Cell structure (B1)

• plant and animal cells are eukaryotic cells
• bacteria cells are prokaryotic cells
• plant and animal cells have a cell membrane, cytoplasm and genetic material enclosed in a nucleus.
• Bacteria cells are smaller, they have cytoplasm and a cell membrane surrounded by a cell wall. The DNA is not in a nucleus but plasmids (single loop)
• the plasma membrane is selectively permeable so only certain things can pass through it.
• cytoskeleton gives shape to the cell and helps move organelles around inside the cell. It consists of microtubules, intermediate filaments and microfilaments.
• Animal cells are made up of: nucleus, cytoplasm, cell membrane, mitochondria and ribosomes.
• Plant cells are made up of: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, chloroplasts, permanent vacuole and cell wall.
• Plant and algal cells also have a cell wall made of cellulose, which strengthens the cell.
• cell membrane controls the movement of substances in and out of a cell.
• Nucleus contains DNA
• mitochondria is where energy is released through respiration
• ribosomes is the site of protein synthesis
• cytoplasm is a jelly-like substance, where chemical reactions happen
• permanent vacuole contains cell sap and is surrounded by a double membrane called the tonoplast
• chloroplasts contain chlorophyll to absorb light energy for photosynthesis
• cell wall is made up of cellulose which strengthens the cell
• Prokaryotic cells (bacteria) are single-cells, no nucleus, have a cell wall, have small rings of DNA called plasmids and are smaller then eukaryotic cells.
• electron microscopes allow you to see sub-cellular structure such as ribosomes, that are too small to be soon with a light microscope
• light microscopes: use light to form images, living samples can be viewed, cheap, low magnification and low resolution.
• electron microscope: use beams of electrons to form images, samples can't be living, expensive, high magnification and high resolution
• magnification= image size/ actual size
• • Most types of animal cell differentiate at an early stage.
  • Many types of plant cells retain the ability to differentiate throughout life.
• In mature animals, cell division is mainly restricted to repair and replacement. As a cell differentiates it acquires different sub-cellular structures to enable it to carry out a certain function. It has become a specialised cell.
• specialised cells are cells that have a specific function and are adapted to carry out that function
• specialised cells: sperm, red blood cell, muscle cell, root hair cell and palisade cells
• sperm cells fertilises an ovum (egg)
• red blood cells transports oxygen around the body
• muscle cells contract and relax to allow movement
• nerve cells carry electrical impulses around the body
• root hair cells absorb mineral ions and water from the soil
• palisade cell enable photosynthesis in the leaf
• Sperm cells adaptations: long tail for swimming, lots of mitochondria for energy
• red blood cells adaptations: no nucleus (more room to carry oxygen), contains haemoglobin (binds to oxygen molecules), concave disc shape (increase surface area to volume ratio)
• Muscle cell adaptations: long, thin fibres to allow for large surface area for muscle contraction, contains lots of mitochondria from respiration (contract)
• nerve cell adaptations: dendrites to make connections with other neurones or effectors and myelin sheath unsulates the axon to increase the speed of impulses
• root hair cell adaptations: large surface area to absorb water and minerals and lots of mitochondria for active transport
• palisade cell adaptations: lots of chloroplasts to absorb light energy and located at the top of the leaf where it can absorb the most light
• Animal and plant cells are eukaryotic
• Genetic material (DNA) forms chromosomes and is contained in a nucleus