chitin in fungi o Supports and protects cell o Found outside of the cell membrane  Phospholipids o Heads contain glycerol & phosphate and are hydrophilic (attract water). o Tails are made of fatty acids and are hydrophobic (repel water). o Make up a bilayer where tails point inward toward o each other. o Can move laterally to allow small molecules (O2, CO2, & H2O to enter).  Cytoplasm o Jelly-like substance enclosed by cell membrane. o Provides a medium for chemical reactions to take place. o Consists of cytosol and cellular organelles except for the cell nucleus. cytosol is made up of water, salts, organic molecules and many enzymes that catalyze reactions.  Nucleus o Controls the normal activities of the cell. o Contains the DNA in chromosomes. DNA is condensed & wrapped around proteins forming as chromosomes in dividing cells. o Bounded by a nuclear envelope (membrane) with pores.  Nuclear Envelope o Double membrane surrounding nucleus, also called nuclear membrane. o Contains nuclear pores for materials to enter & leave nucleus and is connected to the rough ER.  Nucleolus o Inside the nucleus, cell may have 1 to 3 nucleoli. o Disappears when cell divides. o Makes ribosomes that make proteins.  Centrioles o Made of bundle of microtubules. o Appear during cell division forming mitotic spindle, helps pulling chromosome pairs apart to opposite ends of the cell.  Mitochondrion o Generate cellular energy (ATP). o More active cells like muscle cells have MORE mitochondria, both plants & animal cells have mitochondria. o Site of cellular respiration.  Endoplasmic Reticulum o Production Factory, makes proteins and lipids. o System of membranous channels and vesicles. o Internal production & delivery system of the cell.  Rough ER is studded with ribosomes, site of protein synthesis and processing. Makes membrane proteins and proteins for export out of cell.  Smooth ER lacks ribosomes. Site of synthesis of phospholipids and packaging of proteins into vesicles. Makes cell products that are used inside the cell.  Ribosomes o Made of proteins and rRNA, “Protein factories” for cell. o Join amino acids to make proteins.  Golgi Apparatus o The assembly factory. Packages, modifies, and transports materials to different location inside/outside of the cell. o Receives protein and also lipid filled vesicles from the ER, packages, processes, and distributes them within the cell or for export out of the cell (secretion).  Vesicles o Small compartments separated from the cytosol by at least one lipid bilayer. o Store, transport, or digest cellular products and waste. o Vesicles form while taking in (endocytosis) or discharging (exocytosis) materials.  Lysosomes o Break down food into particles and also destroy old cellular components. o Contain hydrolytic enzymes and are involved in intracellular digestion.  Vacuoles o Fluid filled sacs for storage. Plant cells have a large central vacuole. o No vacuoles in bacterial cells  Chloroplasts o Use energy from sunlight to make own food (glucose). Energy from sun stored in the chemical bonds of sugars. o Outer membrane smooth. Inner membrane modified into sacs called thylakoids o Thylakoids in stacks called grana & interconnected o Stroma – gel like material surrounding thylakoids

CARBOHYDRATES

 Carbohydrates, along with lipids, proteins, nucleic acids, and other compounds are known as biomolecules because they are closely associated with living organisms.  Carbohydrates are polyhydroxy aldehydes or ketones, or substances that yield such compounds on hydrolysis. Importance of Carbohydrates  They provide energy through oxidation.  They supply carbon for the synthesis of cell components.  They serve as a form of stored chemical energy.  They form part of the structures of some cells and tissues. Occurrence of Carbohydrates  Almost 75% of dry plant material is produced by photosynthesis. Most of the matter in plants, except water, are carbohydrate material.  cellulose which are structural component of the plants, starch the energy reservoir in plants, and glycogen (animal starch) found in animal tissues and human body in smaller quantities.  Plant products are the major source of carbohydrates and average human diet contains 2/3 of carbohydrates.  Recommended percentages in the daily diet: o Recommended carbohydrates: 60 % o Recommended sucrose: less than 10% Classes of Carbohydrates  Monosaccharide: single polyhydroxy aldehyde or ketone unit.  Disaccharide: two monosaccharide units linked together by a covalent bond.  Oligosaccharides: 3 to 10 monosaccharide units.  Polysaccharide: very long chains of hundreds or thousands of monosaccharide units, either straight or branched chains. Stereochemistry of Carbohydrates  Glyceraldehyde, simplest carbohydrate, in two isomeric forms that mirrors each other:  Glyceraldehyde is a chiral molecule- cannot be superimposed on its mirror image. Two mirror images are enantiomers of each other. Chirality  Chiral molecules have the same relationship to each other that your left and right hands have when reflected in a mirror.  Achiral objects can be superimposed on the mirror images, for example, drinking glasses, spheres, and cubes.  Fischer projections are a convenient way to represent mirror images in two dimensions. Optical Activity  A levorotatory (–) substance rotates polarized light to the left.  A dextrorotatory (+) substance rotates polarized light to the right.  Molecules which rotate the plane of polarized light are optically active. Monosaccharide  The monosaccharides are the simplest of the carbohydrates, since they contain only one polyhydroxy aldehyde or ketone unit.  Monosaccharides are classified according to the number of carbon atoms they contain.  Most monosaccharides have a sweet taste (fructose is sweetest; 73% sweeter than sucrose).  They are solids at room temperature, they are extremely soluble in water. Disaccharides  Two monosaccharides can be linked together through a glycoside linkage to form a disaccharide. o Maltose: malt sugar o Lactose: milk sugar o Sucrose: table sugar Oligosaccharides  Raffinose; found in peas and beans Polysaccharide  Contain hundreds or thousands of carbohydrate units.  Polymers of glucose: starch, glycogen, and cellulose. Starch  Starch is a polymer consisting of D-glucose units.  Starches (and other glucose polymers) are usually insoluble in water because of the high molecular weight, but they can form thick colloidal suspensions with water. o Amylose: consists of long, unbranched chains of glucose (from 1000 to 2000 molecules) connected by α(1→4) glycosidic linkages. 10 – 20% in plants. o Amylopectin consists of long chains of glucose (up to 105 molecules) connected by α(1→4) glycosidic linkages, with α(1→6) branches every 24 to 30 glucose units along the chain. 80 – 90% in plants. Glycogen  Glycogen, also known as animal starch, is structurally similar to amylopectin, containing both α(1→4) glycosidic linkages and α(1→6) branch points.  Glycogen is abundant in the liver and muscles; on hydrolysis it forms glucose, which maintains normal blood sugar level and provides energy. Cellulose  Cellulose is an important structural polysaccharide, and is the single most abundant organic compound on earth. It is the material in plant cell walls that provides strength and rigidity; wood is 50% cellulose.

including reproduction, blood clotting, inflammation, and fever. PROTEINS  Proteins (Greek proteios, “primary” or “of first importance”) are biochemical molecules consisting of polypeptides joined by peptide bonds between the amino and carboxyl groups of amino acid residues.  Most organisms use 20 naturally-occurring amino acids to build proteins. The linear sequence of the amino acids in a protein is dictated by the sequence of the nucleotides in an organisms’ genetic code. Characteristics of Proteins  Proteins are very large polymers of amino acids with molecular weights that vary from 6000 amu to several million amu. o Glucose (C6H12O6 ) = 180 amu o Hemoglobin (C2952H4664O832N812S8Fe4 ) = 65,000 amu  Proteins are too large to pass through cell membranes, and are contained within the cells where they were formed unless the cell is damaged by disease or trauma.  Proteins can take the form of zwitterions. Protein Function  Catalytic function: Nearly all reactions in living organisms are catalyzed by proteins functioning as enzymes. Without these catalysts, biological reactions would proceed much more slowly.  Structural function: In animals structural materials other than inorganic components of the skeleton are proteins, such as collagen (mechanical strength of skin and bone) and keratin (hair, skin, fingernails).  Storage function: Some proteins provide a way to store small molecules or ions, e.g., ovalbumin (used by embryos developing in bird eggs), casein (a milk protein) and gliadin (wheat seeds), and ferritin (a liver protein which complexes with iron ions).  Protective function: Antibodies are proteins that protect the body from disease by combining with and destroying viruses, bacteria, and other foreign substances. Another protective function is blood clotting, carried out by thrombin and fibrinogen.  Regulatory function: Body processes regulated by proteins include growth (growth hormone) and thyroid functions (thyrotropin).  Nerve impulse transmission: Some proteins act as receptors for small molecules that transmit impulses across the synapses that separate nerve cells (e.g., rhodopsin in vision).  Movement function: The proteins actin and myosin are important in muscle activity, regulating the contraction of muscle fibers.  Transport function: Some proteins bind small molecules or ions and transport them through the body. Protein Class by Structure  Fibrous proteins are made up of long rod-shaped or stringlike molecules that can intertwine with one another and form strong fibers. Protein Classes by Composition  Simple proteins contain only amino acid residues.  Conjugated proteins also contain other organic or inorganic components, called prosthetic groups. o Nucleoproteins – nucleic acids o Lipoproteins - lipids o Glycoproteins - carbohydrates o Phosphoproteins – phosphate groups o Hemoproteins - heme o Metalloproteins – iron or zinc Protein Structure  There are four levels of organization in proteins structure: primary, secondary, tertiary, and quaternary. o The primary structure of a protein is the linear sequence of the side chains that are connected to the protein backbone. o The a-helix is held in this shape by hydrogen bonding interactions between amide groups, with the side chains extending outward from the coil. o The tertiary structure of a protein refers to the bending and folding of the protein into a specific three-dimensional shape. o When two or more polypeptide chains are held together by disulfide bridges, salt bridges, hydrogen bond, or hydrophobic interactions, forming a larger protein complex. Amino Acids  The amino acids are classified by the polarity of the R group side chains, and whether they are acidic or basic: o Neutral, nonpolar o Neutral, polar o Basic, polar (with additional amino acid group) o Acidic, polar (with additional carboxylate group)  Because amino acids contain both an acidic and a basic functional group, an internal acid-base reaction occurs, forming an ion with both a positive and a negative charge called a zwitterion.  Since the pH of the solution affects the charge on the amino acid, at some pH, the amino acid will form a zwitterion. This is called the isoelectric point.  Cysteine is the only amino acid that contains a sulfhydryl (thiol, R—SH) group. Thiols are easily oxidized to form disulfide bonds (R—S—S—R). This allows cysteine to dimerize to form cysteine. Peptides  Short chains are referred to as peptides, chains of up to about 50 amino acids are polypeptides, and chains of more than 50 amino acids are proteins.  Amino acids in peptide chains are called amino acid residues. o The residue with a free amino group is called the N-terminal residue, and is written on the left end of the chain. o The residue with a free carboxylate group is called the C-terminal residue, and is written on the right end of the chain. Oxytocin and Vasopressin  Vasopressin and oxytocin are nonapeptide hormones secreted by the pituitary gland. Six of the amino acid residues are held in a loop by disulfide bridges formed by the oxidation of two cysteine residues. o Vassopressin is known as antidiuretic hormone (ADH) because it reduces the amount of urine formed, which causes the body to conserve water. It also raises blood pressure. o Oxytocin causes the smooth muscles of the uterus to contract, and is administered to induce labor. It also stimulates the smooth muscles of mammary glands to stimulate milk ejection. Adrenocorticotropic Hormone  Adrenocorticotropic hormone (ACTH) is a 39-residue peptide produced in the pituitary gland. It regulates the production of steroid hormones in the cortex of the adrenal gland. Hemoglobin  A hemoglobin molecule in a person suffering from sicklecell anemia has a one-amino acid difference in the sixth position of the two b-chains of normal HbA (a glutamate is replaced with a valine). Protein Hydrolysis  The peptide bonds in proteins can be broken down under acidic or basic conditions into smaller peptides, or all the way to amino acids, depending on the hydrolysis time, temperature, and pH.

Protein Denaturation  Denaturation is caused when the folded native structures break down because of extreme temps. or pH values, which disrupt the stabilizing structures. The structure becomes random and disorganized.  Heat denaturation is used to prepare vaccines against some diseases. The denatured toxin can no longer cause the disease, but it can stimulate the body to produce substances that induce immunity.  Heavy-metal poisoning is often treated with large doses of raw egg white and milk; the proteins in the egg and milk bind to the metal ions, forming a precipitate, which is either vomited out or pumped out. ENZYMES  The catalytic behavior of proteins acting as enzymes is one of the most important functions that they perform in living cells. o Without catalysts, most cellular reactions would take place too slowly to support life. o With the exception of some RNA molecules, all enzymes are globular proteins. o Enzymes are extremely efficient catalysts, and some can increase reaction rates by 1020 times that of the uncatalyzed reactions.  •Enzymes are well suited to their roles in three major ways: they have enormous catalytic power, they are highly specific in the reactions they catalyze, and their activity as catalysts can be regulated. Catalytic Efficiency  Catalysts increase the rate of chemical reactions without being used up in the process. o Although catalysts participate in the reaction, they are not permanently changed, and may be used over and over. o Enzymes act like many other catalysts by lowering the activation energy of a reaction, allowing it to achieve equilibrium more rapidly

Cell Structure and Function: A Comprehensive Guide for High School Biology, Schemes and Mind Maps of Biochemistry

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Partial preview of the text

Download Cell Structure and Function: A Comprehensive Guide for High School Biology and more Schemes and Mind Maps Biochemistry in PDF only on Docsity!

CELL

CARBOHYDRATES