Science Unit 2

Cilia & Flagella

Provide movement capability. Cilia-Short-Used to move substances outside human cells, Flagella-Whip-like extensions-Found on sperm cells

VACUOLES

Storage tanks for food, water, and waste products. -Plants have very large water vacuoles.

NUCLEUS

"Control center" of the cell-Location of chromosomes (genetic material for cell).-Coordinates all cell activities.-Prokaryotes do not have a nucleus, they have a nucleoid region.

CELL WALL

*Made of cellulose, pectin, and lignin. *Is "selectively permeable" *Found in plant, bacterial, and some fungal cells. *Provides strength and support to the cell. *Structure surrounding plasma membrane

Principles of Cell Theory

-All living things are made of cells -Smallest living unit of structure and function of all organisms is the cell -All cells arise from preexisting cells (this principle discarded the idea of spontaneous generation)

Lysosomes

Break down large food particles into smaller ones -Found in animal cells but rarely in plant cells -Known as the "clean up crew" -Recycle parts of the cell to be used again. -Digestive 'plant' for proteins, lipids, and carbohydrates -Cell breaks down if lysosomes rupture. -

CYTOPLASM

Jellylike substance found inside the cell membrane. -All chemical reactions occur here. -Viscous (thick) fluid containing organelles Components of cytoplasm are: -Interconnected filaments & fibers -Fluid = cytosol -Organelles (not nucleus)

Mitochondria

"Peanut" shaped organelle in cytoplasm. -Has tiny amount of it's own DNA (mDNA) -Known as the "Powerhouses" of the cell because they supply energy to the cell in the form of ATP (adenosine triphosphate -Sugar (glucose) is broken down to release energy here through a process called respiration. -Humans have 3,000-5,000 in each cell. (depends on cell type) -Double-layered outer membrane with inner folds called cristae

Animal Cells

-Animal cells are typical of the eukaryotic cell; enclosed by a plasma membrane and containing a membrane-bound nucleus and organelles. -Unlike the eukaryotic cells of plants and fungi, animal cells do not have a cell wall. This feature was lost in the distant past by the single-celled organisms that gave rise to the kingdom Animalia. -Most cells, both animal and plant, range in size between 1 and 100 micrometers and are thus visible only with the aid of a microscope.

Cell Function

-Cells take in energy and oxygen. -Cells secrete, and store chemicals. -Cells break down substances. -All parts of the cell work together to perform these functions.

Plant Cells

-Plant cells have retained the protective cell wall structure of their prokaryotic ancestors. -The basic plant cell shares similar construction with the typical eukaryote cell, but does not have centrioles, lysosomes, cilia, or flagella, as does the animal cell. -Plant cells do, however, have a number of other specialized structures, including a rigid cell wall, central vacuole,and chloroplasts. -Although plants (and their typical cells) are non-motile, some species produce gametes (sperm cells) that do exhibit flagella and are, therefore, able to move about.

CELL MEMBRANE

-Protects and supports the cell -Contains cholesterol. -Has holes called pores. -Controls what goes in and out of the cell. -Outer membrane of cell that controls cellular traffic -Contains proteins that span through the membrane and allow passage of materials. -Proteins are surrounded by a phospholipid bi-layer.

Rough Endoplasmic Reticulum

-Ribosomes attached to surface-Manufacture proteins-Not all ribosomes attached to rough ER-May modify proteins from ribosomes

RIBOSOMES

-Small organelles that make proteins. -Ribosomes can be found: -floating freely in the cytoplasm. -attached to the ER (endoplasmic reticulum) -Ribosomes are made in the nucleolus and move out through the nuclear membrane.

No cell wall in animal cells

-The lack of a rigid cell wall allowed animals to develop a greater diversity of cell types, tissues, and organs. -Specialized cells that formed nerves and muscles—tissues impossible for plants to evolve—gave these organisms mobility. -The ability to move about by the use of specialized muscle tissues is a hallmark of the animal world.

Cells Have Large Surface Area-to-Volume Ratio

-This restricts the size of cells. They cannot function if they become too large. -Some cells are long and thin (muscle cells) and some have "frilly edges" that can increase surface area. Round cells are always very small. -Therefore most cells are microscopic!

Cell Organelles

-Tiny organs that perform all functions needed for cell survival, growth, and reproduction. -Some organelles in plant cells are different than in animal cells.

Cytoskeleton

-Tiny tubules made of protein found inside the cytoplasm. -Give the cell structure and support -Can also help in cell movement (ex. Amoeba) -Filaments & fibers 3 functions: mechanical support anchor organelles help move substances

Chloroplasts

Contain a green pigment called chlorophyll -Chlorophyll absorbs the sunlight to make energy through the process of photosynthesis. -Makes food (glucose) for the cell. -Chloroplasts are found only in plant cells!

Mitochondria & Chloroplasts

Endosymbiosis -proposal that eukaryotic organelles evolved through a symbiotic relationship -one cell engulfed a second cell and a symbiotic relationship developed -mitochondria and chloroplasts are thought to have evolved this way

Golgi Bodies

Flat stack of folded membranes. -Proteins that are made are packaged into vesicles for transport around and outside of the cell. -Other compounds are also transported and packaged by the golgi bodies.

Chromosomes

Found inside the nucleus and direct all activities of the cell.-DNA is highly twisted into rod-shaped organelles.-Responsible for passing on genetic traits in an organism.-DNA and special proteins (histones) make up these structures- Usually in the form of chromatin- Contains genetic information- Composed of DNA- Thicken for cellular division- Set number per species (i.e. 23 pairs for human)

NUCLEOLUS

Located inside the nucleus.-Site where ribosomes are produced.

Smooth Endoplasmic Reticulum

No attached ribosomes-Has enzymes (special proteins) that help build molecules-Carbohydrates-Lipids

Endoplasmic Reticulum

Passageways that transport materials (especially proteins) within the cell-Allow organelles to communicate with one another-2 kinds of ER. -Rough ER has ribosomes attached.-Smooth ER have no ribosomes attached.

Peroxisomes

Peroxisomes are similar to lysosomes. -They contain oxidizing enzymes (enzymes which add oxygen to compounds) rather than digestive enzymes. -Adding oxygen can neutralize many substances which would otherwise be toxic. -One poison which the peroxisomes can prevent from doing harm to the cell is hydrogen peroxide (H2O2). -This reaction is important in liver and kidney cells where the peroxisomes detoxify various toxic substances that enter the blood. About 25% of the ethanol people drink is oxidized this way.

Nuclear Membrane

Surrounds the nucleus-Controls what goes in and out of the nucleus.-Has small openings called nuclear pores for allowing certain materials in and out.-Confines the 'nucleoplasm' inside.