Cell parts {organelle}| {cell organelle} are plant cell wall, plasma membrane, nucleus, nucleolus, mitochondria, plastid, lysosome, Golgi complex, smooth endoplasmic reticulum, rough endoplasmic reticulum, centriole, and vacuole.
Two-layer phospholipids {plasma membrane} {membrane, cell}| {cell membrane} surround cytoplasm and have integrated proteins. Phospholipid polar ends point toward outsides. Non-polar ends are between layers. Unsaturated fatty acids and other non-polar molecules can diffuse quickly through non-polar cell membrane.
proteins
Cell membrane has 25% of cell protein. Membrane proteins can help make phospholipids. Membrane proteins have patterns caused by external and internal electric forces.
proteins: channels
Membrane proteins {permion} can have channels that allow cations to pass from side with high concentration to side with low concentration. Cations control permion opening and closing. By active transport using energy from ATP and proteins, molecules can go across membrane from side with low concentration to side with high concentration.
proteins: receptors
Protein receptors {cell surface receptor} bind circulating proteins and can facilitate transport across cell membranes.
Plant cells have cellulose layers {cell wall}| around plasma membranes, for cell support.
In cytoplasm, animal cells have oblong bodies {mitochondrion}| with double membranes. Inner membrane has many folds {cristae}, holding oxidative-phosphorylation and TCA-cycle enzymes. Mitochondria have small DNA circles.
Cells can have cell membrane {vacuole}| surrounding liquid, oil, food, starch, or protein. Protozoa vacuoles can fill with water and then pump water out.
Animal and lower plant cells have chromosomes, which have centers {centromere}| where microtubules attach. After chromosome duplication, microtubules pull one chromosome to one side and the other chromosome to other side, preparing cell nucleus and cell to split into two cells.
Animal and plant cells have DNA-containing oval bodies {nucleus, cell}|, surrounded by double membrane. Nuclear membranes extend into cytoplasm as endoplasmic reticulum tubes and end at Golgi complex.
Cell nuclei can have spherical bodies {nucleolus}| that synthesize rRNA.
Cell cytoplasm contains protein tubules {microtubule}| to transport molecules.
structure
13 columns of parallel tubulin filaments {protofilament} can combine in linear sequences. Tubulins are globular proteins and are 900-amino-acid biglobular alpha-tubulin and beta-tubulin dimers. Microtubules have 25-nm outside diameter and 14-nm inside diameter. Microtubules contain only water molecules.
forms
Two conformations have different bending around subunit junction: symmetrical form and unstable form. Brain microtubules are stable, but muscle and mitotic microtubules are unstable.
connection
Microtubules connect sideways by proteins {microtubule associated proteins} (MAP).
functions
Vesicles, granules, mitochondria, and chromosomes move along microtubule outsides, using ATPase molecules like kinesins and dyneins. Microtubules are cytoskeleton components, which also have actin and other proteins. Groups of microtubules and other proteins make cilia, flagella, and centrioles. Microtubules make pairs or triples. Cilia have nine triples in circle with middle pair.
anesthetics
Some anesthetics bind to microtubules.
Neuron cytoplasm contains protein filaments {neurofilament}|.
Animal and lower plant cells have microtubule-organizing centers {centrosome}| {spindle pole body}. Spindle pole bodies have RNA and separate to cell sides during mitosis. Centrosomes have centrioles and other proteins.
In cell division, centrioles duplicate, microtubules align between centrioles and connect to duplicated-chromosome centromeres, and centrioles separate, pulling half the chromosomes one way and half the other. Centrioles organize spindle between them during cell division and can duplicate themselves. Bodies have nine microtubule triplets in one circle, with no central microtubules.
Animal and lower plant cells have two separate cylindrical bodies {centriole}|, perpendicular to each other, near cell nucleus, which are centrosome parts. Centrioles organize spindle between them during cell division and can duplicate themselves. Centrioles have nine microtubule triplets in one circle, with no central microtubules.
Ribosomes, Golgi complexes, lysosomes, and endoplasmic reticulum are similar organelles {microsome}|.
Nucleated cells have cytoplasm membrane-tube networks {endoplasmic reticulum}| (ER), extending from cell nucleus. Endoplasmic reticulum can have attached ribosomes {rough endoplasmic reticulum} or no attached ribosomes {smooth endoplasmic reticulum}. Neurons, unlike other cells, have much rough endoplasmic reticulum. ER adds sugars to proteins.
All cells, except mature sperm cells and red blood cells, have tubular-membrane networks {Golgi complex}| that store cell products, such as plant-cell cellulose, before secretion. Golgi complexes are near cell nucleus. Golgi complex adds sugars to proteins.
Free-floating or rough-endoplasmic-reticulum RNA-protein complexes {ribosome}| synthesize cellular proteins.
Cells have membrane-surrounded regions {lysosome}| containing enzymes {lysozyme} that can catabolize {autophagy, lysosome} large molecules, such as membranes and poorly folded, denatured, foreign, damaged, or used proteins, and remove sugars from proteins. Ubiquitin recognizes and binds to such proteins, marking them for later break down. Autophagosomes fuse with lysosomes.
Double-layer membranes {phagophore} can form in cytoplasm. Phagophores increase if nutrients, growth factors, and/or oxygen have low concentration.
process
Phagophore membranes close around damaged cell molecules and make spheres {autophagosome}. Autophagosome formation needs apg8 protein, similar to ubiquitin, which undergoes phosphoglycerolipidation with phosphatidylethanolamine to integrate into membrane. Ubiquitin recognizes and binds damaged proteins, marking them for later break down.
lysosomes
After autophagosome formation, membrane proteins leave, and autophagosomes fuse with cell lysosomes. Lysosomes contain lysozyme, which removes sugars from proteins and catabolizes {autophagy, autophagosome} large molecules, such as membranes and poorly folded, denatured, foreign, damaged, or used proteins.
Structures {proteosome}| break peptide bonds using ubiquitin.
Cell organelles {processing body} {P-body} can store used mRNAs and break them down using RNAses, such as Dhh1p. They affect RNA interference using Argonaute protein.
Plant-cell bodies {plastid}| can synthesize or store food. Plastids include chloroplasts, leucoplasts, and chromoplasts.
Plastids {chloroplast}| can contain chlorophyll for photosynthesis.
Plastids {chromoplast}| can contain color pigments.
Plastids {leucoplast}| can store starch.
Nucleated cells have regions {cytoplasm}| inside cell membrane but outside cell nucleus.
Cells have gel {protoplasm}| that contains cell organelles.
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Date Modified: 2022.0225