and Energy

CELL PROCESS

PHOTOSYNTHESIS • The sun is the source of energy for most living things

• Example:• Plants get energy from the sun• Cow gets energy from the plants• Human gets energy from the cow

• Plants make their own food• Organisms that make their

own food are called autotrophs

• Organisms that cannot make their own are heterotrophs

• The processes by which a cell captures energy in sunlight and uses it to make food is called photosynthesis

• Process of Photosynthesis • Sun’s energy captured

in the chloroplasts and absorbed by chlorophyll

• Water and carbon dioxide chemically react to produce sugars C6H12O6 and oxygen O2

• Sugar is used to carry out cell functions

• Oxygen is given off as a waste product

• The first stage of photosynthesis is capturing the sun’s energy

• In plants, this energy process occurs in the leaf cells

• Chloroplasts are organelles in those cells that contain chlorophyll

• The green color comes from the chlorophyll which absorbs light

CAPTURING THE SUN’S ENERGY Stage 1

Stage 1

• Chlorophyll functions like solar “cells”• Solar cells capture light energy

and uses it to power devices• Similarly, chlorophyll captures light

energy and uses it to power the second stage of photosynthesis

• In the next stage of photosynthesis, the cell uses the captured energy to produce sugars

Stage 2

• Some of the sugars are used for food

• The cells break down the sugar molecules to release the energy they contain

• This energy can then be used to carry out the plant’s functions

• Some sugar molecules are converted into cellulose

• Other sugar molecules may be stored in the plant’s cells for later use. When you eat potatoes or carrots, you are eating the pant’s stored energy

• The cell needs two raw materials for this stage:

• Water and carbon dioxide

• Water is absorbed by the roots and moves up to the plant’s leaves

• Carbon dioxide enters the plant through small openings on the undersides of the leaves called stomata

• Once in the leaves, the water and carbon dioxide move into the chloroplasts

Stage 2

The photosynthesis equation

The events of photosynthesis can be summed up by the following chemical equation:

light energy

6CO2 + 6H2O C6H12O6 + 6O2

Carbon water sugar oxygendioxide

6 Carbon atoms 6 Carbon atoms 18 Oxygen atoms 18 Oxygen atoms 12 Hydrogen atoms 12 Hydrogen atoms

No atoms are lost or

gained in the process

• Through the process of photosynthesis, plants produced almost all the oxygen in Earth’s atmosphere

• Animals use oxygen which is the waste product of plants and plants use carbon dioxide which is the waste product of animals

Plants give off Oxygen

Animals give off carbon dioxide O

2

RESPIRATION

• Before food can provide your body with energy, it must pass through your digestive system

• There, food is broken down into molecules

• These molecules then pass into your bloodstream

• Next, the molecules travel to all the cells in your body

• Inside the cells, the energy in the molecules is used to perform all your body’s functions

ENERGYENERGY

• Because living things need a continuous supply of energy, the cells of all living things carry out respiration continuously

• Photosynthesis—carbon dioxide and water produce sugars and oxygen

• Respiration—sugars and oxygen produce carbon dioxide and water

• Photosynthesis and Respiration can be thought of as opposite processes

PLANTS

ANIMALS

• Living organisms get energy from sunlight or food and “save” it in the form of carbohydrates including sugars and starches

• When cells need energy, they “withdraw” it by breaking down the carbohydrates in the process of respiration

• Like photosynthesis, respiration is a two-stage process

• The first stage takes place is the cytoplasm

• There, molecules of sugar are broken down into smaller molecules

• Oxygen is not involved, and only a small amount of energy is released.

• The second stage of respiration takes place in the mitochondria

• There, the small molecules are broken down into even smaller molecules

• These chemical reactions require oxygen, and they release a great deal of energy

• This is why the mitochondria are called the “powerhouses” of the cell

ENERGY

ENERGY

• The energy released by the mitochondria is stored as chemical energy that is immediately ready to be used by the cells

ENERGY

ENERGY

• Two other products of respiration are carbon dioxide and water

• The carbon dioxide diffuses out of the cell

• When you breathe in, you take in oxygen

• When you breathe out, you release carbon dioxide and water which are the waste products of respiration

The respiration equationAlthough respiration occurs in a series of complex steps, the overall process can be summarized in the following equation:

C6H12O6 + 6O2 6CO2 + 6H2O +

ENERGYSugar oxygen carbon dioxide water

Fermentation

• Some cells are able to obtain energy without using oxygen

• For example, single celled organisms living under water without oxygen

• These organisms obtain their energy through fermentation, a process that does not require oxygen

• The amount of energy released during fermentation lower than the amount released during respiration

Alcohol Fermentation

• Yeast breaks down sugar to produce alcohol, carbon dioxide, and small amount of energy

• The products of alcoholic fermentation are important to bakers and brewers

• Carbon dioxide produced by yeast creates air pockets in bread dough, causing it to rise

• Carbon dioxide also causes the bubbles in alcoholic drinks such as beer and sparkling wine

Feel the burn!

Lactic acid fermentation

• Another type of fermentation takes place at times in your body

• You run as fast as you can for as long as you can and no matter how hard you breath, your muscle cells used up the oxygen faster than it can be replaced

• Because your cells lack oxygen, fermentation occurs to produce energy

• One product of fermentation is lactic acid

• When lactic acid builds up, you feel pain in your muscles

CELL DIVISION• Cells grow and divide over and over

• The regular sequence of growth and division that cells undergo is known as the cell cycle

• During the cell cycle, a cell grows, prepares for division and divides into two new cells called "daughter cells"

• Each of the daughter cells begins the cell cycle again

• The cell cycle is divided into three main stages: • Interphase• Mitosis and • Cytokinesis.

Interphase

• Interphase is the period before cell division

• The first part: the cell grows to full size

• Produces new ribosomes and enzymes

• Copies made of mitochondria and chloroplasts

• The second part: an exact copy of the DNA is produced in the nucleus in a process called replication

• The chromatin appears as a dense mass within the nucleus

• DNA holds all the information that the cell needs to carry out its functions

• At the end of DNA replication, the cell contains two identical sets of DNA

• Once the DNA has replicated The cell produces structures that it will use to divide into two new cells At the end of interphase, the cell is ready to divide

Mitosis• Scientists divide mitosis into four phases:

prophase, metaphase, anaphase, and telophase

• During prophase, the threadlike chromatin in the nucleus condenses to form double-rod structures called chromosomes

• Each chromosome has two rods because the DNA replicated

• Each identical rod in a chromosome is called a chromatid The two chromatids are held together by a structure called a centromere

• As the cell progresses through metaphase, anaphase, and telophase, the chromatids separate from each other and move to opposite ends of the cell

• Then two nuclear envelopes form around the new chromosomes at the two ends of the cell

Cytokinesis

• Cytokinesis is the final stage of the cell cycle

• The cytoplasm divides and the organelles are distributed into each of the two new cells

• Cytokinesis usually starts at the same time as telophase

• When cytokinesis is complete, two new cells, or daughter cells are formed

• Each daughter cell has the same number of chromosomes as the original parent cell

• At the end of cytokinesis, each cell enters interphase, and the cycle begins again

• Cytokinesis in animal cells

• During cytokinesis in animal cells, the cytoplasm pinches into two cells

• Each daughter cell gets about half of the organelles

• Cytokinesis is different in plant cells

• A plant cell’s rigid cell wall cannot squeeze together

• A cell plate forms across the parent cell

• The cell plate gradually develops into new cell membranes between the two daughter cells

• New cell walls then form around the cell membranes

• DNA replication ensures that each daughter cell will have the genetic information it needs to carry out its activities

• Before scientists could understand how DNA replicates, they had to know its structure

• In 1952, Rosalind Franklin uses an x-Ray method to photograph DNA molecules

• Her photographs helped scientists figure out the structure of DNA in 1953

THE STRUCTURE OF DNA

• The strands of a DNA molecule look like a twisted ladder

• The two sides of the DNA ladder are made up of molecules of sugar called deoxyribose and phosphates

• Each rung is made up of a pair of molecules called nitrogen bases

• Nitrogen bases are molecules that contain the element nitrogen and other elements

• DNA has four kinds of nitrogen bases:• Adenine • Thymine• Guanine, and • Cytosine

• The capital capital letters A, T, G, and C are used to represent the four bases

Replication of DNA

• DNA replication begins when the two sides of the DNA molecule unwind and separate, somewhat like a zipper unzipping

• The molecule separates between the paired nitrogen bases

• Nitrogen bases that are floating in the nucleus connect with the bases on each half of the DNA molecule

• The bases on one side of the ladder then connect with the bases on the other side

• Adenine (A) only pairs with thymine (T)

• Guanine (G) only pairs with cytosine (C)

• This pairing pattern is the key to understanding how DNA replication occurs

• The order of the bases in each new DNA molecule exactly matches the order in the original DNA molecule

• Once the new bases are attached, two new DNA molecules are formed

CELL DIFFERENTIATION

• When a cell divides by mitosis, it produces two daughter cells that are identical to it and each other

• Then, how do cells in multicellular organisms become different from one another?

• Differentiation is the process by which cells carry out specialized functions

• As cells differentiate, they become different from one another

• They also form groups of other, similarly specialized cells

• These groups then form tissues and organs

Differences in Structure

• Multicellular organisms begin their lives as one cell

• After three mitosis cycles differentiaton begins

• The single cell becomes an organism with specialized structures

• For example,• A single plant cell can differentiate into:

• leaf cells, transport cells and root cells look different.

• As cells differentiate their organelles differentiate also to carry out different functions

• For example,

• Plant leaves contain cells that carry out photosynthesis

• Root cells are underground and do not carry out photosynthesis

• Leaf cells have many chloroplast to capture sunlight

• Root cells have no chloroplast but have more vacules to absorb water from the soil Nucleu

s

A Root Cell

• When cells differentiate, they become organized

• Similar cells group into tissues that carry out specific functions

• For example, Muscle cells in animals group into long strands of muscle tissue that move legs or arms

Voluntary Muscle

Striated Muscle

Smooth Muscle

Cardiac Muscle

Skeletal Muscle

xylem

• Groups of tissues combine to form organs, such as leafs of a plant or the heart of an animal

Nerve Tissue

Blood Tissue

Phloem Tissue

Epidermal Tissue

ChlorophyllCardiac Muscle Tissue

HEART

LEAF

• Groups of organs form organ systems, such as the digestive system

Arteries

Veins

Intestines

Stomach

Pancreas

Heart

Moo

Circulatory

System

Digestive System

• As differentation continues, increasing specialization occurs

• For example, • The retina of your eye

consists of 7 different types of cells

• Each type of cell has a specialized job to do

• The cells of your retina differentiated early in your development before you were born

• During an organism’s development, the instructions that determine how its cells will differentiate are coded in the DNA in each cell’s nucleus

• When and how much they differentiate depends on their DNA and the type of organism

• Some cells differentiate completely during an organism’s development

• Other cells do not specialize until later in the life of an organism.

DIFFERENTIATION IN ACTION

Cell Differentiation Among Animals

• Many adult animals such as insects and some crustaceans and reptiles can grow a tail to replace a lost one

• Cells at the point of the injury differentiate, forming new muscle, bone, blood, and nerves

Sometim

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differe

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leads to

regenera

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an entir

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duplicate

organism

• The replacement of lost body parts does not occur in humans

• Once human cells differentiate, they usually lose the ability to become other types of cells

• Humans do produce certain cells called stem cells that can differentiate throughout life

• Stem cells respond to specific needs in the body by becoming specialized

• For example, • You need a constant supply of new

blood cells to your replace older cells

• Everyday, stem cells produce a steady supply of blood cells

Cell Differentiation Among Animals

• Cells differentiate in plants much the same way they do in animals

• Differentiated cells become root, stem, and leaf cells

• Cells continue to differentiate within each kind of organ

• For example, some cells in the plant’s stem specialize as tubes that transport food and water throughout the plant

• Many plants grow throughout their lives• Certain cells in the roots and stems

increase size by rapid cell division and differentiation

• Differentation can lead to growth of new roots, stems, and leaves

• For example, • A leaf of an African violet plant that is cut off

and put into water will begin to differentiate into root cells and stem cells, and a whole new plant will grow

• Gardeners use this technique to create many plants from one original plant