EUKARYOTIC CELL ORGANELLES AND

STRUCTURES

Cytoplasm:

• The cytoplasm is the cellular region between the nuclear membrane and the plasma membrane; It consists of a fluid called cytosol (which contains dissolved solutes, stores nutrients, secretory products and pigment granules) and organelles-the metabolic machinery of the cytoplasm and the cell. Function: Provides moisture and nutrition.

Nucleus:• Function: It is the control center of the cell;

responsible for transmitting genetic information and providing the instructions for protein synthesis.

• The nucleus contains chromatin-granular, threadlike material composed of DNA and histone proteins both of which make up genes. When a cell is ready to divide, chromatin coils, condenses, and becomes chromosomes.

Nuclear Envelope

• The Nuclear envelope is a double-membrane structure surrounding the nucleus. It is pierced by the pores and the outer membrane is continuous with the cytoplasmic endoplasmic reticulum.

• It functions to separate the nucleoplasm from the cytoplasm and regulates passage of substances to and from the nucleus.

• The Nucleolus is a dense, spherical (nonmembrane bound) body made of ribosomal RNA and proteins: functions in making ribosomes. A single nucleus has one or more nucleoli.

Ribosomes:

• Ribosomes are non-membranous organelles. Function: to make proteins; ribosomes are free in the cytoplasm or bound to rough ER (endoplasmic reticulum). Proteins to be used within the cytosol are produced by the free - floating ribosomes; proteins to be inserted into membranes or exported from the cell are made by the ribosomes attached to the rough ER.

Endoplasmic reticulum:• It is a network of canals extending from the

plasma membrane to the nucleus. Function: to transport proteins out of the cells. Two types: Rough ER-has ribosomes attached to it, and functions to attach polysaccharide groups to proteins as they are made by the ribosomes to be exported from the cell; Smooth ER-has no ribosomes attached; and functions to make lipids and hormones (steroids) to be exported from the cell, or sometimes used by that cell.

Golgi apparatus:

• Is a group of flattened sacs arranged like a stack of bowls; functions to modify and package proteins and lipids into vesicles-small, spherically shaped sacs that bud from the outside surface of the Golgi body. After modifications are done, these are shipped outside the cell.

vesicles-membrane bodies with many functions-usually storage or transportation

• Lysosomes: vesicles from a Golgi apparatus that contains digestive enzymes. Function to break down food, cellular debris, and foreign invaders such as bacteria. Not present in plant cells.

• Peroxisomes: sacs in the cytoplasm that contain powerful oxidase enzymes. Function:to use molecular oxygen to detoxify harmful substances by changing it to water. Common in liver and kidney cells; also in photosynthesizing plant cells.

Mitochondria:

• look like kidney beans or linked sausages; these are the powerhouse of the cell; function as sites of aerobic respiration-where energy in the form of ATP is obtained from carbohydrates.

• Most numerous in cells having a high energy requirement(muscle cells, or liver cells). Each contains an inner membrane and outer membrane. The inner membrane has many long folds called cristae-these enlarge the surface area of the inner membrane, allowing more space for chemical reactions to occur during times of great energy production. The outer membrane serves as a boundary between the mitochondrion and the cytosol.

• ****Mitochondria also have their own DNA-this is unique. New mitochondria can only arise when existing ones grow and divide. Theory is mitochondria developed from prokaryotic cells that lived inside eukaryotic cells-?????

• Cell Fibers-microtubules, intermediate filaments, and microfilaments-all function in making the shape of or in coordinating the movements of the cytoskeleton-internal scaffolding of the cell within the cytoplasm.

• Flagella-long, hair-like structure-whips for movement (are the tails on sperm)

• Cilia-hundreds of tiny, hair-like structures-whip for movement (in mucosa areas-bronchial tubes, nasal passages, etc)

• Microvilli-fingerlike extensions of the plasma membrane used to increase surface area. (intestines-absorb food).

• Centrioles-two dots that form near nucleus during cell division-will make a microtubule spindle in animal cells during mitosis (located in centrosomes-areas containing centrioles)

In Plants:

• Chloroplasts-carry out photosynthesis• Plastids – store nutrients and pigment

molecules• Cell walls-made of cellulose or chitin-

provide support for cell. (found in plants, fungi, protists, bacteria).

• (Large)Vacuole -membrane bodies usually used for storage