Nucleus -contains DNA organized in chromosomes which carry genetic information
-inside the nucleus is the nucleolus which is where the DNA gives instructions which will be used to make RNA
-basically the nucleus directs protein synthesis
-when RNA goes into the ribosomes, specific polypeptide chains are formed which make proteins Peroxisomes Oxidative organelles
-have enzymes which trasnfer hydrogen to oxygen making hydrogen peroxide-this reaction serves a purpose
-oxygen is used to break fatty acids into smaller molecules that are transported to the mitochondria where they are used for cellular respiration
-in the liver peroxisomes detoxify alcohol
-they also convert the harmful hydrogen peroxide that they create back to water Mitochondria Sites of cellular respiration
-extract energy from sugars and fats
-this energy is used to make ATP
-has a smooth outer membrane and folded inner membrane (the foldings are called cristae and they have a large surface area to maximize the production of ATP)
-the inner membrane divides the mitochondria into the innermembrane space and the mitochondrial matrix that has enzymes to help with cellular respiration Chloroplasts Site of photosynthesis
-converts energy from the sun which is captured by the chlorophyll into chemical energy
-the chemical energy can be used in the synthesis of organic compounds within the cell
-they have two main parts: the thylakoids and the stroma Bubbles the fish enjoys making oxygen bubbles by opening the treasure chest in the fish tank.
(ii) Stroma is a homogenous mixture in which grana are embedded. It contains several enzymes that are used for the synthesis of carbohydrates and proteins. It also contains its own DNA and ribosomes and hence semi-autonomous organelle.
Cancer Cell. 2003 Jun;3(6):525-30.
Id proteins in cell growth and tumorigenesis.
Sikder HA1, Devlin MK, Dunlap S, Ryu B, Alani RM.
Since the gene encoding Id1 was cloned in 1990, Id proteins have been implicated in regulating a variety of cellular processes, including cellular growth, senescence, differentiation, apoptosis, angiogenesis, and neoplastic transformation. The development of knockout and transgenic animal models for many members of the Id gene family has been particularly useful in sorting out the biologic relevance of these genes and their expression during normal development, malignant transformation, and tumor progression. Here we review the current understanding of Id gene function, the biologic consequences of Id gene expression, and the implications for Id gene regulation of cell growth and tumorigenesis.
Cellular differentiation programs are tightly controlled through the coordinated regulation of gene expression. Basic helix-loop-helix (bHLH) transcription factors regulate the differentiation programs of multiple cell lineages (reviewed in Norton, 2000). These proteins share a common sequence motif of a stretch of basic amino acids responsible for site-specific DNA binding adjacent to a helix-loop-helix dimerization domain. The Id family of helix-loop-helix proteins does not possess a basic DNA binding domain and functions as a dominant-negative regulator of basic HLH proteins through the formation of inactive heterodimers with intact bHLH transcription factors (Figure 1). The Id family of proteins (comprised of 4 members designated Id1–Id4) has been demonstrated to bind the ubiquitously expressed bHLH E-proteins or cell lineage-restricted bHLH transcription factors, leading to inhibition of lineage-specific gene expression and differentiation (Norton et al., 1998). Hence, the name Id refers to both inhibition of differentiation and inhibition of DNA binding. Transcriptional inhibition by Id proteins is mediated via inhibition of DNA binding of bHLH or other activator proteins at E boxes (CANNTG), N boxes (CACNAG), or Ets sites (GGAA/T) present in the promoter regions of regulated genes (reviewed in Zebedee and Hara, 2001). Since cellular differentiation programs are frequently altered during the development of neoplastic disease, it is not surprising that Id proteins would play a role in this process. Indeed, a clue to the potential role of Id genes in tumorigenesis came with the observation that, in general, high Id expression levels are found in proliferative, undifferentiated cells—a feature which is characteristic of tumor cells (Israel et al., 1999). Over the past several years, the particular mechanisms underlying the effects of Id genes on cell growth and differentiation have been investigated. Here we review data supporting the critical role of Id gene regulation in the development of normal cellular differentiation programs. We also review mechanisms of Id gene regulation of cellular growth controls and the cell cycle machinery and evaluate the contribution of dysregulated Id gene expression to the process of tumorigenesis.