CELLS Cell Theory The three main parts of cell theory: All living things are made up of one or more cells Cells are the basic units of organization in living things All cells come from other cells Cell Membrane Structure: Semi-permeable and selective barrier surrounding the cell Function: boundary for the cell, controls which substances pass in and out Nucleus Structure: Double membrane structure with pores; contains a inner region called a nucleolus Function: Stores genetic material (DNA), which controls the cell's activities Nucleolus Is an organelle in the nucleus that plays a key role in the transcription and processing of ribosomal RNA (rRNA). Mitochondrion ’Powerhouse’ of the cell, responsible for energy production Structure: Double membrane structure, inner membrane is highly folded into internal cristae Function: Site of aerobic respiration, releasing energy in the form of ATP from sugar Smooth Endoplasmic Reticulum Structure: A membrane network that is bare and without ribosomes Function: Produces fats/lipids which are used in the production of new cellular membranes Rough Endoplasmic Reticulum u Structure: A membrane network that is studded with ribosomes u Function: transports proteins, produced by ribosomes on its surface Golgi (Body) Apparatus Structure: An assembly of vesicles and folded membranes located near the cell membrane Function: Involved in the sorting, storing, modification and export of secretory products, bundles proteins into packages for transport. Ribosomes Structure: Two subunits made of RNA and protein Function: functions as a micro-machine for making proteins, building proteins using instructions from the cell's DNA. Cytoplasm Internal gel-like fluid inside the cell. It is the medium for chemical reactions. It provides a platform upon which other organelles can operate within the cell. Chromosomes & DNA Chromosomes A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. DNA is coiled around proteins called histones, which provide the structural support. Chromosomes help ensure that DNA is replicated and distributed appropriately during cell division. Genes Genes are sections of a chromosome/DNA that code for particular traits Gametes Gametes are an organism’s reproductive cells Sex Cells Sperm and egg cells Haploid cells (contain only one copy of each chromosome) Somatic Cells Somatic cells are all of the cells in the body except sperm and egg cells Karyotype Chromosomes are taken from the nucleus, stained and put into homologous pairs. The image produced is a karyotype (image of all chromosomes of a cell) Sex Chromosomes A sex chromosome is a type of chromosome involved in sex determination. Humans and most other mammals have two sex chromosomes, X and Y, that in combination determines the sex of an individual. Females have two X chromosomes in their cells Males have one X and one Y. Autosome Chromosomes An autosome is one of the numbered chromosomes that contain genetic information for an organism. Autosomes are not involved in sex determination Humans have 22 pairs of autosomes and one pair of sex chromosomes (XX or XY). Autosomes are numbered roughly in relation to their sizes. Homologous Chromosomes Pairs of matching chromosomes Share the same structural features (e.g. same size, same banding patterns, same centromere positions) Diploid Cells Diploid refers to the presence of two complete sets of chromosomes in an organism's cells, with each parent contributing a chromosome to each pair. Humans are diploid, and most of the body's cells contain 23 chromosomes pairs. Haploid Cells Haploid refers to the presence of a single set of chromosomes in an organism's cells. Sexually reproducing organisms are diploid (having two sets of chromosomes, one from each parent). In humans, only the egg and sperm cells are haploid. DNA Structure DNA is a very long, thin molecule consisting of two chains or "backbones" that twist around each other. This structure is known as a double helix. If you could straighten out a DNA molecule, it would look like a ladder. Each "rung" of the ladder is made up of two smaller molecules, known as nucleotide bases. Complimentary Pairs Base pairings that join the two sides of the DNA ladder structure Adenine pairs with Thymine Cytosine pairs with Guanine James Watson, Francis Crick, Rosalind Franklin & Erwin Chargaff Watson and Crick worked as a team to unravel the secret of the structure of DNA (deoxyribonucleic acid), which they identified as a double helix in 1953. They performed no experiments themselves, having just interpreted the experimental results of others. Rosalind Franklin worked on identifying the structure of DNA between 1951 and 1953, Franklin came very close to solving the DNA structure but she was beaten to publication by Crick and Watson who used her work to identify the structure Erwin Chargaff was responsible for discovering the ratios of Adenine (A) to Thymine (T) , and Guanine (G) to Cytosine (C) are equal. His discovery helped contribute to the formation of the complementary base pairing discovery. DNA vs RNA DNA contains the instructions needed for an organism to develop, survive and reproduce. DNA is located in the nucleus RNA is a ribonucleic acid that aids in protein synthesis RNA is found in the Cytoplasm Cell Cycle Cell Cycle Two types of cell division take place in the human body: Cell division for growth and repair is called mitosis. Cell division for the production of sex cells is called meiosis. Sex cells – that is, eggs and sperm – are needed for sexual reproduction. Mitosis Mitosis occurs during the division of all cells in the body except in the production of sex cells. Without mitosis your bones and hair would not grow and you would quickly lose cells due to damage. For example, skin cells are replaced every 10 to 30 days In mitosis, one cell splits in half to create two new cells. The cell that divides is called the parent cell. The two new cells are called daughter cells. Each daughter cell has its own nucleus, which contains the DNA it needs to grow and function. The daughter cells are genetically identical to each other. They are also identical to the parent cell that made them. Stages of Mitosis Prophase – the cell Prepares for division: the chromosomes condense and the nucleus starts to break down Metaphase – the chromosomes line up along the Middle of the cell Anaphase – the chromosomes separate and are dragged Away from each other Telophase – Two nuclei form, each with its own set of identical DNA
