Cell Structure and its function Dr Kalpana B
Cell Structure and its function Dr. Kalpana. B Assistant professor Physiology
At the end of this class students should: • Draw labelled structure of a cell • Draw the structure of cell membrane and list its functions • List the functions of various cell organelles
LEVELS OF ORGANIZATION Living Levels: 1. CELL (makes up ALL organisms) 2. TISSUE (cells working together 3. ORGAN (heart, brain, stomach …) 4. ORGAN SYSTEMS (respiratory, circulatory …) 5. ORGANISM copyright cmassengale 3
Cell Structure • Cell Membrane • Cytoplasm • Nucleus
Cell or Plasma Membrane • Composed of double layer of phospholipids and proteins-(fluid mosaic model) • Controls what enters or leaves the cell Outside of cell Proteins Carbohydrate chains Cell membrane Inside of cell (cytoplasm) Protein channel copyright cmassengale Lipid bilayer 5
• Diameter 7. 5 nm • Made up of lipids and proteins • Lipids- 20 -40% phospholipids and cholesterol • Proteins-60 -70% • Lipoproteins • Glycoproteins • carbohydrates
Phospholipids • Heads contain glycerol & phosphate and are hydrophilic (attract water) • Tails are made of fatty acids and are hydrophobic (repel water) • Make up a bilayer where tails point inward toward each other copyright cmassengale 7
Functions • Contributes to semi-permeability nature of cell membrane. • Cholesterol-contributes to fluidity of membraneflexible.
Cell Membrane Proteins • Aid in cell recognition • Peripheral proteins • Integral proteins copyright cmassengale 9
ü INTRINSIC PROTEINS – ENZYMES ü PERIPHERAL PROTEINS- CYTOSKELETON ü TRANSMEMBRANE PROTEINS CHANNELS CARRIERS PUMPS RECEPTORS
Functions of proteins • • • Structural support As channels and pores. Carrier proteins Act as enzymes Receptors Helps in transmission of impulses.
Carbohydrate layer Found in combination with lipids and proteins Functions • Forms connection for adjacent cells-membrane junctions. • Form antigens • Receptors for binding hormones
Functions of the cell membrane • • PROTECTIVE FUNCTION AS A SEMI PERMEABLE MEMBRANE ABSORPTIVE FUNCTION-ABSORBS NUTRIENTS EXCRETORY FUNCTION-EXCRETES WASTES PRODUCT. • EXCHANGE OF GASES • MAINTENANCE OF SIZE AND SHAPE OF THE CELL • Links adjacent cells together by junctional complexes –tissues.
ORGANELLS IN CYTOPLASM • Membrane-bound intracellular compartments. • Contain specific chemicals to perform specific cellular function.
ENDOPLASMIC RETICULUM • Interconnected network of tubular and vesicular structure • Forms the link between nucleus and cell membrane Two types • Rough endoplasmic reticulum • Smooth endoplasmic reticulum
Functions of RER • Contains ribosomes • Anchorage of newly synthesize proteins. Functions of the SER • synthesis of lipids, processing of sugars, and detoxification of drugs and poisons • Site of steroid synthesis • sarcoplasmic reticulum
GOLGI APPARATUS • • • Cluster of flattened membranous sacs Stores, modifies and packages proteins Forms glycoprotein Acrosome in male germ cells Molecules transported to and from the Golgi by means of vesicles
LYSOSOMES • Digest foreign molecules & damaged organelles • Contain digestive enzymes-hydrolases • Digestion and removal of worn out and dead cells of tissue(auto digestion)
MITOCHONDRIA • Surrounded by a DOUBLE membrane • Folded inner membrane called CRISTAE –enhances enzymatic reaction. • Respiratory enzymes are present in cristae. • Cristae contains matrix • Matrix contains DNA and RNA • Power plant” of the cell
The Control Organelle Nucleus • Controls the normal activities of the cell • Contains the DNA Bounded by a nuclear envelope (membrane) with pores • Usually the largest organelle copyright cmassengale 21
Nuclear Envelope • Double membrane surrounding nucleus • Also called nuclear membrane • Contains nuclear pores for materials to enter & leave nucleus • Connected to the rough ER copyright cmassengale 22
• Each cell has fixed number of chromosomes that carry genes • Genes control cell characteristics copyright cmassengale 23
Inside the Nucleus The genetic material (DNA) is found copyright cmassengale 24
PEROXISOMES Function to rid the cell of toxic substanceshydrogen peroxide
RIBOSOMES • Protein synthesis machinery. • Free floating in cytoplasm. • Bound to rough-Endoplasmic Reticulum (RER) in Eukaryotes. • Consists of multiple subunits composed of RNA-protein complexes.
CENTROSOMES • Centrosome is the cellular organelles situated near the center of the cell close to the cell • Movement of the chromosome during cell division
CYTOSKELETON • Provides shape and structure • Helps move organelles around the cell • Made of three types of filaments
• References • Text Book of medical physiology-AP Krishna • Physiology for B. Sc. Nursing –Dr A. K jain
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