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A2.2 Cell structure

SEK CIUDALCAMPO

Created on September 25, 2023

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A2.2. Cell structure

Unity and diversity - Cells

Guiding questions

  • What are the features common to all cells and the features that differ?
  • How is microscopy used to investigate cell structure?
A2.2.1 Cells as the basic structural unit of all living organisms

The Cell Theory

  • All living things are made of cells
  • Cells are the basic units of life
  • All cells arise from other cells.

A2.2.1 Cells as the basic structural unit of all living organisms

The Cell Theory

  • All living things are made of cells
  • Cells are the basic units of life
  • All cells arise from other cells.

A2.2.1 Cells as the basic structural unit of all living organisms

The Cell Theory

  • All living things are made of cells
  • Cells are the basic units of life
  • All cells arise from other cells.

A2.2.1 Cells as the basic structural unit of all living organisms
NOS

The Cell Theory

(observation)
A2.2.1 Cells as the basic structural unit of all living organisms
NOS

The Cell Theory

Deductive reasoning: generating predictions from theories.

A2.2.1 Cells as the basic structural unit of all living organisms

To what extent does scientific collaboration need to occur in the same time frame or location?

A2.2.2 Microscopy skills
AoS!

PRACTICAL

NOS
A2.2.3 Developments in microscopy

Magnification is the ability to make small objects seem larger

Resolution is the shortest distance between two separate points that can still be distinguished as distinct objects

A2.2.3 Developments in microscopy

Electron microscopy

A2.2.3 Developments in microscopy
A2.2.3 Developments in microscopy

Freeze Fracture microscopy

Discovery: integral proteins are scattered through the center of membranes, supportting the Fluid Mosaic Model of the cell membrane
A2.2.3 Developments in microscopy

Cryogenic electron microscopy

The samples are frozen at cryogenic temperatures (-180ºC or lower): - Improves resolution - Reduces damage from the electron beam - Allows visualizing molecules (e.g. proteins)
The structure of the SARS-CoV 2 coronavirus spike protein was first elucidated using cryogenic electron microscopy
A2.2.3 Developments in microscopy

Immunofluorescence

A2.2.3 Developments in microscopy

Fluorescent dyes and light microscopy

Fluorescence dyes are commonly used to visualise biological structures and monitor drug delivery within the body.

Hippocampal neurons and synaptic vessicles

Intestine section

A2.2.4 Structures common to cells in all living organisms
A2.2.4 Structures common to cells in all living organisms

DNA

Plasma Membrane

Genetic material

Cell individualization Transport

Ribosomes

Cytoplasm (and cytosol)

Substances diffusion Metabolic reactions

Protein synthesis

A2.2.5 Prokaryote cell structure AND A2.2.6 Eukaryote cell structure
A2.2.5 Prokaryote cell structure AND A2.2.6 Eukaryote cell structure
A2.2.5 Prokaryote cell structure
A2.2.5 Prokaryote cell structure

CELL ENVELOPES

- (Capsule: adhesion to surfaces) - Cell wall: - Shape - Turgor pressure - Cell membrane: - Regulates exchange of materials
A2.2.5 Prokaryote cell structure

CYTOPLASM AND ORGANELLES

- Cytoplasm: gel-like fluid substance- metabolic reactions- 70S* Ribosomes: - protein translation- (Pili and flagella: - attachment, DNA swaping, locomotion)
* S = Svedberg units, a measure of particle density
A2.2.5 Prokaryote cell structure

GENETIC MATERIAL

- DNA chromosome:- Single - Naked - Loop - Nucleoid- Plasmids - Circular and naked - Smaller - Can be exchanged - Antibiotic resistance genes
A2.2.6 Eukaryote cell structure
A2.2.6 Eukaryote cell structure
PLASMA MEMBRANE - Separation - Exchange control COMPARTMENTALIZED CYTOPLASM - Create higher concentrations - Separate damaging substances - Control conditions (e.g. pH) - Separate metabolic reactions
A2.2.6 Eukaryote cell structure
MEMBRANE-BOUND CYTOPLASMIC ORGANELLES Endoplasmic Reticulum - Rough ER: protein synthesis - Smooth ER: lipid synthesis Golgi apparatus: protein processing Vesicles: transport Lysosomes: hydrolysis Vacuoles: storage and osmotic balance
A2.2.6 Eukaryote cell structure
MEMBRANE-BOUND CYTOPLASMIC ORGANELLES Mitochondria: cellular respiration
A2.2.6 Eukaryote cell structure
80S Ribosomes

Free: synthethise cell proteins Attached to the rER: synthethise secretory and membrane proteins

A2.2.6 Eukaryote cell structure
Cytoskeleton
A2.2.6 Eukaryote cell structure
NUCLEUS

Chromosomes: DNA with histones

Double membrane with pores

Compare and contrast the structure of prokaryote and eukaryote cells [8 marks]

A2.2.8 Differences in eukaryotic cell structure between animals, fungi and plants
Plant Cell
A2.2.8 Differences in eukaryotic cell structure between animals, fungi and plants
Centrioles - Microtubule organization - Cell division Flagella: - Whimp-like structures - Made of microtubles - Cell locomotion Cilia: - hair-like structures - made of microtubules - movement of substances past the cell Lysosomes: - Vesicles with hydrolytic enzymes
A2.2.8 Differences in eukaryotic cell structure between animals, fungi and plants
Cell wall - Cellulose - Protection - Maintains osmotic pressure and shape Vacuole - Larger than in animal cells - Regulates osmotic pressure Chloroplasts - Double membrane organelles - Photosynthesis - Chlorophyll (green pigment) Other plastids - storage functions (e.g. amyloplasts)
A2.2.8 Differences in eukaryotic cell structure between animals, fungi and plants
Centrioles Cell wall - Made of chitin (polysaccharide) Vacuoles: - Break down molecules - Storage of ions and others Buds: - Daughter cells (fungi reproduce through budding)

FUNGAL CELLS

A2.2.9 Atypical cell structure in eukaryotes
Multinucleate cells Anucleate cells
A2.2.10 Cell types and cell structures viewed in light and electron micrographs
AoS!
A2.2.10 Cell types and cell structures viewed in light and electron micrographs
AoS!
A2.2.10 Cell types and cell structures viewed in light and electron micrographs AND A2.2.11 Drawing and annotation based on electron micrographs
AoS!
A2.2.10 Cell types and cell structures viewed in light and electron micrographs AND A2.2.11 Drawing and annotation based on electron micrographs
AoS!
A2.2.10 Cell types and cell structures viewed in light and electron micrographs AND A2.2.11 Drawing and annotation based on electron micrographs
AoS!
A2.2.10 Cell types and cell structures viewed in light and electron micrographs AND A2.2.11 Drawing and annotation based on electron micrographs
AoS!

Secretory vessicles

A2.2.10 Cell types and cell structures viewed in light and electron micrographs AND A2.2.11 Drawing and annotation based on electron micrographs
AoS!
A2.2.10 Cell types and cell structures viewed in light and electron micrographs AND A2.2.11 Drawing and annotation based on electron micrographs
AoS!
Nucleus Chromosome
Vacuole and cell wall Ribosomes Plasma membrane Microvilli
A2.2.7 Processes of life in unicellular organisms

MR HM GREN

A2.2.7 Processes of life in unicellular organisms

Response to stimuli

Metabolism

Movement

Homeostasis

Growth

Reproduction

Excretion

Nutrition

MR HM GREN

A2.2.7 Processes of life in unicellular organisms
Paramecium Chlamydomonas
A2.2.7 Processes of life in unicellular organisms
How do Paramecium and Chlamydomonas carry out the 8 functions of life?
A2.2.12 Origin of eukaryotic cells by endosymbiosis
First cells originated in water

Topics A1.1 (Water) and A2.1 (origin of cells)

A2.2.12 Origin of eukaryotic cells by endosymbiosis
A2.2.12 Origin of eukaryotic cells by endosymbiosis
A2.2.12 Origin of eukaryotic cells by endosymbiosis

Symbiotic ancestors of mitochondria were aerobic bacteria

Cellular respiration

A2.2.12 Origin of eukaryotic cells by endosymbiosis

Symbiotic ancestors of chloroplasts were photosynthetic bacteria

A2.2.12 Origin of eukaryotic cells by endosymbiosis
NOS
A2.2.12 Origin of eukaryotic cells by endosymbiosis
Evidence of endosymbiosis
A2.2.12 Origin of eukaryotic cells by endosymbiosis
Evidence of endosymbiosis
A2.2.12 Origin of eukaryotic cells by endosymbiosis
Evidence of endosymbiosis
A2.2.12 Origin of eukaryotic cells by endosymbiosis
Evidence of endosymbiosis
A2.2.13 Cell differentiation as the process for developing specialized tissues in multicellular organisms
Different patterns of gene expression are triggered by changes in the environment
A2.2.14 Evolution of multicellularity
Multicellularity has evolved repeatedly
A2.2.14 Evolution of multicellularity
A2.2.14 Evolution of multicellularity
Advantages of multicellularity Cell specialization

Larger body size

Linking questions

  • What explains the use of certain molecular building blocks in all living cells?
  • What are the features of a compelling theory?