Cell Structure and Functions

Discovering Cells

• What do all the things in this picture have in common?

• They are all organisms or living things

• All living things are made of cells

• Cells are the building blocks of life

• They are the smallest things that have all the characteristics of life

• The diversity of living things are determined by the amazing variety of ways in which cells are put together

• Cells carry out the basic processes of life

– Respiration (obtaining oxygen or carbon dioxide)– Eliminating waste – Obtaining food– Reproducing, and– Growing or developing

• Cells make these functions happen – For example, cells in your digestive system absorb food – The food provides an organism energy and materials

needed for growth/development

• Cells function similarly in all organisms regardless of the organism they are part of

Francesco Redi’s Experiment

• Prior to the early 1800s, people believed in Spontaneous Generation— Life can come from nonliving things

• Rats came from garbage– Frogs came from mud– Flies grew out of rotten meat

Flies cannot get to rotten meat and no flies hatch

Flies smell meat and lay eggs on

screen which drop through then hatch

Flies lay eggs directly

on rotten meat then

hatch

Conclusion—Life can only

come from life!

The Cell Theory

• In 1838, German botonist, Matthias Schleiden, concluded that all plants are made of cells

• German physiologist,Theodor Schwann, concluded that all animals are also made up of cells

• Schwann stated that all living things are made up of cells

• All Living things are composed of cells• Cells are the basic unit of all living things• All cells come from other cells• The cell theory is true for all living things• Since cells are common to all living things, they

provide information about the functions that living things perform

The Cell Theory

Cell OrganellesCell Membrane

Controls what goes in and out of cell

Cytoplasm

Environment for cell structures

Nucleus

Cell reproduction

Vacuole Storage of water and food

Mitochondria Conversion of food to energy

Chloroplasts Production of food in plants

Cell Wall Strength and structure for plants

Organelles

• There are even smaller structures inside of cells called organelles

• Just as your stomach, lungs, and heart have different functions in your body, each organelle has a different function within the cell

Cell Wall• The cell wall is a rigid

layer of nonliving material that surrounds the cells of plants

• A cell wall helps to protect and support the cell • The cell wall is made mostly of a strong material called

cellulose • Although the cell wall is tough, many materials, including water

and oxygen can pass through easily

• Animal cells and many single celled organisms do not have cell walls

Cell membrane• All cells have a cell membrane

• In plant cells, it is inside of the cell wall

• The cell membrane is the outside boundary of animal cells

• This membrane controls what goes into the cell and what goes out

C

Cell Wall Cell Membrane

The Nucleus• The nucleus is the control center,

directing all of the cell’s activities

• The nucleus surrounded by a membrane called the nuclear envelope

• Materials pass in and out of the nucleus through pores in the nuclear envelope

• Nucleus is where cell reproduction takes place

– Chromatin in the nucleus contains genetic material which insructs the cell to divide to form new cells

• The nucleolus is where ribosomes are made

• Ribosomes are the organelles where proteins are produced

The Nucleolus

The Cytoplasm

• The cytoplasm is a clear thick fluid between the cell membrane and the nucleus

• In the cytoplasm are many organelles that perform specific functions in the cell

Mitochondria and Endoplasmic Reticulum

• Mitochondria are known as the “powerhouses” of the cell because they convert energy in food to energy the cell can use to carry out its functions

• The endoplasmic reticulum are passageways that help form proteins and other materials

• They also carry material throughout the cell

Ribosomes

• Attached to some of the endoplasmic reticulum are small, bodies called ribosomes

• Ribosomes function as factories to produce proteins from the endoplasmic reticulum, the proteins are transported to the Golgi bodies

Golgi Bodies

• Golgi bodies receive proteins and other newly formed materials from the endoplasmic reticulum

• They then distribute materials to other parts of the cell

• Golgi bodies also release materials outside the cell

Chloroplasts

• Only plant cells have organelles called chloroplasts

• Chloroplasts contain a chemical called chlorophyll

• Chlorophyll captures energy from sunlight and uses it to produce food for the plant

• Chlorophyll makes leaves look green

Vacuoles

• Vacuoles are large sacs that float in the cytoplasm• Vacuoles are the storage areas of the cells• Most plant cells have one large, water-filled, central

vacuole• Vacuoles can also store waste products• Animal cells have smaller vacuoles

vacuoles

Lysosomes

• Lysosomes are structures that surround food particles entering the cell and digest them with chemicals

• Lysosomes also break down old cell parts and release the substances so they can be used again

• Every cell and everything in the cell is made up of elements and compounds

• Elements are individual atoms of the same type• Compounds are made of elements chemically bonded in

specific arrangements

Chemical Compounds in Cells

OxygenHydrogen

Atoms (Elements) Compound

• Cells function similarly in all organisms because—

– All organisms’ cells are made out of identical chemical compounds

– All organisms’ cells use identical chemical compounds

– All organisms’ cells produce many identical chemical compounds

Inorganic and Organic Compounds

• Water is an example of an inorganic compound

• An inorganic compound does not contain the element carbon

• Most compounds that contain carbon are called organic compounds

• Most living things contain carbon• Important inorganic compounds—

– Carbohydrates, – lipids, – proteins, and– nucleic acids

Water

• Water is a compound • Each water molecule is made up of two

hydrogen atoms and one oxygen atom

• Water makes up about two thirds of your body

• Water plays many important roles in cells

• Water dissolves chemicals that cells need • Most chemical reactions within cells need water For Example

—– Plants need water to convert the energy into food – Water helps plant cells keep their size– It helps keep the temperature of cells from changing too rapidly

Carbohydrates • A carbohydrate is an energy-rich organic compound made of

elements carbon, hydrogen, and oxygen

• Sugars and starches are examples of carbohydrates

• Sugars are produced when plants make their own food

• Plant cells store excess energy in large molecules called starches or complex carbohydrates

• Some starches are stored as potatoes, pasta, rice and bread

• In addition to providing energy for the cell, carbohydrates are make up some cell parts

– For example• Cellulose in plant cell walls is a type of carbohydrate• Carbohydrates are also found in cell membranes

Lipids• Fats, oils and waxes are all lipids • Energy-rich organic compounds made of carbon, hydrogen,

and oxygen • Lipids contain more energy than carbohydrates• In addition to their function as an energy source

lipids also make up most of the cell membrane

• Most body parts are protein

• Protein molecules must be broken down into amino acids

Skin

Hair

Muscles

Finger and Toe nails

Bird feathers

Spider webs

Fish scales

Proteins

Structure of Proteins

• Protein molecules are made up of smaller molecules called amino acids

• There are only 20 common amino acids, but can combine to form thousands of different proteins

• The 20 amino acids are like the 26 letters of the alphabet that can combine thousands of words

Functions of Proteins

• Much of the structure of cells is made up of proteins

• Proteins form parts of cell membranes

• Proteins also make up many of the organelles within the cell

Enzymes

• Enzymes are proteins speed up chemical reactions in cells

• Without enzymes, many chemical would either take too long or not occur at all – For example—

Enzymes in your saliva speed up the digestion of food by breaking down starches into sugars in your mouth

Nucleic Acids• Large molecules of carbon, oxygen,

hydrogen, nitrogen, and phosphorus

• Made of four different kinds of nucleotides

• Differences among living things depends on the order of the nucleotides in the DNA

• Nucleic acids contain the instructions that cells need to carry out all the functions of life.

• There are two kinds of nucleic acids

• Deoxyribonucleic acid or DNA

– DNA is the genetic material determines traits which are passed from parent to offspring

– DNA also directs all cell functions Most of the DNA in a cell is found in the chromatin in the nucleus

• Ribonucleic acid or RNA – Plays an important role in the

production of proteins

– RNA is found in the cytoplasm as well as in the nucleus

Cell Diversity

• Cells come in many shapes

– Nerve cells have long, fingerlike extensions which help transmit information

– Red blood cells have a flattened shape so that they can fit through tiny blood vessels

• Some cells contain certain organelles but not others– For example, not all plant cells have

chloroplasts– Since root cells grow

underground, they have no need for chloroplasts

• Cells may also have more of a particular kind of organelle– For example, cells that

produce proteins, like liver cells, contain many more ribosomes than other cells

Liver Cell

Ribosomes

Vacuole

The Cell Environment• Cells must let things enter and leave it

• The cell membrane allows some substances to pass through it while other substances cannot

• Waste materials move out of the cells

• Oxygen, food molecules, and water move into the cell

Diffusion

• Substances that can move into and out of a cell do so by one of three methods: 1. Diffusion is the process by which molecules move from

an area of higher concentration to an area of lower concentration

2. Osmosis is the diffusion of water molecules through a the cell membrane 3. Active and Passive Transport

-Diffusion and osmosis do not require the cell to use its own energy—this is called passive transport

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

• Cells have several ways of moving materials by active transport 1. Transport proteins in the cell membrane “pick up” molecules outside the cell and carry them in, using energy Transport proteins also carry molecules out of the cell in a similar way

Cell membrane may contain many transport proteins Each transport protein can carry a specific substance.

2.Transport by engulfingFirst the cell membrane surrounds and engulfs, or encloses a particle

Once the particle is engulfed, the cell membrane wraps around the particle and forms a vacuole within the cell

The cell must use energy in this process

• Cells are so small that they are measured in units called micrometers

• One micrometer is one millionth of a meter • One square centimeter of your skin surface contains more

than 100,000 cells

• Cell are usually visible only through a microscope

100,000 cells

Observation of Cells

• Untill around the year 1600, no one knew cells existed

• Around 1590, invention of the microscope made it possible to see cells

• Two early discoverers of cells are Robert Hooke and Antonj van Leeuwenhoek

• Hooke conceived the name “cells” because under a microscope, they looked like the monistary rooms, called cells, that monks lived in

Robert Hooke

• Hooke built his own compound microscope

• He used his microscope to observe the structure of a thin slice of cork

• He calculated that a cubic inch of cork had about twelve hundred million cells (1,200,000,000)

Antonj van Leeuwenhoek

• van Leeuwenhoek was a Dutch businessman who built simple microscopes in his spare time

• He looked at drops of pond water and noticed many tiny organisms moving through the water

• He called these moving organisms “animalcules” meaning "little animals"

• )

Levels of Cell Organization• Organisms consisting of only one cell are

called unicellular

• Organisms consisting of two or more cells are called multicellular

The lowest level of organization is the SINGLE CELL

• Multi-celled organisms have individual cells that are specialized to perform specific functions

The second level of organization is TISSUE• A group of the same types of cells working together to

perform a function

Voluntary Muscle

Striated Muscle

Smooth Muscle

Cardiac Muscle

Skeletal Muscle

xylem

• A group of tissues working together to perform a function

Nerve Tissue

Blood Tissue

Phloem Tissue

Epidermal Tissue

Chlorophyll

Cardiac Muscle Tissue

The Third level of organization is the ORGAN

HEARTLEAF

• A group of organs working together to perform a function

Arteries

Veins

Intestines

Stomach

Pancreas

Heart

Moo

The 4th level of organization is the ORGAN SYSTEM

Circulatory System

Digestive System

The 5th level of organization is ORGANISM

• A group of organ systems working together to perform a function