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NSCI 1413 (15)
Lecture 14

NSCI 1413 Lecture 14: Cells

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Natural Science
NSCI 1413
Guy Robinson

Cell Theory ● All living things are composed of cells ● Cells are the basic unit of all organisms ● All cells arise from preexisting cells Prokaryotes vs. Eukaryotes ● Internal membranes ○ Prokaryotes:​ No ○ Eukaryotes:​ Yes ● DNA ○ Prokaryotes:​ Circular, naked ○ Eukaryotes:​ Condensed w/ histones ● Ribosomes ○ Prokaryotes:​ Very small ○ Eukaryotes:​ Larger ● Metabolism ○ Prokaryotes:​ Anaerobic or aerobic ○ Eukaryotes:​ Aerobic ● Cytoskeleton arrangement: ○ Prokaryotes:​ Absent ○ Eukaryotes:​ Present ● Number of cells: ○ Prokaryotes:​ Mainly unicellular ○ Eukaryotes:​ Mainly multicellular w/ many cell types ● Cell size: ○ Prokaryotes:​ Very small (1-10µm) ○ Eukaryotes:​ Larger (10-100µm) Organelles ● Nucleus:​ Holds genetic material; only in eukaryotes​Nuclear Envelope:​ selectively permeable; porous ● Nucleolus:​ synthesizes ribosome components; present during interphase; not membrane boud; made of chromatin ● Ribosome:​ site of protein synthesis; found in cytoplasm and ER ● Endoplasmic Reticulum: 1. Rough:​ site of protein synthesis due to attached ribosomes 2. Smooth:​ assists in synthesis of steroid hormones and lipids, connects rough ER to golgi, detoxifies ● Golgi Apparatus:​ package substances produced in rough ER and secrete to other cell parts or to membrane for export ● Lysosome:​ sac of hydrolytic enzymes; principal site of intracellular digestion; not found in plants ● Peroxisome:​ breaks down2​2​O​ via catalase; detoxifies alcohol in liver cells ● Mitochondrium:​ site of cell respiration; outer double membrane and inner membranes (cristae); contain their own DNA ● Vacuole:​ membrane-bound storage site; small vacuole = vesicle; contractile pump out excess water ● Plastid:​ double membrane; only found in plants and algae 1. Chloroplast:​ site of photosynthesis; contain grana (thylacoids) within stroma; contain their own DNA 2. Leucoplast:​ store starch; found in roots like turnips and potatoes 3. Chromoplast:​ store cartenoid pigments; responsible for red/orange color of certain vegetables and plants ● Cytoskeleton:​ complex network of protein filaments w/I cytoplasm; provides cell shape; enable cell motility; anchor organelles to cell membrane 1 1. Microtubules:​ hollow tubes made of tubulin; make up cilia, flagella, spindle fibers i. Cilia and Flagella:​ move cells; consist of 9 pairs of microtubules around 2 singlet microtubules (9+2) ii. Spindle Fibers:​ help separate chromosomes during mitosis and meiosis; 9 triplets with no microtubules in center 2. Microfilaments:​ help support cell shape; aka actin filaments; enable: i. Actin filaments to form cleavage furrow during cell division ii. Ameoba to move by sending out psuedopods iii. Skeletal muscle to contract as they slide among myosin filaments ● Centrioles, Centrosomes, and Microtubule Organizing Centers (MTOC):​ non-membranous structures that lie outside nuclear membranes; organize and give rise to spindle apparatus in cell division ○ 2 centrioles at right angles make up one centrosome; consists of 9 triplets of microtubules in a circle ○ Plants lack centrosomes but have MTOCs; in animals MTOC = centrosome ● Cell Wall:​ structure that lies outside the cell membrane that provides shape and rigidity to the cell; plants (cellulose) and fungi (chitin); lamina formed between new cells during cell division; not present in animals ● Plasma Membrane:​ se
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