Anatomy of Cell

The Cell as a single-celled animal

Ø Respiration

Ø Ingestion & Digestion of nutrients

Ø Elimination of wastes

Ø Perform functions

Ø Reproduction

Cytoskeleton provides structure and holds organelles in place

Microtubules provide structure and also transport mechanism for substances from one part of the cell to another.

Proteins of the Cell Membrane

Ø Integral Proteins

Ø Span entire plasma membrane

Ø Interact with intra and extracellular fluids

Ø Pores for passage of water or other substances

Ø Gates for some ions & facilitated diffusion

Ø Peripheral proteins

Ø Attached only to one surface

Ø Mostly intracellular (G-proteins are a good example)

Ø Attached to intracellular end of integral proteins

Ø Act as enzymes when signaled by integral proteins

Ø Carry message into cell

Proteins of the Cell Membrane

Ø Glycoproteins

Ø Carbohydrate plus protein

Ø Extracellular

Ø Negative charge to resting cell membrane

Ø Many are hormone receptors (e.g. insulin)

Carbohydrates of the Cell

Ø Glycoproteins (form “Glycocalyx”)

Ø Cell membrane hormone receptors (extracellular)

Ø Glycogen (intracellular)

Ø Energy storage (animal starch)

Ø Insoluble polysaccharide

Ø Liver and skeletal muscle

Ø Modest energy storage compared to fat

Lipids of the Cell Membrane
(Plasma Membrane)

Ø Phospholipids (bi-layer)

Ø Cholesterol: in bi-layer. Helps determine degree of permeability of cell membrane to water-soluble substances.

Ø Triglycerides: Energy storage in adipose tissue.

Organelles

Ø Carry out specific functions within the cell:

Ø Endoplasmic reticulum

Ø Ribosomes

Ø Golgi apparatus

Ø Lysosomes

Ø Peroxisomes

Ø Mitochondria

Ø Proteasomes

Ø Nucleus

Ø Cytoskeleton

Ribosomes

Ø Critical component of protein synthesis.

Ø Assemble transfer RNA for packaging into peptides and new proteins

Ø Located in the cytosol and on the rough endoplasmic reticulum.

Endoplasmic Reticulum

Ø Smooth ER

Ø Interconnected canals and tubules

Ø Digestion of some compounds

Ø Storage of Ca++ ions used in muscle contraction

Ø Synthesizes carbohydrates and Lipids

Ø synthesis of lipids and steroids, metabolism of carbohydrates, regulation of calcium concentration, drug detoxification, attachment of receptors on cell membrane proteins, and steroid metabolism

Endoplasmic Reticulum

Ø Rough (granular) ER

Ø Covered with Ribosomes for protein synthesis.

Ø Production of most proteins needed by the cell

Ø Synthesizes phospholipids and cholesterol

Ø Synthesizes the enzymes of glycolysis

Mitochondria

Ø Number, size and activity vary widely in tissues.

Ø Main location for energy production via phosphorylation of ADP to ATP.

Ø Convoluted inner membrane (matrix) Contains components of Citric Acid (Krebs) cycle.

Ø Outer surface of inner membrane contains cytochromes which make up the electron transport system.

Ø Contain DNA & processes for self replication.

Nucleus and Nucleoli

Ø Nucleus

Ø Bilayer nuclear membrane

Ø Largest of the organelles

Ø Contains genetic material (DNA) for cell reproduction)

Ø Contains DNA codes for protein synthesis

Ø Contains nucleolus

Ø Nucleoli (may be multiple nucleoli)

Ø Produces ribosomes for protein synthesis.

Ø Thus, contains the information for the cell functions.

Other organelles and cell components

Ø Lysosomes: Digestion (e.g. non-functioning organelles)

Ø Peroxisomes: Degradation of amino acids, fatty acids and toxic foreign substances. Produce H2O2

Ø Cilia: Movement of extracellular fluid and contents.

Ø Microvilli: Increase surface area for absorption (brush border of small intestine).

Ø Flagella: Locomotion (sperm cell)

Ø Proteasome : Degrades proteins

The Chemical Basis of Life

Elements

There are 26 elements in the human body

There are 11 major elements,4 of which (C,H,O,N) make up 96%

There are 15 trace elements that make up less than 2%

Important elements of Human Body

Major elements

Oxygen , Carbon, Hydrogen, Nitrogen, Calcium, Phosphorus, Potassium, Sulphur, Sodium, Chlorine and Magnesium

Trace Elements

Iron, Copper, Zinc, Molybdenum, Iodine and Oxygen

• Necessary for cellular respiration
• Lungs -> Blood -> RBC -> Hb -> Tissue -> Cell -> Mitochondria -> Oxidative phosphorylation - > ATP (Energy)
• Oxygen derived free radicals -> Dangerous
• Treatment - Pneumonia, emphysema, RDS and some heart diseases. decompression sickness, Carbon monoxide poisoning, Gas Gangrene.

Importance of Major elements

Carbon - Component of most organic and inorganic molecules

Hydrogen - component of water and most organic molecules. Necessary for energy

Nitrogen - Component of Amino Acids, Proteins and Nucleic Acids.

Calcium - Components of bones and teeth; triggers muscles contraction.

Phosphorus - Backbone of nucleic acids, Imp for energy transfer.

Potassium - imp for nerve function.

Importance of Trace Elements

Iron - Component of haemoglobin in blood, redox reactions

Copper - Component of Many enzymes

Zinc - Component of some enzymes

Molybdenum - Component of some enzymes

Iodine - component of thyroid hormone.

Metabolism

Metabolism is the set of chemical reactions that occur in living organisms in order to maintain life.

Catabolism

Hydrolysis reactions

Break down larger food molecules in to the smaller chemicals units

Release energy.

Anabolism

Dehydration synthesis

Build larger and more complex chemical molecules from smaller subunits.

Require energy

Organic Molecules

Most Important major groups of organic substances are:

Carbohydrates

proteins

Lipids

Nucleic Acid, Nucleotides and related molecules

Carbohydrates

All contain C, H, O

Divided into 3 types characterized by the length of their carbon chains.

Monosaccharides (Simple Sugars)

•Simple sugars with short carbon chains

•Six carbon sugar – hexose

•Five carbon sugar – pentose

•Most imp simple sugar – Glucose is primary source of chemical energy)

•Pentose – ribose and deoxy ribose are structural component of RNA and DNA

Disaccheride (Double sugars)

Polysaccharides (Complex Sugars)

•Sucrose , maltose and lactose are disaccharides

•Glycogen is a polymer of glucose – polysaccharide

Proteins

• Structural proteins – form structure of cell. Tissues and organ

• Functional proteins – ex: enzymes

• Proteins are chain like polymers made up of multiple subunits or building blocks called amino acids.

Amino Acids

Proteins are made up of 20 commonly occurring amino acids 8 are essential amino acids cannot be produced by the body 12 are non-essential amino acids It consists of An amino group.

A carboxyl group

A hydrogen atom

A side chain (R)

•OH from the carboxyl group of one amino acid and H from the amino group of another amino acid split off to form water plus a new compound called a peptide.

•Proteins are polypeptides.

Level of proteins structure

Four levels of increasing complexity

- Primary

- Secondary

- Tertiary

- Quartnary

Classification of Proteins According to biological function

Structural V/S Functional

•

• Loses its shape – lose its function
• Sensitive to various environmental factors including high temperature, low or high pH and high ionic strength
• If chemical environment is restored, proteins may be renatured and function normally.

Denaturation

•Proteins can also be broken apart by enzymes, called proteases, that digest the covalent peptide bonds between amino acids that are responsible for the primary structure. This process is called proteolysis and is irreversible. Cells contain proteases that are found in lysosomes, membrane bound organelles inside the cell. When cells are disrupted, lysosomes break and release these proteases, which can damage the other proteins in the cell.

Lipids

All Lipids are hydrophobic

Tryglycerides / Fat

Most abundant lipids

Most concentrated source of energy

2 types of building blocks

Glycerol and fatty acids

Each glycerol unit is joined to three fatty acids.

Types of Fatty Acids

•Saturated and unsaturated

• Saturated – all available bonds of its hydrocarbon chain are filled with hydrogen atoms

• Unsaturated – one or more double bonds in its hydrocarbon chain because not all the chain;s carbon atoms are saturated with hydrogen atoms.

Figure

Saturated – straight, pack closely together and are solid at room temperature

•Unsaturated – more double bonds-more unsaturated. They are liquid at room temperature.

Phospholipids

Similar to triglycerides

One of the three fatty acids attached to glycerol in a triglyceride is replaced by another type of chemical structure cantoning phosphorus and nitrogen.

Figure

•The cell membrane is composed of two layers, each composed of trillions of Phospholipid molecules oriented in a special manner

•The structure that surrounds each of your cells (the plasma or cell membrane) is formed from a Phospholipid bilayer. The polar heads of the phospholipids are all facing the aqueous environments of the outside, and the inside of the cell, while the non-polar tails form a fatty layer on the inside

Steroids

The general structure of cholesterol consists of two six-membered rings side-by-side and sharing one side in common, a third six-membered ring off the top corner of the right ring, and a five-membered ring attached to the right side of that. The central core of this molecule, consisting of four fused rings, is shared by all steroids, including estrogen (estradiol), progesterone, corticosteroids such as cortisol (cortisone), aldosterone, testosterone, and Vitamin D.

Prostaglendins

Also called tissue hormones

•Lipids composed of 20 – carbon unsaturated fatty acids that contain a 5 –carbon ring

Figure

Functions of Lipids

Nucleic Acid

DNA - Adenine and Guanine – purines – double ring structures

Thymine and Cytosine – pyrimidines – single ring structures

RNA - similar except Uracil

DNA

•Double helix

•Phosphate – sugar : outside

•Bases : inside

•Bases of two chains join by hydrogen bond - Base pair

•Base pair sequence is unique in each individual

•DNA – master molecule – that stores information of all genes.

•

RNA

•Mostly single stranded

•Each strand is sequence of ribonucleotides copied from DNA.

Nucleotides - ATP

•Composed of

– Adenosine

• Ribose

• Adenine – nitrogen containing molecule

– Three phosphate subunits

•High energy bonds present between phosphate groups

•Cleavage of bonds release energy

Nucleotides

•NAD & FAD

– Used as coenzymes to transfer energy- carrying molecules from one chemical pathway to another

•cAMP

– Made from ATP by removing two phosphate groups to form a monophosphate

– Used as an intracellular signal

Combined Forms

• Lipoproteins - lipid + proteins

• Glycoproteins – carbohydrates + proteins