Chapter 7

Cell Structure and Function

Section 7-1

The History of the Cell Theory and Microscopes

Historical View of the Cell Theory

• As science improves, so do improvements in scientific instruments, and improved scientific instruments lead to new discoveries.

1590 – Zacharias Janssen

• Built first simple microscope (one set of lenses)

1670’s Anton Van Leeuwenhoek

• Made improvements

• 270x magnification

• Saw bacteria, protozoa, sperm cells, red blood cells and yeast cells

1665 – Robert Hooke• Produced a compound microscope

• Saw hollow boxes and named them “cells”

1665 – Robert Hooke

1831 – Robert Brown• Saw central structure in plant cells,

called this structure a nucleus

1838 – Theodore Schwann

• Concluded that all animals are made of cells

1838 – Matthias Schleiden• Concluded that all plants are

made of cells

1839 – Johannes Purkinje• Stated that “the cell is the unit of

function of life”

1858 – Rudolf Virchow• Concluded that “ cells come only from

previously existing cells”

The Cell Theory1. All living things are composed of

cells

2. Cells are the basic units of structure and function

3. New cells are produced from existing cells

Section 3-2

Prokaryotes and Eukaryotes

Eukaryotes• Have a nucleus and membrane

covered organelles

Prokaryotes• Don’t have a nucleus and

membrane covered organelles

Eukaryotic Cell Structures

Plasma Membrane• Separates the cell from its

environment

• Controls the transport of materials in and out

• Allows some materials but not others to pass through this is called…–Selectively permeable

Endoplasmic Reticulum• Extensive network of tube-like

structures that forms a passageway that functions in the transport of materials throughout the cells

Ribosomes• Site of protein

synthesis

• Attached to the walls of the ER or move freely in the cytoplasm

Golgi Bodies• Stack of tiny, flattened sac-like

tubes used in secretion

• Package protein molecules in a membrane and send the package to the cells surface

Mitochondria• Where cellular respiration takes

place to release energy

• “Mighty Mitochondria”

• Powerhouse of the cell

Microtubules• Tubes that serve as support for the

cell

Microfilaments• Thin threads attached to the cell

membranes, play a role in movement

Lysosomes• Vesicles that contain enzymes

used in digestion• Fuses with food vacuoles to

digest food into smaller pieces• Digest old cell structures to

dispose of them or even entire cells

Nucleus• Regulates all the cells activities

Chromosomes• Long coiled fibers that carry the

material of heredity

• Made of protein and DNA

Nucleolus• Composed of

RNA

• Involved in the passage of RNA into the cytoplasm

Centrioles• Small cylinders in the cytoplasm

that play a role in cell division

Cilia

Flagella

Chloroplasts• Organelle found only in plants,

used to make food

Vacuoles• Spherical, bubble-like storage

sacs

• Plant cells have very large vacuoles compared to animal cells

Cell Wall• Rigid structure

that surrounds the cell membrane

• Made of cellulose

• Permits most things to pass through

Cell Wall

Section 3-3

Cellular Processes

The Big Idea• Cells need to regulate the

movement of dissolved molecules on either side of the membrane

Cell membrane• Regulates what enters and leaves the cell

and also provides protection and support

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

Cell membrane• Made of a double layered sheet called a

lipid bilayer

Outsideof cell

Insideof cell(cytoplasm)

Cellmembrane

Proteins

Proteinchannel Lipid bilayer

Carbohydratechains

Cell Wall• Provide support and protection for

cell

• Found in more than just plants

• Contrary to popular belief, not selectively permeable

Cell Walls

Diffusion Through Cell Boundaries

• One of the more important functions of the cell membrane is to regulate the movement of dissolved molecules from one side of a membrane to the other

Concentration• The mass of solute in a given

volume of solution

• Mass/volume

• What is the concentration of 12 grams of salt in 3 liters of water?

• What is the concentration of 12 grams of salt in 6 liters of water?

In a solution, particles move constantly

Diffusion• Process by which molecules of a

substance move from areas of high concentration to areas of low concentration

Diffusion

Diffusion

Equilibrium• When the concentration of the

solute is the same throughout a system

• Because diffusion depends on random particle movements, substances diffuse across membranes without energy being used

• Even during equilibrium, particles still move, but there is no net change in concentration

Osmosis• The diffusion of water

Osmosis

Isotonic• The concentration of solutes is

the same inside and outside the cell

Hypertonic• Solution has a higher solute

concentration than the cell

Hypotonic

• Solution has a lower solute concentration than the cell

Facilitated Diffusion• Movement of specific molecules across

cell membranes through protein channels

HighConcentration

LowConcentration

CellMembrane

Glucosemolecules

Proteinchannel

•Only go from high concentrations to low concentrations

•Does not require energy

Types of Active Transport

• Sometimes cells must move materials in the opposite direction–Low concentrations to high

concentrations

Active Transport• Energy requiring process that

moves materials across a cell membrane against a concentration gradient

Active TransportMolecule tobe carried

Moleculebeing carried

Energy

Molecular transport• Small molecules and ions are

actively transported

Carrier proteins• Proteins that act like pumps

Endocytosis• The process of taking material into the cell

by means of infolding of the membrane

Food particle engulfing Forms a vacuole

Phagocytosis

• Cell eating

• White blood cells do this

Pinocytosis• Cell drinking

Exocytosis• Forces contents out of the cell

• Endocytosis in reverse

Section 3-4

The Diversity of Cellular life

Unicellular Organism• Single celled

• Do everything a living organism does

Multicellular Organism• Many celled

• Depend on communication and cooperation among specialized cells

Specialization

• When cells develop in different ways to perform different tasks

Red Blood Cells• Transport

oxygen

Pancreatic Cells• Make

proteins

• Packed with ribosomes

Skeletal Muscle• Generate force

• Packed with mitochondria

• Overdeveloped cytoskeleton

Nerve Cell• Send messages

Guard Cells• Open and close the stomata

Levels of Organization

Cells Tissues Organs

Organ Systems

Tissues• Group of similar cells that perform

specific function

• Ex.) smooth muscle

Organ• Group of tissues that work

together to perform a specific function

• Ex.) stomach

Organ System• Group of organs that work together to

perform a specific function

• Ex.) digestive system

• This organization creates a division of labor that makes multicellular life possible

Biological Organization