Tiny building blocks that make up all living things
Types of cells
Prokaryotic
Eukaryotic
Prokaryotic cells
Simple and small
Genetic material is not enclosed in a nucleus
Do not have membrane-bound organelles
Prokaryotic cells
Bacteria
Archaea
Eukaryotic cells
Complex and larger
Genetic material is inside a nucleus
Have membrane-bound organelles for specific functions
Eukaryotic cells
Plants
Animals
Fungi
Protists
Prokaryotic cells are simpler and lack organelles, while eukaryotic cells are more complex and have organelles that help with different tasks
Understanding the differences between prokaryotic and eukaryotic cells helps us learn more about living things
Animal cell
Does not have a cell wall
Does not have chloroplasts
Does not have large central vacuoles
Plant cell
Has a cell wall made of cellulose
Has chloroplasts that contain chlorophyll
Has large central vacuoles
Animal cells
Do not have a cell wall, chloroplasts, or large central vacuoles
Plant cells
Have a cell wall, chloroplasts, and large central vacuoles
Organisms
can be Prokaryotes or Eukaryotes
Prokaryotic
single-celled organien
Plant and Animal Cells have Similarities and Differences
Plant cells usually have all the bits that animal cells have, plus a few extra things that animal cells don't have
Rigid cell wall-made of cellulose. It supports the cell and strengthens it.
Permanent vacuole - contains cell sap. {a week solution of sugar and salts}. cell sap is a very strong substance which helps keep the cell turgid.
Chloroplasts- these are where photosynthesis occurs, which makes food for the plant (see page 57). They contain a green substance called chlorophyll, which absorbs the light needed for photosynthesis.
Bacterial Cells Are Much Smaller
Bacterial cell structure
Cell membrane
Cell wall
Cytoplasm
Bacteria don't have chloroplasts or mitochondria.
Bacterial cells don't have a 'true' nucleus-instead they have single circular strand of DNA that floats freely in the cytoplasm. They may also contain one or more small rings of DNA called plasmids
Cell Differentiation
The process by which a cell changes to become specialised for its job
Cell Specialisation
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Stem cells
Undifferentiated cells that can divide to produce lots more undifferentiated cells and differentiate into different types of cell
Examples of Specialised Cells
SPERM CELLS are specialood for REPRODUCTION
NERVE CELLS are specialized for RAPID SIGNALLING
MUSCLE CELLS are specialised for CONTRACTION
ROOT HAIR CELLS are specialised for absorbing WATER and MINERALS
PHLOEM and XYLEM CELLS are specialised for TRANSPORTING SUBSTANCES
Chromosomes
Coiled up lengths of DNA molecules that contain genetic information
Body cells normally have two copies of each ohromosome-one from the organism's 'mother', and one from its father'.
The Cell Cycle
1. Growth & DNA Replication
2. Mitosis
Multicellular organisme use mitosis to grow or replace cells that have been damaged.
The end of the cell cycle results in two new cells identical to the original cell, with the same number of chromosomes.
Embryonic Stem Cells
Can turn into ANY Type of Cell
Adult Stem Cells
Can only turn into certain cell types, not any cell type
Stem cells from embryos and bone marrow can be grown in a lab to produce clones (enefically identical cals) and made to differentials into specialised calls to use in medicine or research.
Potential uses of Stem Cells
Replace faulty blood cells
Replace insulin-producing cells for diabetes
Replace nerve cells for spinal injuries
Arguments against Stem Cell Research
Embryos are potential human lives and shouldn't be used for experiments
Curing existing patients is more important than rights of embryos
Scientists should focus on developing other sources of stem cells instead
In some countries stem cell research is banned. It's allowed in the UK as long as it follows strict guidelines.
Plant Stem Cells
Found in the meristems (parts of the plant where growth occurs) and can differentiate into any plant cell type
Stem cells can be used to grow more plants of rare species and to grow crops of identical plants with desired features