B1 cell biology

Question 1

properties of prokaryotic cells

Answer 1

no nucleus

genetic material stored in single loop of dna

no chloroplasts or mitochondria

some prokaryotic cells contain plasmids
plasmids can replicate and move between cells so genetic info can be shared

Question 2

cell membrane

Answer 2

controls what goes in and out of the cell - selectively permeable

Question 3

ribosomes

Answer 3

responsible for synthesising (making) proteins

Question 4

mitochondria

Answer 4

organelles where aerobic respiration happens
releases energy out body needs to function

Question 5

permeable vacuole

Answer 5

fluid filled sac that stores water
enclosed in a membrane
can make up to 90% of plant volume

Question 6

differentiation in plants

Answer 6

can differentiate throughout life
which means plants are always able to create new tissues

Question 7

differentiation in animals

Answer 7

earlier on in development
in mature animals cells mostly divide to replace and repair ones that are already there
new tissues are rarely created by cell differentiation

Question 8

when does differentiation occur

Answer 8

when cells acquire different sub cellular structures

Question 9

flagella

Answer 9

some bacteria have flagella l
whip like structures used for movement

Question 10

sun cellular structures inside bacteria

Answer 10

flagella
cytoplasm
plasmids
cell wall and cell membrane

Question 11

what is cell differentiation

Answer 11

where a cell develops new sub cellular structure to let it perform a specific function
this makes the cell specialised

Question 12

embryos

Answer 12

cell differentiation in animals starts during an organisms development

organisms start one

these cells divide to form embryos that differentiate to produce that perform all the body’s functions

Question 13

sperm cell

Answer 13

specialised

flagellum

middle section-provides sperm with energy

head-carries nucleus

acrosome-found at tip of head, contains digestive enzymes to penetrate the egg cell

Question 14

nerve cells

Answer 14

specialised to send electrical signals around the body
axon
myelin sheath
dentrites

Question 15

axon

Answer 15

part of the cell that electrical signals travel along

nerve cells have a long axon - this increases the distance electrical impulses can travel

Question 16

myelin sheath

Answer 16

sheath made of material called myelin

surrounds axon on nerve cell

this increases speed of transmission of electrical signals and stop’s electrical nerve signals leaking out

Question 17

dendrites

Answer 17

branches of nerve cells

several dendrites spread outwards form the cell body to transfer electrical messages to other neurons

electrical messages travel between neurons and synapses

Question 18

xylem cells

Answer 18

specialised to transport water up the stem of a plant and into the leaves

open ended cells- xylem vessels are made up of a series of connected dead xylem cells

the end walls of the dead cells are broken to allow water to move through

lignin- strengthens cell walls of xylem cells

Question 19

phloem

Answer 19

The phloem is specialised to transport food products to parts of the plant where they are needed. Phloem vessels are made up of columns of living cells.

The end walls of phloem cells contain small holes to allow food products to move up and down the phloem vessels throughout the plant

Question 20

resolution

Answer 20

Resolution is the ability to distinguish between (tell apart) two or more objects that are close together.

Question 21

magnification

Answer 21

Magnification tells us how many times larger an image seen through a microscope is compared to the real object.

Magnification = image size ÷ actual size

Question 22

light microscope

Answer 22

A light microscope passes light through a specimen and creates a magnified image using lenses.

Light microscopes allowed bacteria to be seen for the first time. They also allowed us to see plant cells and animal cells as separate objects

Question 23

electron microscope

Answer 23

Electron microscopes work in a similar way to light microscopes. However, electrons are passed through the specimen instead of light

allowed scientists to see sub-cellular structures more clearly.
They also allowed scientists to study how structures such as mitochondria, chloroplasts and ribosomes function.

Question 24

Light Microscope Experiment

Answer 24

Put a thin sample of tissue (e.g. onion epidermis) onto a microscope slide.

Add a few drops of a suitable stain/dye (e.g. iodine).

Place a coverslip on top of the tissue and place the slide onto the microscope stage.

Use the objective lens with the lowest magnification, and focus on the sample.

Increase the magnification and refocus to see different features of the cell.

Question 25

growing microorganisms

Answer 25

cultures of microorganisms can be used to see the effects of antibiotics and disinfectants which both kill bacteria

microorganisms can be grown in:
-solution of nutrient broth, this contains carbohydrates as an energy source minerals and sometimes other chemicals
-agar gel plate

Question 26

contamination

Answer 26

if bacteria that are not being investigated grow during culturing microorganisms, then the investigation has been contaminated

risks:
ruins test results
serious health + safety issues

sources:
skin
air
soil
water

prevention:
cultures must be pure

Question 27

aseptic techniques

Answer 27

flames
boiling
controlled temp (25 degrees)
lids- taped shut and put upside down so air doesn’t get in + to prevent condensation forming on lid and dripping onto agar

Question 28

the cell cycle

Answer 28

series of events involved in cell growth and division
it involves motor which allows for the growth, repair and asexual reproduction of cells

Question 29

cell cycle initial stage

Answer 29

extra ribosomes, mitochondria and other sub cellular structures are produced
the cells chromosomes are replicated so that there are two sets of the cells chromosomes

Question 30

cell cycle- mitosis

Answer 30

the two sets of chromosomes are pulled to opposite ends of the cell

the nucleus divides into two

mitosis ensures that both daughter cells have the same chromosomes as eachother and the parent cell

this is important for processes that require identical cells to be produced

Question 31

cell cycle- cell division

Answer 31

the cytoplasm and cell membranes are divided resulting in the production of two identical cells

Question 32

enzymes

Answer 32

a protein which increases the rate of a reaction
known as biological catalysts
active site:
to catalyse a reaction the reacting chemical must bind to the enzymes active site

the active site will only fit specific substrates

Question 33

factors affecting diffusion

Answer 33

-temperature
-membrane surface area
-concentration gradient:
1)the concentration gradient is linked to the difference in concentration between two areas
2)the bigger the difference in concentration between two areas, the greater the concentration gradient and the faster the rate of diffusion.

Question 34

exchange surfaces

Answer 34

ventilation
large surface area
thin membrane
blood supply

Question 35

active transport in humans and plants

Answer 35

important for:
sugar absorption in gut- allows sugar molecules to be absorbed from the gut and into the into the blood, even when when the sugar conc in blood is higher

mineral absorption in plants- means that plants are able to absorb mineral ions that at are necessary for healthy growth, even though the conc of minerals is usually lower in the soil than in the root hair