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Question 1

difference between prokryotic and eukaryotic cells

Answer 1

prokaryotic - bacterial cells. much smaller. cytoplasm and cell membrane surrounded by cell wall. the genetic material is not enclosed in nucleus. a single DNA loop, one or more small rings of DNA - plasmids
eukaryotic - animal and plant cells. genetic material enclosed in a nucleus

Question 2

cell membrane

Answer 2

holds cell together, seperates the inside of the cell from outside and controls what enters and leaves the cell

Question 3

cytoplasm

Answer 3

jelly-like substance where chemical reactions happen, surrounds sub-cellular structures, anaerobic respiration

Question 4

DNA

Answer 4

genetic material that controls activities of cells

Question 5

ribosomes

Answer 5

site of protein synthesis in cell

Question 6

mitochondria

Answer 6

where aerobic respiration happens (energy is released to fuel cellular activities)

Question 7

chloroplasts

Answer 7

green pigment called chlorophyll which absorbs light energy and has enzymes which are needed for photosynthesis

Question 8

cell wall

Answer 8

made of cellulose which gives cells extra support, defining it’s shape

Question 9

permenant vacuole

Answer 9

contains cell sap - solution of sugars and salts dissolved in water
helps support the shape of the cell
used for storage of certain materials

Question 10

how are nerve cells specialised

Answer 10

have elongated structures which allows them to coordinate info from cns with rest of body
- the axon is covered with a fatty sheath which speeds up nerve impulses

Question 11

how are muscle cells specialised

Answer 11

have lots of mitochondria to provide sufficient energy by aerobic respiration for muscle contraction
they also contain layers of fibres which allow them to contract

Question 12

how are sperm cells specialised

Answer 12

middle of cell has lots of mitochondria for energy by aerobic respiration for tail to move forwards quickly

Question 13

how are root hair cells specialised

Answer 13

they absorb mineral ions and water from soil
small hairs which increase surface harea so rate of osmosis is quicker
thinner walls so shorter diffusion distance
mitochondria for energy for active transport for mineral ions
permenant vacuole more concentrated so good gradient for faster rate

Question 14

how are xylem cells specialised

Answer 14

transport tissue for water and dissolved ions
cells are dead (no cytoplasm or organelles) to allow free passage of water
outer walls thickened with lignin, strengthening the tubes, which helps support the plant

Question 15

how are phloem cells specialised

Answer 15

transport of dissolved sugars and amino acids
made of living cells which are joined end to end.
they have holes called sieve plates which form tubes allowing sugars and amino acids to flow

Question 16

why is cell differentiation important?

Answer 16

so that it can get a structure and composition of subcellular structures which enables it to carry out a certain function

Question 17

differentiation in plants vs animals

Answer 17

plants retain ability to differentiate throughout life but most animals differentiate at an early stage

Question 18

how has electron microscopy increased understanding of sub-cellular structures?

Answer 18

has a much higher magnification and resolving power than light microscope. this means it can be used to study cells in finer details. this has enabled biologists to see and understand more sub-cellular structures

Question 19

light vs electron microscope - how they work

Answer 19

electron - ises beams of electrons. the wavelength of electron beam is much smaller than visible light so they have higher magnification and resolution
light - uses light and lenses to form magnified mage of a specimen

Question 20

magnification

Answer 20

size of image / size of real object

Question 21

how to prepare a microscope slide

Answer 21

• they are prepared on slide to be observed under a light microscope
  use tweezers to get a layer of cells. add a drop of water to a clean slide. place tissue into water on slide. add iodine stain so that structures within the cell can be observed. then place a cover slip on top of the specimen

Question 22

what is diffusion

Answer 22

spreading out of particles of any substances in solution, or particles in gas, resulting in net movement from an area of high concentration to area of lower concentration.

Question 23

factors affecting rate of diffusion and why

Answer 23

concentration difference - larger concentration difference means faster rate of diffusion
surface area - larger the surfacte area, the faster rate of diffusion as more particles pass through
temperature - higher temperature means faster diffusion because particles have more energy so move around faster

Question 24

define osmosis

Answer 24

movement of water molecules across a partially permeable membrane from a region of higher water concentration to an area of lower water concentration

Question 25

how is the small intestine adapted to its role

Answer 25

it absorbs digested food molecules into the bloodstream through its walls
- has highly folded surface - many vilus, which increases the surface area
- has only one layer of epithelial cells which decreases diffusion distance
- each villus has a good blood supply which maintains a concentration gradient

Question 26

how are lungs adapted for its function

Answer 26

adapted for gas exchange between air in alveoli and the blood so cells have oxygen for aerobic respiration and to remove carbon dioxide
- it has millions of alveoli and the shape of the alveoli is spherical which means larger surface area
- wall of each alveoulus is one cell thick and a good blood supply which decreases diffusion distance and maintains a concentration gradient

Question 27

how are gills adapted to its role?

Answer 27

gas exchange between water flowing through gills and blood to supply cells with oxygen for aerobic respiration and remove carbon dioxide
- each gill has smaller plates called filaments which are covered in projections called lamellae which increases surface area
- dense capillary network which ensures a good blood supply, and flows in opposite direction to water passing through gills maintaining a concentration gradient

Question 28

how roots in plants are adapted for exchanging minerals

Answer 28

• root network is branched and surface of roots have root hair cells which have specialised structure with root hairs which increases surface area

Question 29

how are leaves in plant adapted to its role?

Answer 29

• have stomata which are tiny openings and cover the lower side of leaf which decreases diffusion distance for carbon dioxide and oxygen
• lower layer of the leaf is made from spongy mesophyll cells which allow air to circulate inside the leaf

Question 30

define active transport

Answer 30

movement of substances from an area of low concentration to an area of higher concentration using energy from respiration

Question 31

active transport in plants

Answer 31

so that mineral ions can be absorbed from the soil into root hairs as the soil has dilute concentrations. this is required by plants because they need mineral ions for healthy growth

Question 32

active transport in animals

Answer 32

sugar molecules in low concentrations to be absorbed into the blood from the gut. sugar molecules are used for cell respiration

Question 33

microscope practical - onion cells

Answer 33

Use tweezers to peel back a layer of epidermal tissue
Add a drop of water to a clean slide
Spread the epidermal tissue out on the slide
Ensure the tissue is one cell thick
Add a drop of dye / iodine / stain so structures are visible / clear
Place a cover slip over the top
Tap gently to remove air bubbles
Dab away any excess dye from the slide