Microscope and cells Flashcards
Primary cell wall
- made up of cellulose fibres arranged in network
- tough, flexible, non-living
- middle lamella made up of pectic
Plasmadesmata
Cytoplasmic strands that run through pits linking cells and allowing for communication
Secondary wall
- found on inside of primary wall
- made up of cellulose fibres
- has substance called lignin between cellulose strands. Makes walls impermeable
Functions of cell walls
- gives support to the cell
- gives shape to the cell
- protects the inner living parts of the cell
- prevents cell from bursting when turgid
Cell membrane
Boundary that surrounds the cytoplasm of all cells. Contains the content of the cell and controls what can enter and exit.
Phospholipids
- arranged in two rows
- has a phosphate head that is hydrophilic and two fatty acid tails that are hydrophobic
- heads face outwards, tails face inwards
- phospholipids can move to allow small molecules through membrane
Protein molecules (cell membrane)
- found between phospholipids (some are partly through whilst others are completely)
- proteins are not static
- many different proteins
Types of protein molecules (cell membrane)
- glycoprotein : carbohydrate attached to free surface.
- channel protein: water-filled channel that runs through it allowing outside and inside of cells to connect and transport substances
- transport proteins: used for active transport
-glycolipids and cholesterol: make membrane more strong, flexible and less permeable to water-soluble ions and monosaccharides
Diffusion
The movement of molecules from a region of high concentration to a region of low concentration down a diffusion gradient until dynamic equilibrium is reached
Factors affecting rate of diffusion
- concentration gradient : steeper gradient, faster diffusion will occur
- size of molecules: larger the molecules, the slower diffusion occurs
- pressure: the greater the pressure, the faster the molecules move as they collide more rapidly and gain more energy
- temperature: the higher the temperature, the faster molecules move
Facilitated diffusion
Large, polar molecules and ions required channel proteins or carrier proteins to cross the membrane
Osmosis
The movement of water molecules from a region of high water potential to a region of low water potential through a selectively permeable membrane until equilibrium is reached
Factors affecting water potential
- amount of solutes: the more solutes, the less the water has to move and potential to move is therefore lowered
- increased pressure will raise their potential to move
- increased temperature increases water potential
Isotonic solution
Same concentration of solutes and solvents
Hypertonic
More solutes, less solvents
Hypotonic
Fewer solutes, more solvents
Active transport
Movement of molecules from a region of low concentration to a region of high concentration against the diffusion gradient. ATP is required in order to happen
Proteins involved in active transport
- channel proteins: channel running through them use energy to pull the molecules through
- transport / carrier proteins: collect the molecule on their upper surface towards the outside of the cell and use energy to bend and pull molecule through
Endocytosis
Cell membrane folds inwards to engulf a large amount of solids or liquids (phagocytosis or pinocytosis)
Exocytosis
Waste is expelled out of cell in the opposite direction
Nucleus
- surrounded by double semi-permeable membrane
- nuclear pores link nucleus to cytoplasm
- nucleoplasm forms inner substance
- has chromatin network made up of chromosomes and is embedded in the nucleoplasm
- nucleolus is made up of RNA and protein is also embedded in the nucleoplasm
Nucleus function
- controls the cell activities as it has the instructions in the DNA to make proteins. Proteins form enzymes
- stores the genetic / hereditary info about the cell
Cytoplasm
Jelly-like substance that fills the cell. Made up of 70% water and dissolved substances such as minerals, organic molecules and gases.
Cytoskeleton
Network made up of protein fibres and microtubules that gives cytoplasm jelly-like property, shape and enables cell functions such as cell division and movement.
Cytosol
Watery matrix of cytoplasm that moves around cell in process called cyclosis (transporting substances and organelles to different parts of the cell where needed)
Mitochondrion
- rod shaped organelle
- surrounded by double semi-permeable membrane
- outer membrane is smooth
- inner membrane is folded to form cristae
- liquid inner substance called matrix which contains ribosomes
- mDNA can be found in matrix
Mitochondria function
Provides the cell with energy in the form of ATP which is formed when glucose is broken down during cellular respiration
Leucoplast / amyloplasts (plastid)
No colour
Found in roots and tubers as they store starch
Chromoplast (plastid)
Contains yellow, orange and red pigments. Found in fruits, vegetables and petals of flowers.
Function is to attract insects, birds etc for pollination and seed dispersal.
Chloroplast (plastid)
Contain green pigment chlorophyll and is found in leaves and green fruit and stems Function is to photosynthesize and convert radiant energy into chemical energy.
Ribosomes
Small structure made up of two sub units of protein and ribosomal RNA.
No membrane surrounding
Can be singular of found in groups (polyribosomes).
Site of protein synthesis
Rough endoplasmic reticulum
- has ribosomes attached to outside
- maze of flattened, parallel membranes
- swollen cisternae at ends which can break of into vesicles
- protein molecules can be found in lumen
- function is to transport proteins made by ribosomes to diff parts of body + is the network of membranes that compartmentalises the cytoplasm into different compartments
