2.1.1 cell structure

Question 1

prokaryotic cells

Answer 1

• no true nucleus (free loop of DNA)
• very few organelles
• exist as single cells.
• bacteria

Question 2

eukaryotic cells

Answer 2

• true nucleus
• lots of organelles
• exist as single cells but usually form multi-cellular organisms

Question 3

examples of eukaryotes

Answer 3

animal, plant, fungi

Question 4

describe organelles

Answer 4

• membrane bound compartments
• provide the conditions for different cellular reactions to
  take place

Question 5

what do all the organelles together make up?

Answer 5

the ultrastructure (part which can only be seen by an electron microscope)

Question 5

cilia on surface of cell

Answer 5

• “beat” in a co-ordinated way to move substances over the surface of the cell

Question 6

example of a cell with cilia on its surface

Answer 6

ciliated epithelium -
found on the cells lining the airways - sweep mucus up and away from the
lungs to the back of the throat

Question 7

microvilli on surface of cell

Answer 7

• folds in the cell surface membranes of cells which carry out a lot of secretion or absorption
• increase the surface area of the cell

Question 8

examples of microvilli

Answer 8

the cells lining the intestines increase the SA for the absorption of digested food into the bloodstream

Question 9

flagellum on surface of cell

Answer 9

• these stick out as long projections from the cell, and have membrane around them
• allow the whole cell to move

Question 10

all organelles in a eukaryotic cells

Answer 10

• nucleus
• nuclelous
• chromatin
• Golgi apparatus
• Golgi vesicle
• RER
• SER
• ribosomes
• centrosome
• vacuole
• secretory vesicle
• mitochondria
• cytoskeleton
• intermediate filament

Question 11

all structures in a plant cell

Answer 11

• cell wall
• nucleus
• nucleolus
• RER
• SER
• mitochondria
• ribosomes
• chloroplasts
• Golgi apparatus
• LARGE & PERMANENT vacuole
  -plasmodesmata
  -nuclear envelope
  -nuclear pores

Question 12

similarities and differences in eukaryotic and prokaryotic cells

Answer 12

prokaryotes
- no nucleus
- circular DNA
- proteins fold and condense DNA
- extra plasmids
- no membrane bounds organelles
- peptidoglycan cell walls
- smaller 70s ribosomes
- cytoskeleton
- binary fission
- unicellular
- cell surface membrane

eukaryotes
- nucleus
- linear DNA
- DNA wrapped around histones
- extra DNA present in chloroplasts and mitochondria
- membrane bound organelles
- chitin in fungi, cellulose in plants
- larger 80s ribosomes
- more complex cytoskeleton
- asexual or sexual reproduction
- uni or multi cellular
- cell surface membrane

Question 13

what is the membrane around the LARGE and PERMANENT vacuole called?

Answer 13

tonoplast

Question 14

structures in plant cell that aren’t in animal

Answer 14

1. chloroplasts- site of photosynthesis
2. large permanent vacuole
3. plasmodesmata
4. cellulose cell wall

Question 15

describe large and permanent vacuole

Answer 15

• contains sap (various storage molecules + water).
• a membrane around it called the tonoplast
  -involved in maintaining turgor in plant cells

Question 16

describe the plasmodesmata

Answer 16

cytoplasmic connections between neighbouring plant cells,
allowing substances to move from cell to cell

Question 17

describe cellulose cell wall

Answer 17

gives “tensile strength”
- supports the plant cell & prevents bursting when water enters the cell.

Question 18

describe plasma membrane

Answer 18

• found around animal cell surface
• found inside plant cell
• made of lipids + proteins

Question 19

function of plasma membrane

Answer 19

• regulates movement of substances into and out of cell
• receptor molecules on it, which allow it to respond to chemicals

Question 20

describe the nucleus

Answer 20

• surrounded by nuclear envelope (double membrane)
• contains nuclear pores
• contains chromatin
• contains nucleolus

Question 21

function of the nucleus

Answer 21

• contains the genetic material
• contains instructions on how to make proteins
• pores allow RNA to leave nucleus
• nucleolus makes ribosomes

Question 22

describe ribosomes

Answer 22

• free floating in cytoplasm or attached to rough endoplasmic reticulum
• made of proteins and RNA
• no membrane

Question 23

function of ribosomes

Answer 23

site of protein synthesis

Question 24

describe RER

Answer 24

• system of membranes enclosing a fluid filled space
• surfaced covered with ribosomes

Question 25

function of RER

Answer 25

• folds and processes proteins that have been made at the ribosomes
• involved in transport of proteins

Question 26

describe SER

Answer 26

• system of membranes enclosing a fluid filled space
• no ribosomes

Question 27

function of SER

Answer 27

synthesises and processes lipids and carbohydrates

Question 28

describe vesicle

Answer 28

small fluid filled sac in cytoplasm, membrane bound

Question 29

function of vesicle

Answer 29

• transports substances in and out of cell via plasma membrane and between cells
• some formed by Golgi apparatus
• some formed by endoplasmic reticulum
• some formed at cell surface

Question 30

describe lysosome

Answer 30

• membrane bound
• no clear internal structure
• contains digestive enzymes

Question 31

function of lysosome

Answer 31

• contains digestive enzymes
• can be used to digest invading cells
• breaks down worn down components

Question 32

describe Golgi apparatus

Answer 32

• fluid filled flattened sacs
• formed of cisternae

Question 33

function of Golgi apparatus

Answer 33

it produces and packages lipids and proteins into vesicles and modifies them. can be secretory vesicles or lysosomes.

Question 34

describe mitochondria

Answer 34

• double membrane
• inner membrane is folded to form cristae
• inside is the fluid matrix
• contain (mt)DNA
• produce their own enzymes
• reproduce themselves

Question 35

function of mitochondria

Answer 35

• site of aerobic respiration , where ATP is produced
• found in large number in active cells that need the energy

Question 36

describe chloroplast

Answer 36

• small flattened structure
• double membrane
• contains grana which are attached by membranes called thylakoids
• grana are linked together by llamelae
• fluid is called stroma

Question 37

function of chloroplasts

Answer 37

• site of photosynthesis
• some parts take place in grana
• other parts in stroma

Question 38

describe centriole

Answer 38

small, hollow cylinders made of microtubules

Question 39

function of centrioles

Answer 39

separates chromosomes in cell divison by producing spindle fibres

Question 40

describe cilia

Answer 40

• small hair like structures
• outer membrane and ring of 9 pairs of microtubules inside
• with a single pair of microtubules in the middle

Question 41

describe flagellum

Answer 41

• longer than cilia
• 2 microtubules in the centre, with 9 pairs of microtubules surrounding them inside.

Question 42

describe cytoskeleton

Answer 42

network of protein fibres/ threads

Question 43

describe microfilaments

Answer 43

-made from protein ACTIN
- each filament is about 7nm diameter
- gives support & mechanical strength to cell to help it keep its shape
- allows whole cells to move
- allows a cell to split into 2 daughter cells at the end of mitosis

Question 44

describe microtubules

Answer 44

• made of protein sub-units called TUBULIN
• each microtubule is about 18-30nm
  diameter
• provide shape and support
• move organelles through cytoplasm from one part of the cell to another-
  form a “track” for organelles and vesicles to move along
• make up the spindle needed for chromosome movement during
  mitosis/meiosis
• make up cilia, flagella & centrioles

Question 45

describe intermediate fibres

Answer 45

• made up of lots of proteins
• 10nm in diameter
• anchor the nucleus within the cytoplasm
• extend in between cells, helping to anchor cells in place together on a
  “basement membrane” – stabilising the structure of tissues