Cells are small so they can exchange materials with their surroundings. Because cells interact with their environment through the plasma membrane, it is necessary to have a small surface area / volume ratio.
Prokaryotic Cells Are Simple Compared To Eukaryotic Cells: Prokaryotic cells do not contain membrane bounded organelles.
Specific to animal cells Eukaryotic cells contain membrane bounded organelles that carry out specialized functions.
Specific to plant cells Eukaryotic cells contain membrane bounded organelles that carry out specialized functions.
-Bounded by two phospholipid bilayers (nuclear envelope). -Nuclear pores are scattered over the surface (proteins in : RNA out). -Nucleolus is the region of intensive ribosomal RNA synthesis. The nucleus is the information center of the cell and contains our hereditary information.
Chromosomes: Packaging the DNA DNA of eukaryotes is divided into several linear chromosomes. When cells are not dividing, chromosomes are fully extended in thin threadlike strands called chromatin. Chromosomes are only visible when tightly coiled (around histones) during cellular division.
A system of membranous channels and saccules. Rough ER: -site of protein synthesis and processing. -studded with ribosomes Smooth ER: -lacks ribosomes -site of phospholipid synthesis and the packaging of proteins into vesicles sent to the Golgi apparatus Endomembrane System
- Delivery System for the Cell The Golgi Apparatus functions in the collection, packaging, and distribution of molecules synthesized at one part of the cell and utilized at another location.
Proteins made in the Rough ER are packaged in the Smooth ER and sent to the Golgi Apparatus in a vesicle for further processing and distribution
Lysosomes are packages of enzymes used to digest phagocytized food particles or to breakdown old organelles.
Other enzyme-bearing, membrane enclosed vesicles found in eukaryotes are called microbodies. Some examples are glycoxysomes and peroxisomes.
-Site of protein synthesis -Made of ribosomal RNA and protein -Consists of a large and a small subunit
Energy-Related Organelles The two energy-related organelles of eukaryotes are chloroplasts (photosynthesis) and mitochondria (respiration).
Chloroplasts Not found in animal cells Site of photosynthesis
Chloroplast structure Bound by two membranes enclosing a fluid- filled stroma that contains enzymes. Membranes inside the stroma are organized into thylakoids that house chlorophyll. Chlorophyll absorbs solar energy used for photosynthesis
Solar energy + carbon dioxide + water carbohydrate + oxygen Photosynthesis (chloroplasts)
Mitochondria Mitochondria are found in plant and animal cells.
Mitochondrion structure Mitochondria are bounded by a double membrane surrounding fluid- filled matrix. The inner membranes of mitochondria are cristae. The matrix contains enzymes that break down carbohydrates and the cristae house protein complexes that produce ATP.
solar energy + carbon dioxide + water carbohydrate + oxygen Photosynthesis (chloroplasts) Respiration (mitochondria) carbon dioxide + water + energy (ATP)
The Cytoskeleton The eukaryotic cytoskeleton is a network of filaments and tubules. The cytoskeleton contains three types of elements responsible for cell shape, movement within the cell, and movement of the cell.
Actin filaments occur in bundles or mesh-like networks. Each actin filament is composed of two protein chains loosely twined together Are responsible for interior cellular movements and cellular extensions.
Microtubles are small hollow cylinders made of the globular protein tubulin. Microtubules help maintain the shape of the cell and act as tracks along which organelles can move.
Intermediate filaments are ropelike assemblies of fibrous polypeptides that support the plasma membrane and nuclear envelope.
Actin Filaments, Microtubules, and Intermediate Tubules: -maintain cell shape -allow organelles to move within the cytoplasm -sometimes involved in cell movement
Centrioles Are the major microtubule organizing center for the cell, cilia, and flagella. Help assemble microtubules in the cell (microtubule-organizing centers; MTOC) Only found in animal cells
Cell Movement Cells exist in a gel – sol state. Cells can crawl by the formation of a pseudopod. Arrangement of actin filaments allows a cell to ‘crawl’
Cilia and flagella Cilia (small and numerous) and flagella (large and single) are involved in cell movement. 9 + 2 structure
Special Things About Plant Cells The central vacuole serve’s as a central storage compartment (water, sugars, ions and pigments). -not found in animal cells Cell Wall - protects and supports the plant cell. Primary and secondary walls, middle lamella -not found in animal cells
Evolution of the Eukaryotic Cell Endosymbiotic hypothesis: eukaryotes arose from a symbiotic relationship between various prokaryotes. -Heterotrophic bacteria became mitochondria. -Cyanobacteria became chloroplasts. -Host cell was a large eukaryotic cell.