Biology: Characteristics of Living Things

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Questions and Answers

What is the primary function of chloroplasts in plant cells?

To facilitate cellular respiration

To provide structural support

To regulate the movement of substances

To convert solar energy into chemical energy (correct)

How does the structure of the phospholipid bilayer contribute to its function?

It prevents all substances from crossing the membrane

It offers rigidity and structural stability to the cell

It allows selective permeability due to hydrophilic and hydrophobic properties (correct)

It creates an impermeable barrier to water molecules

What components of the cell membrane play a role in the transport of materials?

Proteins and cholesterol

Only carbohydrates and cholesterol

Carbohydrates and protein receptors

Phospholipids and integral proteins (correct)

In which condition do particles move equally in both directions across a membrane?

Dynamic Equilibrium Signup and view all the answers

What role does cholesterol play in the structure of the cell membrane?

It helps maintain fatty acid mobility Signup and view all the answers

What is a characteristic of the fluid-mosaic model of the cell membrane?

It is comprised of various movable parts Signup and view all the answers

Which statement best describes the semi-permeable nature of the cell membrane?

It selectively allows certain substances to enter or exit Signup and view all the answers

What is the significance of the hydrophilic and hydrophobic regions of phospholipids in the cell membrane?

They allow the formation of bilayers in aqueous environments Signup and view all the answers

What is the primary driving force behind diffusion in passive transport?

Kinetic energy of molecules Signup and view all the answers

Which scenario describes a hypertonic solution in relation to a cell's cytoplasm?

The solution has a higher concentration of solute and lower concentration of water. Signup and view all the answers

How do carrier proteins facilitate the process of facilitated diffusion?

By undergoing changes in shape to transport molecules across the membrane. Signup and view all the answers

Which statement is true regarding osmosis?

Osmosis is the net movement of water from high concentration of water to low concentration of water. Signup and view all the answers

What effect does placing cells into a hypotonic solution have on them?

Cells will swell and may burst. Signup and view all the answers

Dialysis involves the movement of materials across which type of barrier?

Semi-permeable membranes that restrict certain solutes. Signup and view all the answers

Which type of passive transport involves the use of transport proteins for polar molecules?

Facilitated diffusion Signup and view all the answers

What is the fate of water movement in an isotonic solution?

Water moves in and out at equal rates. Signup and view all the answers

What role do stomata play in plant physiology?

They regulate gas exchange and water loss. Signup and view all the answers

Which tissue is primarily responsible for the transport of water in plants?

Xylem Signup and view all the answers

How does root pressure assist in water movement within plants?

It increases positive pressure to push water up. Signup and view all the answers

In which part of the plant does photosynthesis primarily occur?

Palisade Mesophyll Signup and view all the answers

What is the primary function of auxin in plants?

To promote cell elongation. Signup and view all the answers

What is the purpose of a waxy cuticle in plants?

To reduce water loss. Signup and view all the answers

What process describes the movement of sugars from the leaves to other parts of the plant?

Pressure Flow Theory Signup and view all the answers

What adaptation helps reduce water loss in plant leaves under arid conditions?

Thick epidermis or hair structures Signup and view all the answers

What is the effect of light direction on plant growth, known as phototropism?

Plants grow towards the light source. Signup and view all the answers

What role do guard cells play in plant leaf structure?

Regulate the opening and closing of stomata. Signup and view all the answers

Which of the following correctly describes turgor pressure?

It prevents plants from wilting. Signup and view all the answers

Which process is primarily responsible for the upward movement of water in plants due to evaporation?

Transpiration pull Signup and view all the answers

What is a characteristic of phloem tissue in plants?

It moves sugars and requires living cells. Signup and view all the answers

Which environmental response is known as gravitropism?

Roots grow downwards in response to gravity. Signup and view all the answers

Study Notes

Biology

Study of living things

Characteristics of Living Things

Need for energy (eating or making waste)
Exchange of gases (respiration)
Growth
Movement
Response to stimuli
Reproduction

Where do Living Things Come From?

Abiogenesis: theory that life can be made from non-living things (spontaneous generation)
Biogenesis: theory that life is produced by other living things

Francesco Redi's Experiment

Questioned spontaneous generation of maggots on meat
Experiment on meat with three treatments:
- Open air (control)
- Sealed
- Screened off
Hypothesis: meat would decay in all jars, but maggots would only appear where there was contact with flies
Result: maggots only appeared in the open container
Conclusion: hypothesis supported ; maggots came from flies, not spontaneously from meat.

The Debate Continued

John Needham
- believed in abiogenesis
- boiled chicken broth
- bacteria grew, believed to favour his hypothesis
Lazzaro Spallazani
- believed in biogenesis
- repeated Needham's experiment, but drew off air
- nothing grew; favoured his hypothesis
Louis Pasteur
- designed an experiment to resolve the argument
- boiled nutrient broth in three treatments:
  - Open
  - Closed
  - S-neck (open to air, but not atmospheric dust)
- Prediction: no growth in S-neck flask
- Result: no growth in S-neck flask
- Conclusion: hypothesis supported; growth of microorganisms needs a source (external/atmosphere).

Microscopes and Cell Theory

Magnification
- Enlarges images
- How many times bigger image compared to actual specimen
- e.g., 5000X
Resolution
- Clarity of image under a microscope
- Often depends on quality of lens
- How far apart two objects need to be to be seen separately, not blurred
- e.g., 10 µm

Types of Microscopes

Modern Compound Microscope
- Series of lenses producing a magnified image
- Multiple objective lenses in a revolving nosepiece
Dissecting Microscope (Stereoscope)
- Two objectives and two eyepieces
- Produces 3D images
- Used for viewing larger, more opaque specimens
- Lower Magnification
Electron Microscopes
- Use beam of electrons instead of light
- Focused by magnetic fields
- Produces 2D images or 3D images
- Very powerful magnification (up to 1.2 million ×)
- Transmission Electron Microscope (TEM)
  - Beam of electrons passes through very thin section (stained) specimen
  - Magnifications from 10,000 to 100,000 ×
- Scanning Electron Microscope (SEM)
  - Specimen "painted" with electron-dense material (gold)
  - Electrons strike, reflected and sensor produces 3D image
  - Magnification of up to 300,000 x
Confocal Laser Scanning Microscope (CLSM)
- Laser beams direct through planes, creates 2D images
- Images merged to create 3D images
- Good for thick specimens.
Scanning Tunneling Microscope (STM)
- Greater magnification than electron microscope
- Electron flow from tip to atoms on surface
- 3D image from surface contours.

Cell Theory

All living organisms are made of one or more cells.
The cell is the most basic unit of life.
All cells arise from pre-existing cells.

What have we discovered?

Stem cells are used in creating treatments and cures for diseases
Genes use DNA to direct cells' activities.
Genetic sequencing can map genes which helps study cell activity and develop treatments for genetic disorders.
Cancer and tumors are caused by damage to genes where cells grow uncontrollably.
Scientists will study the sequences of cancer-causing genes to understand how they impact cell activity.
Sub-cellular particles, like viruses and prions have been discovered which are not made up of cells.
- Viruses are made of genetic material in a protein coat that invades cells' reproductive machinery
- Prions are proteins which convert into deadly disease particles
More has been discovered about cell components and how these components/processes allow the cell to function correctly.

Cell Structures and their functions

Nucleus
- Controls cell activities
- Contains DNA
- Surrounded by a nuclear envelope
- Contains the nucleolus
Nucleolus
- Center of the nucleus
- Synthesizes ribosomes
Ribosomes
- Turn DNA into proteins, responsible for growth and cell reproduction activities.
Mitochondria
- Powerhouse of the cell
- Uses oxygen to make cell energy (ATP)
- Performs cellular respiration
Lysosome
- Vesicles containing enzymes that break down particles and dispose of waste.
Vacuole
- Stores food and water
- Transport
- Plants generally have a large central vacuole whereas animals have many small vacuoles.
Endoplasmic Reticulum & Ribosomes
- Attached to nucleus
- Rough ER (RER) has ribosomes which transport DNA
- Smooth ER (SER) has no ribosomes which synthesizes lipids (fats) required by the cell
Golgi Apparatus
- Modifies and repackages lipids and proteins.
- Disposes of waste products.
Centrioles
- Involved in cell division
Cytoskeleton
- Supports the structure of the cell
- Facilitate transport
- Intricate network of fiber-like structures - only present in animal cells
Cell Membrane
- Protective barrier around the cell
- Semi-permeable (regulates movement of substances in and out)
- Made of phospholipids, proteins, carbohydrates, and cholesterol
- Role: to maintain equilibrium
Cell Wall
- Rigid, supportive structure
- Shapes plant cells (along with large vacuole)
- Enclosed membrane
- Made of cellulose
Chloroplasts
- Site of photosynthesis (plant cells)
- Solar energy converted into chemical energy (glucose)
- Made up of two membranes
- Contains chlorophyll

Cell Transport

Passive Transport
- Diffusion: particles move away from high concentration regions toward lower concentration regions. (e.g., O2 and CO2)
- Osmosis: Water moves from higher to lower water concentration.
- Facilitated diffusion: transport proteins help polar molecules and ions diffuse passively down a concentration gradient (e.g., aquaporins and carrier proteins)
Active Transport:Requires energy to move solutes against a concentration gradient using carrier proteins (e.g, sodium-potassium pump)
Bulk Transport:
- Exocytosis: cells excrete molecules using vesicles (that fuse with the membrane)
- Endocytosis
  - Phagocytosis: cells take in large materials to be digested
  - Pinocytosis: cells take in fluid and small solutes
  - Receptor-mediated endocytosis: uses receptors to identify specific materials.

Dialysis

Method to filter waste and regulate material concentration using dialysis tubing (permeable membranes)
Used to treat those with damaged kidneys
Involves use of machines that circulate blood past membranes in a fluid (solute) mix.

Plant Organization

Cells → Tissues → Organs → Organ Systems → Organisms
An organism is a complex of interacting dependent systems

Organ Systems (Plant)

Shoot systems include everything above the ground involved in capturing energy from sunlight
Root systems are mostly below ground and involved in obtaining water and nutrients and anchoring the plant.

Specialized Plant Cells

Xylem: non-living cells that conduct water and minerals up from the roots to leaves.
One-way transport.
Phloem: form sieve tubes and connected to companion cells that transport sugars from the leaves to other parts of the plant.
Two-way transport

Plant Adaptations/Growth

Plants adapt via features or behaviors in their environment for survival or reproduction.
- Larger leaves increase surface area which allows them to capture sunlight.
- Dark leaves can absorb more light
- Wax cuticle and thick epidermis reduces water loss in plant
Tropisms (Directional Growth):
- Phototropism: growth towards/away from light
- Gravitropism: growth towards/away from gravity
  - Roots grow toward, shoots grow away.
- Thigmotropism: growth towards/away from physical object.

Calculating Surface Area & Volume Ratios

Area and volume calculations help determine efficient cell/plant structure which allows for survival & reproduction.
The surface area often increases rapidly compared to volume in smaller cells, which contributes to efficient nutrient uptake and waste removal in plants/cells.

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Description

This quiz explores the foundational concepts of biology, focusing on the characteristics that define living things and the origins of life theories including abiogenesis and biogenesis. Additionally, it discusses Francesco Redi's experiment that challenged spontaneous generation, providing insights into scientific inquiry and debate.