Cell biology

• Common structures in animal and plant cells and their functions

  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
• Nucleus


  • Contains DNA that codes for specific proteins required for the formation of new cells
  • Encased within a nuclear membrane
• Cytoplasm


  • A liquid substance where chemical reactions take place
  • Contains enzymes, the biological catalysts that speed up chemical reactions
  • The place where organelles are found
• Cell membrane


  Controls what substances that can enter and leave the cell
• Mitochondria


  The place of aerobic respiration, providing energy to the cell
• Ribosomes


  • The place of protein synthesis
  • Found on a structure called the rough endoplasmic reticulum
• Additional structures in plant cells

  • Chloroplasts
  • Permanent vacuole
  • Cell wall
• Chloroplasts


  • The place where photosynthesis occurs, producing food for the plant
  • Contains chlorophyll, a green pigment essential for capturing light in photosynthesis
• Permanent vacuole


  • Contains cell sap
  • Found within the cytoplasm
  • Improves cell rigidity
• Cell wall


  Made of cellulose, providing the cell with strength
• Structures in bacterial cells

  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Single circular strand of DNA
  • Plasmids
• Cell wall (in bacterial cells)

  Made of a different compound known as peptidoglycan
• Single circular strand of DNA (in bacterial cells)

  As they have no nucleus, the DNA floats freely in the cytoplasm
• Plasmids (in bacterial cells)


  Small rings of extra DNA
• Calculation of the size and area of sub-cellular structures

  1. Identify a geometric shape (like a circle or rectangle) that closely resembles the structure

  2. Use the conventional rules to calculate the size/area of that shape (for instance, length x width for rectangles) to determine the size or area of the structure
• Chromosomes


  Coiled strands of DNA containing genetic material
• Gene


  A specific sequence of DNA that codes for a protein and determines a particular trait
• Cells


  • Have 23 pairs of chromosomes, received one set from each parent, totalling 46 chromosomes
  • Sex cells or gametes have only 23 chromosomes
• Cell Cycle


  1. Interphase

  2. Mitosis

  3. Cytokinesis
• Interphase


  Cell and organelles grow and multiply, protein synthesis, DNA replicates
• Mitosis


  Chromosomes align at cell equator, cell fibres pull chromosomes to opposite sides
• Cytokinesis


  Cytoplasm and cell membranes divide, resulting in two identical daughter cells
• Mitosis


  • Plays a significant role in growth and development
  • Essential in replacing damaged cells
  • Critical in asexual reproduction
• Stem cell


  A cell that hasn't yet acquired a specific function and has the ability to divide to create more similar cells, some of which will later acquire different functions
• Types of stem cells

  • Embryonic stem cells
  • Adult stem cells
  • Meristems in plants
• Embryonic stem cells


  Originate from fusion of egg and sperm, can differentiate into any cell type
• Adult stem cells


  Can be found in bone marrow, able to develop into various cell types
• Meristems in plants


  Found at tips of roots and shoots, can transform into any plant cell
• Therapeutic cloning


  Generating an embryo with identical genes as the patient, facilitating various therapeutic applications
• Benefits of using stem cells in medicine

  • Can be used to replace damaged or diseased body parts
  • Unwanted embryos from fertility clinics could be used
  • Research into the process of differentiation
• Risks of using stem cells in medicine

  • We do not completely understand the process of differentiation
  • Removal of stem cells results in destruction of the embryo
  • People may have religious or ethical objections
  • If growing stem cells are contaminated, an infection can be transferred
• Diffusion


  The process where particles of a substance in solution or gas particles spread out, moving from an area of higher concentration to an area of lower concentration
• Movement across cell membranes

  Small molecules like oxygen, glucose, amino acids, and water can move across; larger molecules like starch and proteins cannot
• Diffusion in the human body

  • Oxygen diffuses into red blood cells in the lungs
  • Carbon dioxide diffuses from red blood cells into the lungs
  • Urea diffuses from liver cells into blood plasma
• Factors influencing the rate of diffusion

  • Concentration gradient
  • Temperature
  • Surface area of the membrane
• Surface area to volume ratio

  Calculated by determining volume and surface area, and expressing the ratio in the smallest whole numbers
• Diffusion in single-celled organisms

  • Can use diffusion for molecule transport due to high surface area to volume ratio
  • Diffusion is sufficient to meet their lower metabolic demands
• Diffusion in multicellular organisms

  • Cannot rely on diffusion alone due to smaller surface area to volume ratio
  • Various surfaces and organ systems have adaptations to facilitate molecule transportation
• Adaptations for diffusion


  • Lungs: Alveoli and capillaries
  • Small intestine: Villi
  • Fish gills: Gill filaments and lamellae
  • Plant roots: Root hair cells
  • Plant leaves: Stomata and guard cells
• Osmosis


  The net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) through a partially permeable membrane