Euakryotic Cells Flashcards
Nucleus
Is surrounded by a nuclear envelope, which is a double membrane with nuclear pores (larges holes containing proteins regulating the exit of RNA and ribosomes from the nucleus). The interior is called nucleoplasm ( full of chromatin with a ratio 1:2 of DNA/protein complex containing genes. During cell division, the chromatin condenses and the chromosomes become visible. The nucleolus is the dark region of chromatin (responsible for producing ribosomes).
Cytoplasm
This is the solution within the cell membrane. It contains enzymes for glycolysis (part of respiration) and other metabolic reactions together with sugars, salts amino acids, nucleotides and everything else needed for the cell to function.
Mitochondrion
Is a rod-shaped organelle (8 micrometer) and is the site of aerobic respiration. It is surrounded by a double membrane (the outer membrane is simple and quite permeable whilst the inner membrane is highly folded into cristae, increasing the surface area). Within the inner membrane, there’s the matrix with contained small circular strands of DNA and it is studded with stalked particles (which is the site of ATP respiration).
Chloroplast
Is where photosynthesis takes place. It contains starch grains, ribosomes and circular DNA. It is enclosed by a three membranes and the third one is called thylakoid membrane. It contains chlorophyll and other photosynthetic pigments arranged in photosystems with stalked particles (site of photosynthesis and ATP synthesis).This is also folded into thylakoid disks and are stacked into piles (known as grana). Between the thylakoid and the inner membrane, there is the stroma.
Ribosomes
Are the sites of protein synthesis. It is made from RNA and protein and are produced in the nucleolus of the nucleus. The are situated in the cytoplasm or attached to the rough endoplasmic reticulum. They are normally found in groups called polysomes.
Eukaryotic cells have the 80s type.
Smooth endoplasmic reticulum
Is a series of membrane channels used for producing mainly lipids and transporting materials needed by the cell
Rough endoplasmic reticulum
A series of membrane channels studded with ribosomes. When the ribosomes synthesise proteins, the RER processes it (by adding carbohydrates,by enzymatically modifying the polypeptide chain) before being exported by the Golgi body.
Golgi body
Is a series of flattened membrane vesicles formed from the endoplasmic reticulum. It’s function is to transport the ribosomes produced by the RER out the cell via the cell membrane.
While parts of the RER fuse with one side of the Golgi body’s membrane, the other side small vesicles bud off and move towards the cell membrane where they fuse and releasing their contents by exocytosis.
Vacuoles
Are membrane bound sacs containing water and dilute solutions of salts and other solutes. Plant cell vacuoles are filled with cell sap (to keep cells rigid/turgid) and most cells form small vacuoles when needed. Some unicellular protoctists have feeding vacuoles for digesting food, contractile vacuoles for storing excess water.
Lysosomes
Are small membrane bound vesicles formed from the RER containing digestive enzymes. It’s function is to decompose unwanted chemicals, toxins, organelles or even whole cells, so that the materials maybe recycled. They can also fuse with a feeding vacuole to disgest its contents.
Cytoskeleton
A network of protein fibres used for support, transport and motility. It is attached to the cell membrane giving it its shape and puts the organelles in place.
Three types of protein fibres:
Microtubules, intermediate filaments and microfilaments.
They all have corresponding motor protein moving the protein fibre as well as the contents (eg. Organelles, chromosomes, other cytoskeleton fibres).
Centriole
A pair of microtubules involved in cell division.
Unidulipodium (cilium and flagellum)
A long flexible tail extending from the cytoplasm and is used for movement. It contains a lot of microtubules and motor proteins to perform its function.
Two types:
Flagella ( one or two and longer than the cell) and cilia (identical in structure but smaller and many of them)
Microvilli
Are small finger like projections of the cell membrane (found on epithelial cells of the kidney/intestines). It increases the surface area of absorption.
Cell membrane
A thin layer containing phospholipids and proteins round the outside of all cells. It separates the insides of the cell from the outside and controls what exits and enters the cell.
Cell wall
A thick layer outside the membrane for strength and rigidity. It consists of a network of fibres and are freely permeable to solutes. Plant cells are mainly made up of cellulose in three layers ( primary cell wall, secondary cell wall and the middle lamella). Plasmodesmata (channels) in the plant cell walls link the cytoplasm of adjacent cells.
Fungal cell walls are made of chitin.
Animal cells have a cell coat of glycocalyx.
