Biology Unit 4: Cell Structure & Function *This presentation contains copyrighted material.

Discovery of Cells 1600’s Robert Hooke 1820’s: Rene Dutrochet 1830’s: Robert Brown Matthias Schleiden Theodore Schwann Rudulph Virchow Discovery of light microscope Named box-like structures in cork “cells” Cells are found in various parts of organisms All cells have a nucleus All plants are composed of cells All animals are composed of cells All cells come from living cells

Cell Theory Three parts: All living things are made of cells The cell is the basic unit of structure and function in living things All cells come from existing cells

Unicellular Organisms Cell is the organism In terms of numbers > dominate life on Earth YeastVolvox aureus Euglena Chlamydomonas

Multicellular Organisms Made up of many cells Great variety of organisms All depend on specialized cells –Cells develop in different ways to perform different tasks –Ex: Red blood cells transport oxygen throughout body Red blood cells

Multicellular Organisms (cont.) Levels of organization Cell - Ex: muscle cell Tissue - group of similar cells perform a particular function –Ex: muscle tissue Organ - group of tissues that work together –Ex: stomach Organ system - group of organs that work together to perform specific function –Ex: digestive system

Smooth muscle tissue Muscle cell Stomach Digestive System

Types of Cells Eukaryotic –Genetic material contained in nucleus –Plants, animals, fungi and protists Prokaryotic –Genetic material NOT contained in nucleus (*No nucleus*) –Bacteria

The Eukaryotic Cell

Cell Structure Like a factory Two major parts: cytoplasm & nucleus Organelles (“little organs”) –Act like specialized organs –Some structures developed from early prokaryotes Ex: mitochondria & chloroplasts

Cytoplasm Gelatin-like material inside the cell membrane, outside the nucleus Contains organelles Site of most cell activity –Factory floor where products are assembled, finished & shipped

Nucleus Control center of the cell > boss or CEO –Responsible for overall function of factory Determines what proteins will be made Contains hereditary information > DNA

Nucleolus Small, dense region of nucleus Assembly of ribosomes begins here

Nuclear Envelope Membrane around nucleus only Has small pores that allow information and ribosomes to move in and out of nucleus

Ribosomes Responsible for assembling proteins –Workers on assembly line in factory –Responds to orders from boss > nucleus Located throughout cytoplasm

Endoplasmic Reticulum Site where lipid components of cell membrane are assembled –Also assembles proteins exported from cell –Assembly line in factory Two types: –Rough ER - appears bumpy due to ribosomes on surface –Smooth ER - No ribosomes

Endoplasmic Reticulum

Golgi Apparatus Prepares proteins and other materials for storage or use outside cell Like finishing & packing department in factory –Finishing touches put on before ready to leave factory –Sorted & stored or shipped outside of cell

Lysosomes Small organelles filled with enzymes Maintenance crew for factory Break down carbs, lipids & proteins for use by cell Remove “junk” - waste and dead material found in cell

Vacuoles Saclike structures that store nutrients –water, salts, proteins & carbs Storage rooms of factory

Mitochondria Convert nutrients in food into energy for cell use –Local power plant for factory –Source of energy

Chloroplasts Capture energy from sunlight and convert it into chemical energy > photosynthesis –Solar power source for factory Only in plant cells –Chlorophyll > chemical that causes plant cells to be green

Cytoskeleton Network of protein fibers that helps cell maintain its shape –Microtubules and microfilaments –Support structure of factory (beams & columns that support walls & roof) Also used to move cell membrane

Cell Membrane Phospholipid bilayer Regulates what enters & leaves the cell –Like gate into the factory Provides protection & support –Gives the cell its shape

Cell Wall Outside cell membrane Provides protection & support Present in plants, algae, fungi and many prokaryotes *Never in animal cells Plant Cell

Cell Wall (algae)

Cell Wall (bacteria > prokaryote)

Movement Across Cell Boundaries

Diffusion Molecules spread into available space –across membrane –from area of higher concentration to area of lower concentration –without use of energy > passive transport Equilibrium - when concentration is same throughout a system

hill.com/sites/ /student_vie w0/chapter2/animation__how_diffusion _works.html

Osmosis Diffusion of water through a selectively permeable membrane –Membrane allows only certain substances to pass through –Type of diffusion - does not require use of energy > passive transport

How Osmosis Works Isotonic - “same strength” –Same concentration on both sides Hypertonic - “above strength” –Higher concentration outside cell –Water leaves, cells shrink Hypotonic - “below strength” –Lower concentration outside cell –Water comes in, cells swell

hill.com/sites/ /student_vie w0/chapter2/animation__how_osmosis_ works.html

Facilitated Diffusion Movement of specific molecules across membranes through transport proteins –Could not cross without them –Does not require use of energy > passive transport

hill.com/sites/ /student_vie w0/chapter2/animation__how_facilitate d_diffusion_works.html

Active Transport Cells move materials in direction opposite diffusion –Against concentration difference (gradient) Requires energy Small molecules or ions (K, Ca, Na) carried by transport proteins or “pumps” in membrane

Active Transport (cont.) Larger molecules & clumps of material transported by: Endocytosis - movement of materials into cell through vesicles (pockets) of cell membrane –Phagocytosis- “cell eating” –Pinocytosis- “cell drinking” Exocytosis - movement of materials out of cell through vesicles