56 terms

Biology Chapter 7


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Cell theory
The cell theory states that all iving things are mad of cells, cells are basic units of structure that function in living things and new cells are produced from existing cells
How do microscopes work
Most microscopes use lenses to magnify the image of an object by focusing on light and electrons
Light microscope
A typical light microscope allows light to pass through the specimen and uses to lenses to form an image
The first set of lenses located just of above specimen produced and enlarged image of the specimen
Second near the eye magnifies the image further
The light waves can only magnify things up 1000x due to diffracted or scattered.
Another problem with the light microscopy is that most living cells are nearly transparent making it difficult to see the structure within them
Chemical Dyes
Using chemical stains or dyes can usually solve this problem. Some of the stains are so specific that they reveal only compounds or structures within the cell
florescent dyes can be viewed through a florescent microscope.
This allows us to see movements with dyes
Electron microscopes
Electron microscopes used beams of electrons not ligt
Offer much higer resolutions
Transmission electron microscope
Transmission microscope makes it possible to explore cell structures and large protein milecules
Tissues must be cut thin so it can be examined with a flat image
Magnifies up to 200,000x
Scanning electron microscope
Scanning microscopes scan the surface of a specimen
Do not have to be cut into thin slices
Produce 3d images up 100,000x magnification
Electon microscope problems
Electrons have to be placed in a vacuum meaning a living organism cannot be examined
Also all water has to be removed from objects in electron microscope
Prokaryotes and Eukaryotes and their differences
Prokaryotic cells do net separate genetic materials with nucleas
In eukaryotic cells the nucleus separates the genetic material from the rest of the cell.
Prokary less complex than eukary
Mycoplasma is the are only ,2 micrometers meaning it cant be views uder a light microscope
All cells have DNA
All cells have a flexible barrier called the cell membrane
Nucleus is large membrane enclosed structure that contains cells DNA and it controls the cell
Prokary are simple but still have to grow reproduce etc, they have the ability to move through water
Bacteria are prokary
Eukary have various structure inside and are highly specialized.
How can the eukaryotic and prokartyiotic cell be divided
The eukaryotic cell can be divided into two major parts the nucleus and cytoplasm.
Cytoplasm is the fluid portion of the cell outside of the nucleus
Prokaryotic cells have cytoplasm as well even though they do not have a nucleus
Many cellular structures act as if they are specialized organs. These structures are known as organelles literally little organs
Understanding what each Organelle does is key to knowing how the cell works
The nucleus is the main office of the cell and it is the central control of the cell
The nucleus contains nearly all the cells DNA and with it the coded instruction for making proteins and other important molecules
Nucleus surrounded by a nuclear envelope composed of 2 membranes.
The nuclear envelope is dotted with thousands of nuclear pores which allow materials to move into and out of the nucleus.
Like messages, instuctions and blueprints moving in and out of a main office, a steady stream of proteins, RNA and other molecules move through the nucleus pores
Nuclei contain small dense region known as nucleolus
The nucleolus is where the assembly of ribosomes begins.
Chromosones contain the genetic information of that is passed from one generation of the cells to another
When a cell divides its chromosomes condense and can be seen under a microscope.
Vacuoles store materials like water salts proteins and carbs, they are large sack like membrane enclosed structures.
In many plants cells there is a single large central vacuole filled with liquids. The pressure of the central vacuole in the cells increases their rigidity making it possible for plants to support heavy structures like leaves and flowers.
Vacuoles are found is some unicellular organisms and in some animals
The paramecium contains and organelle called a contractile vacuole. By contracting rhythmically this specialized vacuole pumps excess water out of the cell.
Nearly all eukaryotic cells contain smaller membrane enclosed structure called vesicles They are used to store and moved materials between cell organelles as well as to and from the cell surface.
Lysosomes break down lipids carbs and proteins into small molecules that can be used by the rest of the cell. They are also involved in breaking down organelles that have outlives their usefulness. They are small organelles filled with enzymes that function as the junk cleanup crew. They breakdown junk that may clutter up the cell.
Lysosomes are found in all animals cells and a few plant cells.
Eukaryotic cells are given their shape and interal organization by a newwork of protein filaments known as the cytoskeleton
Certain parts of the cytoskeleton can transport materials in the cell. Kind of like conveyor belts
Microfilaments are threadlike structures made up of a protein called actin
They form extensive networks in some cells and produce a tough flexible framework that supports the cell
Microfilaments are threadlike structures made up of a protein called actin
They form extensive networks in some cells and produce a tough flexible framework that supports the cell
Microfilaments also help cells move
Microfilament assembly and disassembly is responsible where they form a structure known as the mitotic spindle which helps separate chromosomes.
Micro tubes are hollow structures made up of proteins known as tubulins
They play critical roles in maintaining cell shape
In animal cell structures are also formed from tubulins
Centrioles are located near the nucleus to organize cell division
Not found in plant cells
Cell movement
Cell can control the cell with chemical energy resulting in controlled movements

Projections come out of the cell known as cilia and flagella that enable us to swin rapidly through liquids
Ribsomes are small particles of RNA and protein found throughout the cytoplasm in all cells,
Ribosomes produce proteins by follow coded instructions that come from the DNA
Endoplasmic recticulum
Endoplasmic reticulum or ER is in an internal membrane.
Rough ER make proteins found on the surface
New proteins are put into the Rough ER where they can be chemically modified.
Rough ER mostly exports proteins
In smooth ER the proteins are not on the surface
Smooth ER contains collections of enzymes that perform specialized tasks including the synthesis of membrane lipids and detoxification of drugs.
Golgi apparatus
Rough ER proteins move to Golgi apparatus which looks like a stack of flattened membranes
Proteins come into the Golgi through the vesicles and leave through the vesicles
Chloroplasts and mitochondria both are involved in energy
Chloroplasts are biological equivalents of solar power plants, the convert energy from the sun into food through a process called photosynthesis
Surrounded by 2 membranes
Inside organelle are large stacks of other membranes which contain the green pigment chlorophyll
Nearly all eukaryotic cells including plants contain mitochondria
Mitochondria are the power plants of the cell. They convert chemical energy stored in food into compounds that are move convenient for the cell to use
Two membranes and outer and inner enclose mitochondria. The inner is folded up inside the organelle
Mitochondria in humans come from their mother.
Mitochondria and chloroplasts contain their own DNA
This suggests that they may have descended from independent microorganisms.
Cell membrane
The cell membrane regulates what enters and leaves the cell and also protects and supports the cell
Cells are surrounded by a barrier known as the cell membrane
All cells contain a cell membrane that regulates what eners and leaves the cell and also protects and supports the cell
The composition of nearly all cell membranes is a double layered sheet called a lipid bilayer which gives the cell membranes a flexible structure and forms a strong barrier between the cell and its surroundings
Many lipids have oily fatty acid chains attached to chemical groups that interact strongly with water

Many lipids have oily fatty acid chains attached to chemical groups that interact strongly with water
The fatty acid portions of such a lipid are hydrophobic or water hating while the opposite end of the molecule is hydrophilic meaning water loving.
When such lipids are mixed with water their hydrophobic fatty acid tails cluster together while their hydrophobic fatty acid tails cluster together while their hydrophilic tails are attracted to water this forms a lipid bilayer.
The head groups of lipids in a bilayer form an oily layer inside the membrane from which water is excluded.
Most cell membranes contain protein molecules that are embedded in the lipid bilayer. Carbohydrate molecules are attached to many of these proteins
Because the proteins embedded in the lipid bilayer can move around and float among the lipids and because so many different kinds of molecules make up the cell membrane scientists call it a fluid mosaic
Some of the proteins form channels and pumps that help to move material across the cell membrane
Many of the carbohydrate molecules act like chemical identification cars allow individual cells to identify with one another.
Although many substances can cross biological membranes some are too large or to strongely charged to cross the lipid bilayer.
If a substance is able to cross a membrane the membrane is said to be permeable to it
A membrane is impermeable to substances that cannot pass across it
Most biological membranes are selectively permeable meaning that some substances can pass across and some can't these membranes can also be called semipermeable.
Cell wall
Many cells including most prokaryotes also produce a strong supporting layer around the membrane known as the cell wall.
The main funtions of the cell wall is to provide support and protections for the cell
Prokaryotes plants algae fungi and many prokaryotes have cell walls. Animal cell do not have cell walls
Cell walls lie outside the cell membrane and the most are porous enough to allow water oxygen carbon dioxide and certain other substances to pass through easily.
Passive transport
The movement of materials across the cell membrane without using cellular energy is called passive transport
Every living cell exists in a liquid environment
In any solution solute particles tend to move from an area where they are more concentrated to and area when they are less concentrated
The process by which particles move from an area of high concentration to an ara of low concentration is called diffusion
Diffusion is the driving force behind the movement of many substances across cell membrane.
Diffusion depends upon random particle movements. Substances diffuse across membranes without requiring the cell to use additional energy.
How do molecules cross the cell membrane
Cell membranes have proteins that act as carriers or channels making it easy for certain molecules to cross
Molecules that cannon directly diffuse across the membrane pass through special protein channels in a process call facilitated diffusion
Hundreds of different proteins have been found that allow particular substances to cross cell membranes
Facilitated diffusion
The movement of molecules by facilitated diffusion does not require any additional use of the cells energy.
Lipid bilayer
The inside of a cells lipid bilayer is hydrophobic or water hating. This makes water have a tough time passing through the membrane
Many cells contain water channel proteins, known as aquaporins, that allow water to pass right through them. Without aquaporins, water would diffuse in and out of cells very slowly.
Osmosis is the diffusion of water through a selectively permeable membrane.
Osmosis involves the movement of water molecules from an area of higher concentration to an area of lower concentration.
same strength
Hyper tonic
above strength
below strength
Osmotic Preassure
For organisms to survive they must have a way to balance and intake and loss of water
The net movement of water in or out of a cell exerts a force known as osmotic pressure.
Osmotic pressure does not occur in cells that take in water very slowly.
Active transport
The movement of materials against a concentration difference is known as active transport. Active transport require energy
The active transport of small molecules or ions across a cell membrane is generally carried out by transport proteins or protein bumps that are found in the membrane itself
Bulk transport
Larger molecules and even solid clumps of material may be transported by movements of the cell membrane known as bulk transportBulk transport can take several forms depending on the size and shape of the material moved in or out of the cell
Pumps in cells
The transport of these larger materials sometimes involves changes in the shape of the cell membrane.
Small molecules and ions carried across membranes by proteins in the membrane that act like pumps
Many cells use such proteins to move calcium potassium and sodium ions across cell membranes
Changes in protein shape seem to play and important role in the pumping process
Endocytosis is the process oftaking material into the cell by means of infoldings, or pockets, of the cell membrane.
The pocket that results breaks loose from the outer portion of the cell membrane and forms a vesicle or vacuole within the cytoplasm.
In phagocytosis, extensions of cytoplasm surround a particle and package it within a food vacuole. The cell then engulfs it.
Amoebas use this method for taking in food.
Engulfing material in this way requires a considerable amount of energy and, therefore, is a form of active transport
In pinocytosis, cells take up liquid from the surrounding environment by forming tiny pockets along the cell membrane.
The pockets fill with liquid and pinch off to form vacuoles within the cell.
During exocytosis, the membrane of the vacuole surrounding the material fuses with the cell membrane, forcing the contents out of the cell.
How do individual cells maintain homeostasis
To maintain homeostasis unicellular organisms grow, respond to environment and reproduce
A single celled organism or unicellular organism does everything you would expect you would expect a living thing to do
Just like other living things unicellular organisms must achieve homeostasis relatively constant internal physical and chemical conditions
What do unicellular organsims do
Every unicellular organism needs to find sources of energy or food, to keep concentrations of water and minerals within certain levels, and to respond quickly to changes in its environment.How do the cells of multicellular organisms work together to maintain homeostasis?
What do multicellular organisms do
The cells of multicellular organisms become specialized for particular tasks and communicate with one another
to maintain homeostasis.The cells of multicellular organisms are interdependent
The cells of multicellular organisms become specialized for particular tasks and communicate with one another in order to maintain homeostasis.
Cell speciallization
The cells of multicellular organisms are specialized with different cell types playing different roles
Some cells are specialized to move other to react to the environment and still others to produce substances that the organism needs
No matter what the role, each specialized cell contributes to the overall homeostasis of the organism
Tissues are groups of similar cells that perform a particular function
To perform a complicated takes many groups of tissues work together as an organ
Each tissues performs a specific task so an organ completes a series of specialized tasks.
Organ systems
A group of organs that work together is called and organ system
Cellular communication
Cells in a large organism communicate by means of chemical signals that are passed from one cell to another
These cellular signals can speed up or slow down the activities of the cells that reieve them and can cause a cell to change what it is doing
Cellular junctions
Some cells for connection or cellular junctions with neighboring cells
These junctions sometime hold cells firmly together
Other junctions allow small molecules carrying chemical messages to pass directly from one cell to the next
Cell response
To respond to one of these chemical signals a cell must have a receptor to which the signaling molecules can bind. Sometimes these receptors are on the cell membrane although the receptors for certain types of signals are inside the cytoskeleton
The chemical signals sent by various types of cell can cause important changes in cellular activity.