Microscope and cells

Question 1

Primary cell wall

Answer 1

• made up of cellulose fibres arranged in network
• tough, flexible, non-living
• middle lamella made up of pectic

Question 2

Plasmadesmata

Answer 2

Cytoplasmic strands that run through pits linking cells and allowing for communication

Question 3

Secondary wall

Answer 3

• found on inside of primary wall
• made up of cellulose fibres
• has substance called lignin between cellulose strands. Makes walls impermeable

Question 4

Functions of cell walls

Answer 4

• gives support to the cell
• gives shape to the cell
• protects the inner living parts of the cell
• prevents cell from bursting when turgid

Question 5

Cell membrane

Answer 5

Boundary that surrounds the cytoplasm of all cells. Contains the content of the cell and controls what can enter and exit.

Question 6

Phospholipids

Answer 6

• 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

Question 7

Protein molecules (cell membrane)

Answer 7

• found between phospholipids (some are partly through whilst others are completely)
• proteins are not static
• many different proteins

Question 8

Types of protein molecules (cell membrane)

Answer 8

• 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

Question 9

Diffusion

Answer 9

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

Question 10

Factors affecting rate of diffusion

Answer 10

• 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

Question 11

Facilitated diffusion

Answer 11

Large, polar molecules and ions required channel proteins or carrier proteins to cross the membrane

Question 12

Osmosis

Answer 12

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

Question 13

Factors affecting water potential

Answer 13

• 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

Question 14

Isotonic solution

Answer 14

Same concentration of solutes and solvents

Question 15

Hypertonic

Answer 15

More solutes, less solvents

Question 16

Hypotonic

Answer 16

Fewer solutes, more solvents

Question 17

Active transport

Answer 17

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

Question 18

Proteins involved in active transport

Answer 18

• 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

Question 19

Endocytosis

Answer 19

Cell membrane folds inwards to engulf a large amount of solids or liquids (phagocytosis or pinocytosis)

Question 20

Exocytosis

Answer 20

Waste is expelled out of cell in the opposite direction

Question 21

Nucleus

Answer 21

• 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

Question 22

Nucleus function

Answer 22

• 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

Question 23

Cytoplasm

Answer 23

Jelly-like substance that fills the cell. Made up of 70% water and dissolved substances such as minerals, organic molecules and gases.

Question 24

Cytoskeleton

Answer 24

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.

Question 25

Cytosol

Answer 25

Watery matrix of cytoplasm that moves around cell in process called cyclosis (transporting substances and organelles to different parts of the cell where needed)

Question 26

Mitochondrion

Answer 26

- 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

Question 27

Mitochondria function

Answer 27

Provides the cell with energy in the form of ATP which is formed when glucose is broken down during cellular respiration

Question 28

Leucoplast / amyloplasts (plastid)

Answer 28

No colour Found in roots and tubers as they store starch

Question 29

Chromoplast (plastid)

Answer 29

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.

Question 30

Chloroplast (plastid)

Answer 30

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.

Question 31

Ribosomes

Answer 31

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

Question 32

Rough endoplasmic reticulum

Answer 32

- 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