Cell Theory -The cell is the structural and functional unit of life Human adults are made up of an estimated 100,000,000,000,000 cells Organismal activity depends on the collective activity of cells The anatomy of a cell determines its function within the body –the function of a cell is determined by: the overall shape of the cell the action of each of its organelles -subcellular structures suspended in the cytosol the different types of proteins (enzymes) that are found in the cell

Cell Diversity

The Cell and Organelles

Cellular Organelles Specialized subcellular functional units, which accomplish a specific task for the cell –Membranous organelle is bordered by a phospholipid bilayer –cell membrane –mitochondria –endoplasmic reticulum –Golgi complex –lysosomes –nucleus

–Nonmembranous NOT surrounded by a phospholipid bilayer –ribosomes –centrioles -The organelles work together

Cell (Plasma) Membrane -Organelle that defines the outer boundary of a cell Separates the intracellular fluid (ICF or cytosol) from the extracellular fluid (ECF) outside of a cell -Controls the chemical composition of the ICF –selectively controls the movement of SMALL POLAR chemicals into/out of the cell ions, monosaccharides, amino acids, nucleotides, water… Made from different macromolecules which interact with each other including: –Lipids (98%) Phospholipids (75%) Cholesterol (23%) –keeps membrane lipids in a liquid state

–Proteins –Carbohydrates

Plasma Membrane Anatomy Phospholipids are arranged in a bilayer (sandwich) Proteins, carbohydrates and cholesterol are important molecules found in plasma membrane

Phospholipids in a Bilayer The polar heads of each layer face outward towards the water molecules in the ECF and ICF The non-polar tails face inward toward each other This arrangement makes most of the thickness of the membrane NON-POLAR and creates an extremely effective barrier against the movement of polar substances into or out of the cell This membrane structure is consistent within the membranous organelles of the cell

Fluid Mosaic Model -Descriptive model for the physical state (liquid) of the cell membrane –the macromolecules of the cell membrane do not remain stationary allowed to move laterally (side to side)

Cell Membrane Proteins -Integral or transmembrane proteins –completely pass through the bilayer extracellular portion is exposed to the ECF intracellular portion is exposed to the ICF transmembrane portion made of alpha helices –different types of integral proteins based on function channels, pores, carriers, and transporters –allow the movement of polar molecules across the membrane receptors –bind to specific chemicals in the EFC and cause a change in the function of the cell

Peripheral –attached only to the intracellular surface of the cell membrane (located in the ICF) -capable of detaching and moving into the cytosol

Integral Membrane Proteins

Peripheral Membrane Proteins

Membrane Carbohydrates -The small polysaccharides that are part of the plasma membrane are always immersed in the ECF –covalently bound to an integral membrane protein or a phospholipid head 2 varieties –Glycolipids polysaccharides are covalently bound to the polar head of a phospholipid –Glycoproteins polysaccharides are covalently bound the extracellular portion of an integral membrane protein

Ribosomes -Synthesize all proteins in the body Made of: –protein –ribosomal RNA Move within the cell between 2 locations –Free ribosomes are located in the cytosol synthesize proteins that remain inside the cell -Membrane-bound ribosomes are temporarily associated with the endoplasmic reticulum synthesize: –integral membrane proteins –secreted proteins –move out of the cell into the ECF

Nucleus Largest organelle of a cell –only intracellular organelle visible with a compound light microscope (plasma membrane is also visible) Control center of the cell –contains the “genetic library” encoded in the sequences of nucleotides in molecules of DNA code for the amino acid sequences of all proteins determines which specific proteins are to be made in a particular cell type –determines the function of that cell

Consists of 3 parts: –nuclear envelope –chromatin –nucleolus Some cells are anuclear (no nuclei) and some are multinucleated

Electron Micrographs of the Nucleus

Nuclear Structure Nuclear envelope –double membrane structure containing nuclear pores -controls the movement of substances into or out of the nucleus Chromatin –molecules of DNA Nucleolus –dark-staining spherical body within the nucleus –location of ribosome production

Mitochondria Double membrane organelle which functions to synthesize ATP for the cell -Outer membrane faces the cytoplasm –Inner membrane contains many folds called cristae increases surface area to maximize ATP synthesis - Intermembrane space is the fluid filled area between the 2 membranes -the matrix is the fluid filled area in the center of the mitochondria

Mitochondria

Endoplasmic Reticulum (ER) Membranous “network within cytoplasm” –interconnected tubes of membranes –space within the tube is called the cisterna Two varieties –rough ER has ribosomes located on its membrane –smooth ER does not have ribosomes on its membrane

- ER may be used for storage or transport

ER Smooth ER –Storage site of intracellular calcium (Ca 2+ ) required for the functioning of the: Nervous system Muscular system Endocrine system –Location of enzymes (in cisterna) which: synthesize lipids –steroids –phospholipids detoxify drugs/toxins

Rough ER –proteins that are synthesized in the cisterna of rough ER are transported to the Golgi complex for modification Golgi Complex -Layers of flattened membranous sacs -Modifies proteins synthesized at the rough ER –addition of carbohydrates to make glycoproteins –the removal of some amino acids makes proteins biologically active -Following modification, the proteins are transported to the plasma membrane

Golgi Apparatus

ER, Golgi Complex and Plasma Membrane

Lysosomes Spherical membranous bags containing hydrolytic (digestive) enzymes -hydrolyze bacteria and viruses that infect a cell –hydrolyze old, worn out organelles allows cells to “recycle” the macromolecules that make up organelles

The Cell and Organelles