Cell Flashcards
What is cell?
Building blocks of the body, providing structure for the body’s tissues and organs, ingesting nutrients and converting them to energy, and performing specialized functions. Cells also contain the body’s hereditary code, which controls the substances synthesized by the cells and permits them to make copies of themselves.
What is protoplasm?
The different substances that make up the cell are collectively called protoplasm. —water, electrolytes, proteins, lipids, and carbohydrates.
Three lipids of cell membranes
Phospholipids, Sphingolipids and Cholesterol
Hydrophobic and Hydrophilic ends of Phospholipids
Phosphate end is Hydrophilic and Fatty acid end is Hydrophobic
Sphingolipid and their functions
Derived from amino alcohol sphingosine, present in nerve cells. Function: protection from harmful environmental factors, signal transmission, and adhesion sites for extracellular proteins.
Function of Cholesterol
Help determine the degree of permeability (or impermeability) of the bilayer to water-soluble constituents of body fluids and controls much of the fluidity of the membrane as well.
Types of cell membrane proteins
Integral: which protrude all the way through the membrane and function as carrier, ion channels and receptors to transport molecules from ECF to ICF.
Peripheral: which are attached only to one surface of the membrane and do not penetrate all the way through. Function: Often attached to integral proteins, act almost entirely as enzymes or as controllers of transport of substances through cell membrane pores.
Glycoproteins, Glycolipids and Glycocalyx
Glycoproteins: Carbohydrates attached to proteins
Glycolipids: Carbohydrates attached to lipids
These Glyco (carbohydrate) portion protrude or dandling outside of the cell membrane - providing a loose carbohydrate coat to the entire cell surface called Glycocalyx
Cell membrane carbohydrate (Glycocalyx) functions
- Many of them have a negative electrical charge, which gives most cells an overall negative surface charge that repels other negatively charged objects.
- The glycocalyx of some cells attaches to the glycocalyx of other cells, thus attaching cells to one another.
- Many of the carbohydrates act as receptors for binding hormones, such as insulin.
- Some carbohydrate moieties enter into immune reactions.
What is cytosol?
The jelly-like fluid portion of the cytoplasm in which the particles are dispersed is called cytosol and contains mainly dissolved proteins, electrolytes, and glucose.
Endoplasmic Reticulum and Ribosomes
ER: Interconnected network of tubular structure called cisternae and flat vesicles. Function: helps process molecules made by the cell and transports them to their specific destinations inside or outside the cell.
Rough ER: contains ribosomes on their surface and involved in protein synthesis
Smooth ER: does not contain ribosomes, involved in lipid synthesis, intracellular calcium storage and detoxification of medications and poisons and carbohydrate metabolism
Ribosomes: Present on rough ER surface and free in cytoplasm. composed of RNA and protein, function in synthesis of new proteins.
Golgi apparatus
Four or more stacked layers of thin, flat and enclosed vesicles, close to nucleus.
Function: receipt, processing, manufacturing, packaging and transport substances.
Receives vesicles on the cis site of GA which are pinched off from the ER and after processing these vesicles leaves from the trans site into the cytosol to form lysosomes, secretory vesicles and other cell membrane structures.
Lysosomes
Double layer vesicular structures breaking off from GA, consisting of hydrolase enzymes and functions as intracellular digestive system by digesting bacteria, food particles and damaged cell structures.
Causes regression of tissues
Peroxisomes
Similar structure as lysosomes but breaking off from smooth ER. Self replicative
Function: contains oxidase + catalase enzymes to oxidize poisonous substances. Also, catabolism of long chain fatty acids.
Secretory vesciles
Storage vesicles containing of secretory substance produced by ER and GA. Released from GA into cytoplasm.
Mitochondria
Powerhouse of the cell. Function - to produce ATP from glucose, fatty acid and amino acid
Self-replicative, contains Mitochondrial DNA
Inner membrane contains infolding known as Cristae - provides large surface area for reactions - contains oxidative enzymes.
Matrix - contains dissolved enzymes
Microfilaments
Fibrilar protein
Present in ectoplasm (outer zone of cytoplasm) - provides cell elasticity. Eg: actin filaments
Intermediate filaments
rope like structure - work in association with microtubules.
Provide support and strength to tubular structures. Eg: Desmin (muscle cells); neurofilaments (nerve cells) and Keratin (epithelial cells)
Microtubules
Polymer of tubulin protein
Provides cell shape and movement; track like structure for movement of intracellular organelles; participate in cell division
Eg: centrioles, mitotic spindle and cilium
Nucleus
Control centre of the cell
Sends message for cell to grow, mature, replicate or die.
Contains DNA which composed of genes - major roles determining characteristics of structural protein, enzyme protein and nuclear activity and also, cell reproduction.
Pinocytosis
Ingestion of small protein molecules into the vesicle.
1. Binding of protein with receptors in the coated pits on cell membrane
2. Clathrin lattice structure beneath the coated pits and surrounded by actin and myosin filaments
3. Entry of calcium into the cell activates contractile proteins which leads to invagination of the ECF fluid and protein molecule
4. Clathrin sheet mediates pinching off the vesicle from the membrane - produces pinocytic vesicles
Phagocytosis
Ingestion of large particles
1. particles attach to cell receptor
2. cell starts evaginating outward from the point of attachment
3. More receptors attaching to the particle and closing off vesicle and pushed into the cell by contractile protein
4. stem of the vesicle pinched off from membrane to produce phagocytic vesicle
Autolysis
Due to cell damage the contents of lysosomes leaked out in the cell and leads to entire cell digestion called autolysis. If the damage is slight then only portion is removed and cell repaired.
Which bactericidal enzymes contained in lysosomes?
1) lysozyme, which dissolves the bacterial cell wall; (2) lysoferrin, which binds iron and other substances before they can promote bacterial growth; and (3) acid at a pH of about 5.0, which activates the hydrolases and inactivates bacterial metabolic systems.
Autophagy
To eat oneself
Worn-out organelles are brought to lysosomes by a double membrane structure called autophagosome which invaginates these components and form a vesicle that fuses with lysosome. Structures digested in smaller molecules and reused.
Importance: During tissue development, cellular components turnover, cell survival during nutrition scarcity and maintenance of homeostasis.
Role of Hyaluronic acid and chondroitin sulfate
Synthesized in GA - contains large polysaccharides and small proteins
1. major component of proteoglycans secreted in mucus and glandular secretion
2. component of ground substance act a filler between collagen fibre and cell
3. Cell migration and proliferation
4. Component of organic matrix such as cartilage and bones
Pseudopodium
Projects out of the cell for ameboid movement and remainder of the cell is pulled towards pseudopodium
Examples of ameboid movement
WBC movement into the tissue from blood to form macrophages.
Fibroblast movement at the site of damage for repair.
Movement of fertilized ovum
Chemotaxis
initiation of ameboid locomotion process. Agents cause it called chemotactic agents
Which ions and conditions are required for ciliary movement?
Magnesium and Calcium are required.
1, ATP
2. ionic condition
Types of cilia and movement
Motile cilia - wheep like movement (forward and backward strokes) eg: in respiratory passage for movement of mucus and in fallopian tube for movement of fertilized cell
Sperm cell shows qausisinusodial movement
Non-motile cilia:
Sensory antennae
Eg: renal epithelial cells
Function; signal transduction, chemical and physical sensation, cell growth
