Cell Structure, Mitosis & Binary Fission Flashcards
1
Q
DNA in eukaryotes
A
- DNA enclosed in nucleus
- long + linear
- Attached to proteins (histones)
2
Q
DNA in prokaryotes
A
- DNA free-floating in cytoplasm (no nucleus)
- circular
- not attached to proteins (histones)
3
Q
What is chromatin?
A
DNA and histone proteins in nucleus during most of cell cycle (no chromosomes yet)
4
Q
What is a chromatid?
A
One of 2 identical copies of a chromosome held together by a centromere before cell division
5
Q
What is mitosis?
A
- Cell replication which produces two genetically identical daughter cells
- gives genetic stability
- used for tissue growth, repair, cell replacement, asexual reproduction
6
Q
What is prophase?
A
- chromosomes condense
- centrioles move to opposite sides
- nuclear membrane breaks down
- spindle fibres form
7
Q
What is metaphase?
A
- chromosomes line up at equator
- centromere of each chromosome attached to spindle
8
Q
What is anaphase?
A
- spindle fibres contract and pull on centromeres
- centromeres split
- sister chromatids pulled to opposite poles
9
Q
What is telophase?
A
- chromatids reach opposite poles (begin to uncoil - chromosomes)
- nuclear membranes form
10
Q
What is interphase?
A
- longest phase
- DNA content doubled via replication
- cell organelles replicated (mitochondria + ATP content increased)
- increase in protein synthesis
11
Q
What is cytokinesis?
A
- follows mitosis
- splitting of cytoplasm in two
- two new cells form (cell-surface membrane and, in plants, cellulose cell wall forms)
12
Q
How is algae different?
A
- similar to plant cells (carry out photosynthesis, contain same organelles)
- NOT plant cells (cells undifferentiated and unicellular)
13
Q
How are fungi different?
A
- NOT plant cells or animal cells
- contain cell walls (chitin not cellulose)
- do not photosynthesise so no chloroplasts
14
Q
What organelles do prokaryotes sometimes contain?
A
- slime capsule surrounding cell wall
- one or more plasmids
- one or more flagella
15
Q
Are viruses cells?
A
No they are acellular and non-living
16
Q
What do viruses not contain?
A
Nucleus, organelles, cell-surface membrane, cytoplasm
17
Q
What does a typical virus contain?
A
Genetic material, capsid, attachment proteins on outside
18
Q
Nucleus
A
- Bound by double membrane
- nuclear membrane has nuclear pores (communication with cytoplasm)
- nucleoplasm (granular, jelly-like material)
- nucleolus (smaller sphere inside, site of rRNA production + makes ribosomes)
- contains DNA
- site of DNA replication + transcription (making mRNA)
19
Q
Ribosomes
A
- made up of protein + rRNA
- either in cytoplasm singularly or attached to RER
- site of protein synthesis
20
Q
Smooth endoplasmic reticulum
A
- flattened membrane sacs which form internal transport system
- lacks ribosomes
- production + transport of lipids & carbohydrates
21
Q
Rough endoplasmic reticulum
A
- flattened membrane sacs which form internal transport system
- surface has ribosomes (that produce secretory proteins, sent to Golgi)
- synthesis + transport of proteins
22
Q
Golgi apparatus and vesicles
A
- flattened membrane sacs
- adds carbohydrates to proteins from RER to form glycoproteins
- packages proteins into Golgi vesicles for secretion
- produces lysosomes (type of Golgi vesicle that releases lysozymes)
- abundant in secretory cells e.g. pancreas
23
Q
Lysosomes
A
- sacs of hydrolytic enzymes (enzymes have to be kept apart from rest of cell or will destroy it)
- breaks down dead cells, material, digests worn-out organelles
- formed by Golgi apparatus
24
Q
Mitochondria
A
- double membrane
- folds of inner membrane = cristae
- fluid centre = mitochondrial matrix (contains enzymes for respiration, DNA, ribosomes)
- loop of mitochondrial dna
- site of aerobic respiration
25
Chloroplasts
- only found in plant cells + algae
- flattened biconvex discs surrounded by two membranes
- membrane system consisting of many flattened sacs = thylakoids
-> form stacks called grana (provide large surface area for chlorophyll molecules which absorb light for photosynthesis)
- membrane system surrounded by stroma (contains enzymes, sugars, starch granules)
26
What organelles are found in plant cells but NOT animal cells?
- cell wall
- chloroplasts
- vacuole
27
Cell wall
- found in plants and fungi
- provides structural strength to cell
28
What is a plant cell wall made up of?
Cellulose
29
What is a fungi cell wall made up of?
Chitin (nitrogen-containing polysaccharide)
30
Cell vacuole
- found in plant cells
-filled with fluid surrounded by single membrane (tonoplast)
- makes cells turgid (provides support)
- temporary store of cell sap (sugars, amino acids, pigment)
31
Cell membrane
- found in all cells
- phospholipid bilayer
- controls entrance and exit of molecules
32
How are specialised cells organised?
Tissues —> organs —> systems
33
What kinds of cells undergo mitosis?
Eukaryotic
34
Do eukaryotes have membrane-bound organelles?
Yes
35
Ribosomes in eukaryotes
Larger than prokaryotes
80s
36
Cell wall in eukaryotes
Does NOT contain murein
37
Do prokaryotes have membrane-bound organelles?
No
38
Ribosomes in prokaryotes
Smaller than eukaryotes
70s
39
Cell wall in prokaryotes
Murein cell wall
40
How do prokaryotes divide?
Binary fission
41
What is binary fission?
Asexual division in prokaryotes
42
What is stage 1 of binary fission?
Cell growth - prepare for division
43
What is stage 2 of binary fission?
DNA replication - circular chromosome replicated once, plasmids may be replicated multiple times
44
What is stage 3 of binary fission?
Movement of DNA - each replicated circular chromosome moves to opposite poles of cell, plasmids distributed randomly between two poles
45
What is stage 4 of binary fission?
Cell wall growth - membrane starts to divide and new cell walls form between 2 DNA molecules
46
What is stage 5 of binary fission?
Cytoplasm division - cytoplasm of original cell divided into 2 identical daughter cells
47
How to calculate mitotic index?
(Number of cells undergoing mitosis)/(total number of cells) x100
48
How to calculate the number of cells/bacteria in a population
Number of cells at beginning x 2^number of divisions
49
Do viruses undergo cell division?
- No
- they attach to specific host cells using attachment proteins (which are complementary to receptors on host cells£
- inject nucleic acid
- host cell produces more viruses (using copies of nucleic acids + proteins)
- viruses released by lysis of cell
50
What is cancer?
uncontrolled cell division leading to a tumour that invades surrounding tissue
51
What is a tumour?
An abnormal growth of cells
52
What causes cancer?
Mutations in genes that control the speed of cell division
53
What kinds of cancer treatments are there?
- drugs and radiotherapy disrupt cell cycle (can affect normal healthy cells)
54
How are epithelial cells adapted for the absorption of digested food products?
- cell surface membrane folded into microvilli - provides large surface area for absorption
- numerous mitochondria - provide energy (ATP) for active uptake of digested food molecules
