1Organisms and Cells

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50 m 140 m

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

a: © Geoff Bryant/Photo Researchers, Inc.; b: Courtesy Ray F. Evert/University of Wisconsin Madison;c: © Barbara J. Miller/Biological Photo Service; d: Courtesy O. Sabatakou and E. Xylouri-Frangiadak

Multicellular organisms are arranged from simple to complex according to their level of cellular grouping.

cell tissue

organ organ system

organism

The Levels of Organization

Cells

Smallest living unit Most are microscopic

Cells have 3 main jobs make energy

need energy for all activities

need to clean up waste produced while making energy

make proteins proteins do all the work in a cell,

so we need lots of them

make more cells for growth

to replace damaged or diseased cells

The Jobs of Cells

Our organellesdo all thesejobs!

ATP

Principles of Cell Theory All living things are made of cells

Smallest living unit of structure and function of all organisms is the cell

All cells arise from preexisting cells(this principle discarded the idea of spontaneous generation)

Why study cells? Cells Tissues Organs Bodies

bodies are made up of cells cells do all the work of life!

Cells have 3 main jobs make energy

need energy for all activities need to clean up waste produced

while making energy make proteins

proteins do all the work in a cell, so we need lots of them

make more cells for growth to replace damaged or diseased cells

The Jobs of Cells

Our organellesdo all thesejobs!

ATP

Cell Size

Cell Types

Prokaryotic

Eukaryotic

Cell Type: Prokaryotes Prokaryotes, which includes all bacteria, are the simplest cellular

organisms. They have genetic material but no nucleus.

Typical bacteria cellBacteria cells

Cell Types: Eukaryotes Eukaryotic cells contain a

membrane-bound nucleus and numerous membrane -enclosed organelles

Cell size comparison

Bacterial cell

Animal cell

micron = micrometer = 1/1,000,000 meter diameter of human hair = ~20 microns

most bacteria 1-10 microns

eukaryotic cells 10-100 microns

Organelles Organelles do the work inside cells

each structure has a job to do keeps the cell alive; keeps you alive

Model Animal Cell

They’re likemini-organs!

cytoplasmjelly-like material holding organelles in place

20Photograph of a Cell Membrane

KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

Function separates cell from outside controls what enters or leaves cell

O2, CO2, food, H2O, nutrients, waste recognizes signals from other cells

allows communication between cells Structure

double layer of fat phospholipid bilayer

receptor molecules proteins that

receive signals

Cell membrane

lipid “tail”

phosphate“head”

3.3 Cell Membrane

Cell membranes are composed of two phospholipid layers.• The cell membrane is selectively permeable.

Some molecules can cross the membrane while others cannot.

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Cell Membrane

Polar heads are hydrophilic “water loving”

Nonpolar tails are hydrophobic “water fearing”

Makes membrane “Selective” in what crosses

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Cell Membrane

Hydrophobic molecules pass easily; hydrophilic DO NOT

What is the function of the protein channels?

They provide passageways for materials to cross the membrane.

Lesson Overview Cell Structure

But they can do much more

Nucleus Control center of cell

Double membrane

Contains Chromosomes Nucleolus The nucleus is a home to the cell’s

chromosomes and DNA. What are chromosomes you ask?Chromosomes: They are genetic structures that contain information to make new cells. Basically, the instructions for how to make new cells.

Terms/Structures continued Nucleus: The nucleus is a structure usually located near the

center of the cell. The nucleus is a home to the cell’s chromosomes and

DNA. What are chromosomes you ask? Chromosomes: They are genetic structures that contain

information to make new cells. Basically, the instructions for how to make new cells.

Terms/Structures continued Nucleolus: This structure is found inside the nucleus. It

is responsible for making ribosomes. We will get to this term in a bit. Thanks for your patience!