Topic 2: Nucleus Flashcards Preview

Dr Perera's Biology > Topic 2: Nucleus > Flashcards

Flashcards in Topic 2: Nucleus Deck (34):
1

Nucleus

Contains DNA in the form of chromatin or chromosomes and controls hereditary characters of an organism
Maintenance of cell structure and function
Controls cell division
Site of DNA synthesis
Pores allow exchange of mRNA
covered with double membrane, outer layer is connected to ER
Responsible for protein synthesis

2

Nucleolus

Site for synthesis and maturation of rRNA and assembly of ribosomal subunits
No membrane cover
Found in nucleus
Disappears at beginning of cell division

3

Nucleoplasm

Fluid interior portion
Contains chromosomes, nucleolus

4

Nuclear wall

Contains many pores which facilitate the movement of various substances in and out of the nucleus

5

Chromosomes

Fine thread like structures found in the nucleoplasm
Not visible in a non dividing cell
contains a complex of DNA coated in histone proteins

6

Vacuoles (Not function)

Membrane bags without inner structures
Smaller in animal cells than plant cells
Membrane containing vacuolar sap
Found in most cells

7

Contractile vacuoles

Water balance in fresh water protozoans

8

Vacuoles function

Food vacuoles, formed by phagocytosis, engulfing of food into a vacuole where it is being digested by the lysosome
Contractile vacuoles- remove extra water from fresh water single cell organisms
Plant vacuoles- store food, various ions and pigment
Vesicles- membrane bound organelles associated with transport within the cell

9

Tonoplast

Membrane lining the vacuole

10

Centriole

In animal cells, protists and fungi
Two identical cylindrical structures lying at right angles to each other
made up of microtubules
used during cell division to form spindle fibres which pull chromosomes to respective poles

11

Cilia and flagella

Projections that extend from a cell
Eleven hollow tubules which run longitudinally- two central and nine peripheral tubules arranged as 9+2 pattern
Generated by the centrioles

12

Functions- cilia and flagella

Collect food materials
Swim
Locomotion
CNS- help to move cerebro-spinal fluid within this cavity

13

Peroxisomes

Form hydrogen peroxide by removing hydrogen from certain reactions
Oxidise amino acids and uric acid and detoxify alcohol

14

Glyoxysomes

Germinating seeds
Conversion of fatty acids to sugars

15

Endosomes

Animal cells
Carry materials from cell surface to lysosomes for digestion

16

Cytoskeleton

gives support to the cell
important in animal cells which don't have a cell wall

17

Microtubules

Thickest network of fibres in cell
Straight hollow tubes formed from globular proteins

18

Microfilaments

Thinnest network of fibres in cell
AKA actin fibres
Maintenance of cell shape

19

Plastids

Plant cells
Proplastids are precursors of all types of plastids
Types include leucoplasts, chromoplasts, chloroplasts

20

Leucoplasts

AKA amyloplasts
Starch storage plastids found in yams and leaf epidermal cells

21

Chromoplasts

Contain pigments
Give colour to flowers
Generally covered with green chloroplasts hence during autumn leaves get ready to fall then the chlorophyll breaks down and leaves become yellow and orange

22

Chloroplasts

Sites of photosynthesis
Convert light energy to chemical energy

23

Chloroplast structure

Double membrane
Flattened disks - thylakoids- stacked up to form grana
Chlorophyll located in grana, DNA, ribosomes and enzymes are also contained here
Grana are connected to each other by tube like extensions called lamellae
Stroma has fluid where dark reaction of photosynthesis occurs

24

Elaioplasts

contain oils

25

Endosymbiosis evidence for mitochondria and chloroplasts

Appear morphologically similar to bacteria
Surrounded by an outer membrane similar to cell membrane while inner membrane invaginates to form lamellae or cristae
Semi-autonomous, remaining their own genome
Retain own machinery for synthesising proteins (ribosomes)
Metabolism is like existing prokaryotes (cyanobacteria-chloroplast, purple bacteria-mitochondria)
Some chloroplasts still have the bacterial peptidoglycan wall between the inner and outer membranes

26

Cell wall

Rigid structure made of microfibrils of cellulose chains arranged in layers.
Pectin, lignin, subarin and cutin can be embedded in these layers
Provides extra strength to the plant cell
Exerts pressure on cell membrane to stop further expansion and force water to leave cell when plant cell is immersed in low concentration solution

27

Plasmodesmata

Inter cellular connections between plant cells
Cytoplasmic strands that pass along channels through the cell wall

28

Inter cellular connections between animal cells

Tight junction
Anchoring junction
Communicating junction

29

Tight junction

AKA occluding junction
no movement of materials between cells

30

Anchoring junction

AKA desmosomes
Extending fine fibrils from a protein plaque
Provides site of attachment for mechanical support

31

Communicating junction

AKA gap junction
Pores are formed between adjacent cells through protein molecules aligned in a circle
allow small molecules and electrical signals to move

32

Protista

Unicellular, some are multicellular such as sea weeds
some able to do photosynthesis
euglina, algae, chlamydomonas

33

Fungi

non-photosynthetic, therefore heterotrophs
obtain organic molecules by digesting other organisms or their products
can be saprophytic or parasitic
Consists of network (mycelium) of filamentous hyphae
Cell wall made of chitin

34

Yeast

unicellular fungus
feeds saprophytically on sugars
anaerobic respiration