Biology T1

• The nucleus contains the genetic material (DNA) which controls all cellular activity
• Ribosomes are involved in protein synthesis.
• Mitochondria are responsible for producing energy through aerobic respiration.
• The cytoplasm is where most chemical reactions take place, including protein synthesis.
• The nucleus is the control centre of the cell, containing DNA which controls all activities within the cell.
• Differentiation is the process by which a cell changes to become specialised at its job.
• Differentiation in an animal cell occurs in the developing stage of an organism. This ability is lost in the early stages of development.
• Plant cells never loose the ability to differentiate because they never become specialised.
• Differentiated cells in mature animals are used to repair and replace skin and blood cells.
• Sperm, Root hair cells, Muscles, Xylem, Phloem and Nerve Cells are all examples of specialised cells.
• Sperm cells have a long tail and a streamlined head for swimming, enzymes in their head to digest through the egg cell membrane and mitochondria to provide the cell with energy.
• Nerve Cells are long to cover more distance and have branched connections at their ends to connect to others, forming a network around the body.
• Muscle cells are long to have space to contract and relax. They also have lots of mitochondria to generate the energy needed to contract.
• Root hair cells have a large surface area to absorb water and minerals from the soil.
• The phloem has few sub-cellular structures so that the movement of amino acids and sugars up and down from the leaves to the growing parts of a plant (translocation) can occur efficiently .
• The xylem walls of the xylem are made up of dead cells and are hollow to transport water up the stem to the leaves through transpiration.
• Embryonic stem cells can turn into any type of cell.
• Stem cells are undifferentiated cells that can divide to produce more undifferentiated cells. Depending on the instructions given, they can become specialised cells.
• Stem cells are found in the bone marrow in adults and in early human embryos. They have the ability to differentiate into any type of cell.
• Stem cells can be grown in labs to produce clones. They can be made to differentiate into specialised cells to be used in medicine and research.
• Adult stem cells can cure diseases through bone marrow transplants.

  Embryonic stem cells can replace faulty cells e.g insulin-producing cells and nerve cells.

  Therapeutic cloning allows embryos to have the same genetic makeup as a patient to avoid rejection.
• Stem cells that are grown in a lab can become contaminated with a virus that can make the patient sicker.
• Stem cells in plants can be used to make identical plants.
• Stem cells in plants are found in the meristem.
• • Stem cells in the meristem can differentiate into any type of cell for their whole life
  • These cells can be used to create clones quickly and easily
• Stem cells in plants can be used to create plants with desirable features such as disease resistance and can also be used to grow rarer plants.
• Chromosomes are made of DNA and proteins and are found in the nucleus of a cell.
• The cell cycle is a process that makes for growth repair and development.

  Body cells in multicellular organisms divide to produce new cells as a series of stages through this process.
• Organisms use mitosis for …

  • grow, develop and repair damaged cells .
• In growth and DNA replication..

  1. DNA is spread out in strips in an undivided cell.
  2. It has to grow and increase sub-cellular structures before dividing.
  3. It duplicates its DNA so there is one copy for each cell.
• In Mitosis…

  1. Chromosomes line up in centre and cell fires separate them.
  2. Membranes form around the chromosomes, becoming nuclei. The nuclei has divided .
  3. The cytoplasm and the cell membrane divine last
  4. The cell has now produced 2 new daughter cells and they contain the same DNA as each other and the parent cell.
• The Villi are located in the small intestine and are finger-like projections that increase the surface area for absorption.
• How are the Alveoli specialised for oxygen diffusion?


  Enormous surface area

  Moist lining for dissolving gases

  Thin walls

  A good blood supply
• Gas exchange occurs in the millions of alveoli in the lungs.
• How are exchange surfaces adapted ?


  • Thin membrane - short distance to diffuse

  • Large surface area - lots of substances can diffuse at once

  • Lots of blood vessels to get things in and out of the blood quickly

  • Good blood supply - increase effective exchange

  • Often well ventilated (alveoli)
• Multicellular organism need exchange surfaces because they have a smaller surface area compared to their volume .
• Substances in single-celled organisms can diffuse directly through a cell membrane because they have a large surface area compared to their volume.
• Where in humans does active transport take place?

  In taking glucose from the gut

  Kidney tubules

  Villi and digestion
• What is needed for active transport to occur?

  Energy from respiration .
• Active transport allows plants to absorb minerals from a very dilute solution against a concentration gradient.