Cells

An Overview of Cells

• Cells are the basic units of structure and function in living things.

• Cells form the parts of an organism and carry out the all of the organism’s processes and functions.

An overview of cells

• The structure of an organism is determined by the arrangement of its cells.

• One square centimeter of your skin contains more than 100,000 cells.

Microscopes

• In 1590, microscopes were invented.

• Microscopes made it possible for scientists to discover and begin to learn about cells.

Cell Theory

• Cell theory is a widely accepted explanation of the relationship between cells and living things

1. All living things are composed of cells.

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

3. All cells are produced from other cells.

Inside Cells

• Cells are made up of even tinier structures.– Called organelles– Each one carries out specific functions

Cell Wall

• Rigid layer of nonliving material that surrounds the cells of plants and some other organisms.

• Animals do not have cell walls.

• Helps protect and support the cell.

Cell Membrane

• All cells have cell membranes.

• These are right behind the cell wall in cells that have them. In cells that don’t it is the outside barrier.

• Control what substances come into and out of a cell.

The Nucleus

• Controls all of the functions of the cell– The cell’s brain

Parts of the nucleus

• Nuclear Envelope– Surrounds the nucleus and protects it.– Materials pass in and out through the nuclear

envelope’s pores

• Chromatin– Strands that contain the genetic material and

direct the cell’s functions

• Nucleolus– Creates the cell’s ribosomes

Cytoplasm

• Clear, thick, gell-like fluid between the cell membrane and the nucleus

Mitochondria

• Rod-shaped

• Convert energy in food molecules to energy the cell can use to carry out its functions

Endoplasmic Reticulum

• Maze of passageways

• Carry proteins and other materials from one part of the cell to another

Ribosomes

• Small, grainlike

• Produce proteins

Golgi Bodies

• Receive proteins and other newly formed materials from the endoplasmic reticulum, package them ,and distribute them to other parts of the cell

Chloroplasts

• Only found in plants and some other organisms

• Large green structures

• Capture energy from sunlight and use it to produce food for the cell

• These make leaves green

Vacuoles

• Large, water-filled sac

• Most plant cells have one large vacuole

• Some animal plants have one, others don’t.

• Store food and other materials needed by the cell

Lysosomes

• Small, round structures

• Break down large food parts into smaller ones

• Break down old cell parts and release the substances so they can be reused

Elements

• An element is any substance that cannot be broken down into simpler substances.

• The smallest unit of an element is an atom.

• Elements are made up of only one type of atom.

• Elements are listed in the Periodic Table.

• What are some examples of elements?

Compounds

• When two or more elements chemically combine, they form a compound.

• The smallest unit of a compound is called a molecule.

• What are some examples of compounds?

Organic and Inorganic

• Most compounds that contain the element carbon are considered organic.

• Compounds that don’t contain carbon are called inorganic.

• Some important groups of organic compounds found in living things are carbohydrates, lipids, proteins, and nucleic acids.

Carbohydrates

• A carbohydrate is an energy-rich organic compound made of carbon, hydrogen, and oxygen.

• Sugars and starches are carbohydrates.

• Sugar molecules can combine to form starches.

Carbohydrates

• Plant cells store excess energy in starches.

• When you eat a starch your body breaks it down into glucose, a sugar that your cells can use to produce energy.

• Carbohydrates are a part of some cell parts.

Lipids

• Lipids are energy-rich, organic compounds, made of carbon, hydrogen, and oxygen.

• Fats, oils, and waxes are all lipids.• Lipids contain more energy than

carbohydrates.• Cells store energy in lipids for later use.• Lipids are a part of some organelles,

especially the cell membrane.

Proteins

• Proteins are large organic molecules made of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

• Meat, eggs, fish, nuts, and beans are all high in protein.

Proteins

• Protein molecules are made up of smaller molecules called amino acids.

• Much of the structure of cells is made up of proteins.

• The proteins known as enzymes are important because they speed up chemical reactions in living things.

• Feathers, a spider’s web, and fingernails are all made mostly of proteins.

Nucleic Acids

• Nucleic acids are very long organic molecules made of carbon, oxygen, hydrogen, nitrogen, and phosphorus.

• They contain the instructions that cells need to carry out the functions of life.

Nucleic Acids

• There are two types of nucleic acids: DNA and RNA.

• DNA carries information about an organism, is passed from parent to offspring, and directs all of the cell’s functions.

• RNA plays an important role in the production of proteins.

Water and Living Things

• Water makes up two thirds of your body.

• Most chemical reactions within cells could not take place without water.

• Water also helps cells keep their size and shape.

• Water keeps the temperature of cells from changing too quickly.

Diffusion

• Diffusion is the main method for small molecules to move across the cell membrane.

• Molecules move from an area of higher concentration to an area of lower concentration.

Osmosis

• Osmosis is the diffusion of water.

• Many cellular processes depend on osmosis because they need water to happen.

Osmosis

• Osmosis can cause a cell to swell if too much water enters it or shrink if too much water leaves it.– This happens because the cell wants an

equal concentration of water inside and outside of the cell.

– If there is too much salt outside of the cell, water will move out of the cell.

– If there is not enough salt outside the cell, water will move into the cell.

Active transport

• Osmosis and diffusion do not require energy because the materials are naturally balancing themselves.

• If a cell moves a substance from a lower concentration to a higher concentration it requires energy and is called active transport.