cell biology

• eukaryotic cells are animal and plant cells. they are 5µm to 100µm in size. linear DNA is found in the nucleus. they divide by mitosis.
• prokaryotic cells are bacteria and archaea. they are 0.2µm to 2µm in size. circular DNA is found in the cytoplasm and plasmids. they divide by binary fission.
• diffusion is the net movement of particles from a high concentration to a low concentration. the rate is affected by temperature, concentration gradient and surface area.
• osmosis is the net movement of water molecules from a high concentration to a low concentration through a partially permeable membrane.
• active transport is the net movement of particle from a low concentration to a high concentration (against the concentration gradient), using energy in the form of ATP
• an isotonic solution as the same concentration of solute as the cell
• a hypertonic solution as a higher concentration of solute than the cell
• a hypotonic solution has a lower concentration of solute than the cell
• plasmolysed is when the cell membrane has come away from the cell wall
• stem cells are undifferentiated cells that can divide to make different types of cells. found in human embryos (embryonic stem cells can make all types of cells), or in some organ tissues eg bone marrow (adult stem cells can only make certain types of cells and their capacity to divide is limited)
• uses of stem cells:

  • treat conditions where cells are damaged or not working properly such as diabetes or paralysis
  • therapeutic cloning is when a cloned embryo of a patient can be used as stem cells to treat them
  • however there is an infection risk and some people have ethical or religious objections
• in plants, stem cells are found in meristems. they can be used to clone plants to protect them from extinction or to make crop plants with special features
• animal cell

  A) nucleus

  B) cytoplasm

  C) cell membrane

  D) mitochondria

  E) ribosomes

  
• plant cell

  A) cell membrane

  B) permanent vacuole

  C) cellulose cell wall

  D) mitochondria

  E) nucleus

  F) cytoplasm

  G) chloroplasts

  
• root hair cell

  A) vacuole

  B) cytoplasm

  C) nucleus

  D) cell wall

  E) cell membrane

  
• bacteria cell

  A) pili

  B) ribosomes

  C) DNA

  D) slime capsule

  E) plasmids

  F) cell wall

  G) cytoplasm

  H) cell membrane

  I) flagellum

  
• turgid guard cell

  A) nucleus

  B) vacuole

  C) cell wall

  D) chloroplast

  E) stoma

  
• sperm cell

  A) acrosome

  B) nucleus

  C) mitochondria

  D) flagellum

  
• xylem

  A) one way flow

  B) water and minerals

  C) hollow tube

  D) lignin walls can withstand water pressure

  
• phloem

  A) organic molecules

  B) sieve plates

  C) two way flow

  D) thin cellulose wall

  E) live cells kept alive by companion cells

  
• the cell cycle

  • specialised cells leave the cell cycle as they cannot undergo mitosis

  A) interphase

  B) nuclear division by mitosis

  C) cytokinesis - cell division

  D) growth of cells, performs function, DNA replication

  
• mitosis is nuclear division which results in the production of two genetically identical diploid cells (body cells)

  • prophase - nucleus disappears and chromosomes become visible
  • metaphase - chromosomes line up in middle along the equator
  • anaphase - chromatids are moving away from each other to opposite poles of the cell, pulled by spindles which are fibres
  • telophase - chromosomes are at opposite ends and two nuclei are starting to surround the chromosomes on both sides

  
• meiosis - produces four genetically different haploid gametes

  • prophase I - chromosomes thicken, line up with homologous pairs, crossing over - chromosomes transfer genetic information and exchange between each other
  • metaphase I - line up in middle in pairs
  • anaphase I - chromosomes pulled away by spindle fibres
  • telophase I - two new nuclei
  • prophase II - chromosomes thicken, spindles form
  • metaphase II - line up in middle in single file
  • anaphase II - chromatids pulled away by spindle fibres
  • telophase II - 4 new nuclei