CHAPTER - 7 CELLS

7.1 Life is Cellular Mid 1600’s –using simple microscopes Section Outline The History of Cell Theory Mid 1600’s –using simple microscopes Robert Hooke looked at a slice of cork and he observed “cells.” Anton van Leewuenhoek observed living things in pond water

Cell Theory All living things are composed of cells. Cells are the basic unit of structure and function in organisms. New cells are produced from existing cells.

All cells have in common… They are surrounded by a barrier – cell membrane They contain DNA – carries biological information

Two Basic Cell Types                                                                                                                                                                                                                                                          Prokaryotic Eukaryotic

Two Basic Cell Types (cont.) Prokaryotic In general are smaller and more simple Have genetic material that is not contained in a nucleus (nucleiod region) Example – Bacteria “Pro” = before, karyon = kernel prokaryotes evolved before nuclei developed

Two Basic Cell Types (cont.) Eukaryotic Generally larger and more complex Contain a nucleus in which genetic material is separated from the rest of the cell Contain dozens of structures with internal membranes – membrane bound organelles

Eukaryotic Cells Cont. All multicellular organisms are made up of eukaryotic cells. Animals contain Eukaryotic cells.

Cell size typical 5-50 micrometers Cell membrane Cytoplasm Prokaryotic Cell Nucleus Eukaryotic Cell Organelles

Both - ribosomes

Eukaryotic Cell Structure Cell Membrane Serves as a boundary between cell and external environment Flexibility – to vary shape Controls movement of substances in and out of cell Maintains chemical balance

The Structure of Cell Membranes Outside of cell Inside (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains

Eukaryotic Cell Structure (cont.) Cell wall Boundary outside the cell membrane Thicker & inflexible Who has cell walls? Plants, fungi, and most bacteria Plants have cellulose for support – fiber in our diet Fungi have cell walls of chitin

Eukaryotic Cell Structure (cont.) Nucleus The “Brain of the Cell” Contains Hereditary Material(DNA) DNA gives instructions for making proteins Chromatin: tangles of long DNA strands; form chromosomes during cell division. Nucleolus – produces ribosomes which assemble enzymes and other proteins

Eukaryotic Cell Structure (cont.) Cytoplasm Clear/jelly-like material Lies outside the nucleus and surrounds organelles.

Eukaryotic Cell Structure (cont.) Ribosomes Makes (synthesizes) proteins. Bound = attached to the ER Free = floats in the cytoplasm

Eukaryotic Cell Structure (cont.) Endoplasmic reticulum (ER) System of internal membranes that move proteins and other substances through the cell. Membrane of the ER is connected to the outer membrane of the Nucleus Some coated with ribosomes – “rough” ER Proteins are made = pinch off to form a vesicle around the protein.

Eukaryotic Cell Structure (cont.) Golgi Apparatus A series of flattened, membrane-bound sacs. Receive protein and lipids from vesicles from the ER. Processes, packages, and distributes substances to the cell membrane and other organelles. Modifies proteins and repackages them in new vesicles for new destinations.

Eukaryotic Cell Structures Lysosomes Contains specific enzymes to digest molecules, food particles, & old organelles. It’s membrane prevents it from destroying the cell’s proteins.

Eukaryotic Cell Structure (cont.) Vacuoles A sac of fluid surrounded by a membrane Stores food, enzymes, waste material and other materials needed by the cell. Stores and pumps excess water out of plants. The central vacuole is very large in plants!

Eukaryotic Cell Structure (cont.) Mitochondria Organelles that break down food to generate ATP (energy) “Powerhouse” of the cell. ATP = cellular energy Have a highly folded inner membrane - provides a large surface area in a small space.

Mitochondria

Eukaryotic Cell Structure (cont.) Chloroplasts Site of photosynthesis. Transforms light into useable chemical energy and stores them as food molecules (sugars and starches) Chlorophyll – is a green pigment that traps energy from the sun and gives plants their green color.

Chlorophyll

Eukaryotic Cell Structure (cont.) Cytoskeleton Contains tiny rods and filaments that form a cell framework. Composed of microtubules and microfilaments.

Cytoskeleton Figure 7-11 Cytoskeleton Cell membrane Endoplasmic reticulum Microtubule Microfilament Ribosomes Mitochondrion

Eukaryotic Cell Structures (cont.) Cilia – short numerous hair-like projections of the plasma membrane. Flagella – longer whip-like structures.

Plant Cell Figure 7-5 Plant and Animal Cells Section 7-2 Nuclear envelope Ribosome (attached) (free) Smooth endoplasmic reticulum Nucleus Rough endoplasmic reticulum Nucleolus Golgi apparatus Mitochondrion Cell wall Cell Membrane Chloroplast Vacuole

Animal Cell Figure 7-5 Plant and Animal Cells (attached) Ribosome Centrioles Nucleolus Nucleus Nuclear envelope Rough endoplasmic reticulum Golgi apparatus Smooth Mitochondrion Cell Membrane Ribosome (free) (attached)

Levels of Organization Plants & Animals have many highly specialized cells that are arranged. Cells  Tissues  Organs  Organ systems

Levels of Organization Muscle cell Smooth muscle tissue Stomach Digestive system