2 Cells (34/34)

Question 1

2.1.1 Outline the cell theory.

Answer 1

Cell Theory:

• All living organisms are composed of cells, and the products o cells 9e.g. hair and scales).
• Cells are the smallest units of life.
• Cells only come from pre-existing cells.

Question 2

2.1.2 Discuss the evidence of the cell theory.

Answer 2

1590- Jansen: Microscope
1665- Hooke: studies cork –> ‘cell’
1675- van Leeuwenhoek: unicellular organisms
1838- Schleiden: plants are made of cells
1839 Schwann: all animals are made of cells
1840- Purkinje: cell content ‘protoplasm’
1855- Virchow: ‘all cells come from cells’

Cell theory is widely accepted and is supported by modern technology (electron microscope allowed us to study the ultra structure of cells)

Question 3

2.1.3 State that unicellular organisms carry out ___ ___ _______ __ ____.

Answer 3

unicellular organisms carry out_ all the functions of life.

Question 4

2.1.4 Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropriate SI unit.

Answer 4

molecules:
-Hydrogen atom 0.1 nm
-DNA double helix 2 nm diameter
cell membrane thickness:
-Cell membrane 7.5 nm thick
viruses:
-Large virus (HIV) 100 nm
bacteria:
-Bacteria 1-4 µm
organelles:
-Ribosomes 25 nm
-Mitochondria 0.5-5 µm
-Chloroplast 2-10 µm
-Nucleus 10-20 µm
cells:
-Eukaryotic 10-100 µm
-Prokaryotic 1-5 µm

Question 5

2.1.5 Calculate the linear magnification of drawing and the actual size of specimens in the images of known magnification.

Answer 5

Real size = magnification size (with your ruler)/magnification

Magnification = magnified size (ruler)/ real size (scale bar)

Magnified size = real size * magnification

Question 6

2.1.6 Explain the importance of the surface area to volume ratio as a factor limiting cell size.

Answer 6

The smaller the volume the greater the surface area to volume ratio.
The size of a cell is limited, because it needs to exchange materials with the environment. If the cell is too large, there is not enough surface area to exchange materials for all the function w/in the cell.
Ways of increasing surface area w/o increasing volume as much:
-protruding extensions (ex: mitochondria’s christa)
-flattening the cell

Question 7

2.1.7 State that multicellular organisms show ______ _______.

Answer 7

multicellular organisms show_ emergent properties.

Emergent properties: ‘the whole is greater than the sum of its parts’ –> cells interact and work together to form an efficient organism together

Question 8

2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.

Answer 8

every cell contains all the genetic information to carry out every task, however only a small section of DNA is activated in order to perform a specific task.
Euchromatin - active genes
Heterochromatin - inactive genes
cells affect each other –> the differentiation of one cell is determined by the cells position relative to others and chemical gradients

Question 9

2.1.9 Sate that stem cells retain the capacity to ______ and have the ability to ____________ along different pathways.

Answer 9

Sate that stem cells retain the capacity to divide and have the ability to _ differentiate _ along different pathways.

Question 10

2.1.10 Outline one therapeutic use of stem cells.

Answer 10

Cell therapy - cells that do not work well are replaced with healthy functioning cells.

Use: bone marrow transplant

• bone marrow contains stem cells
• cells in bone marrow produce blood cells
• leukemia patients receive transplant

Use: skin for burn victims

Use: corneas for those w/ failing eyesight

Question 11

2.2.1 Draw and label a diagram of the ultrastructure of Escherichia coli (E. coli) as an example of a prokaryote.

Answer 11

include:

• pili
• ribosomes
• capsule
• plasma membrane
• cell wall
• cytoplasm
• cytosol
• nucleoid region (DNA)
• flagellum

http://www.tokresource.org/tok_classes/biobiobio/biomenu/metathink/required_drawings/prokaryote_500.jpg

Question 12

2.2.2 Annotate the diagram with the functions of each named structure.

Answer 12

Function:

• pili: protein tubes that are used for attachment (attachment pili) and conjunction (conjunction or sex pili)
• ribosomes: consists of RNA ad proteins, play a key role in protein synthesis (translation)
• capsule:
• plasma membrane: controls which materials enter and leave the cell, either b active or passive transport. it is selectively permeable.
• cell wall: made of protein-sugars, gives the cell shape, protects the bacterium from external damage and prevents bursting if the cell has take up a lot of water. anchors pili and flagella
• cytoplasm: watery fluid that contains enzymes that control metabolic rxns. contains organelles.
• cytosol
• nucleoid region (DNA): contains the DNA which contains the genetic information. area from which all processes in the cell are controlled
• flagellum: long thread-like structures, made of protein. allow the bacterium to more in a fluid environment

Question 13

2.2.3 Identify structures from 2.2.1 in electron micrographs of E.coli.

Answer 13

look at those :P

Question 14

2.2.4 Sate that prokaryotic cells divide by ______ _______.

Answer 14

prokaryotic cells divide by_ binary fission.

Question 15

2.3.1 Draw and label a diagram of the ultrastructure of a liver cell as an example of an animal cell.

Answer 15

include:
- microvillus
- granule
- vesicle
- Golgi apparatus
- free ribosomes
- chromatin
- rough endoplasmic reticulum
- plasma membrane
- pinocytotic vescicle
- smooth endoplasmic reticulum
- lysosome
- nuclear envelope
- nuclear pore
- nucleus
- mitochondria
- ribosomes

Question 16

2.3.2 Annotate the diagram with the functions of each named structure.

Answer 16

functions: XXX
- granule
- vesicle
- Golgi apparatus
- free ribosomes
- chromatin
- rough endoplasmic reticulum
- plasma membrane
- pinocytotic vescicle
- smooth endoplasmic reticulum
- lysosome
- nuclear envelope
- nuclear pore
- nucleus
- mitochondria
- ribosomes

Question 17

2.3.3 Identify structures from 2.3.1 in electron micrographs of liver cells.

Answer 17

see EMs :P

Question 18

2.3.4 Compare prokaryotic and eukaryotic cells.

Answer 18

Similar: contain DNA, ribosomes and plasma membrane
Different
-P: naked DNA E: DNA associated w/ proteins(histones)
-P: circular DNA E: linear DNA
-P: DNA found in cytoplasm (nucleoid area) E: DNA enclosed in nuclear envelope
-P: 70s (mass and size) ribosomes E: 80s ribosomes
-P: no mitochondria but uses plasma membrane and mesosomes for respiration E: mitochondria
-P: no internal membranes E: compartmentalized cells, areas with different functions

Question 19

2.3.5 Sate three differences between plant and animal cells.

Answer 19

1. cell wall –> P: cellulose cell wall and plasma membrane A: only plasma membrane
2. chloroplast –> P: present in photosynthetic cells A: absent
3. vacuole –> P: large, permanent vacuole, filled w/ cell sap A: small, temporary vacuoles may be present
4. reserve food –> P: carbohydrates stored as starch and also plant oils A: carbohydrate storage as glycogen and some stored as animal fat

Question 20

2.3.6 Outline two roles of extracellular components.

Answer 20

1. PLANT: cellulose: Cell wall: provides support and strength, determines shape, prevents the cell from bursting when filled with water by preventing expansion (turgid), cellulose is a carbohydrate: plants can use the cell wall to store carbs, barrier against pathogens
2. ANIMAL: bone cartilage and connective tissue: extra cellular matrix (ECM): cartilage gel contains glycoproteins, associated with water and collagen–> firmness and resilience

Question 21

2.4.1 Draw and label a diagram to show the structure of a membrane.

Answer 21

do so and check in the book

Question 22

2.4.2 Explain how the hydrophobic and hydrophilic properties of phosphilipids help to maintain the structure of cell membranes.

Answer 22

Hydrophobic: polar
-Phosphate heads: face outward toward the fluid inside and outside of the cell
Hydrophilic: non polar
-2 fatty acid tails: face inward away from water inside and outside the cell, pull together to stay away from the water–>keep the cell wall together

Controlling the in/out of molecules is aided by this since neither polar nor nonpolar molecules can easily pass through both layers

proteins which have different polarities can allow select molecules to enter the cell

Integral proteins: go through the cell like a channel–> hydrophilic inside and ends, hydrophobic facing the fatty acid tails on the outside middle.
peripheral proteins: found on either side of membrane–> interact with phosphate heads (polar), not necessarily permanent, some have a carb group attached (glycoprotein).
cholesteral: positioned between 2 fatty acid tails(np)–> reduces fluidity and permeability.

Question 23

2.4.3 List the functions of membrane proteins.

Answer 23

• Hormone Binding Sites
• Immobilized Enzymes
• Cell Adhesion
• Cell to Cell Communication
• Channels for Passive Transport
• Pumps for Active Transport

(HICCCP –> Hiccup)

Question 24

2.4.4 Define diffusion and osmosis.

Answer 24

diffusion: the movement of gas or liquid particles from a region of high concentration to a region of low concentration
osmosis: the passive movement, or diffusion of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration

Question 25

2.4.5 Explain passive transport across membranes by simple diffusion and facilitated diffusion.

Answer 25

simple diffusion and facilitated diffusion are both passive transport–> they do NOT require energy, but the direction of diffusion is controlled by the CONCENTRATION GRADIENT
simple diffusion: small, n-p molecules, diffuse w/o additional assistance
facilitated diffusion: p molecules (ions) need channel proteins or transport proteins
Channel proteins form a hydrophilic core through which p molecules can pass
transport proteins: specific binding site, change in structure carries molecule in/out of cell, return to original shape
ex: glucose

Question 26

2.4.6 Explain the role of protein pumps and ATP in active transport across membranes.

Answer 26

active transport REQUIRES energy ATP.
can move particles against the concentration gradient
active transport proteins/ carrier proteins work like passive transport proteins, but with require ATP and work against the concentration gradient
EX: sodium-potassium pump

Question 27

2.4.7 Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus and plasma membrane.

Answer 27

1. vesicles are used for intercellular transport
2. fluid mosaic model of membranes –> membranes are made up of many phospholipids which can rotate, change shape, position
3. RER produced protein (ribosomes) in membrane
4. protein travels to the golgi body to be packaged in a membrane made from the golgi’s membrane = vesicle
5. Vesicle travels to the outer cell membrane, since the membranes are made of the same material (phosphilipids) they fuse
6. Protein can be expelled by exocytosis

RER, golgi, nucleur membrane and plasma membrane can all exchange membrane sections

Question 28

2.4.8 Describe how the fluidity of the membrane allows it to change shape, break and re-form during endocytosis and exocytosis.

Answer 28

Endocytosis: IN
-process by which the cell takes up a substance by surrounding it w/ membrane 
-requires ATP
-used for highly polar/large molecules
-phagocytosis: solids 
-pinocytosis: liquids 
Exocytosis: OUT
-v.v. ~ materials are removed from cells 
-requires ATP

Question 29

2.5.1 Outline the stages in the cell cycle, including interphase (G1, S, G2), mitosis and cytokinesis.

Answer 29

interphase: cell growth
~G1: period of cell growth & increase in # of cell organelles
~S: (S)ynthesis: DNA replicates
~G2: mitosis prep.
mitosis: process of nuclear division
cytokinesis: occurs after mitosis & is the actual physical division of the cell and is therefore not included in mitosis

Question 30

2.5.2 Sate that tumours (cancer) are the result of ___________ ____ ________ and that these can occur in any _____ or ______.

Answer 30

tumours (cancer) are the result of_ uncontrolled cell division_ and that these can occur in any organ or tissue.

Question 31

2.5.3 Sate that interphase is an active period in the life of a cell when many _______ _____ occur, including _______ _______, ___ _______, and __ _____ __ __ ____ _____ ____ _________.

Answer 31

Sate that interphase is an active period in the life of a cell when many metabolic reactions occur, including _protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts.

Question 32

2.5.4 Describe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase, and telophase).

Answer 32

prophase:
-DNA super coils and condenses
- Chromosomes are made of two genetically identical sister chromatids
-Centrosomes move to opposite poles and spindle fibres form between them
-Nuclear membrane breaks down
metaphase:
-Spindle fibres attach to centromere of chromosomes
-Fibres contract and chromosomes line up at equator of cell
anaphase:
-Sister chromatids separate and move to opposite poles
-chromatids are now regarded as individual chromosomes
telophase:
-Chromosomes condense and nuclear membranes reform
Cytokinesis occurs (cell splits in two)

Question 33

2.5.5 Explain how mitosis produces two genetically identical nuclei.

Answer 33

• during interphase (S), DNA was replicated to produce two copies of the genetic material
• 2 identical DNA molecules are identified as sister chromatids and are held together by a single centromere
• during mitosis (anaphase), the sister chromatids separate and move to opposite poles of the cell
• when the cell divides (cytokinesis), the two resulting nuclei will each contain one of the chromatid pair and thus be genetically identical

Question 34

2.5.6 State that _____, _______ ________, ____ _____ and ______ _________ involve mitosis.

Answer 34

growth, embryonic development, tissue repair and asexual reproduction involve mitosis.