Eukaryotic Cells

Golgi apparatus

"the shipping and recieving" center of the cells endomembrane system. It modifies, store, and exports substances from the cell.

process of phagocytosis

How can cells use the food that eukaryotes take in? One In phagocytosis, for the purpose of acquiring nutrients, the cell first surrounds a nutrient with its plasma membrane. Once the plasma membrane completely surrounds the nutrient, the membrane pinches off to form a vesicle inside the cytoplasm of the cell. This vesicle, containing the engulfed food item, is called a food vacuole. Lysosomes fuse with these food vacuoles, and their digestive enzymes break down the food items.

Peroxisomes

Peroxisomes are the hazardous waste-handlers of the cell . They contain enzymes that break down toxic molecules by removing hydrogen. The hydrogen atoms are then combined with molecular oxygen (O2) within the peroxisome, producing hydrogen peroxide — this product is the inspiration for the organelle's name. Hydrogen peroxide is also toxic to cells, so the peroxisome must immediately convert the hydrogen peroxide to water. Peroxisomes are therefore a great example of the compartmentalization of harmful materials and volatile chemical reactions within a membrane-bound organelle.

contractile vacuole

The contractile vacuole controls the continual diffusion of fresh water (osmosis) into cells by pumping out excess water. (tonoplastsin plants cell controls osmotic balance as well).

rRNA and ribosome connection?

The rRNA combines with proteins to form the small and large subunits of the ribosomes, which are the protein-producing factories of the cell. These subunits move into the cytoplasm where a large and small subunit will assemble together to become a ribosome.

similarity and difference of mitochandria and chloroplasts

They are both energy types of power houses. Except they perform different functions. Because chloroplasts produce carbohydrates from water, CO2, and the energy in sunlight, whereas mitochondria break carbohydrates down to store energy in the form of ATP.

centriole

They are within the centrosome. They help organize the mitotic spindle and function in cytokinesis in SOME ANIMALS.

chlorophyll

This photosynthetic pigment is housed within chloroplasts. It absorbs light energy. This energy is then used in the chloroplasts to perform photosynthesis. These pigments are contained within the membranes of the thylakoids. The thylakoids form towers called grana that look like stacks of dinner plates (Figure 9). Within the thylakoid, light energy is converted into ATP, which in turn powers the construction of sugars in the stroma. In the stroma, CO2 molecules are used as building blocks to construct carbohydrates.

Why are mitochondria and chloroplasts semi-autonomous?

endosymbiotic theory

vesicle

membrane-bound transport organelle called a transport vesicle

rough endoplasmic reticulum (RER)

suspended un the cytolsal outside of cell. It connects to nuclear envelope and appears rough because it is studded with ribosomes. It the site of secretory protein synthesis (proteins are made for export and are packaged into vesicles for transport), and is also a source of membrane phospholipids.

Which two cellular structures give shape and support to plant cells?

the cell wall and tonoplast/central vacuole

Mitochandria

the enegery powerhouse of the cell. These organelles synthesize ATP, the cells main energy source, through respiration.

Food Vauole

A vesicle inside the cytoplasm of the cell which contains an engulfed food item. It will bind with the lysosome to be digested. (Process of phagocytosis)

nuclear pore

An opening in the nuclear envelope which permits the movement of large molecules, such as messenger RNA, out of the nucleus.

plamsodesmata

Are gaps in the cell walls of adjacent PLANT CELLS that allow cell to cell communication.

Autophagy

Autophagy is the process of breaking-down and recycling malfunctioning or worn-out cell organelles. This process reclaims vital molecules from worn-out organelles — valuable materials that would otherwise be lost.

Chloroplasts

Chloroplasts perform photosynthesis, which is the conversion of light energy, carbon dioxide (CO2), and water into carbohydrates like sugars and starch. The chloroplast is bound by two membranes called the outer and inner membranes. Chloroplasts house photosynthetic pigments, such as CHLOROPHYLL molecules that absorb light energy.

nucleolus

Darker staining region of the nucleus where ribosomal RNA is produced and ribosome subunits are assembled.

Relate the forms of different cell structures to their functions.

Eukaryotic cells have a nucleus and membrane-bound organelles. None of these structures are possessed by prokaryotes. The nucleus contains chromosomes: long strands of DNA. DNA contains the instructions for creating proteins required by the cell. The nucleus also contains the ribosome-subunit-producing area called the nucleolus. Structures of the nucleus are enclosed by the double-layered nuclear envelope. During protein synthesis the instructions for making a protein are transcribed from DNA onto a messenger RNA molecule. The mRNA then leaves the nucleus and fuses with a ribosome. The ribosome constructs the protein based on the instructions on the mRNA transcript. Proteins produced in the rough endoplasmic reticulum are often destined for secretion outside of the cell. These proteins are placed in a membranous transport sac called a transport vesicle, which travels to the Golgi apparatus. In the Golgi apparatus, the proteins are modified and then placed into another vesicle that releases the substance outside of the cell membrane via exocytosis. The smooth endoplasmic reticulum is responsible for synthesizing lipids and detoxifying the cell. Lysosomes are vesicles containing digestive enzymes. Lysosomes fuse with food vacuoles brought into the cell by phagocytosis. The enzymes digest the food item, after which the nutritive molecules diffuse into the cytoplasm. Mitochondria break down glucose to produce ATP. Peroxisomes contain enzymes that break down toxic substances within the cell.

difference between prokaryotes and eukaryotes

The compartments in eukaryotic cells are mainly organelles: membrane-bound structures enclosed by a semi-permeable phospholipid membrane that is very similar in composition to the plasma membrane. Membrane-bound organelles are the primary feature that distinguishes eukaryotic cells from prokaryotic cells. Another major difference between prokaryotes and eukaryotes is the number, shape, and location of the chromosomes. In prokaryotic cells, a single circular chromosome is localized in the nucleoid, whereas eukaryotic cells have many linear chromosomes contained within a double membrane-bound organelle called the nucleus.

The endomembrane system includes

The endomembrane system is a set of organelles in a eukaryotic cell that are functionally interrelated. The endomembrane system includes the nuclear envelope, endoplasmic reticulum, Golgi apparatus, plasma membrane, and other organelles derived from these structures.

endosymbiotic theory

The endosymbiotic theory suggests that ancient free-living host prokaryotes obtained mitochondria and chloroplasts by engulfing other energy-processing prokaryotes. The engulfed prokaryotes benefited by living safely within the host cell's cytoplasm and gaining nutrients. In exchange, the engulfed prokaryotes provided their host cells with energy. The symbiotic, or mutually beneficial, relationship between the engulfed cell and the host cell ultimately evolved to a point where the two cells were no longer independent. Much of the prokaryotic DNA was transferred to the nucleus of the host cell, and the engulfed cell became an integrated organelle, either a mitochondrion or a chloroplast.

Evolved differences of eukaryotic cells from prokaryotic cells?

The first organisms on Earth were likely prokaryotic. These organisms consumed carbohydrates, amino acids, and other biological molecules; such food molecules were likely replenished at a very slow rate in the primordial seas. This would have led to extreme food competition among these early prokaryotes, and it is theorized that this competitive pressure drove the evolution of new and more efficient metabolic pathways (of prokaryotes). Using new food sources required the development of more complicated chemical reactions. Digestion of some molecules would have required specific environmental conditions that differed from those inside the cytoplasm. How did early eukaryotes cope with these new physiological demands? One evolutionary solution to this complex problem was to restrict chemical reactions to specific compartments within the cell. The evolution of compartmentalization allowed eukaryotic cells to exploit a wide range of new food sources thanks to the greatly expanded range of chemical reactions that could be performed within a cell.

different ribosomes/functions and where they are made?

The nucleolus synthesizes ribosomal RNA (rRNA). (ribosomes made in the nucleus, but ribosomes synthesize proteins in cytoplasm or in another organelle called the rough endoplasmic reticulum (RER), which is suspended in the cytosol outside of the nucleus). Some ribosomes float freely in the cytoplasm, and these ribosomes are usually in charge of making proteins that will be used inside the cell. Ribosomes responsible for producing proteins that will be exported from the cell are attached to the rough endoplasmic reticulum.

nucleolus

The nucleolus synthesizes ribosomal RNA (rRNA). (ribosomes made in the nucleus, but ribosomes synthesize proteins in cytoplasm).

Structure of Nuclues? Composed of?

The nucleus is bound in a double membrane called the NUCLEAR ENVELOPE that is made up of two phospholipid bilayers. The nuclear envelope also contains prominent NUCLEAR PORES. These protein-lined channels allow large molecules, such as messenger RNA, to enter or leave the nucleus. The nucleus also contains a dark-staining area called the NUCLEOLUS. The nucleolus synthesizes ribosomal RNA (rRNA).

Why is the nucleus important?

The nucleus is the control center of the cell (the brain), processing inputs from the cytoplasm, storing and retrieving information, and carrying out instructions contained within the genetic material in the nucleus. The nucleus contains the cell's chromosomes. Chromosomes are made up of DNA, which contains the genetically transmitted instructions for reproduction and for synthesizing proteins and RNA.

cristae

To maximize the surface area on which chemical reactions occur, the inner membrane is folded, forming pockets called cristae.

Vacuoles

Vacuoles are large vesicles derived from the ER and Golgi apparatus. They serve as the cells storage tanks.

Stroma

Within the inner membrane of the chloroplast is the stroma, a fluid-filled area between the inner membrane and membrane-bound compartments called thylakoids. The thylakoids form towers called grana that look like stacks of dinner plates. Within the thylakoid, light energy is converted into ATP, which in turn powers the construction of sugars in the stroma. In the stroma, CO2 molecules are used as building blocks to construct carbohydrates.

mRNA

a eukaryote's DNA never leaves the protected confines of the nucleus. Instead, a transcript of the blueprint is made in the form of a messenger RNA (mRNA) molecule. True to its name, the mRNA carries the transcribed instructions out of the nucleus to a ribosome. The ribosome constructs the protein as instructed on the mRNA transcript.

exocytosis

allows the cell to secrete a wide variety of materials.

smooth endoplasmic reticulum (ER)

also connects to nuclear envelope. Does NOT contain ribosomes. It is primarily involved in lipid synthesis and in breaking down toxic substances in the cell. It also stores calcium.

centrosome

centrosome is the microtubule organizing center of the cell and functions primarily in ANIMAL cell division.

Central vacuole/tonoplast

used to store substances within cell. The central vacuole of PLANT CELLS retains water to give the plant cell rigidity and support. They also serve as storage sites for the materials used by the cell, such as pigment, as well as for toxic substances. In plant cells, the large central vacuole, or tonoplast, also helps control osmotic balance. Plants store ions in the central vacuole which, like the cytoplasm of the freshwater protists, causes water to diffuse into the cell. When filled with water, tonoplasts force the cytosol against the cell wall. This gives the plant cell, and therefore the entire plant, a firm and turgid structure (able to stand straight). When water is not available, the tonoplasts shrink, the plant cells become more flaccid, and the plant wilts.

Lysosome

vesicles containing powerful enzymes that digest food items engulfed by the cell (food vacuole in the cell brought in by phagocyte). The RER and Golgi apparatus produce another membrane-bound organelle — the lysosome. In addition to their digestive functions, lysosomes can also use their digestive enzymes to recycle cellular components by autophagy. Autophagy is the process of breaking-down and recycling malfunctioning or worn-out cell organelles.