Chapter 7 A View of the Cell

What is a cell? Cells are the basic units of living things. Plants, animals, people, and bacteria are made of cells. The smallest cells are bacteria called mycoplasma. The largest cells are bird eggs. The longest cells are nerve and muscle cells.

Microscopes Scientists use compound light microscopes to look at cells. These magnify objects up to 1500 times. Used to see plant and animal cells, and small organisms Larger microscopes, called electron microscopes, were invented in the 1940s Used to magnify up to 500,000 times Scanning electron microscopes (SEM): scan cell surfaces Transmission electron microscopes (TEM): study structures inside cells

The Cell Theory: 3 Main Ideas Developed in the 1830s 1. All organisms are made of cells. 2. The cell is the basic unit of organization of organisms. 3. All cells come from preexisting cells.

2 main types of cells Prokaryotes Bacteria Eukaryotes Plants animals

Prokaryotes Have no membrane bound nucleus Has a nucleoid region- coiled DNA Has ribosomes that make proteins Have no internal membrane-bound structures (organelles) Very small Very simple

Eukaryotes Have a nucleus Have membrane-bound structures called organelles Are larger Are more complex Include algae, yeast, plants, animals, people

The Plasma Membrane The plasma membrane is the boundary between the cell and its environment It is made of 2 layers of phospholipids, called a bilayer Hydrophilic heads face out, hydrophobic tails face in

Function of the plasma membrane It controls what enters and exits the cells, it is selectively permeable Nutrients enter, wastes leave Homeostasis, or balance, is maintained

Fluid Mosaic The model of the plasma membrane is called the fluid mosaic model. It is fluid because the membrane is flexible. It is a mosaic because it is made of phospholipids with proteins, cholesterol and carbohydrates embedded in it.

Fluid Mosaic Cholesterol in the cell membrane is used to stabilize the membrane and keep phospholipids from sticking together. Carbohydrates on the surface help cells recognize each other. Proteins in the membrane are used for transporting molecules through the lipids.

Cytoplasm Cytoplasm is the clear, gelatinous fluid found inside a cell It holds and supports all the organelles

Nucleus The nucleus is an organelle in eukaryotic cells It is surrounded by a double membrane It holds our DNA, found on chromosomes “Control center” of the cell It is the largest organelle

CHROMOSOMES Shape- strand like, X structure Size- Very small Made of- Deoxyribonucleic acid Function- An organized way to hold DNA together, carries genes for the cell Location- In the nucleus

RIBOSOMES Ribosomes are made by the nucleolus (located attached to the nucleus) Ribosomes produce proteins

SMOOTH ENDOPLASMIC RETICULUM Aka Smooth ER (SER) Function- Synthesizes lipids, including fatty acids, phospholipids, and steroids. It also regulates the amount of sugar released into the bloodstream

ROUGH ENDOPLASMIC RETICULUM Rough ER (RER) Has ribosomes attached to the outside giving it a rough appearance Function- 1. to make more membranes 2. to make proteins that are secreted by the cell

GOLGI APPARATUS- GOLGI BODY Named after Italian Biologist Camillo Golgi Shape- a series of flattened sacs that looks like pita bread Function- serves as a molecular warehouse and finishing factory. It receives and modifies substances manufactured by the Endoplasmic Reticulum.

VESICLE Shape- round Very small It is made up of phospholipids It functions as a transport vehicle for the cell It transports proteins from the Golgi apparatus to the cell membrane so they can exit the cell

LYSOSOME Small and Round membranous sac filled with digestive enzymes Function- the lysosome digests food vacuoles and damaged organelles, also helps destroy harmful bacteria Only in animal cells

MITOCHONDRIA Membrane bound organelles in plant and animal cells that make energy Glucose from food is converted to ATP, the energy molecule used by our cells “Power house” of the cell Has a highly folded inner membrane

CYTOSKELETON The cytoskeleton is a support structure in the cell It helps a cell maintain shape Microtubules are thin, hollow cylinders made of protein Microfilaments are thin, solid protein fibers Cilia are short, numerous, hair like projections that move a cell with a wave like motion Flagella are longer projections that move a cell with a whip like motion

CELL WALL Thick wall ONLY in plant cells Made of cellulose, used to give structure to cell walls It protects and supports plant cells The cell wall goes around the cell membrane

VACUOLE Found only in plant cells Used for temporary storage Store food, enzymes, water, and waste

CHLOROPLAST Only in plant cells Capture light energy and produce glucose and ATP Contain a green pigment called chlorophyll to trap light energy

Animal Cells and Plant Cells Animal cells, in general, are smaller than plant cells and have a cell membrane but no cell wall. Plant cells, in general, are larger than animal cells, are square or rectangular shaped, and have a large vacuole, a cell wall, and chloroplasts.