Biology - B2.1 - Cells, Tissues and Organs - Revision Cards in GCSE Biology

B2.1.1 - Animal and Plant Cells

Light microscopes - used in school, electron microscopes - magnify things thousands of times larger
Parts of a cell:
- nucleus - control cell activities
- cytoplasm - where many chemical reactions happen
- cell membrane - controls movement in and out of cell
- mitochondria - where energy is released during aerobic respiration
- ribosomes - where protein synthesis happens
Parts of a cell only in plants and algal cells
- rigid cell wall - made of cellulose, for support
- chloroplasts - contain chlorophyll: photosynthesis - absorb light energy
- permanent vacuole - contains cell sap

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Bacteria - very small; can only be seen with a powerful microscope
Bacteria have a cell membrane and wall that surround a cytoplasm - they don't have a nucleus - the genetic material is in the cytoplasm
Bacteria multiply = colony - can be seen with naked eye
Yeast - single cell organism
Yeast has a nucleus, cytoplasm and membrane, surrounded by a cell wall

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Many different types of cells - as an organism matures, cells develop into particular types - structure is linked to function
Many mitochondria - lots of energy - sperm cell, muscle cell
Many ribosomes - lots of protein - gland cells: produce enzymes
Tails - able to move - sperm cells
Receptor cells structured to detect stimuli - cone cells in eye: light sensitive
Nuerons - specialised cells to carry impulses from receptors to CNS
Many chloroplasts - photosythesis - mesophyll cells of a leaf
Increased surface area - take up more water and ions - roots

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Liquid and gas molecules - move around quickly due to lots of energy
Diffusion - spreading out of gas particles or any substance in a solution
Net movement - depends on concentration of particles on each side
Particles move radomly - net movement from area of high concentration to low concentration
Concentration gradient - difference in concentration between two areas
Larger concentration difference = faster rate of diffusion
Examples of diffusion:
- O2 into cells of the body from blood stream as cells respire and use oxygen
- CO2 into actively photosynthesising plant
- simple sugars and amino acids from gut

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When multicellular organisms develop, cells differentiate - different cell = different functions
Tissue - group of cells with similar structure and functions
Animal tissues include:
- muscle tissue - contract to cause movement
- glandular tissue - protect substances eg. enzymes or hormones
- epithelial tissue - covers some parts of the body
Plant tissues include:
- epidermal tissue - covers the plant
- mesophyll - can photosythesise
- xylem and phloem - transport substances around plant

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Organs - made of tissues
Stomach - organ made of:
- muscular tissue - churn stomach contents
- glandular tissue - produce digestive juices
- epithelial tissue - cover inside and outside of stomach
Leaf, stem and root - plant organs containing epidermal tissue, mesophyll, xylem and phloem
Groups of organs = organ systems - perform particular function
Digestive system - several organs, including small intestine

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Food eaten - must be changed from insoluble -> soluble molecules - then can be absobed by blood - done by digestive system
Digestive system - muscular tube including
- glands - eg. pancreas and salivary gland - produce digestive juices
- stomach and small intestine - digestion occurs
- liver - produces bile
- small intestine - absorption of soluble food occurs
- large intestine - water absorbed from undigestive food, producing faeces

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