The Cell in ActionChapter 4

Exchange with the environmentSection 1

Introduction An organism must be able to obtain energy

and raw materials and get rid of wastes These functions keep cells healthy so that

they can divide Cell division allows organisms to grow and

repair injuries The exchange of materials between a cell

and its environment takes place at the cell’s membrane

What is Diffusion? Diffusion: the movement from areas of

high concentration to areas of low concentration Diffusion happens within and between

living cells Diffusion also happens between non-living

things Diffusion does not require energy

What is Diffusion? Diffusion of Water

Osmosis: the diffusion of water through cell membranes So important to life processes so it gets a

special name Important to cell processes Also occurs in plant cells

Semipermeable: only certain substances can pass through

Moving Small Particles Channels: where small particles (such as sugars)

cross the cell membrane Made up of proteins in the cell membrane

Particles move by either passive or active transport Passive transport: the movement of particles across

a cell membrane without the use of energy Particles move from areas of high concentration to an

area of low concentration Examples: diffusion, osmosis

Moving Small Particles Particles move by either passive or

active transport Active transport: a process of transporting

particles that requires the cell to use energy

Usually involves the movement of particles from an area of low concentration to an area of high concentration

Moving Large Particles Large particles move into and out of the cell by

processes called endocytosis and exocytosis Endocytosis: the active-transport process by which a

cell surrounds a large particle (ex: large protein) and encloses the particle in a vesicle to bring the particle into the cell

Moving Large Particles Exocytosis

Exocytosis: active-transport process in which large particles (ex: wastes) leave the cell A vesicle forms around a large particle within the cell The vesicle carries the particle to the cell membrane The vesicle fuses with the cell membrane and releases

the particle to the outside of the cell

Cell energySection 2

From Sun to Cell Nearly all of the energy that fuels life

comes from the sun Photosynthesis: process in which plants

capture energy from the sun and change it into food

From Sun to Cell Photosynthesis

Pigments: molecules in plant cells that absorb light energy Chlorophyll is the main pigment used

Plants use the energy captured by chlorophyll to change carbon dioxide and water into food Food is in the form of the simple sugar glucose

Glucose is a carbohydrate Photosynthesis also produces oxygen

Getting Energy from Food Animal cells have different ways of

getting energy Cellular respiration: uses oxygen to break

down food Fermentation: the breakdown of food

without the use of oxygen

Getting Energy from Food Cellular respiration

During cellular respiration, food (such as glucose) is broken down into CO2 and H2O, and energy is released

Most of the process of cellular respiration takes place in the cell membrane of prokaryotic cells

In eukaryotic cells, cellular respiration takes place mostly in the mitochondria

Getting Energy from Food Connection between photosynthesis and

respiration Photosynthesis: cells use CO2 to make

glucose, and the cells release O2 Cellular respiration: cells use O2 to break down

glucose and release energy and CO2

Each process makes the materials that are needed for the other process to occur elsewhere

Getting Energy from Food Fermentation

When muscle cells can’t get the oxygen needed for cellular respiration, they use fermentation to get energy Causes burning sensation

Another type of fermentation occurs in some bacteria and in yeast

The Cell CycleSection 3

The Life of a Cell Cell cycle: the life cycle of a cell

Begins when the cell is formed and ends when the cell divides and forms new cells Before a cell divides, it must make a copy of

its DNA DNA is organized into chromosomes

Copying chromosomes ensure that each new cell will be an exact copy of its parent cell

The Life of a Cell Making More Prokaryotic Cells

Prokaryotic cells have ribosomes and a singular, circular DNA molecule but don’t have membrane-enclosed organelles

Binary fission: cell division in bacteria; means “splitting into two parts”

The Life of a Cell Eukaryotic Cells and Their DNA

The chromosomes of eukaryotic cells contain more DNA than those of prokaryotic cells do Homologous chromosomes: chromosomes

that have the same sequence of genes and the same structure

The Life of a Cell Making More Eukaryotic Cells

The eukaryotic cell cycle includes three stages: Interphase

Cell grows and copies its organelles and chromosomes Mitosis

Chromatids separate Complicated chromosome separation process Ensures that each new cell receives a copy of each

chromosome Four phases: prophase, metaphase, anaphase, telophase

Cytokinesis Cell splits in two; these cells are identical to each other and

the parent cell

1. Interphase– Before mitosis begins, chromosomes

are copied. Each chromosome is then two chromosomes.

2. Mitosis– Prophase: mitosis begins; the nuclear

membrane dissolves.; chromosomes condense into rod-like structures.

– Metaphase: the chromosomes line up at the equator

Interphase

Prophase Metaphase Anaphase Telophase Cytokinesis

Interphase

Prophase Metaphase Anaphase Telophase Cytokinesis

2. Mitosis– Anaphase: chromatids separate and

move to opposite sides of the cell– Telophase: nuclear membrane forms

around each set of chromosomes; chromosomes unwind; mitosis stops

3. Cytokinesis– Cell pinches in two

Mitosis and the Cell Cycle Cytokinesis

In animal cells, division of the cytoplasm begins at the cell membrane Cell membrane begins to pinch inward to form a

groove, which eventually pinches all the way through the cell Two daughter cells form

Division of cytoplams In cells with cell walls, a cell plate forms in the

middle of the cell Cell plate contains the materials for the new

membranes and cell walls