cell structure and function discovering cells looking inside cells chemical compounds in cells the...

Cell Structure and Function

Discovering Cells

Looking Inside Cells

Chemical Compounds in Cells

The Cell in Its Environment

Table of Contents


What is a Cell?

*A cell is the basic

unit of life.

*All life activities

take place inside

cells.


Discovery of Cells

*Robert Hooke—first man to see cells (1663) -looked at thin slices of cork -saw empty boxes and called them cells -never realized that cells are living things


*Anton van Leeuwwenhoek

-father of microbiology

(1600’s)

-improved and developed

many types of microscopes

-discovered microscopic, one

celled organisms and called

them “animalcules”,

meaning “little animals”.


*Matthias Schleiden (1838)

-stated all plants are

made of cells

*Theodor Schwann (1839)

-stated all animals are

made of cells


*Rudolph Virchow (1855)

-stated all cells come

from other cells.

*The work of these men

led to the “Cell Theory”

Cell Structure and Function - Discovering Cells

The cell theory states:

1. All living things are

made of cells.

2. Cells are the basic units of

structure and function in

living things.

3. All cells come from other

cells.


SequencingConstruct a flowchart showing how the work of Hooke, Leeuwenhoek, Schleiden, Schwann, and Virchow contributed to scientific understanding of cells.

Discovering Cells

Hooke sees cells in cork.

Leeuwenhoek sees many one-celled organisms.

Schleiden concludes that all plants are made of cells.

Schwann concludes that all animals (and all living things) are made of cells.

Virchow proposes that new cells form only from cells that already exist.

- Discovering Cells


Links on Cell Theory

Click the SciLinks button for links on the cell theory.

- Discovering Cells


End of Section:Discovering

Cells


Eukaryotic vs. Prokaryotic

*All cells are either eukaryotic or prokaryotic.

-Eukaryotic cells —complex cells with a nucleus. All animal and plant cells are eukaryotic.

-Prokaryotic cells—simple cells without a nucleus. All bacteria and cyanobacteria (blue-green bacteria) are prokaryotic.


Structure of Animal CellsAnimal cells are typical eukaryotic cells.

Most contain the following structures:

*Cell Membrane

-Surrounds the cell

-Has pores

-Controls what gets

in and out

Cell Structure and Function - Looking Inside Cells

*Nucleus—control center of cell

-directs all of the cell’s activities

Nuclear Envelope

Nucleolus

Chromatin

Pores


*Cytoplasm—gel-like material inside the cell.

*Organelles—many tiny structures inside the cell. Each has its own job to do.

-Organelles include:


1.Mitochondria—“powerhouses” of the cell because they convert energy in food molecules to energy the cell can use to carry out its functions.

- Looking Inside Cells


2. Endoplasmic reticulum —folded tube

like membranes that move materials

throughout the cell.

3. Ribosomes—small protein factories

found on the “er” or in the cytoplasm


Ribosomes

Endoplasmic reticulum


4. Golgi bodies —packaging centers that wrap up and package proteins and send them to other parts of the cell or out of the cell.


Golgi Body


5. Lysosomes—garbage

collectors that contain

enzymes used to break down

large molecules and old cell

parts.


6. Vacuoles—sacs that store water, dissolved material or waste products. They are larger in plant cells than in animal cells.


Structure of Plant Cells

*Plant cells contain all the same structures and organelles as animal cells plus a few more.

Plant cells can do everything that animal cells can do plusmake food.


-Cell wall—a ridged structure outside the cell membrane made of cellulose. It supports and protects the plant cell.

-Chloroplasts—tiny disks that contain chlorophyll. Photosynthesis takes place here.

-Larger Vacuoles—to store water


Plant and Animal Cells



Cell Variety

*Cells differ in size, shape, and

function. They will not all look like the

diagrams.


*Examples:

-Nerve cell—0ne meter long with many extensions: carries impulses to the brain.

-Red Blood Cell—microscopic, round and flexible: carries oxygen throughout the body.


Structure of Bacteria Cells*Bacteria cells have no nucleus and no

membrane-bound organelles. -They are prokaryotic. -Their parts include:

Capsule Cell wall Cell membrane Cytoplasm DNA floating in cytoplasm Ribosomes

Some have flagella


Diagram of a Bacteria Cell

Cytoplasm

DNA

Capsule

Cell wallCell Membrane

Ribosomes

Flagella


Plant and Animal Cells Activity

Click the Active Art button to open a browser window and access Active Art about plant and animal cells.



Before you read, preview Figure 12. Then write two questions you have about the illustrations in a graphic organizer like the one below. As you read, answer your questions.

Q. How are animal cells different from plant cells?

A. Plants cells have a cell wall and chloroplasts, which animal cells to not have.

Q. What do mitochondria do?

A. Mitochondria convert energy in food molecules to energy the cell can use.

Plant and Animal Cells


Previewing Visuals


The Cytoplasm and Organelles

Click the Video button to watch a movie about cytoplasm and organelles.



Specialized Cells

Click the Video button to watch a movie about specialized cells.



End of Section:Looking Inside

Cells


What are Cells Made Of?

*Cell Chemistry begins with atoms:

-Atom—basic units of matter

-Elements—any substance that

cannot be broken down into

simpler substances (made of

only one type of atom)


-All known elements are listed on

the Periodic Table of the Elements


-The elements found in living cells

include mostly carbon, hydrogen,

nitrogen, oxygen, phosphorus

and sulfur: (CHNOPS)


Molecules and Compounds *Atoms combine to form molecules.

-Molecules—two or more atoms bonded together (different or

same) Ex: H2O O2 NaCl -Special molecules made of different elements only are called

compounds Ex: H2O CO2

Cell Structure and Function - Chemical Compounds in Cells

Carbon dioxide, which is found in gas bubbles, is a chemical compound. So is water.


-When just the right molecules and

compounds get together in just

the right way, cells are formed.

-Compounds in living organisms

are classified as either organic or

inorganic.


*Organic compounds contain the

elements; carbon and hydrogen.

*They make up foods and cell membranes.

*Four basic groups:


1.Carbohydrates—make up 1% of a cell; contain carbon, hydrogen, and oxygen; used for energy; examples are sugars and starches; most important carbohydrate for living things is glucose.


2. Lipids—make up 10% of a cell;

contain carbon, hydrogen and

oxygen; store and release

energy; found in cell membranes;

examples are fats, oils and waxes.


3. Proteins—make up 15% of a cell;

made of amino acids that contain

carbon, hydrogen, oxygen and

nitrogen; used to build cell parts

and for growth and repair of cell;

examples are enzymes.


4. Nucleic Acids—make up 4% of a cell; contain carbon, hydrogen, oxygen, nitrogen, and phosphorus; carry genetic information; found in chromosomes, mitochondria, chloroplasts, and nucleus; examples are DNA and RNA


Compounds in Bacteria and Mammals

All cells contain carbohydrates, lipids, proteins, and nucleic acids, as well as water and other inorganic compounds. But do all cells contain the same percentages of these compounds? The graph compares the percentage of some compounds found in a bacterial cell and a cell from a mammal.

- Chemical Compounds in Cells



Red bars represent percentages of compounds in bacterial cells; blue bars represent percentages of compounds in mammalian cells.

Reading Graphs:

What do the red bars represent? What do the blue bars represent?




About 70%; the percentages are the same.

Interpreting Data:

What percentage of a mammalian cell is made up of water? How does this compare to the percentage of water in a bacterial cell?




Proteins

Interpreting Data:

Which kind of compound–proteins or nucleic acids–makes up the larger percentage of a mammalian cell?




They are similar, though mammalian cells have a lower percentage of nucleic acids, and bacterial cells have a lower percentage of lipids and fewer proteins.

Drawing Conclusions:

In general, how do a bacterial cell and mammalian cell compare in their chemical composition?


Cell Structure and Function - Chemical Compounds in Cells

*Most inorganic compounds are made from elements other than carbon. Example: Water

-water makes up two-thirds of your body

-70% of a cell’s cytoplasm is water -many substances must be dissolved in water in order to be used by cells.


Type of Compound

Elements Functions

As you read, compare and contrast carbohydrates, proteins, and lipids in a table like the one below.

Carbohydrate Carbon, hydrogen, oxygen

Store and provide energy and make up cellular

parts

Protein Carbon, hydrogen, oxygen, nitrogen, and

sometimes sulfur

Make up much of the structure of cells and speed up chemical

reactions

Lipid Carbon, hydrogen, oxygen

Store energy


Comparing and Contrasting


Links on Proteins

Click the SciLinks button for links on proteins.



End of Section:Chemical

Compounds in Cells


Cell Transport

*The cell membrane controls what gets in and out of the cell. This is called Cell Transport.

-Substances pass through pores.-The membrane is selectively-permeable (meaning only molecules of a certain size can get through).

Cell Structure and Function - The Cell in Its Environment

A Selective Barrier

The cell membrane protects the contents of the cell and helps control the materials that enter and leave.


Types of Transport

*Passive Transport —cell uses

no energy to move materials into or out

of the cell.

-Two types of Passive Transport:

1. Diffusion

2. Osmosis


*Diffusion is a type of passive transport in which molecules move from high to low concentration.

-Oxygen and carbon dioxide move

into a cell by diffusion.

-Molecules move through tiny pores in

the cell membrane.

-Diffusion requires no energy from the

cell.


Diffusion

In diffusion, molecules move from an area of higher concentration to an area of lower concentration.

- The Cell in Its Environment


Ratios The concentration of a solution can be expressed as a ratio. A ratio compares two numbers. It tells you how much you have of one item in comparison to another. For example, suppose you dissolve 5 g of sugar in 1 L of water. You can express the concentration of the solution in ratio form as5 g:1 L, or 5 g/L.

Practice Problem

Suppose you dissolve 7 g of salt in 1 L of water. Express the concentration of the solution as a ratio.

7 g:1 L or 7 g/L



*Osmosis is a type of passive

transport in which water moves

from high to low concentration.

-Plants get water into their roots

by osmosis.

-Osmosis also requires no energy

from the cell.


Osmosis

In osmosis, water diffuses through a selectively permeable membrane.



Equilibrium

*Both diffusion and osmosis will continue until the cell reaches a point where the concentrations are equal both inside and outside the cell. This is called equilibrium.


*Active Transport —cell must

use energy to move substances

in or out.

-Cell will move things from low to

high concentration.

-Transport proteins are needed.


Passive and Active TransportPassive and active transport are two processes by which materials pass through the cell membrane. Active transport requires the cell to use its own energy, while passive transport does not.



Endocytosis—process used by cells to move very large substances into the cell.


Exocytosis —process used by cells to move very large substances out of the cell.


Building VocabularyA definition states the meaning of a word or phrase. After you read the section, reread the paragraphs that contain definitions of Key Terms. Use all the information you have learned to write a definition of each Key Term in your own words.

Key Terms: Examples:


selectively permeable The cell membrane is selectively permeable, which means that some substances can pass through the membrane while others cannot.

diffusion Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration.

osmosis Osmosis is the diffusion of water molecules through a selectively permeable membrane.

Key Terms: Examples:passive transport

active transport

The movement of dissolved materials through a cell membrane without using cellular energy is called passive transport.

Active transport is the movement of materials through a cell membrane using cellular energy.


More on Cellular Transport

Click the PHSchool.com button for an activityabout cellular transport.



End of Section:The Cell in Its Environment


types

typesmade ofincludeinclude

Graphic OrganizerOrganic

Compounds

Carbo-hydratesLipids Proteins

StarchesAmino acids

SugarsFats, oils, and waxes DNA

Nucleic acids

RNA


End of Section:Graphic Organizer

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