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