Cell Biology

Question 1

EUKARYOTIC

Answer 1

Plant and animal cells are both eukaryotic cells.

Question 2

How is the DNA of a eukaryotic cell stored?

Answer 2

Enclosed within a nucleus.

Question 3

PROKARYOTIC

Answer 3

Bacterial cells are prokaryotic cells.

Question 4

How is the DNA of a prokaryotic cell stored?

Answer 4

Single circular chromosome found in the cytoplasm - sometimes also plasmids

Question 5

Ribosomes

Answer 5

the site of protein synthesis in cells

Question 6

mitochondria

Answer 6

generate energy inside of the cell

Question 7

Why do we need mitosis?

Answer 7

• growth
• development
• repair

Question 8

Cell Cycle

Answer 8

1. Growth
2. DNA replication (mitosis)
3. Division (Cytokineses)

Question 9

fancy word for cell division

Answer 9

cytokineses

Question 10

fancy word for DNA replication

Answer 10

mitosis

Question 11

When a cell is not dividing the DNA:

Answer 11

Condensed into 46 chromosomes, organised in 23 pairs

Question 12

For mitosis, the cell duplicates each…

Answer 12

chromosome

Question 13

Step by step explanation of mitosis

Answer 13

1. Each chromosome is duplicated (the duplicate remains attached to the original at this point)
2. When the cell is ready to divide, the chromosomes line up along the centre of the cell.
3. Cell fibres from either side of the cell attach to their respective half of each chromosome pair.
4. The fibres pull the arms of the chromosomes to the opposite side of the cell.
5. The cell splits into two as the cytoplasm and cell membrane divides.

Question 14

What is binary fission?

Answer 14

The process by which prokaryotic organisms like bacteria divide and reproduce.

Question 15

Binary fission is NOT the same as

Answer 15

mitosis or meiosis

Question 16

How is DNA in bacteria cells organised?

Answer 16

Large circular strand of DNA (contains vital genes)

And PLASMIDS which are loops of DNA that contain non-essential genes

Question 17

Some bacteria cells have ______ which helps them to move easily. NOT ALL

Answer 17

flagellum plr (flagella)

Question 18

Why is binary fission also a method of asexual reproducion?

Answer 18

Bacteria are single-celled organisms and binary fission is a form of cell division to multiply.

Question 19

Before a bacterial cell can divide, it needs to do 2 main things:

Answer 19

1. Grow
2. Replicate genetic material

Question 20

Explain the process of binary fission step-by-step:

Answer 20

1. Replicates all DNA
2. The strands of DNA move to opposite sides of the cell to prepare for cell division.
3. Plasmids, although there are now twice the number, are arranged randomly so when division happens, each daughter cell might have a different number of plasmids.
4. New cell wall formed along the centre of the cell, seperating the two strands of DNA
5. Cell divides

Question 21

colony of bacteria =

Answer 21

population

Question 22

My explanation of how to calculate how many bacterial cells can be produced over a period of given time…

Answer 22

Divide the period of time given by the mean division time of the bacterial cell(s). This will give the power.

Then you multiply the number of cells you started with, can be 1 or 1000 or x, by 2 (because each time binary fission occurs, the number of cells doubles (x2), to the power we found before.

Question 23

Example: A bacterial cell has a mean division time of 30mins.
How many cells would it produce after 3 hours?

Answer 23

3h = 180m

180/30 = 6

1 x 2^6 = 64

the answer is 64

Question 24

Optimum conditions for bacterial growth:

Answer 24

warm

moist

plenty of nutrients

Question 25

there are two types of stem cells in humans

Answer 25

embryonic / adult

Question 26

Diffusion =

Answer 26

When substances (particles) move down their concentration gradient, from a high concentration to a low concentration.

Question 27

Osmosis =

Answer 27

diffusion but just with water

Question 28

Osmosis and Diffusion require no energy therefore they are _______ processes?

Answer 28

passive

Question 29

Example of how osmosis is used?

Answer 29

To keep cells in plants turgid

Question 30

Example of how diffusion is used?

Answer 30

In lungs - alveoli vs. blood stream

Question 31

Active transport Grade 9 definition =

Answer 31

The movement of molecules across a cell membrane, from a region of lower concentration, to a region of higher concentration, that requires energy from cellular respiration.

Question 32

Active transport requires energy so it is a _______ process

Answer 32

active

Question 33

Active transport always needs...

Answer 33

membrane

Question 34

Where does energy for active transport come from?

Answer 34

Cellular respiration

Question 35

Cellular respiration is responsible for all energy that the cell uses - it occurs in the _________

Answer 35

mitochondria - glucose is broken down to release energy

Question 36

Energy released by the breaking down of glucose in mitochondria can be stored by the cell in molecules known as...

Answer 36

ATP - takes energy to the parts of the cell/ organism that need it

Question 37

Example of active transport: root hair cells and minerals from soil - step-by-step answer

Answer 37

- Plants need minerals from soil e.g. Magnesium + Nitrates - Root hair cells have a high concentration of these minerals - Need active transport in order to retreave those from the soil too - Root hair cells are specialised to have many mitochondria (for cellular respiration - energy - active transport)

Question 38

SPECIALISED EXCHANGE SURFACES examples

Answer 38

Humans: alveoli/villi Plants: leaf/root hair cell

Question 39

3 common features of all specialised exchange surfaces

Answer 39

1) large surface area - rate of diffusion is higher since more area for diffusion to happen across at the same time. 2) very thin - short distance for substances to diffuse across - diffusion takes place more quickly. 3) exchange surfaces are permeable to the substances that they specifically need to exchange.

Question 40

features of specialised exchange surfaces in animals only

Answer 40

1. good blood supply 2. good supply of external medium (thing that comes from the outside) both maintain a steep concentration gradient, enabling efficient exchange of substances.

Question 41

STEM CELLS are able to:

Answer 41

1. divide by mitosis 2. able to differentiate into specialised cells

Question 42

stem cell that can differentiate into any type of cell

Answer 42

embryonic stem cell

Question 43

Adult stem cells in bone ______

Answer 43

bone marrow -> can differentiate into red blood cells, white blood cells, and platelets

Question 44

Adult stem cells can

Answer 44

replace damaged cells

Question 45

Adult stem cells cannot

Answer 45

form new tissues like embryonic stem cells

Question 46

Where are plant stem cells found?

Answer 46

meristem tissue - part of plant that don't stop growing, roots/shoots tips

Question 47

What kinds of specialised cells can a stem cell in a plant differentiate into?

Answer 47

phloem/xylem cells palisade cells root hair cells

Question 48

Unlike embryonic stem cells that stop existing when we are fully developed humans, plant stem cells...

Answer 48

persist for the plant's entire life

Question 49

How are the sperm and egg specialised for their function?

Answer 49

1. SPERM - They have a tail so they can swim to the egg - They have many mitochondria so that more energy is released and they can swim quickly - They are haploid cells, so that at fertilisation a diploid zygote is formed. 2. EGG - Large so that it can provide nutrients for the embryo - Haploid - The cell membrane only allows fertilisation by a single sperm