Cell Structure and Division

Question 1

What are eukaryotes?

Answer 1

• plant cells
• animal cells
• has cell membrane, cytoplam, nucleus
• genetic material made of DNA

Question 2

What subcellular structures does an animal cell have?

Answer 2

• cell membrane = controls what goes in and out of cell, partially permeable
• ribosome = protein synthesis
• cytoplasm = suspends cell structures, site of cell structures
• mitochondria = aerobic respiration
• nucleus = controlls cell processes, DNA stored here

Question 3

What subcellular structures does a plant cell have?

Answer 3

• cytoplam
• cell membrane
• cell wall = strengthens cell, made of cellulose
• nucleus
• ribosome
• mitrochondria
• cell vacuole = filled with cell sap, stores nutrients and supports cell
• chrloroplasts = chlorophyll, traps light energy for photosynthesis

Question 4

What is the difference between eukaryotes and prokaryotes?

Answer 4

• pro. = smaller than euk.
• no nucleus
• DNA loop floating in cytoplasm
• may have small rings of DNA = plasmids

Question 5

What are the levels of organisation in an organism?

Answer 5

• cells
• tissues
• organs
• organ systems

Question 6

What adaptations does phloem cells have to perform its function?

what is its function!!!!

Answer 6

• elongated cells to trasnport sugars over long distances
• companion cells have many mitochondria for active transport

transport sugars made in leaves to rest of plant

Question 7

What adaptions do xylem cells have to perform their function?

function?

Answer 7

• hollow tubes (lumen) - no end walls to allow water and minerals flow
• lignin in walls to provide strength and support

transports water and mineral ions throughout plant

Question 8

What adaptations do sperm cells have to perform their function?

function!

Answer 8

• enzymes in head to digest coating of egg
• many mitochondria to provide energy for swimming
• tail for swimming

carry genetic material to egg cell

Question 9

What adaptations does a muscle cell have to perform their function?

function!!!!!

Answer 9

• lots of mitochondria to provide energy for contraction
• protein fibres shorten to make cells contract, shortens structure

provide movement

Question 10

What adaptations does a nerve cell have to perform its function?

Answer 10

• dendrites make connections with other cells
• fatty myelin sheath speeds up impulse
• axon = long, carries impulses across body

cary electrical impulses around body

Question 11

Describe differentiation in animal cells throughout its life

Answer 11

• most types of cells differentiate at early stage
• early embryo cells = unspecialised
• mature animals = repair of damaged tissues/ replacement of worn out cells

Question 12

Describe differentiation in plant cells throughout its life

Answer 12

• cells continue to divide and differentiate throughout life of plant
• **meristems **responsible for division

Question 13

What is magnification?

Answer 13

• how many times bigger an image is than the object that is viewed

Question 14

What is resolution?

Answer 14

• measure of smallest distance between two points that still can be distinguished

poor resolution = blurred with magnified

Question 15

How do you calculate magnification?

Answer 15

size of image/ size of real object

Question 16

How are unwanted microoganisms kept from contaminating a culture?

Answer 16

• sterilise petri dishes + culture media before use
• inoculating loops passed through flame
• lid stops microorganisms falling into agar from air (fixed in place with tape)
• work near a flame

Question 17

How do bacteria multiply?

Answer 17

• binary fission

Question 18

When were the first light microscopes developed?

Answer 18

400 years ago

Question 19

When was the electron microscope invented?

and what were they like?

Answer 19

• 1930s
• higher magnification
• higher resolution
• can see sub-cellular structures

Question 20

What kind of bacteria is used for the investigation of comparing different antibiotics or antiseptics?

Answer 20

• bacterial lawn on agar distributed by spreader
• agar becomes cloudy
• no bacteria = clear agar

Question 21

How are the antiseptic or antibiotics placed in the agar?

Answer 21

• small paper discs soaked with solutions of antibiotics/ antiseptics

Question 22

What is the clear area around the paper disc called?

Answer 22

• zone of inhibition

Question 23

How do you compare different antibiotics or antiseptics?

Answer 23

• measure 2 diameters of clear area
• calculate mean (more accurate)

Question 24

Describe the cell cycle

Answer 24

1) cell growth = number of subcellular structures increase
2) DNA replicates = forms 2 identical copies of each chromosome
3) Mitosis = chromosomes separate, nucleus divides in 2
4) Cell division = cytoplasm + cell membrane divides = 2 new identical cells made

Question 25

Describe the stages of mitosis

Answer 25

- newly replicated chromosomes **joined together** - move to **centre of cell** - chromosomes pulled apart, moved to opposite ends (**poles**) of the cell - nucleus divides

Question 26

What is mitosis used for?

Answer 26

- growth - repair of worn out or damaged cells

Question 27

What are stem cells?

Answer 27

- undifferentiated cells that divide to make new cells

Question 28

What do cells in an early embryo do and how do scientists use them?

Answer 28

- **unspecialised** - **differentiates** to produce all types of cell needed to make adult organism - **clone cells** from early human embryos in lab - made to differentiate into different types of cells

Question 29

What are stem cells in adult animals used for?

Answer 29

- can only produce **limited range** of cell types - **replace** worn out or damaged cells | bone marrow = exception, can product many types of cells

Question 30

Describe the process of therapeutic cloning

Answer 30

- egg cell nucleus **replaced with patient's nucleus** from cell - **embryo** made that has **same genes** as patient - **stem cells** removed to treat patient - not rejected, since it has same genes as patient

Question 31

What are the advantages of therapeutic cloning?

Answer 31

- may treat **diseases** and **replace faulty organs** - **wider range of cells** produced than adult stem cells - stem cells **not rejected** by patient - **many cells produced**, some used in research

Question 32

What are the disadvantages of therapeutic cloning?

Answer 32

- stem cells may **transfer viral infection** - **ethical or religious objections** (kills embryo?) - human eggs in **short supply**, collecting = risks - **side effects** of stem cells not known

Question 33

What are the benefits of growing plants from stem cells?

Answer 33

- large numbers of new plants produced **quickly + cheaply** - rare species cloned **prevent extinction** - crop plants with **useful features** (eg disease resistance) -> **cloned** = large number of useful plants for farmer

Question 34

What is diffusion?

Answer 34

- net movement from an area of higher concentration to lower concentration

Question 35

What affects the rate of diffusion?

Answer 35

- **concentration gradient** = increases chance of particles moving from high concentration to low concentration - **temperature** = increases kinetic energy of particles, moves faster - **surface area** = more membrane for particles to move across

Question 36

How is the small intestine adapted for efficient diffusion?

Answer 36

- **vili** and **microvili** increase SA - wall of vili = **thin** - good **blood supply**

Question 37

What are the lungs adapted to increase the rate of diffusion?

Answer 37

- **alveoli** increase SA - **thin walls** - surrounded by **capillaries** - good **ventilation** (conc. grad.)

Question 38

What is osmosis?

Answer 38

- diffusion of water from dilute solution to more concentrated solution through a partially permeable membrane

Question 39

How are fish gills adapted to increase diffusion?

Answer 39

- **gill filaments** increase SA - filaments **well supplied with blood** - **thin walls** reduce diffusion pathway - good ventilation

Question 40

How are roots and leaves of plants adapted for efficient diffusion?

Answer 40

- **extension** of root hair cells = high SA - **large internal surface area** for diffusion - **thin** = reduces diffusion distance

Question 41

What is active transport?

Answer 41

- moving substances from dilute solution to more concentrated solution | requires energy from respiration

Question 42

What is active transport used for in plants?

Answer 42

- mineral ions from soil to root hair cells

Question 43

What is active transport used for in animals?

Answer 43

- absorbing sugar in small intestine