The nuclear membrane is continuous with the endoplasmic reticulum, while nuclear pores allow substances to enter and exit the nucleus. A eukaryotic cell has a true membrane-bound nucleus and has other membranous organelles that allow for compartmentalization of functions. Like a prokaryotic cell, a eukaryotic cell has a plasma membrane, cytoplasm, and ribosomes.
However, unlike prokaryotic cells, eukaryotic cells have:. They allow different functions to be compartmentalized in different areas of the cell. Typically, the nucleus is the most prominent organelle in a cell. The nuclear envelope is a double-membrane structure that constitutes the outermost portion of the nucleus.
Both the inner and outer membranes of the nuclear envelope are phospholipid bilayers. The nuclear envelope is punctuated with pores that control the passage of ions, molecules, and RNA between the nucleoplasm and cytoplasm.
The nucleoplasm is the semi-solid fluid inside the nucleus where we find the chromatin and the nucleolus. Furthermore, chromosomes are structures within the nucleus that are made up of DNA, the genetic material. In prokaryotes, DNA is organized into a single circular chromosome.
Eukaryotic Nucleus : The nucleus stores chromatin DNA plus proteins in a gel-like substance called the nucleoplasm. The boundary of the nucleus is called the nuclear envelope. The nuclear membrane is continuous with the endoplasmic reticulum. Nuclear pores allow substances to enter and exit the nucleus. Mitochondria are oval-shaped, double membrane organelles that have their own ribosomes and DNA. The endoplasmic reticulum modifies proteins and synthesizes lipids, while the golgi apparatus is where the sorting, tagging, packaging, and distribution of lipids and proteins takes place.
Bacteria have a single circular chromosome in the centre of the cell that holds all the genes needed for that bacterium. Bacteria also have extra circles of DNA called plasmids. Animals, plants and fungi are eukaryotes. They have a membrane-bound nucleus and their chromosomes are linear rather than circular.
This article has been posted to your Facebook page via Scitable LearnCast. Change LearnCast Settings. Scitable Chat. Register Sign In. While the chief component of prokaryotic cell walls is peptidoglycan, the major organic molecule in the plant cell wall is cellulose, a polysaccharide comprised of glucose units. When you bite into a raw vegetable, like celery, it crunches. The dashed lines at each end of the figure indicate a series of many more glucose units.
The size of the page makes it impossible to portray an entire cellulose molecule. Like mitochondria, chloroplasts have their own DNA and ribosomes, but chloroplasts have an entirely different function. Chloroplasts are plant cell organelles that carry out photosynthesis. Photosynthesis is the series of reactions that use carbon dioxide, water, and light energy to make glucose and oxygen.
This is a major difference between plants and animals; plants autotrophs are able to make their own food, like sugars, while animals heterotrophs must ingest their food. The fluid enclosed by the inner membrane that surrounds the grana is called the stroma.
The Chloroplast Structure : The chloroplast has an outer membrane, an inner membrane, and membrane structures called thylakoids that are stacked into grana. The space inside the thylakoid membranes is called the thylakoid space. The light harvesting reactions take place in the thylakoid membranes, and the synthesis of sugar takes place in the fluid inside the inner membrane, which is called the stroma. The chloroplasts contain a green pigment called chlorophyll, which captures the light energy that drives the reactions of photosynthesis.
Like plant cells, photosynthetic protists also have chloroplasts. Some bacteria perform photosynthesis, but their chlorophyll is not relegated to an organelle. When you forget to water a plant for a few days, it wilts. As the central vacuole shrinks, it leaves the cell wall unsupported. This loss of support to the cell walls of plant cells results in the wilted appearance of the plant.
The central vacuole also supports the expansion of the cell. When the central vacuole holds more water, the cell gets larger without having to invest a lot of energy in synthesizing new cytoplasm. Privacy Policy. Skip to main content. Cell Structure. Search for:. Eukaryotic Cells. Characteristics of Eukaryotic Cells A eukaryotic cell has a true membrane-bound nucleus and has other membranous organelles that allow for compartmentalization of functions.
Learning Objectives Describe the structure of eukaryotic cells. Mitochondria are responsible for ATP production; the endoplasmic reticulum modifies proteins and synthesizes lipids; and the golgi apparatus is where the sorting of lipids and proteins takes place. Peroxisomes carry out oxidation reactions that break down fatty acids and amino acids and detoxify poisons; vesicles and vacuoles function in storage and transport.
Animal cells have a centrosome and lysosomes while plant cells do not. Plant cells have a cell wall, a large central vacuole, chloroplasts, and other specialized plastids, whereas animal cells do not. Key Terms eukaryotic : Having complex cells in which the genetic material is organized into membrane-bound nuclei. The Plasma Membrane and the Cytoplasm The plasma membrane is made up of a phospholipid bilayer that regulates the concentration of substances that can permeate a cell.
Learning Objectives Explain the structure and purpose of the plasma membrane of a cell. Key Takeaways Key Points All eukaryotic cells have a surrounding plasma membrane, which is also known as the cell membrane. The plasma membrane is made up by a phospholipid bilayer with embedded proteins that separates the internal contents of the cell from its surrounding environment.
Only relatively small, non- polar materials can easily move through the lipid bilayer of the plasma membrane. Passive transport is the movement of substances across the membrane that does not require the use of energy while active transport is the movement of substances across the membrane using energy. Osmosis is the diffusion of water through a semi- permeable membrane down its concentration gradient; this occurs when there is an imbalance of solutes outside of a cell compared to the inside the cell.
Key Terms phospholipid : Any lipid consisting of a diglyceride combined with a phosphate group and a simple organic molecule such as choline or ethanolamine; they are important constituents of biological membranes hypertonic : having a greater osmotic pressure than another hypotonic : Having a lower osmotic pressure than another; a cell in this environment causes water to enter the cell, causing it to swell.
The Nucleus and Ribosomes Found within eukaryotic cells, the nucleus contains the genetic material that determines the entire structure and function of that cell.
Learning Objectives Explain the purpose of the nucleus in eukaryotic cells. Found within the nucleoplasm, the nucleolus is a condensed region of chromatin where ribosome synthesis occurs. Chromatin consists of DNA wrapped around histone proteins and is stored within the nucleoplasm. Ribosomes are large complexes of protein and ribonucleic acid RNA responsible for protein synthesis when DNA from the nucleus is transcribed.
Key Terms histone : any of various simple water-soluble proteins that are rich in the basic amino acids lysine and arginine and are complexed with DNA in the nucleosomes of eukaryotic chromatin nucleolus : a conspicuous, rounded, non-membrane bound body within the nucleus of a cell chromatin : a complex of DNA, RNA, and proteins within the cell nucleus out of which chromosomes condense during cell division.
Learning Objectives Explain the role of the mitochondria. Key Takeaways Key Points Mitochondria contain their own ribosomes and DNA; combined with their double membrane, these features suggest that they might have once been free-living prokaryotes that were engulfed by a larger cell.
0コメント