Cells Unit 4

Levels of Organization 1. Organism - entire living being 2. Organ System - group of organs working together 3. Organ - tissues working together 4. Tissue - group of cells working together to perform a common function 5. Cell – basic unit of life

Development of the Cell Theory  Early 1600s – Invention of the light microscope  This allowed people to see life at a microscopic level!  1665: Hooke: looked at cork (a plant) under a microscope and called the boxes he saw “cells”  1683: Leeuwenhoek: made a better light microscope that magnifies up to 200X. First to observe small single-celled organisms.  1838: Schleiden: Plants are made of cells  1839: Schwann: Animals are made of cells  1858: Virchow: Cells come from pre-existing cells

Better Technology = Better Understandings Development of better technology like electron and scanning microscopes show more detail so we can observe parts of the cells and cellular processes.

The Cell Theory 1. All living things are composed of one or more cells. 2. Cells are the basic units of structure and function of living things. 3. New cells arise from pre-existing cells.

Basic Cell Types Scientists group cells into two categories:  Prokaryotic – simpler and smaller cells  No nucleus or other membrane-bound organelles  Bacteria and Archaea, which are unicellular  Eukaryotic – larger and more complex cells  Contain nucleus and membrane-bound organelles  Mostly multicellular (fungi, plants, animals). Some unicellular (protists)

Cell Specialization  All cells perform basic functions, but the cells in a multicellular organism are specialized to perform a specific function.  Ex) Heart cells, Muscle cells, Skin cells, Brain cells, Lung cells, etc.  The first cells are stem cells, which have the potential to become any type of cell. Then groups of cells develop differently in a process called cell differentiation.  Different cell types have different structures and perform different activities. This is mainly because they express a different set of genes to make different proteins.

Cell Organelles Nucleus Contains DNA, site where RNA is made Nucleolus – dark region where ribosomes are assembled. Mitochondria Site of cell respiration (breaks down glucose and produces ATP, which is usable energy for the cell)

Organelles RibosomeSite of protein synthesis (production) Endoplasmic Reticulum (Rough or Smooth) Transports materials through the cell. The rough ER has ribosomes. Golgi Body / Golgi Apparatus Site where cell products are packaged for export

Organelles LysosomeContains digestive enzymes to break down waste VacuoleStorage of food, water, or wastes. Plants have 1 central vacuole for water, animals have many small vacuoles. Chloroplasts (plant only) Site of photosynthesis (uses sun’s energy to make glucose)

Organelles CytoplasmFluid inside the cell that contains organelles and is the site of many reactions Cell (Plasma) membraneControls what enters and leaves the cell. Made of phospholipid bilayer. Cell wall (plants only) Provides support (for plant cells) CytoskeletonHelps maintain cell shape (made of microfilaments and microtubules)

Structures for Cell Movement CiliaMany short hair-like projections that draw materials in towards cell FlagellaLong whip-like tail that moves cell through surroundings PseudopodiaTemporary extension of cytoplasm that allows cell to drag itself in one direction

Origin of Eukaryotic Organelles  The Endosymbiotic Theory explains that the mitochondria and chloroplast were at first independent bacteria, which were engulfed in a prokaryotic cell millions of years ago.  This ancestor of eukaryotes continued to replicate these now organelles when it divided.  Evidence: Mitochondria and chloroplast both have double membranes AND their own DNA.

Plant vs. Animal Cells Plant Cells  Cell wall  Have chloroplasts  One central vacuole  Fixed, rectangular shape Animal Cells  No cell wall  Many small vacuoles  Contain centrioles for cell division  Irregular shapes Both eukaryotic cells!

Plant vs. Animal Cells Foldable  Draw and Label organelles  On the inside, list name and function of –  Shared organelles in the middle  Plant only organelles on the left  Animal only organelles on the right

BOTH  Cell Wall  Chloroplast  Central Vacuole  Small Vacuoles  (No cell wall)  (No chloroplast)  Cell Membrane  Nucleus  Mitochondria  Ribosome  Endoplasmic Reticulum (ER)  Golgi Body  Lysosome  Cytoplasm Plant ONLY Animal ONLY

Review – Label each organelle

The Light Microscope Unit 4

Light Microscopes Light passes through lenses to produce an enlarged image of a specimen.

Magnification v. Resolution  Magnification: ability to make an object appear larger (“zoom” in)  Resolution: how clear the image is To calculate the total magnification:  Eyepiece: magnifies specimen 10x by itself  Objectives : 4x, 10x, 20x, 40x, 100x  Total Magnification: Eyepiece x Objective  Ex) total magnification of 40x objective is 10x40 = 400x

Parts of the Microscope  Parts  A. Eyepiece  B. Objective (lens)  C. Stage  D. Course Adjustment  E. Fine Adjustment  F. Arm or Neck  G. Light source  H. Base

The Cell Membrane and Cell Transport Unit 4

The Plasma Membrane  All prokaryotic and eukaryotic cells are surrounded by a plasma membrane.  Thin, flexible boundary that regulates what enters and leaves the cell  Key to maintaining homeostasis & cell communication.  Selective permeability: membrane allows some substances to pass through while keeping others out

Structure of the Plasma Membrane Phospholipid Bilayer: two layers of phospholipids arranged tail-to-tail

Polar Heads Hydrophilic = Loves water Fatty Acid Tails: Hydrophobic = Afraid of water Phospholipids Cell’s environment is mostly water! Hydrophobic tails are repelled by this water and arrange themselves in a double layer.

Other components of Plasma Membrane 1. Transport Proteins: allow specific molecules through 2. Cholesterol: stabilizes the membrane 3. Carbohydrates: important for cell recognition The Fluid-Mosaic Model: Phospholipids create a “sea” in which the other molecules can float Fluidity Animation

Cell Transport  Movement of materials in and out of cell.  Concentration gradient – the difference in concentration inside the cell vs. outside.  Materials can move down concentration gradient (from high to low) on their own (passive transport).  Cells must use energy to move materials from areas of low concentration to high (active transport).

Passive Transport  Does NOT require energy to move molecules from areas of HIGH concentration  LOW  Diffusion  Facilitated Diffusion  Osmosis

Types of Passive Transport 1.Diffusion: substances move from an area of higher to lower concentration. 2.Facilitated diffusion: larger substances are moved from high to low with the assistance of a transport protein (still no energy used!) 3.Osmosis: movement of water through a semi- permeable membrane  Small, neutral molecules can move straight through membrane phospholipids – oxygen, carbon dioxide  Large or charged molecules must go through protein channels – glucose, amino acids

Dynamic Equilibrium o Through passive transport, molecules will reach equilibrium where the concentration inside is the same as outside the cell o Dynamic Equilibrium: molecules continue to move back and forth equally but there is no net change in concentration.

Active Transport  Active transport: movement of solid or liquid particles in and out of a cell that requires input of energy (ATP).  Move large particles and remove wastes.  Move materials against concentration gradient (low  high concentration).

Types of Active Transport 1.Protein pump: membrane protein uses energy to move materials (from low to high) 2.Endocytosis: membrane pinches in to take particles into the cell  Pinocytosis: liquids in  Phagocytosis: solids in 3.Exocytosis: particles surrounded by membrane are moved out of cell

Cell Transport Summary Osmosis (Water)

How Osmosis Works Click for animation

Passive Transport Review Animation

Solutions  Most membranes are permeable to water, but not permeable to many solutes.  Solvent – Dissolving agent (ex. Water)  Solute – Substance that is dissolved (ex. Kool aid mix)  If the concentration of solutes is different on the inside and outside of a cell, water will move across the membrane to equalize the concentrations.

Hypertonic Solutions: contain a high concentration of solute. When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrink. Hypotonic Solutions: contain a low concentration of solute. When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell. Isotonic Solutions: contain the same concentration of solute as the cell. When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds body cells is isotonic.

Turgor Pressure Water pushing out on the plant cell wall – helps give plants their shape. This is why plants wilt if they don’t get enough water

What type of solution are these cells in? A CB HypertonicIsotonicHypotonic

Surface Area to Volume Ratio  As cells increase in size, surface area to volume ratios decrease. This makes cells unable to obtain nutrients or remove wastes (bigger cells = less efficient).  To increase surface to volume ratio, cells divide to stay small or change shape in order to increase surface area or reduce volume (smaller cells = more efficient). *Small cell = LARGE surface area to vol. ratio *Large cell = SMALL surface area to volume ratio

Three Types of Solutions 90% H 2 O 10% solute 95% H 2 O 5% solute 85% H 2 O 15% solute 90% H 2 O 10% solute 90% H 2 O 10% solute 90% H 2 O 10% solute Isotonic (no net movement of water) HypotonicHypertonic