Exploring Cell Structure and Function

Cell Structure & Function

Definitionof Cell A cell is the smallest unit that is capableof performing life functions.

Typical AnimalCell http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif

Cells cells -possessa membrane-boundnucleus -are morecomplex than prokaryoticcells -compartmentalize many cellular functions within organelles and the endomembrane system -possess a cytoskeleton for support and to maintain cellularstructure 4

Cell types Cell components: Membrane boundary Cytoplasm contains organelles Nucleus contains DNA Cells types: Prokaryotic cells: bacteria Do not have nucleus, however, have DNA 10x smaller Eukaryotic cells: Animal cells Plant cells

Two Types of Cells Prokaryotic Cells: Have no membrane covered nucleus Have no membrane - covered organelles Have circular DNA Are bacteria

Figure 3.5 prokaryotic cell This figure shows the generalized structure of a prokaryotic cell.

Two Types of Cells Eukaryotic Cells: Have a nucleus Have a membrane - covered organelles Have linear DNA Are all other cells

Eukaryotic cell Components: 1. Plasma Membrane - And a Cell wall in plants, yeast 2. Nucleus 3. Cytoplasm Organelles: Mitochondria Ribosomes Endoplasmic reticulum Golgi apparatus Lysosomes Peroxisomes Cytoskeleton Vacuoles (plants) Chloroplast (plants)

EukaryoticCells 1 0

Cells Nucleus -storesthe geneticmaterial of the cell in the formof multiple, linear chromosomes -surroundedby a nuclearenvelope composed of 2 phospholipidbilayers -in chromosomes DNA is organizedwith proteinsto formchromatin 1 1

Cells 1 2

Cells Ribosomes -the site of proteinsynthesisin the cell -composedof ribosomal RNA and proteins -found within the cytosolof the cytoplasm and attached to internalmembranes 1 3

Organic molecules of Cells Proteins Carbohydrates Lipids Nucleic acids

Proteins Most diverse and complex macromolecules in the cell Used for structure, function and information Made of linearly arranged amino acid residues

Types of Proteins 1) Enzymes catalyzes covalent bond breakage or formation 2) Structural collagen, elastin, keratin, etc. 3) Motility actin, myosin, tubulin, etc. 4) Regulatory bind to DNA to switch genes on or off 5) Storage ovalbumin, casein, etc. 6) Hormonal insulin, nerve growth factor (NGF), etc. 7) Receptors hormone and neurotransmitter receptors 8) Transport carries small molecules or irons 9) Special purpose proteins green fluorescent protein, etc.

Lipids Hydrophobic molecules Energy storage, membrane components, signal molecules Triglycerides (fat), phospholipids, waxes, sterols Carbohydrates Sugars, storage (glycogen, starch), Structural polymers (cellulose and chitin) Major substrates of energy metabolism

Nucleic Acids DNA (deoxyribonucleic acid) and RNA encode genetic information for synthesis of all proteins Building blocks of life

Ribosomes Site where proteins are made Cell parts are made of proteins Factories of the cell

Cell Structure All Cells have: an outermost plasma membrane genetic material in the formof DNA cytoplasm with ribosomes

Cell Parts Organelles

Surroundingthe Cell

1. Plasma Membrane All membranes are phospholipidbilayers with embedded proteins The outerplasma membrane isolates cell contents controls what gets in and out of the cell receives signals

Plasma membrane Components: Lipids Double layer of phospholipids and cholesterol & other lipids Proteins Carbohydrates Attached to either lipids or proteins Function Allows selective passage in & out the cell

Figure 3.8 plasma membrane The plasma membrane is a phospholipid bilayer with embedded proteins. There are other components, such as cholesterol and carbohydrates, which can be found in the membrane in addition to phospholipids and protein.

Plasma membrane functions It is a boundary of the cell with many functions: Selective permeability allow some substances in and out the cell Immunity distinguish between self and non-self Blood transfusion Organ transplant Viral/ bacterial infection Change in shape immune cells squeeze between the blood vessels cells and go to the pathogen location (skin etc.)

Membrane transport Membrane transport types: Passive Doesn t use energy Molecules are moving from high concentration to low Active Requires energy Molecules are moving from low concentration to high Done with the help of proteins called pumps

Passive transport Types of passive transport: Diffusion transport of substances (or solute when in solution) Osmosis or Diffusion of water transport of solvent molecules (water) Facilitated diffusion transport of solute with help from membrane proteins: Channels Transporters Solution = solvent + solutes

Active transport Moving molecules Against their concentration gradient; can be done only using energy (ATP). Proteins in the membrane called pumps can use ATP to push chemicals from low concentration to high concentration. Example: NA/K-pump

CellMembrane Outer membrane of cell that controls movement in and out of the cell Double layer

CellWall Most commonly found in plant cells & bacteria Supports & protects cells

Cells Structuresin all cells Nucleus Ribosomes Endomembrane System Endoplasmic reticulum smoothand rough Golgi apparatus Vesicles Mitochondria Cytoskeleton

Insidethe Cell

Cytoplasm Gel-likemixture Surroundedby cell membrane Containshereditary material

Nucleus Directs cell activities Separatedfrom cytoplasm by nuclear membrane Containsgenetic material - DNA

The Nucleus The control center of the cell Contains the Cell s DNA DNA Nucleolus Nuclear Membrane

Nuclear Membrane Surrounds nucleus Made of two layers Openings allow material to enter and leave nucleus

Nucleolus Inside nucleus Contains RNA to build proteins

Nucleus Structure Nuclearenvelope TwoPhospholipid bilayers with protein lined pores Each pore is a ring of 8 proteins with an opening in the center of the ring Nucleoplasm fluid of the nucleus

Nucleus DNA is arrangedin chromosomes Chromosome fiber of DNA with proteins attached Chromatin all of the cell sDNA and the associatedproteins

EndoplasmicReticulum Moves materials around in cell Smooth type: lacks ribosomes Rough type (pictured): ribosomes embedded in surface

Ribosomes Each cell contains thousands Make proteins Found on ribosomes & floating throughout the cell

GolgiBodies Protein 'packaging plant' Move materials within the cell Move materials out of the cell

Lysosome Digestive 'plant' for proteins, fats, and carbohydrates Transports undigested materi to cell membrane for removal Cell breaks down if lysosome structure al is disrupted.

Vacuoles Membrane-bound sacs for storage, digestion, and waste removal Contains water solution Help plants maintain shape

3. Cytoplasm with ribosomes Cytoplasm fluid area inside outer plasma membrane and outside DNA region Ribosomes make proteins

NUCLEUS CYTOSKELETON RIBOSOMES ROUGH ER MITOCHONDRION CYTOPLASM SMOOTH ER CENTRIOLES GOLGI BODY LYSOSOME PLASMA MEMBRANE VESICLE Fig. 4-15b, p.59

Nuclearpore bilayerfacingcytoplasm Nuclearenvelope bilayerfacing nucleoplasm Fig. 4-17, p.61

Structures of the Endomembrane System Endoplasmic Reticulum(ER) Continuouswith the outer membrane of the nuclear envelope Twoforms - smoothand rough Transportvesicles Golgi apparatus

Endoplasmic Reticulum (ER) The ER is continuouswith the outer membraneof the nuclearenvelope There are2 types of ER: Rough ER has ribosomes attached Smooth ER no ribosomes attached