Cellular Structure SOL BIO 4.a-c

Cell Theory The cell theory is the unifying theme in biology because it emphasizes the similarity of all living things. All organisms are composed of one or more cells. Cells are the smallest living units of all living organisms. Cells arise only by division of a previously existing cell.

Cell Characteristics Cells contain specialized structures to perform functions necessary for life. Cellular activities necessary for life include chemical reactions that facilitate: acquiring energy reproduction adaptation maintaining homeostasis

Cell Characteristics All cells contain: Genetic material single circular molecule of DNA in prokaryotes double helix located in nucleus in eukaryotes Cytoplasm jelly-like substance that fills the cells interior Plasma membrane encloses the cell – phospholipid bilayer Phospholipids Membrane proteins

Cell Types Cell structure is one of the ways in which organisms differ from each other. 2 Types of Cells Prokaryote Eukaryote

Prokaryotic Cells Earth’s first cells were prokaryotes. The simplest life forms are the prokaryotes. Prokaryotic cells exist in two major forms: eubacteria and archaebacteria.

Prokaryotic Cells Prokaryotes are the Earth’s most abundant inhabitants. They can survive in a wide range of environments and obtain energy in a variety of ways.

Prokaryotic Cells Prokaryotes are cells that lack a nucleus and membrane bound organelles.

Prokaryotic Cells Some use flagellum for locomotion ALL are UNICELLULAR Bacteria and related microorganisms are prokaryotes Rotary motor

Generalized Prokaryotic Cell

Eukaryote Eukaryotes arose from prokaryotes and developed into larger more complex organisms. Eukaryotes are cells that contain a nucleus and organelles surrounded by a membrane, such as mitochondria and chloroplasts.

Eukaryote Can be both unicellular or multi-cellular Examples of eukaryotes are: All fungus, plant, and animal cells

Generalized Eukaryotic Cell

Cell Size Most cells are relatively small because as size increases, volume increases much more rapidly. longer diffusion time

Visualizing Cells

Plant vs. Animal Cell Cellular differences between plant and animal cells Plants have: a cell wall Chloroplast Large vacuole Animal cells do not have these structures

Endosymbiosis Heterotrophic bacteria became mitochondria. Endosymbiotic theory suggests that eukaryotes arose from a symbiotic relationship between various prokaryotes. Heterotrophic bacteria became mitochondria. Cyanobacteria became chloroplasts. Host cell was a large eukaryotic cell.

Endosymbiosis Prokaryotic cell is engulfed Eukaryotic cell Symbiosis

Cell Differentiation Cell specialization occurs during the development of a multi-cellular organism. The genetic information necessary for all cellular functions remains in each cell but may not be used.

Nucleus Stores genetic material Contains DNA site where RNA is made Nucleolus: Chromatin and ribosomal subunits Nuclear envelope: Double membrane with pores Largest organelle BRAIN of the cell – controls protein synthesis

Nucleus

Ribosomes Ribosomes are RNA-protein complexes composed of two subunits that join and attach to messenger RNA. site of protein synthesis assembled in nucleolus

Ribosomes They can be found alone in the cytoplasm or attached to the endoplasmic reticulum. Alone in cytoplasm- makes proteins for use within the cell Attached to RER- makes proteins for export out of the cell

Ribosomes

Endoplasmic reticulum transports materials through the cell Rough ER - studded with ribosomes Attached to nuclear membrane site of protein synthesis and processing Smooth ER - lacks ribosomes site of synthesis of phospholipids and the packaging of proteins into vesicles

Endoplasmic reticulum

Golgi apparatus collection of Golgi bodies Stacked flattened sacks Site where cell products are packaged for export Proteins are modified by being combined with fats or carbohydrates

Golgi apparatus Vesicles then pinch off from the Golgi body to be secreted (outside the cell) Involved in the production of lysosomes

Lysosomes vesicles produced by the Golgi apparatus. Lysosomes contain digestive enzymes and are involved in intracellular digestion of food particles, disease causing bacteria and worn out cell parts

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Vacuoles Found in PLANT and ANMAL cells The vacuole acts a container, storing water and dissolved particles Plants have a large central vacuole for water storage Unicellular animals can use contractile vacuoles for movement

Mitochondria "Powerhouse of the cell" - cellular metabolism Structure- outer and inner membranes, cristae Found in both plant and animal cells Very active cells have more mitochondria

Chloroplasts Chloroplasts are larger and more complex than mitochondria Contain green pigment called chlorophyll that absorbs sunlight in the first step of photosynthesis Found ONLY in PLANTS

Cell Membrane controls what enters and leaves the cell Found in ALL cells Phospholipid bilayer with transport proteins, and cholesterol (for flexibility)

Cell Wall provides support Found in PLANT and BACTERIA cells Made from cellulose

Cytoskeleton Long slender protein tubes and fibers that extend from the nucleus to the plasma membrane. The cytoskeleton contains three types of elements responsible for cell shape, movement within the cell, and movement of the cell: Actin filaments Microtubules Intermediate filaments

Centrioles Cylindrical structures found near the nucleus Made of hollow, tubular structures arranged in bundles Important in cell division Found ONLY in ANIMAL cells

Endoplasmic reticulum Plant vs. Animal Cells PLANT CELL ANIMAL CELL Cell membrane Mitochondria Golgi apparatus Nucleus Cytoskeleton Ribosomes Endoplasmic reticulum Lysosomes HAVE: Cell Wall LARGE vacuoles Chloroplasts DO NOT HAVE: Centrioles HAVE: Centrioles DO NOT HAVE: Cell Wall LARGE vacuoles Chloroplasts