Biology - Cell biology
Cell structure
Animal and plant cells are eukaryotic (complex organisms)
Bacteria cells are prokaryotic
- Single celled
- Do not have a nucleus
- Smaller than eukaryotic cells
- Have small rings of DNA called plasmids
Organisms made up of one cell is known as unicellular, organism made up of more
than one cells is known as multicellular
Cell lengths are measured in micrometres and sub-cellular structures are measured
in nanometres
Bacteria cell
Component Structure and function
Cytoplasm Mainly water and holds ribosomes. Chemical reactions happen here such as the
making of proteins in ribosomes)
Cell wall Provides support, maintains cell shape, and prevents osmotic lysis
Single loop DNA Not held within a nucleus
Plasmids Small circular sections of DNA. Gives bacterial cells resistance to some antibiotics
Cell membrane Controls what substances go in and out of a cell
Ribosome Proteins are made here via protein synthesis
Animal cell
, Component Structure and function
Mitochondria Found in the cytoplasm and are the site of aerobic respiration. Energy from gluco
if released using oxygen
Nucleus Genetic material is enclosed in it and controls the activities of the cell
Plant cell
Component Structure and function
Chloroplasts Site of photosynthesis and contain a green pigment called chlorophyll which absorb light
energy for photosynthesis. The green chlorophyll gives plants their green colour. Most roots
are hidden from the sun and cannot photosynthesise – they do not have chloroplasts and so
are often white, not green
Cell wall Made from cellulose and provides structure for the cell
Permanent Filled with cell sap (water in which dissolved sugars and mineral ions are found). The pressu
vacuole in the vacuole presses the cytoplasm against the wall to keep the cell turgid (swollen)
Cell specialisation
Specialised cells have adaptations to allow them to complete specific functions. This is
known as cell differentiation.
Cell Adaptation Function
Sperm cell Tail Helps them swim towards an egg
Large number of mitochondria Releases energy needed to help them swim
Head of sperm Contains genetic material for fertilisation
Acrosome (covering layer) in the head Contains enzymes so the sperm can penetrate the
egg
Nerve cell Axons (long extensions) with myelin Insulates and speeds up the electrical impulse
sheath surrounding it
Small extensions Picks up signals from neighbouring cells
Muscle cell Large numbers of mitochondria To release energy for muscle contraction
Filaments of proteins Slide over each other to cause muscle contraction
Cell structure
Animal and plant cells are eukaryotic (complex organisms)
Bacteria cells are prokaryotic
- Single celled
- Do not have a nucleus
- Smaller than eukaryotic cells
- Have small rings of DNA called plasmids
Organisms made up of one cell is known as unicellular, organism made up of more
than one cells is known as multicellular
Cell lengths are measured in micrometres and sub-cellular structures are measured
in nanometres
Bacteria cell
Component Structure and function
Cytoplasm Mainly water and holds ribosomes. Chemical reactions happen here such as the
making of proteins in ribosomes)
Cell wall Provides support, maintains cell shape, and prevents osmotic lysis
Single loop DNA Not held within a nucleus
Plasmids Small circular sections of DNA. Gives bacterial cells resistance to some antibiotics
Cell membrane Controls what substances go in and out of a cell
Ribosome Proteins are made here via protein synthesis
Animal cell
, Component Structure and function
Mitochondria Found in the cytoplasm and are the site of aerobic respiration. Energy from gluco
if released using oxygen
Nucleus Genetic material is enclosed in it and controls the activities of the cell
Plant cell
Component Structure and function
Chloroplasts Site of photosynthesis and contain a green pigment called chlorophyll which absorb light
energy for photosynthesis. The green chlorophyll gives plants their green colour. Most roots
are hidden from the sun and cannot photosynthesise – they do not have chloroplasts and so
are often white, not green
Cell wall Made from cellulose and provides structure for the cell
Permanent Filled with cell sap (water in which dissolved sugars and mineral ions are found). The pressu
vacuole in the vacuole presses the cytoplasm against the wall to keep the cell turgid (swollen)
Cell specialisation
Specialised cells have adaptations to allow them to complete specific functions. This is
known as cell differentiation.
Cell Adaptation Function
Sperm cell Tail Helps them swim towards an egg
Large number of mitochondria Releases energy needed to help them swim
Head of sperm Contains genetic material for fertilisation
Acrosome (covering layer) in the head Contains enzymes so the sperm can penetrate the
egg
Nerve cell Axons (long extensions) with myelin Insulates and speeds up the electrical impulse
sheath surrounding it
Small extensions Picks up signals from neighbouring cells
Muscle cell Large numbers of mitochondria To release energy for muscle contraction
Filaments of proteins Slide over each other to cause muscle contraction
