Cell Structure & Function

Objectives Discoveries important to the cell theory State the parts of the cell theory Identify the limiting factor on cell size Describe the relationship to cell shape and function Differentiate between prokaryotic and eukaryotic cells

Cell Theory All living things are composed of cells Cells are the basic units of structure and function of an organism Cells come only from other cells

Diversity Size: limited by the ratio of volume to surface area Shape: depends on the function of the cell Internal Organization: organelles

Limits to Cell Size More demands on the cells DNA increase in volume means more materials are needed nucleus must keep up with cell’s needs volume increase places strain on the nucleus Trouble moving materials across the cell membrane materials have a long way to travel takes more time to travel farther cell needs more food and oxygen greater volume Surface area to volume ratio volume increases more rapidly than surface area surface area must allow needed materials to enter greater volume requires more materials

Prokaryotic vs. Eukaryotic Prokaryotic cells are unicellular and lack organelles and a nucleus Eukaryotic cells have membrane bound organelles and nucleus

Eukaryotic Cells

Objectives Describe the structure and function of the cell membrane Name and describe cell organelles by function Describe the function of the nucleus Differentiate between plant and animal cells

Cell Membrane Selectively Permeable – allows only substances to cross Made of phospholipids Polar heads Non-polar tails Form a bilayer (2 layers)

Membrane Proteins Cell recognition Cell transportation Sites of attachment May be peripheral or integral

Fluid Mosaic Model Membrane behaves like a fluid Proteins are free to move Like beach balls on the surface of water

Organelles

Cytoplasm – gelatin-like substance between the cell membrane and nucleus (cytosol) Mitochondria – site of energy production (ATP); two layers Outer layer – barrier Inner layer – called christae Has its own DNA Ribosomes – smallest organelle; important in protein synthesis; small bits of RNA

Endoplasmic Reticulum – shipping RER – has ribosomes attached; makes proteins for export from the cell SER – makes new parts for cell membrane Golgi Apparatus – modifies proteins; exports from cells Lysosomes – digestion and protection Cytoskeleton – shape and movement Mitrotubules – spindle fibers for cell division Microfilaments - movement

Cilia and Flagella – movement Cilia – short hair-like; many Flagella – long whip-like; 1 or 2 Nucleus – cell activities and inheritance Nuclear envelope – surrounds (membrane) Chromatin – thread-like strands of DNA Chromosomes – condensed chromatin for cell division Nucleolus – site of ribosome production

Plant Cells Cell wall – Outside the cell membrane Supports and protects Made of cellulose Vacuole – storage for enzymes and wastes Plastids – similar to mitochondria Capture light for photosynthesis (chloroplasts) Flattened sacs called thylakoids (photosynthesis)

Multicellular Organization Tissues – cells working together Organ – tissues working together Organ System – organs working together Colonial Organization – genetically identical cells living together

Cell Transportation PASSIVE Osmosis Diffusion Filtration Active Exocytosis Endocytosis  Phagocytosis  Pinocytosis  Ion Pumps Ion Pumps

DNA Deoxyribose Double Helix Nitrogenous Bases Adenine Cytosine Guanine Thymine

Protein Synthesis Replication - Transcription - Translation - DNA makes a copy of itself DNA template used to make RNA RNA moves to cytoplasm to make protein

Cell Division: Mitosis Interphase Prophase Metaphase Anaphase Telophase

Parts of a Cell Structure Plasma Membrane Ribosomes Endoplasmic Reticulum Smooth ER Rough ER Mitochondria Lysosomes Centrioles Golgi Apparatus Nucleus Cilia / Flagella Function Protection Make protein Makes lipids / carbohydrates Transports proteins Energy (ATP) Digestive enzymes Cell division Packages from ER Heredity / Metabolism Movement