Cells
Chapter 3 Cells
3-1 At the Boundary of the Cell
Cells: The Smallest Vessels of Life
n Smallest unit that can carry out all the activities necessary for life.
n Your body is composed of trillions of cells.
n Cells are microscopic
Leewenhoek
n 1st person to observe & describe microscopic organisms & living cells.
n Made the 1st microscope
Robert Hooke
n Examined dead cork cells
Schleiden
n Observed and studied plant cells in 1838.
Theodor Schwann
n Reported in 1839 that animals were made of cells.
Cell Theory
n All organisms are composed of cells
n Cells are the basic unit of organization of life.
n All cells come from other cells.
Cell Membrane
n It is the outer covering of a cell.
n Controls substances enterring and leaving a cell.
n The cell membrane encloses the contents of the cell, allows materials to enter and leave the cell, and is selectively permeable.
Measurements of a cell
n Surface area of a cell is a measurement of the exterior.
n Volume is a measurement of the internal contents.
n When the volume of a cell increases, its surface area increases at a slower rate.
n As a cell size increases, the surface-area-to-volume ratio decreases.
n The size to which a cell can grow is limited by its surface area.
n Surface area is an important factor in limiting cell growth because the cell may become too large to take in food & remove waste.
n All cells are surrounded by water.
n Water is also present inside a cell.
n Membrane is shaped by the water found inside & outside the cell.
Polar molecule
n A molecule that has a partial negative charge on one side & a partial positive charge on the other side.
Hydrogen bond
n Linkage formed when a hydrogen atom in one molecule makes an additional bond to an atom in another molecule.
n “water” “born”
nonpolar molecules
n There is no negative & positive poles.
n Polar & nonpolar substances, like oil & water, will separate after being mixed.
3-2 Membrane Architecture
n Basic building block of a cell membrane is a kind of lipid molecule called a phospholipid.
Phospholipids
n Contain phosphate & nitrogen
n have nonpolar tails & polar heads
n form the lipid bilayer of the cell membrane
Lipid bilayer
n Double layer of phospholipids found in cell membranes & organelles.
2 characteristics of lipid bilayers
n Most polar molecules can’t go across a cell membrane.
n Their phospholipid & protein molecules are not rigidly fixed in place.
Channels
n Proteins act as passageways through which only certain molecules can pass.
n Most of the food & waste pass through
Receptors
n Proteins transmit information into the cell by reacting to certain other molecules.
Markers
n Proteins are the “name tags” of cells giving each an identity.
n Protein that fits into the cell membrane has two polar ends that are attracted by water, floats, & has a nonpolar middle section.
Protein structure is variable
n Page 49
n 3 basic sections in figure 3-11
3-3 Inside the Cell
n Two categories of cells are eukaryotic and prokaryotic cells.
n Refer to table 3-1
Eukaryotic cells
n Large complex cell that contains a nucleus.
n Organisms with these types of cells are called eukaryotes.
Eukaryotic Cell
n Well defined nucleus surrounded by a nuclear envelope.
n Scientist think they evolved 1.5 billion years ago.
n Eukaryotic cells have a system of internal membranes.
n Eukaryotic cells contain specialized structures called organelles.
n Eukaryotic cells are the only cells with membrane-bound organelles.
Prokaryotic cells
n Very small, simple cell that lacks a nucleus.
n “before nucleus”
n organisms are called prokaryotes “ancient life forms”
n Bacteria is an example
Cytoplasm
n The fluid that surrounds all organelles inside the cell.
Ribosome
n Structures on which proteins are made.
Cytosol
n Cytoplasm consists of an aqueous space.
Organelle
n A specialized compartment that carries out one or more specific functions.
Cell functions
n Use energy
n maintain homeostasis
n reproduce
Nucleus
n Directs cell activities
n serves as the storage center for the cell’s DNA, which contains heredity information.
n Nucleus is encased in a double membrane called the nuclear envelope.
n Cell’s activities are regulated by molecules that pass through the nuclear envelope.
Mitochondria
n Energy that drives a cells activities are produced here.
n Powerhouse of a cell.
Chloroplasts
n Found in plant cells and make chemical energy through the process of photosynthesis.
n Chloroplasts & mitochondria contain their own DNA.
Endoplasmic Reticulum
n Helps maintain homeostasis by moving substances from one part of a cell to another.
n The cell manufactures many proteins and lipids on the surface of the ER.
n Rough ER-present of ribosome's
n Smooth-absent of ribosome's.
Golgi Apparatus
n Cell’s packaging & distribution center.
Cytoskeleton
n Mesh-like network of protein fibers that supports the shape of a cell.
Function of the Golgi Apparatus
n Receives proteins & lipids from the ER.
n Packages molecules made in the ER.
n Involve in the distribution of proteins.
Cell Wall
n Only in plant cell’s.
n gives the cell strength and rigidity.
n Contains carbohydrates, cellulose, and protein.
Vacuole
n Found in animal & plant cells, but are more highly developed in plant cells.
n Store waste, nutrients, & water.
Cell Theory
n Cell’s arise from existing cells.
Magnification
n Ability to make an object appear larger.
n Objective lens x ocular lens.
n Most powerful microscope is about 2,000 X
Resolution
n Is its capacity to distinguish different objects that are close to one another.
n Fuzzy images are due to poor resolution.
Light Microscope
n Light passes through one or more lenses to produce an enlarged image of a specimen.
Compound Microscope
n Uses two lenses to magnify cells.
n A light microscope.
Micrograph
n Image produced by a microscope.
Electron Microscope
n Have higher magnifying power than light microscopes.
n Can’t be used to view living organisms.
Scanning Microscope
n STM used to see living organisms.