B1

Question 1

What is a prokaryotic cell with an example

Answer 1

Smaller and simpler cells e.g bacteria

Question 2

What is a eukaryotic cell with an exampls

Answer 2

Complex cells that include all animal and plant cells

Question 3

What are subcellular structures

Answer 3

The different parts of a cell for example there is a nucleus and a cell membrane

Question 4

All subcellular structures in an animal cell and what they do

Answer 4

Nucleus- contains DNA and controls activities of the cell
Cytoplasm- gel-like substance where most chemical reactions occur
Cell Membrane- holds cell together and controls what goes in and out
Mitochondria- transfers energy that the cell needs to work (aerobic respiration)
Ribosomes- where proteins are made in the cell

Question 5

The extra subcellular structures in a plant cell that aren’t in the animal cell and what they do

Answer 5

Cell wall- made of cellulose. supports and strengthens the cell
Permanent vacuole- contains cell sap (weak solution of sugar and salts)
Chloroplasts- where photosynthesis occurs (contains chlorophyll, which absorbs light needed for photosynthesis) which makes food for the plant

Question 6

The subcellular structures of a bacteria cell

Answer 6

Cytoplasm, Cell membrane, Cell wall, may contain plasmids(round rings on DNA) , single circular strand of DNA. NO chloroplasts and NO mitochondria

Question 7

What is the formula for magnification

Answer 7

Magnification= image size ÷ real size

Question 8

Labels of a microscope

Answer 8

Eyepiece, Coarse adjustment knob(moves the stage), Fine adjustment knob(adjusts the focus), stage, light, high power objective lens, low power objective lens

Question 9

What is differentiation

Answer 9

The process by which a cell changes to become specialised for its job

Question 10

4 Examples of specialised cells and what they are specialised for

Answer 10

Sperm cells- long tail, streamlined head, loads of mitochondria, to swim to the egg cell, enzymes to digest through egg cell memebrane
Nerve cells- long to cover more distance to carry signals from one part of the body to another, branched connections to connect to form a network
Muscle cells- lots of mitochondria to provide energy needed for contraction
Root hair cells- hairs that stick out into the soil to get a big surface area for absorbing water and minerals

Question 11

What are chromosomes

Answer 11

Chromosomes are coiled up lengths of DNA molecules. Each one carries a large number of genes

Question 12

The two main stages of the cell cycle and what happens

Answer 12

Growth & DNA replication- the cell that isn’t dividing, duplicates its DNA so that there’s one copy for each new cell
Mitosis- the cell fibres pull apart the chromosomes then membranes form around each of the sets of chromosomes then the cytoplasm and cell membrane divide, this produces a new identical cell

Question 13

What do organisms use mitosis for

Answer 13

To grow or replace cells that have been damaged

Question 14

What are stem cells and what can they do

Answer 14

They are undifferentiated cells that can divide to provide more of themselves. Then they can differentiate into different types of cells depending on the intructions given

Question 15

Why do stem cells excite doctors and medical researchers

Answer 15

They have the potential to turn into any kind of cell

Question 16

Where can stem cells be found

Answer 16

In early human embryos, adults also have stem cells but only in certain areas like bone marrow. Unlike embryonic stem cells these ones can’t become any cell

Question 17

Why might stem cells be good for the future

Answer 17

They may be able to cure many diseases, for example stem cells transferred from the bone marrow of a healthy person can replace faulty blood cells in a patient who recieves them

Question 18

Why are some people against stem cell research

Answer 18

Because they feel that human embryos shouldn’t be used for experiments since one is a potential human life

Question 19

What is diffusion

Answer 19

The spreading out of particles from an area of higher concentration to an area of lower concentration

Question 20

What is osmosis

Answer 20

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

Question 21

What is active transport

Answer 21

Active transport allows is the absorbtion of substances against a concentration gradient. But it needs energy to make it work

Question 22

What does a surface area to volume ratio determine

Answer 22

How easy it is for an organism to exchange substances with its environment because of diffusion

Question 23

How do light microscopes work

Answer 23

They use light and lenses to form an image of a specimen and magnify it

Question 24

How do electronic microscopes work

Answer 24

Use electrons instead of light to form an image. They have much higher magnification than light microscopes

Question 25

Diffusion in cells

Answer 25

Dissolved substances can move in and out of cells by diffusion. Only very small molecules can diffuse through cell membranes like oxygen, glucose, amino acids and water. Big molecules like starch and protein can’t fit through

Question 26

Active transport in humans

Answer 26

When there is a higher concentration of nutrients in the gut it diffuses naturally into the blood but sometimes there’s a lower concentration of nutrients in the gut than in the blood meaning the concentration gradient is the wrong way. Therefor active transport must be used to get all the nutrients from the gut into the blood

Question 27

How can exchange surfaces be adapted to maximise efficiency

Answer 27

They have a thin membrane so substances only have a short distance to diffuse
They have a large surface area so lots of a substance can diffuse at once
In animals they have lots of blood vessels to get stuff in and out of the blood quickly
Alveoli in animals are ventilated so air can move in and out

Question 28

4 examples of things that are adapted for exchanging substances through diffusion

Answer 28

Alveoli- enormous surface area, very thin walls
Villi- increase surface area to absorb more food into blood
Structure of Leaves- stomata and air gaps in spongy mesophyll
Gills- lamellae to increase surface area, thin surface layer of cells

Question 29

Turgid Cell

Answer 29

Water enters a plant cell by osmosis and the vacuole swells and pushes againts the cell wall

Question 30

Flaccid cell

Answer 30

Water lost from a plant cell and the vacuole shrinks and a cell loses its shape