Cell structure

• Define a eukaryotic cell:

  any organism consisting of one or more cells containing DNA in a membrane-bound nucleus and has other membrane-bound organelles
• State four examples of Eukaryotic cells:

  • animals
  • plants
  • fungi
  • protists
• Membranes are important because they keep each organelle separate from the rest of the cell and allow substances to pass through
• Outline the functions of the nucleus:

  • to act as the control centre of the cell through the production of mRNA and protein
  • to store the genetic material of the cell
  • To start the process of cell division
• State the four features of the nucleus:

  • nucleolus
  • nuclear envelope
  • nuclear pores
  • chromatin
• What is the function of the nuclear envelope?

  To control the entry and exits of materials in the nucleus
• The nuclear envelope separates the contents of the nucleus from the cytoplasm and the rest of the cell
• The nuclear envelope's outer membrane is continuous with the endoplasmic reticulum
• Describe the nuclear envelope:

  • It separates the contents of the nucleus from the cytoplasm and the rest of the cell
  • It is a double membrane
  • it has nuclear pores
  • the outer membrane is continuous with the rough endoplasmic reticulum
  • It controls the entry and exits of materials in the nucleus
• In some regions, the outer and inner nuclear membranes fuse together. At these points some dissolved substances and ribosomes can pass through
• Describe the nuclear pores:

  • they are in the nuclear envelope
  • It allows the passage of large molecules, like mRNA, out of the nucleus
  • Substances such as steroids hormones from the cytoplasm may enter the nucleus through it
• Chromosomes of an organism contain genes
• Define the Nucleolus:

  A structure found in the nucleus that contains proteins and RNA and is involved in synthesising new ribosomes
• Define the Chromatin:

  The genetic material consisting of DNA wound around histone proteins
• Describe the Chromatin:

  • The genetic material consisting of DNA wound around histone proteins
  • when the cell is not dividing, it spreads out or extends
  • when the cell is about to divide, it condenses and coils tightly into chromosomes
  • They make up nearly all the organism's genome
• Define chloroplasts:

  Organelles found in plants and algae that are the site of photosynthesis
• What happens to chromatin when the cell is not dividing?

  It spreads out or extends
• What happens to chromatin when the cell is about to divide?

  It condenses and coils tightly into chromosomes
• Function of chloroplasts:

  To trap light energy and convert it into chemical energy
• State the features of chloroplasts:

  • Chloroplast envelope
  • Stroma
  • Grana
  • thylakoids
  • intergranal lamellae
  • Starch grains
  • chlorophyll
  • ribosomes
  • DNA
• Chloroplasts are 4 - 10 μm long
• Chloroplasts contain loops of DNA and starch grains
• What is the function of the chloroplast envelope?

  To control the entry and exits of materials in chloroplasts
• Chloroplasts are found in plant cells and algae
• Starch grains are temporary stores of carbohydrates
• Chloroplasts are abundant in leaf cells, particularly in the palisade mesophyll layer
• Describe the inner membrane of chloroplasts:

  it is continuous with stacks of flattened membrane sacs called thylakoids which contain chlorophyll. Each stack or pile of thylakoids is called a granum. The fluid filled matrix is called the stroma
• What are thylakoids and what do they contain?

  
  

  stacks of flattened membrane sacs in chloroplasts which contain chlorophyll
• What is the stroma, what does it contain, and which stage of photosynthesis is it involved in?

  fluid filled matrix within chloroplasts which contain enzymes involved in the light independent/ second stage of photosynthesis
• What are grana and what stage of photosynthesis is it involved in?

  Grana are stacks of thylakoids in the chloroplast involved in the light dependant/ first stage of photosynthesis
• The first stage of photosynthesis occurs in the thylakoids where light energy is absorbed by chlorophyll to use it to make ATP. Water is split to supply hydrogen ions (protons) for the reaction.
• The second stage of photosynthesis occurs in the stroma of the chloroplast, where hydrogen reduces carbon dioxide using energy from ATP to make carbohydrates
• The first stage of photosynthesis is called the light dependant stage.

  The second stages of photosynthesis is called the light independent stages.
• State two features of Mitochondria:

  • double membrane (envelope)
  • matrix
• Mitochondria are 2 - 5 µm long
• The mitochondria has a double membrane. The inner membrane is folded into cristae which provides a large surface area
• Where is the matrix in the mitochondria?

  in the inner membrane
• State what the matrix contain in the mitochondria:

  • enzymes
  • ribosomes
  • DNA
• Define a Mitochondria:

  An organelle where aerobic respiration (metabolic activity) for ATP production takes place
• Mitochondria is self replicating via binary fission so more can be made if the cell's energy needs to increase