Cell Structure and Function

w The discovery and the basic theory of cells. w Cell size and number. w The two major kinds of cells. w Plant cells and animal cells. w Cell membrane (plasma membrane). w Cytoplasm. w Nucleus. w Ribosomes.

w Endoplasmic reticulum (rough and smooth). w Golgi complex (body). w Lysosomes. w Peroxisomes. w Mitochondria. w Chloroplasts. w Cytoskeleton. w Vacuoles.

The Two Major Kinds of Cells w Each cell must have three features: 1. Plasma (cell) membrane: forms the boundary of the cell. 2. DNA-containing region: inheritable instructions. 3.Cytoplasm: fills interior of the cell between the plasma membrane and DNA region.

w There are two major types of cells prokaryotic lacks a nucleus and does not have an extensive system of internal membranes all bacteria and archae have this cell type eukaryotic has a nucleus and has internal membrane-bound compartments all organisms other than bacteria or archae have this cell type

The Two Major Kinds of Cells w Prokaryotic Eukaryotic

Animal Cell- Eukaryotic

Plant Cell- Eukaryotic

Prokaryotic cell

Animal Cell Plant Cell

w not all eukaryotic cells are alike the cells of plants, fungi, and many protists have a cell wall beyond the plasma membrane all plants and many protists contain organelles called chloroplasts plants contain a central vacuole only animal cells contain centrioles

Cell membrane (Plasma Membrane) w The backbone of cell membranes is a molecule called phospholipid w Each phospholipid molecule has one hydrophilic head (phosphate), and two hydrophobic tails (two fatty acids). w hydrophilic (water-loving) w hydrophobic (water-fearing)

w When surrounded by water, heads point outward, tails point inward. Water is excluded from the middle, thus forming two layers called lipid bilayer. heads tails water Water excluded

Phospholipid molecule

The Lipidbilayer

Another major component of the membrane is a collection of membrane proteins some proteins form channels that span the membrane these are called transmembrane proteins other proteins are integrated into the structure of the membrane for example, cell surface proteins are attached to the outer surface of the membrane and act as markers

Endocytosis and Exocytosis w Refer to Endocytosis and Exocytosis (animation in my website)

Phagocytosis: a form of endocytosis in which cells engulf organisms

Pinocytosis: a form of endocytosis through which a cell takes in fluid

Exocytosis: a process by which substances are moved out of a cell by vesicles

The Nucleus: The Cell’s Control Center (nuclear envelope, chromosomes, nucleolus)

Nuclear envelope w The nuclear surface is bounded by a double- membrane called the nuclear envelope groups of proteins form openings called nuclear pores that permit proteins and RNA to pass in and out of the nucleus

Chromosomes w The nucleus stores hereditary information w The DNA of eukaryotes is packaged into segments and associated with a protein this complex is called a chromosome

Nucleolus The nucleus is the site for the subunits of the ribosome to be synthesized The nucleolus is a dark-staining region of the nucleus It contains the genes that code for the rRNA (ribosomal RNA) that makes up the ribosomal subunits

w The subunits leave the nucleus via the nuclear pores and the final ribosome is assembled in the cytoplasm

Ribosomes, Endoplasmic Reticulum ( Rough and Smooth), Golgi Complex

Ribosomes w Beadlike clusters in the cytoplasm w Are made up of a number of proteins and ribosomal RNA (rRNA), which are produced in the nucleolus w They participate in protein synthesis.

Endoplasmic Reticulum (rough and smooth): system of internal membranes and channels

* The segment of the ER dedicated to protein synthesis is called the rough ER the rough spots are due to embedded ribosomes * The segment of the ER that aids in the manufacture of carbohydrates and lipids is called the smooth ER the surface of this region looks smooth because it contains no embedded ribosomes

Golgi Complex w After synthesis in the ER, the newly-made molecules are passed to the Golgi bodies Golgi bodies are flattened membranes that form collective stacks called the Golgi complex their numbers vary depending on the cell their function is to collect, package, and distribute molecules manufactured in the cell

Lysosomes w Spherical vesicles that contain digestive enzymes. w 1. Digest worn-out organelles and cell debris. w 2. Act as a “minute cellular stomach”. They digest bacteria w 3. Act as “suicide bags” breaking open and spilling their contents and digesting the cell.

w Refer to lysosomes- animation in my website

Peroxisomes w Vesicles containing oxidative and other enzymes, such as catalase. w Catalase detoxifies hydrogen peroxide, converting it into water and oxygen.

Mitochondrion Mitochondria are cellular powerhouses Sites for chemical reactions called cellular respiration The organelle is surrounded by two membranes

Chloroplast w Chloroplasts are the location for photosynthesis w The organelle is also surrounded by two membranes

w Both mitochondria and chloroplasts possess circular DNA that is not found elsewhere in the cell

Cytoskeleton w Three-dimensional latticework of minute protein fibers. w Acts as internal skeleton, supporting the cell’s shape and activities.

Three types of protein fibers: w Microfilaments Microtubules Intermediate filaments w 3-6 nm in diameter nm in diameter 10 nm in diameter w Actin Tubulin Keratin and others w Lengthen and shorten Lengthen and shorten w Cause with other proteins move colored pigment maintain cell shape the contraction of muscles granules around make cell tough w can move organelles help maintain cell shape make up most of w Make up the spindle the matter in skin

Central and Contractile Vacuoles w Found only in plant cells w Occupies 5-95% of the total cell volume w It contains water and stores sugar, proteins, ions, and other materials (orange juice) w It makes surface-to-volume ratio favorable w Review contractile vacuoles in the following slide (video clip)

Name the following organelles:

Label the organelles in this cell

Question w All of the following are likely components of plant cells except: w A. chloroplasts. w B. mitochondria. w C. central vacuole. w D. flagella. w E. cell walls.