Unit 2Chapters 3 & 4

The Cell

Essential Questions

1. What are cells?

2. How do we observe cells?

3. What are the parts of cells and what are their functions?

4. How do things move across the cell membrane?

3-1 Cells

cell: the basic unit of life Has all characteristics of life

Microscopes as Windows to Cells

The first light microscope was developed around 1600.

Robert Hooke – 1665 Observed“compartments,”

cells, in a thin slice of cork Anton van Leeuwenhoek

1700 developed simple light microscopes with high-quality lenses to observe tiny living organisms “animalcules”

Cell Theory1. All living things are made up of one

or more cells

2. Cells are the basic unit of structure and function in living things

3. Cells only come from other cells

Microscopes

Light microscopes (LM) magnify objects up to 1000 times, bacteria or larger

Electron microscopes (1950’s) use a beam of electrons and can magnify up to 1 million times Cells must be killed and preserved

Scanning Electron Microscope (SEM) to study the surface structures of cells

Transmission Electron Microscope (TEM) to explore their internal structure

micrograph: a photograph of the view through a microscope

Eukaryotic Cell

eukaryotic cell: has a nucleus surrounded by its own membrane Protists, fungi, plants, and animals Much larger than a prokaryotic cell ~ 10 to 100 micrometers

Prokaryotic Cell

prokaryotic cell: lacks a nucleus and most other organelles Bacteria and archaea;

found in earliest fossil record

Much simpler in structure than a eukaryotic cell ~1 to 10 micrometers

The DNA is concentrated in the nucleoid region which is not separated by a membrane

3-2 The Cell Membrane

Structure Membranes

regulate the transport of substances across the boundary

Composed mostly of proteins and phospholipids

Phospholipids

Two fatty acids at one end hydrophobic

Phosphate group(PO4

3-) at the other Negatively charged

and hydrophilic

Phospholipid Bilayer

phospholipid bilayer: the phospholipids form a two-layer “sandwich” of molecules that surrounds the organelle or cell Phosphate ends face

the outside Fatty acids inside Fluid mosaic Proteins drift freely

within the membrane

Nucleus

nucleus: houses the cell’s genetic material in the form of DNA, largest organelle

chromosomes: wound up DNA

nucleolus: center of the nucleus; makes ribosomes

Cytoplasm

cytoplasm: the entire region of the cell between the nucleus and the plasma membrane, which consists of organelles and fluid

cytoskeleton: provides structure for a cell

Organelles organelle: each part

of a cell with a specific job to do, “mini-organ” many are enclosed by

their own membranes to help maintain the chemical environment inside that is different then the rest of the cell

Endoplasmic Reticulum(ER)

Works as a highway to move substances through the cell

Ribosomes

Help make proteins

Mitochondria Powerhouse of the cell

Produces energy More active cells have more

mitochondria Folded membrane gives more

surface are for more energy production

Golgi Body

Like a post office Packages proteins

and lipids to send to other places in the cell or to different cells

Centrioles Only in Animal Cells Used during cellular reproduction Small, rod shaped; located near

nucleus

Additions for Plant Cells

chloroplasts: organelle where photosynthesis occurs

cell wall: protects the plant cell and maintains its shape; consists of cellulose and is found outside the plasma membrane

vacuoles: large membrane bound sacs for storage Main water storage in

plants

4-1 Cells and Their Environment

concentration: how crowded particles are

concentrate: a strong form of a juice Most of the water is

taken out

Diffusion diffusion: the net movement of particles of a

substance from where they are more concentrated to where they are less concentrated.

Permeable membrane: a membrane that allows molecules to pass through freely

equilibrium: a system is in balance; the number of molecules going one direction is equal to the number in the other direction.

4-2 Osmosis

osmosis: the passive transport of water across a selectively permeable membrane

Water Balance Water balance in animal cells

if there is too much water moving in the cell may burst too much moving out it may shrivel and die animals in aquatic environments depend on isotonic conditions

Water balance in plant cells a plant cell is healthiest in hypotonic(more water) environments because it remains firm but will not burst. The cell wall is too strong. in an isotonic situation, there is no net movement of water so it

will wilt.

Passive Transport

passive transport: diffusion across a membrane that expends no energy Diffusion and Osmosis

4-3 Active Transport

active transport: a cell uses energy to move molecules or ions across a membrane maintains the cell’s

chemical environment usually from low to high concentration

Ex. in animal cells, K and Na pump; K pumps in, Na out.

Transport of Large Molecules

vesicles: small membrane sacs that specialize in moving products into, out of , and within a cell

exocytosis: vesicle fuses with the plasma membrane and spills contents outside the cell

endocytosis: reverse; takes material into the cell within vesicles that bud inward