Cell Structures Movement & Organelles

Diffusion  Movement of molecules from an area of high concentration to an area of low concentration  Move to the lower concentration

Osmosis  Diffusion of water

Osmotic Conditions  Hypertonic Solution - contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel  Hypotonic Solution - contain a low concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode.  Isotonic Solution – solution where parts are equal in solute and solvent – water moves across the membrane freely 

Cell Membrane  1. regulates the flow of materials in & out of the cell  2. selectively permeable – only certain materials pass thru  3. made up of bilayer of phospholipids with protein molecules jutting thru the layers

Cell Wall  Prokaryotic Cell Wall  Some have a 2 nd outer layer composed of lipoproteins and lipopolysaccharides  Eukaryotic Cell Wall  3 parts – primary, middle lamella and secondary cell wall  Primary cell wall – cellulose  Middle Lamella – polysaccharides = pectins  Secondary cell wall – cellulose and lignin

Cell Wall  Eukaryotic Cell Wall Prokaryotic Cell Wall

Movement Through Membrane  Simple Diffusion  Molecules pass thru phospholipids in the membrane  Only occurs for small non-polar molecules

Movement Through Membrane  Passive Transport  1. Protein channels  A. Proteins can form tunnels thru which molecules can diffuse  B. Polar molecules can travel thru

Movement Through Membrane  2. Facilitated Diffusion  A. Carrier proteins bond to a molecule on one side of the membrane, travel across and releases it on the other side.  B. Carrier proteins bond with specific molecules (like enzymes do)

Movement Through Membrane  Active Transport  Works against a concentration gradient  Requires an input of energy  Contractile Vacuole is an example – it forces excess water out of the cell even if it is against osmosis  online/library/biology107/bi107vc/fa99/terry/images/ATPpumA.gif online/library/biology107/bi107vc/fa99/terry/images/ATPpumA.gif online/library/biology107/bi107vc/fa99/terry/images/ATPpumA.gif

Organelles  Vacuoles – sacs in cell which hold food, water, and enzymes  Vessicles – small vacuoles formed from part of Golgi bodies to hold proteins  Lysosomes – sac contains digestive enzymes to break down food or damaged organelles

Vacuoles and Vessicles  VacuoleVessicle

Organelles  Nucleus – contains cell’s DNA, controls proteins and their production  “Cell’s brain”  Surrounded by nuclear membrane which has pores to allow RNA to pass thru into the endoplasmic reticulum  Nucleolus – inside nucleus, makes ribosomes  Usually each nucleus has several nucleoli

Nucleus

Organelles  Ribosomes  Tiny structure responsible for protein production  Has its own ribosomal RNA  Located in the endoplasmic reticulum

Endoplasmic Reticulum (ER)  Network of tunnels running from nucleus to Golgi bodies  Rough ER contains ribosomes, Smooth ER does not  Function: carry proteins to the Golgi bodies and make new cell membrane

Endoplasmic Reticulum (ER)

Golgi Bodies  Stacks of membranous pouches at the end of the ER  Receive proteins from ER and send them to other organelles by putting them in vessicles

Mitochondria  Where cellular respiration occurs  Eukaryotes have thousands in their cells  Inner folded membrane (cristae) where respiration occurs  Have their own DNA and can replicate themselves

Mitochondria

Cytoskeleton  Network of protein fibers allow the cell to change its shape – four types  1. microtubules- involved in cell reproduction  2. intermediate filaments – strength/shape  3. microfilaments – cell locomotion  4. microtrabeculae  – connect organelles

Plastids (only found in plants)  Chloroplasts  green due to chlorophyll  Have grana and thykaloids  Photosynthesis occurs in thykaloids

Plastids (only found in plants)  Chromoplasts  Are like chloroplasts but not green  Allow photosynthesis to occur in different lighting conditions

Plastids (only found in plants)  Leucoplasts  Colorless, have no pigments  Stores starch proteins and lipids  Releases them when the cell needs them

Unicellular Movement  Cilia  Tiny hairs on outside of cell membrane used for locomotion

Unicellular Movement  Flagella  Large hair on outside of cell membrane used for locomotion  Both are composed of microtubules

Unicellular Movement  Psudopodia – not truly an organelle  Extension of the cytoplasm which the rest of the cytoplasm flows to  Used for movement  Surrounds and captures prey