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Biology HL > 1.1 Introduction to Cells > Flashcards

1.1 Introduction to Cells Flashcards

1
Q

Basic Cell Theory

A
  • All living organisms are composed of one or more cells
  • The cell is the most basic unit of life
  • All cells arise only from pre-existing cells
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2
Q

Spontaneous Generation

A

Idea proposed by Aristotle that certain animals such as fleas could arise from dust, or dead flesh.
Held true for 2000 years until microscopes and Louis Pasteur

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3
Q

Louis Pasteur Experiments

A
  • Two swan neck flasks set up and boiled to sterilise them
  • Exposed one flask to air and other left as swan necked
  • The one exposed to air turned cloudy and microbial growth formed, whereas other did not
  • Hence proving that dust (on which microbes travel) was needed to introduce life
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4
Q

Modern Cell Theory

A
  • The activity of an organism depends on the total activity of independent cells
  • Energy flow (metabolism and biochemistry) occurs within cells
  • Cells contain DNA which is found specifically in the chromosome and RNA found in cell nucleus and cytoplasm
  • All cells are basically the same in chemical composition in organisms of similar species
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5
Q

Exceptions to cell theory

A
  1. Striated muscle - more than one nucleus, very long
  2. Aseptate fungal hyphae - many nuclei, continuous cytoplasm, no end cell wall or membrane
  3. Giant algae - very large, complex structure, only one nucleus
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6
Q

Functions of Living Organisms

A

Metabolism - enzyme catalysed reactions in cell or organism
Response - living things can react or respond to environment

Homeostasis - maintenance and regulation of internal cell conditions

Growth - living things can grow/change size or shape
Reproduction - produce offspring
Excretion - removal of metabolic waste
Nutrition - feeding either by synthesis of organic molecules or absorption

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7
Q

Why are viruses not living?

A
  • Lack complex structures found in cells
  • Very small
  • No cytoplasm or organelles
  • No chromosome, RNA or DNA strand
  • Depend on host cell for metabolism and reproduction
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8
Q

What do Protist cells contain?

A

Contain main strictures found in animal cells but also:

  • Cilia or flagella: for movement
  • Eye spot: for light/dark detection
  • Contractile vacuoles: regulate water levels inside cells
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9
Q

What are Protoctista cells?

A

They are free-living unicellular organisms

They can be autotrophic, heterotrophic or both

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10
Q

Functions of life in Paramecium

A

Metabolism - most metabolic pathways happen in the cytoplasm
Reproduction - nucleus can divide, asexual
Homeostasis - contractile vacuoles fill up with water and expel through plasma membrane to manage water content
Growth - after consuming and assimilating biomass from food it will grow until it divides
Response - wave action from cilia moves cell in response to changes
Excretion - plasma membrane controls this
Nutrition - food vacuoles contain organisms paramecium have consumed

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11
Q

Functions of life in Chlorella

A

Metabolism - most metabolic pathways happen in the cytoplasm
Reproduction - nucleus can divide, by mitosis
Homeostasis - contractile vacuoles fill up with water and expel it through the plasma membrane to manage water content
Growth - after consuming and assimilating biomass from food it will grow until it divides
Response - wave action from cilia moves cell in response to changes
Excretion - plasma membrane, diffusion out of waste oxygen
Nutrition - photosynthesis happens inside chloroplasts to provide algae with food

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12
Q

Surface Area and Volume Ratio

A
  • Rate of metabolism of a cell is a function of its mass/volume, rate of material exchange in and out of the cell is a function of its surface area
  • As the cell grows, volume increases faster than SA (decreased SA:V ratio)
  • If the metabolic rate is greater than the rate of exchange of vital materials, the cell will die
  • Hence division must occur
  • Cells specialised in the transfer of materials will increase SA to optimise this transfer
  • Want a small V but a big SA
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13
Q

Emergent Properties

A

arise from the interaction of component parts, the whole is greater than the sum of its parts.
e.g the heart lungs and vessels show the emergent properties of circulation and gas exchange
Multicellular organisms are capable of completing functions that individual cells could not undertake

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14
Q

What is reductionism?

A

The ability to reduce complex systems into something smaller and more manageable. i.e. looking at the smallest parts of the cell, the billions of chemical reactions that occur within a cell.

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15
Q

Cell Differentiation

A

At certain stages in the sequences of cell divisions, some of the cells are switched on, while others are switched off, depending on the destined role of the cell. (expression of some genes and not others)

The structure of a cell is related to its function, and specialised tissues can develop by cell differentiation.

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16
Q

What are Stem Cells?

A

are undifferentiated cells that can differentiate into specialised cells and can divide to produce more stem cells. They are found in multicellular organisms.

  1. embryonic stem cells - isolated from the inner cell mass of blastocysts (ectoderm, endoderm and mesoderm)
  2. adult stem cells - found in various tissue, regenerative organs
17
Q

Toitipotency

A

totally able to make any cell type
found in zygotes (egg) and morula (16 cell stage)
entire genome activated

18
Q

Pluripotency

A

can differentiate into many different cell types
found in blastocyst (200-300 cells)
inner mass called embryonic stem cells
some parts of genome are inactivated

19
Q

Multipotentcy

A

can differentiate into a few closely related types of cells
found in the gastrula (ectoderm, mesoderm, endoderm)
newly formed cells receive signals which deactivate (or sometimes activate) genes

20
Q

Unipotency

A

can regenerate but can only differentiate into their associated cell type
e.g any cells of a living organism other than reproductive cells

21
Q

Stem Cell Therapy

A

the capacity of stem cells to divide and differentiate along different pathways is necessary for embryonic development and also makes stem cells suitable for therapeutic uses
aim to replace cells damaged or destroyed by disease

22
Q

Stargardt’s Disease

A

Macular dystrophy, active transport protein on photoreceptor cells to malfunction, causes progressive and eventually total, loss of central vision

Embryonic stem cells are treated to divide and differentiate to become retinal cells

  • retinal cells are injected into retina
  • retinal cells attach to the retina and become functional
  • central vision improves as a result of more functional retinal cells
23
Q

Stem Cell Therapy - Leukemia

A

Cancer of blood or bone marrow, resulting in abnormally high levels of poorly functioning white blood cells

  • hematopoietic stem cells (HSCs) are harvested
  • Chemo or radiotherapy is used to destroy diseased white blood cells
  • New white blood cells replace damaged ones as HSCs are transported back into the bone marrow
  • the HSCs differentiate to form healthy white blood cells
    (patients own HSCs can be used)
24
Q

Pros and cons of Embryonic Stem Cells

A
  • obatined from excess embryos (IVF)
  • causes destruction of embryo
  • growth potential is almost unlimited
  • higher risk of tumor development
  • can differentiate into any cell type
  • less chance of genetic damage
  • stem cells not genetically identical to patient
25
Q

Pros and cons of Cord blood

A
  • easily obtained, but limited quantities
  • discarded no matter whether stem cells are harvested or not
  • reduced growth potential
  • lower risk of tumor development
  • limited capacity for differentiation (only blood cells)
  • less chance of genetic damage
  • fully compatible with patient as genetically identical
26
Q

Pros and cons of Adult stem cells

A
  • difficult to obtain
  • patient can give consent
  • reduced growth potential
  • limited capacity to differentiate
  • genetic damage can occur due to accumulation of mutations through life
  • fully compatible with patient as cells are genetically identical
27
Q

Arguments for Therapeutic use of Stem Cells

A
  • pave way for future discoveries
  • may cure serious diseases or disabilities
  • transplants less likely to be rejected
  • do not require death of another human
  • can be taken from embryos that would have died anyway
  • taken from a time where nervous system has not developed
28
Q

Arguments against Therapeutic use of Stem Cells

A
  • involves creation and destruction of human embryos
  • ESC are capable of continued division and may develop into cancerous cells
  • excess embryos are killed
  • alternative technologies may be able to fulfill a similar role with additional cost and effort
  • are we creating human life to destroy it?
  • potential to create human cloning

Biology HL (54 decks)

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