The cell is life's basic unit of structure and function, according to the cell theory.
The cell is the smallest unit of living material that can carry out all the activities needed for life.
It may seem odd that we are still made of cells.
There is a reason for this.
Centralized organization is an important part of unicellular and multicellular organisms.
The surface area-to-volume ratio is the second reason we can't be giant cells.
There is always a lot of exchange between the inside and the outside.
There is lots of space to do these exchanges if this ratio is kept large.
There are parts of living things that have a lot of folds.
Even the largest things are made of cells.
This is a concept that comes up a lot.
To practice calculating the surface area-to-volume ratios of different-sized cubes and spheres, use the volume formulas on the Equations and Formulas sheet.
Scientists have known about cells for hundreds of years.
The development of the electron microscope allowed scientists to figure out what cells do.
There are two different types of cells.
Different types of microscopes are used to study cells.
The compound microscopes commonly found in labs are used to study stained or living cells.
They can increase the size of an organisms up to 1000 times.
Light microscopes can be used to observe a cell, but they can't see the detailed structures of the cell.
They can resolve structures as small as a few nanometers in length.
A prokaryotic cell is relatively easy to understand.
Prokaryotes includebacteria and archaea.
The inside of the cell has a substance called cytoplasm.
The genetic material in a prokaryote is one continuous, circular DNA molecule that is found free in the cell in an area called the nucleoid.
The cell wall of most prokaryotes is composed of peptidoglycans.
ribosomes are smaller in prokaryotes than in eukaryotic cells.
One or more flagella, which are long projections used for movement, and a thick capsule outside of their cell wall, may be some of the reasons why somebacteria have one or more flagella.
The prokaryotic cells used to be independent.
They have become a permanent part of the cells.
Eukaryotic cells are more complex than prokaryotic cells.
Eukaryotes include plants and animals.
Eukaryotic cells are organized into smaller structures.
Some of the structures are the same as in prokaryotic cells.
A good way to remember the difference is that prokaryotes don't have any organelles.
The only substance in their body is the blood.
A cell is like a factory.
Each of the organelles has its own special tasks.
Let's look at the structure and function of each organelle during a tour of a cell.
This is a picture of an animal cell.
The cell has an outer envelope.
A simple thin layer surrounding the cell is actually a complex double-layer structure made up of mostly phospholipids and proteins.
The tails of the acids face inward and the heads face out.
It is a bilayer made of two layers oflipids.
The movement of substances into and out of the cell is regulated by the plasma membrane.
Certain substances, such as O 2 and CO 2, can only pass through the semipermeable portion of the membrane.
Special tunnels can only be used for large and/or hydrophilic things.
The surface area of a cell needs to be large to allow for exchange of materials.
Smaller cells have a better surface area-to-volume ratio.
The cell is made of many different types of cells.
Some of these are related to the lipid bilayer.
The inner or outer surface of the membrane is where they are located.
Others are bound to the cell wall.
The amphipathic nature of theseProteins means that their hydrophilic regions extend out of the cell or into the cytoplasm, while their hydrophobic regions interact with the tails of the membrane phospholipids.
All the way through themembrane, there are some integral proteins.
The fluid-mosaic model is an arrangement of phospholipids and proteins.
This means that each layer of conjugates is flexible, and it is a mosaic because of the different conjugates.
Anything that is hydrophilic should not go through the interior.
This means that the polar heads of thelipids on one side should not flip-flops to the other side.
It's due to the number of activities that take place.
There are several broad functional groups for thetrypsinogen.
junctions between adjacent cells are formed by some membrane proteins.
The docking sites for arrivals at the cell are served by others.
Transport proteins form pumps that use ATP to move solutes.
Others form channels that allow the passage of certain things.
Cell surface markers, such as glycoproteins, are exposed on the extracellular surface and play a role in cell recognition.
The side chains are attached to the surface of the proteins.
They are only found on the outer surface.
Cholesterol is found in the phospholipid bilayer because it helps keep the animal's cell structure stable.
The largest organelle in the cell is the nucleus.
The nucleus is responsible for the cell's ability to reproduce, as well as directing what goes on in the cell.
The home of the hereditary information is here.
The nucleus's most visible structure is the nucleolus, where rRNA is made and ribosomes are assembled.
The ribosomal sites are where the synthesis of genes takes place.
Their job is to make all the proteins that the cell needs.
The ribosomes are made of two parts, the large and small.
The structure is made of rRNA and proteins.
There are two ways in which ribosomes can be attached to the ER.
All forms of life have ribosomes, although they differ in size.
Eukaryotic ribosomes are larger than prokaryotic ribosomes.
The "s" is a measurement used to compare the size of small things.
The ER extends into many regions of the cytoplasm.
The rough ER is the part of the ER that is studded with ribosomes.
The ER can be used to build Golgi bodies, lysosomes or the ER.
The ER that lacks ribosomes is called the smooth ER.
The smooth ER breaks down toxic chemicals.
The disks of the Golgi apparatus are called cisternae.
A Golgi stack can contain anywhere from 3 to 20 cisternae, and they are divided into three parts.
Molecules can move between the different types of cisternae.
The Golgi bodies, which look like stacks of flattened sacs, are involved in the processing of proteins.
The Golgi bodies modify, process, and sort the products once the ribosomes on the rough ER have done their job.
The distribution centers are where materials are sent out of the cell.
They package the final products in small sacs called vesicles, which are used to carry the products to the plasma membrane.
The production of lysosomes is done by golgi bodies.
The Mitochondrion is an important organelle.
The powerhouses of the cell are referred to as Mitochondria.
They are power stations that convert energy from organic molecule into useful energy for the cell.
adenosine triphosphate is the most common energy molecule in the cell.
More of the cell's powerhouses can be found in cells that need a lot of energy.
Mitochondria are rich in muscle cells.
The mitochondrion is an easy organelle to recognize because it has a unique oblong shape and a double membrane.
The matrix is separated from the intermembrane space by the folds of the cristae.
The intermembrane space is separated from the cytoplasm by the outer membrane.
Most of the production is done on the cristae.
The surface area for making ATP is increased by having folds in the membrane.
In biology, folding is used to increase surface area.
This is similar to the surface area-to-volume ratio concept.
Alveoli can be found in the lungs, brain tissue, small intestine, and root hairs in plants.
lysosomes are small structures in the cell.
These sacs are used to break down old, worn-out organelles, debris, or large ingested particles.
The cell's clean-up crew is made up of lysosomes.
The lysosome contains hydrolytic enzymes that only work at acidic pH.
You'll learn about lysosomes when you learn about endocytosis.
During programmed cell death, lysosomes are essential.
The centrioles are small, cylindrical structures that are often found in microtubule organizing centers.
Centrioles are active during cellular division.
When a cell is ready to divide, the centrioles pull the replicated chromosomes apart and move them to opposite ends of the cell.
centrioles are found in animal cells, but not in most plant cells.
vacuoles are not empty.
They are fluid-filled sacs that hold water, food, waste, salts, or pigments.
Hydrogen peroxide (H 2 O 2 ) is produced by peroxisomes, which detoxify various substances.
The hydrogen peroxide is broken down into oxygen and water.
They are common in animals.
The shape of a cell is determined by a network of fibers.
Microtubules and microfilaments are the most important fibers.
The tubulin, which is made up of the Microtubule, is involved in cellular division and movement.
The centrioles, cilia, and flagella are made of small fibers.
Centrioles help chromosomes separate during cell division.
Microfilaments are important for movement.
The structures are made of the actin.
Actin monomers are broken apart to allow microfilaments to grow and shrink.
During cell movement, microfilaments assist in the formation of pseudopodia extensions.
The locomotive properties of Cilia and flagella are found in single-celled organisms.
The Euglena, which has a whiplike flagellum, and the Paramecium, which is covered in cilia, are two examples of organisms with these structures.
In your biology lab, the Paramecium is able to move about in waterways, ponds, and microscope slides.
We usually associate such structures with unicellular organisms, but they aren't the only ones with cilia and flagella.
These structures are found in some human cells.
The cells lining your respiratory tract have cilia that sweep constantly back and forth, helping to keep dust and unwanted debris from descending into your lungs.
Every sperm cell has a flagellum that allows it to swim through the female reproductive organs to fertilize the waiting ovum.
Most plant cells are the same as animal cells, with a few exceptions.
Plant cells have a protective outer covering called the cell wall.
A cell wall is a layer that protects the cell from the elements.
It is found in plants and protists.
Cell walls are used for protection against osmotic changes.
The cell wall in fungi is usually made of a modified polysaccharide.
Chitin is a principle component of arthropods.
Chloroplasts give plants their characteristic green color.
In Chapter 6 we will discuss the role of the chloroplasts in the process of photosynthesis.
Plants and algae have chloroplasts.
The central vacuole of a plant cell is larger than that of an animal cell.
This vacuole is found in mature plants.
A plant with a full vacuole is not dehydrated.
Plants that are dehydrated can't fill their vacuoles.
Plant cells do not contain centrioles, which is different from animal cells.
We've put together a table to help you remember the differences between prokaryotes, plant cells, and animal cells.
The testing board will ask you which cells contain which structures.
Function is closely related to biological structure.
We've talked about the structure of the cell, now let's talk about how fluids andmolecules pass through it.
The size and charge of particles that want to get through are two things that affect the ability of Molecules to move across the cell membranes.
Small, lipid-soluble substances don't have any resistance when they cross the plasma membrane.
The central zone is the only zone where things can pass through the lipid bilayer.
The bilayer won't let a substance pass without help.
It's important to move things across the membranes.
The movement of water and solute across the membranes is called osmoregulation.
Facilitated transport depends on a number of proteins.
Only certain things can be allowed through channels.
Aquaporins are water-specific channels.
Although water is polar, there are usually enough aquaporins for it to traverse the membrane.
Without aquaporins the water wouldn't be able to cross.
Na + and K + are transported across the plasma membrane.
We know how things cross, but we don't know why.
If there is a high concentration of something in one area, it will move to spread out and diffuse into an area with a lower concentration, even if that means entering or exiting a cell.
The substance moves down a concentration.
This is called movement.
Simple diffusion is when the molecule that is diffuse is non-polar.
Facilitated diffusion is when the help of a channel-type protein is required.
Passive transport is when there is no outside energy required to move a substance.
It's like riding a bike downhill.
The input of metabolism is not required for passive transport.
It helps the cell import resources and export waste.
Osmosis is the process of getting water out of a molecule.
Water always wants to move from an area where it is the most concentrated to an area where it is least concentrated.
Water is usually a solution since it is so good at dissolving things.
A solution is made when a liquid solvent is dissolved.
This is the same as saying that water wants to go from where there is lesssolute.
It's like the water is moving to get rid of the particles.
The water can flow freely if there are two areas, but the solute can't.
If a chamber with a solution of water and a solution of sugar are connected by a semipermeable barrier, the solution of water and sugar can't cross.
Water is drawn into the chamber to reduce the concentration.
The total volume of the water chamber will be reduced.
Water will flow into the chamber until the concentration is the same.
The final result is that the concentrations of solutes are the same on 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 888-739-5110 The only difference between the two is that the solute is not absorbed by the membranes.
The cell wall is important in plants.
The cell wall is the same size all the time.
The cell wall can shrink if it loses water and can expand and squeeze against it if it takes in water, which is called plasmolysis.
The term tonicity is used.
The solute concentration is the same inside and outside if the environment is isotonic.
A hypotonic solution has less dissolved solutes than a hypertonic solution.
The tendency of water to move down its concentration can cause cells to explode and can overcome gravity.
The terms isosmotic, hyperosmotic, and hypoosmotic can be heard.
When comparing two solutions, tonicity terms are used, while when comparing a solution to a cell, these words are used.
Isotonic and isosmotic both describe situations in which the concentration is the same on either side of a membranes.
The only difference is the type of Membrane.
Prepare for questions about water potential and solute potential by looking at the Equations and Formulas sheet.
Water potential is the measure of potential energy in water and describes the eagerness of water to flow from an area of high water potential to an area of low water potential.
There are two factors that affect it: pressure potential and solute potential.
The AP Biology Equations and Formulas sheet describes the effect of solute concentration on water flow.
Adding a solute causes water to be less likely to leave the solution and more likely to flow into it.
The water is unlikely to diffuse away because the solution is more concentrated with the added solute.
The more negative the solute potential is, the more solute molecule present.
An area of high water potential is an area of high water concentration.
A red blood cell dropped into a hypotonic solution will expand because water will move into the cell, an area of lower water potential.
The red blood cell will pop eventually.
If a similar experiment is done with a plant cell, water will still move into the cell, but the cell wall will exert pressure, increasing the water potential and limiting the gain of water.
Water potential explains how water moves from soil to plant roots and how plants transport water from roots to leaves.
The number of moles of solute can be divided by the volume of solution to calculate the concentration of a solution.
Less concentrated solutions can be made with stock solutions.
The AP Biology Equations and Formulas sheet contains the equation to do this.
This equation tells you how much of a concentrated solution is required to make a more dilute solution.
The final volume of the solution will be the amount of solvent added minus the amount of stock solution you need to add.
If you wanted to add Tris solution to a new tube or bottle, you would have to add water up to a final volume of 50 mL.
In other words, you should add a lot of water.
A substance might want to move from a lower concentration to a higher concentration.
It's going to take energy to get the substance across the membranes.
It's like riding a bicycle uphill.
It takes a lot more work to ride uphill compared to downhill.
Active transport is movement against the natural flow.
The ATP is used to power some of the proteins.
The sodium-potassium pump is the best example of active transport.
It brings in three Na + and two K + to the cell.
If this pump is not used, the ion will remain in higher concentration.
Primary active transport occurs when the transport is directly utilized.
Secondary active transport is when something is moving with the energy captured from the movement of another substance.
The inside of the cell is always negative, and the sodium-potassium pump is important for setting up the typical charge within the cell.
The difference in charge between inside and outside the cell is important for passing signals in the body.
When particles are too large to enter a cell, the cell uses a portion of the cell's outer shell to absorb the substance.
A vacuole or a vesicle can be formed by the cell's pocket or pinch.
The process is called endocytosis.
The cell drinks liquids in pinocytosis.
The cell takes in food.
A special type of endocytosis involves cell surface receptors that work in tandem with endocytic pits that are lined with aprotein called clathrin.
The ligand is brought into the cell by the invagination of the cell.
The incoming ligand is carried into the cell's interior by a vesicle.
Substances move by bulk flow.
The one-way movement of fluids is called bulk flow.
The movement of blood through a blood vessel and the movement of fluids in xylem and phloem are examples of bulk flow.
The solutes are spread across the membrane.
The process of diffusion can be used to sort substances that have holes in them.
By using machines and concentration gradients, the blood is removed from the body.
Things present at high levels will naturally diffuse out of the blood.
Large particles can be moved out of the cell.
In exocytosis, a cell expels waste products or hormones by fusion of a vesicle with the plasma membrane, which then expels the contents into the extracellular space.
The smallest unit of living organisms are cells.
Cells can be categorized into prokaryotes, which do not have a nucleus, and eukaryotes, which have a nucleus.
The features of prokaryotic cells can include the following.
The inside of the Membrane has a hydrophobic nature.
The size of the molecule and the concentration of the molecule are important.
Chapter 15 contains answers and explanations.
The movement of substances into the cell is dependent on a number of factors.
Key insights into many aspects of cellular structure and function have been provided by the development of electron microscopy.
The causative agent of cholera is vibrio cholerae, a highly pathogenicbacteria that are associated with severe gastrointestinal illness.
In extreme cases, antibiotics are prescribed that target the missing structures in animal cells.
Questions 4 and 5 are based on the information and table.
There is a new unicellular organisms living in thermal pools.
The thermal pools have an average temperature of 45degC and a pH of 3.2.
Microbiologists perform tests to evaluate the structural organization of organisms.
The table summarizes the data from the microscope.
Estradiol is produced from the ovaries.
The molecule travels through the bloodstream.
The researcher was interested in reducing the effect of estrogen on the organisms.
Paramecium lives in freshwater habitats.
Paramecium has evolved strategies to deal with the consequences of this hypotonic environment.
A cotransporter is a piece of equipment that moves two substances across a body of water.
The Na + K + ATPase is able to transport sodium and potassium ion across the plasma membrane.