Section 1.2 – 1.4 in your textbook Cell Structures Section 1.2 – 1.4 in your textbook

Overview From the cell theory we know that cells are living units that make up living organisms 2 main types of cells: Prokaryotic  bacteria Eukaryotic  plants & animals Prokaryotic cells are much simpler than eukaryotic cells

Cell Structures in common… Cell membrane: (membrane means “thin skin”) Barrier/boundary  security guard Keeps all of the “stuff” inside the cell Lets nutrients & water in, lets waste out Keeps harmful stuff out

More about the cell membrane… Also called the “plasma membrane” Selectively permeable If it was impermeable  no movement of materials from inside of the cell to out & vice versa If it was completely permeable  anything could get in & out! “Lipid bi-layer” – two layers of fat molecules Hydrophilic heads (love water) Hydrophobic tails (hate water) Embedded proteins – help move materials across the membrane

Nucleus Control center of the cell Contains DNA Prokaryote  no “true” nucleus  DNA is floating free in the cell Eukaryote  has a true nucleus, surrounded by the nuclear membrane  DNA in the nucleus

DNA Genetic information Deoxyribonucleic acid “nucleic” means: found in the nucleus Long chain molecule organized into threads called chromosomes, which have genes, which contain instructions for making proteins. DNA can make copies of itself so the cell can divide! Also found in the nucleus: RNA…. More about that later!

More terminology… Protoplasm: all of the “stuff inside of the cell membrane. Cytoplasm: everything inside of the cell membrane except the nucleus where all the “action” happens... Fluid + cell organelles + nutrients + waste 2 external structures: Flagella  whip-like tails, used for propulsion Cilia  short, hair-like, used for propulsion & to move materials around outside the cell

Cellular organelles Small, specialized structures found in the cytoplasm Visible only under an electron microscope

Mitochondria “Power Plant” of the cell Provide the cell with energy through cellular respiration. 2 membranes: smooth outer & folded inner Folds on the inner are called “cristae” Enzymes on cristae speed up cellular respiration

Cellular respiration Happens in the mitochondria Energy is released as ATP (adenosine triphosphate) & used by the cell for necessary processes of life More active cells (like muscles) have more mitochondria than less active ones (like fat cells).

Ribosomes Site of protein synthesis Composed of RNA & proteins Smallest organelles in the cytoplasm Large number Mainly found on the endoplasmic reticulum & the nuclear envelope

Endoplasmic reticulum Network of interconnected parallel canals Rough ER: has ribosomes attached, aids in production of proteins Smooth ER: no ribosomes, where lipids are synthesized

Golgi apparatus Looks like a stack of flattened balloons (membranous sacs) Processes proteins from the Rough ER Ends pinch off to form vesicles – last step before ejecting proteins from the cell to be used by the organism

Exocytosis Vesicles from the Golgi apparatus fuse with the cell membrane and their contents (waste, hormones, enzymes, proteins) are released into the extracellular fluid.

Endocytosis Opposite of exocytosis Vesicles formed for transport purposes. Two types of endocytosis: Pinocytosis refers to small particles (cell drinking) Phagocytosis refers to ingestion of large molecules (cell eating)

Lysosomes Surrounded by a membrane Formed by the Golgi apparatus Contain enzymes to break down molecules and discarded cell parts – “cellular digestion” A build up of waste products (that are not broken down) can cause brain damage Only found in animal cells

Microfilaments and microtubules Microfilaments: fibrous structures that provide support, shape and movement for the cell Microtubules: tiny tubes that transport materials in the cytoplasm Collectively called the “cytoskeleton”

Chloroplasts Plant cells produce and store their own food through the process of photosynthesis Chloroplasts drive the process of photosynthesis Contain a green pigment called chlorophyll Only found in plant cells

Cell Wall Not found in animal cells Composed of cellulose Protects and supports plant cells Differing degrees of rigidity: flowers have thin cell walls, trees have thicker, secondary cell walls

Vacuole Plant cells have a large fluid filled space called a vacuole Storage space: sugars, minerals, proteins, water Found in the cytoplasm Provides physical support for the cell: turgor pressure Animal cells have smaller vacuoles (not used for physical support)