PRELIM BIO

Cell

Basic unit of life

What is cell theory?

All living things are made up of cells, cells are the basic units of life, all cells come from preexisting cells

What are cells measured in?

Micrometers (µm)

1mm =

1000 micrometers (um)

Prokaryotic

No membrane bound organelles E.g. Bacteria

Prokaryotic DNA structure

circular DNA

Prokaryotic - Unicellular or Multicellular

unicellular

Eukaryotic

Has a nucleus and other membrane-bound organelles E.g. Plants, Fungi, Animals

Eukaryotic DNA structure

linear

Eukaryotic - Unicellular or Multicellular

both

Microscope Resolution

The ability to distinguish two objects from each other

Microscope Magnification

The process of enlarging an object's appearance compared to its actual size

Specimens can be...

- Whole organism

- Smear of cells

- Thin slice of tissue

Staining is used to see cell structures more clearly

Cell Size

Image Size/Actual size/Magnification

Technologies used to view cells

Light Microscope

Electron Microscope

Confocal Microscopy

Light microscope

- Uses light and 2 lenses (ocular and objective)

- Makes a specimen look bigger

Colour

Electron microscope

- Uses electron beams instead of light

- Much higher magnification and resolution

- Two types: TEM (Internal) & SEM (scans surface)

No colour

Nucleus 'control centre'

Controls cell activities, stores genetic material, regulates gene expression

Smooth ER

lipid synthesis and detoxification

Rough ER

protein synthesis and transport

Golgi Apparatus

modifies and packages proteins and lipids for transport within and out of the cell

Mitochondria 'powerhouse of the cell'

Produces ATP via cellular respiration, powerhouse of the cell

Chloroplasts

Conducts photosynthesis, converts solar energy into chemical energy

Cell Wall

Provides structure, support, and protection

only in plants

Cell Membrane

Controls movement of substances in and out of the cell

Ribosomes

site of protein synthesis

Nucleolus

produces ribosomes

lysosome

breaks down waste and damaged organelles

Vacuole

Stores water, nutrients, and waste; provides structure in plant cells

Electron Micrograph

A photograph or image of a specimen taken using an electron microscope

Rules to drawing biological diagrams

1. Use a sharp pencil

2. Label correctly

3. No shading

4. Indicate magnification and scale

5. Use stippling for texture

Do not use arrows

Cell Membrane

Controls the exchange of material between the internal and external environments of the cell

It is selectively permeable

Permeable

All substances pass through

Impermeable

No substances pass through

Selectively Permeable

Some substances pass through

Why use a model?

To represent something too large or small to be seen

To make predictions

The Phospholipid Bilayer

Hydrophilic phosphate heads

Hydrophobic lipid tails

Tails point inwards towards each other

Integral protein

Cholesterol - STRUCTURE

Glycoprotein - PROTEIN WITH CARB

Glycolipid - LIPID WITH CARB

Peripheral Protein

Moving across membranes depends on...

Size - harder if larger

Lipid Solubility - Pass through lipid membrane easily if lipid soluble

water moves easily through hydrophilic

The permeability of a cell membrane is dependent on a molecules:

Size – Smaller molecules move across membranes quickly, while larger molecules struggle due to limited space within the phospholipid bilayer.

Electrical Charge – Charged molecules have low permeability; neutral ones pass easily

Solubility – Lipid-soluble molecules pass freely; hydrophilic ones need help

Substances move through the membrane either through:

passive transport

active transport

passive transport

The movement of materials across the cell membrane without the expenditure of energy

Concentration Gradient

The difference in concentration between sections of fluid, either within a fluid body or between a selectively permeable membrane.

Diffusion

The movement of any molecule from high to low concentration (down its concentration gradient)

Movement of substances will occur until an equilibrium is reached

Simple Diffusion

The diffusion of substances directly through the phospholipid bilayer, if permeable to the material

- Small

Non-polar

Facilitated Diffusion

The diffusion of substances through the cell membrane via channel and carrier proteins

Osmosis

The passive movement of water into or out of a cell across a selectively permeable membrane, following a concentration gradient.

Moves from an area of high water concentration to an area of low water concentration, until equilibrium is reached.

Example: Absorption of water by plant roots

Solute

The substance that is dissolved in a solution (e.g., salt in saltwater).

Solvent

The substance that dissolves the solute (e.g., water in saltwater).

Dilute

A solution with a relatively small amount of solute compared to solvent.

Concentrated

A solution with a relatively large amount of solute compared to solvent.

Hypotonic

A solution that has a lower concentration of solutes compared to another solution, often leading to water moving into cells.

Isotonic

A solution with the same concentration of solutes as another solution, leading to no net movement of water.

Hypertonic

A solution with a higher concentration of solutes compared to another solution, often causing water to move out of cells.

Active Transport (REQUIRES ENERGY)

the movement of molecules against their concentration gradient, from low to high concentration.

Requirements of active transport:

- The input of extra energy e.g. ATP

- It always occurs across a cell membrane

- It requires carrier proteins to move the molecules

Endocytosis

Brings materials into the intracellular environment

Exocytosis

Removes materials/waste from the cell into extracellular environment

Factors affecting exchange across a membrane

Concentration Gradient:

The greater the difference in concentration, the faster the diffusion rate. Diffusion moves down the gradient.

Distance to Travel:

The shorter the distance, the faster the diffusion. Thicker barriers slow it down.

Surface Area:

A larger surface area increases the rate of diffusion. Cells adapt by forming structures like microvilli.

Structure of the Membrane:

Pores and thin membranes aid diffusion. The thicker the membrane, the slower the rate.

Temperature:

Higher temperatures increase molecular movement, speeding up diffusion.

SA:VOL ratio

The amount of surface area per unit volume of a cell.

As any cell gets bigger, it becomes increasingly difficult for it to exchange substances because its SA:Vol ratio keeps shrinking.

As a cell increases in size, its volume increases faster than its surface area.

Larger cells have smaller SA:Vol

Inorganic Compounds

Compounds that do not contain carbon

Organic compounds

Compounds that contain carbon

Carbohydrate

compound made up of carbon, hydrogen, and oxygen atoms; major source of energy for the human body

Lipid

Energy-rich organic compounds, such as fats, oils, and waxes, that are made of carbon, hydrogen, and oxygen.

Protein

An organic compound that is made of one or more chains of amino acids and that is a principal component of all cells

Nucleic Acids

Molecules like DNA and RNA that store and transfer genetic information.

Photosynthesis

The process by which plants use sunlight to make their own organic compounds

occurs in the chloroplast

CO2 + Water --> Glucose + Oxygen

in the presence of sunlight

Factors affecting photosynthesis rate

Light intensity, CO2 levels and temperature

light-dependent reactions

reactions of photosynthesis that use energy from light to produce ATP and NADPH

Light Independent Reactions (Calvin Cycle)

- Occur in the stroma

- ATP energy used to combine carbon dioxide with hydrogen

Glucose is produced

Cellular Respiration

The process by which organic compounds are broken down to produce ATP energy

This organic compound is mostly glucose

2 types of cellular respiration

1. Aerobic (lots of oxygen)

Anaerobic (not enough oxygen)

Aerobic Respiration

Glucose is broken down through a series of chemical reactions

Glucose + Oxygen + Carbon Dioxide + Water + (ATP)

Where does it occur? When does it occur? which organism does it occur in ?

Mitochondria

All the time

All organisms

Cellular Waste

Substances which cells don't need anymore

3 types of cellular waste

Carbon dioxide

Nitrogenous

H20

Carbon Dioxide

Formed when carbohydrates or lipids are broken down during cellular respiration, CO2 is produced

Makes cells and their surroundings very acidic - reacts with water to make an acid à Destroys cellular structures

Nitrogenous

Waste products which contain nitrogen. Formed when unwanted proteins and nucleic acid are broken down.

Makes cells and their surroundings very basic à Destroys cellular structures

H20

Becomes a problem when:

- Organism has drunk a lot of water

- Organism lives in a freshwater environment (water moves in via osmosis)

Excess water takes up space and could cause the cell to pop (and die)

Waste Removal: cellular level

The movement of wastes from the cytoplasm into the extracellular environment

How are wastes removed?

Passive Transport e.g. CO2, Alcohol, Ammonia, Glucose, Ions, Water

Active Transport e.g. Nitrogenous wastes, Irons, Other Toxins

Waste Removal in Body Systems

Plants:

- Leaves e.g. CO2 and excess H20 are excreted as gases

- Old bark and leaves e.g. wastes

Animals: Circulatory system transports waste away from cells to organs of the excretory system.

- Lungs e.g. CO2, H20

- Liver e.g. prepares waste for removal

Kidneys e.g. filters the blood

Enzymes

Proteins that speed up chemical reactions

Made of chains of amino acids

Each enzyme only catalyses one reaction

How do enzymes work?

Lock and Key model

The induced fit model

Lock and Key model (OLD)

- The active site perfectly fits with the substrate (like a key in a lock)

The Induced fit model

- The active site does not perfectly fit with the substrate

- The substrate causes the enzyme to slightly change its shape

After the reaction, the enzyme returns to its original state

Environmental factors which affect enzymes

Temperature: the temperature at which is works best

- High temperatures break the bonds

- Lower temperatures result in slower molecular movement, therefore slower reaction rates.

pH: pH at which is works best

- Any variation above or below optimum pH reduces the enzymes activity

- Extremes denature the enzyme

Substrate concentration: A more concentrated solution has more substrate more substrate molecules

- As substrate concentration increase, we see rapid increase in reaction rate until a plateau

Plateau = Saturation point

Abiotic

The environment's non-living components

Biotic

The living components of the ecosystem including all the organisms in the area

Species Diversity

The variety of genes within a species.

Genetic Diversity

The variety of species within a habitat or region

Ecosystem Diversity

The variety of ecosystems in a given place

Abundance

The total number of a given organism within a given area

Distribution

How individuals within a population are spaced within their region

Selection Pressures

Any factor that promotes change in characteristics and adaptations of species that helps them survive

Biotic Selection Pressures

availability of food - Low food → decreased population and abundance.

predators - High predators --> decrease in prey population

competitors - High competition --> competition for resources, decreasing population

Abiotic Selection Pressures

Temperature - Affects the organisms survival and reproduction

Oxygen Availability - Low oxygen --> decreased respiration and fewer organisms

Water availability - Low water --> competition for resources, leading to decreased abundance

Effect of positive abiotic pressures

increases population and diversity

Effect of negative abiotic pressures

Decreases population and diversity

Why were cane toads introduced?

To control cane beetles which ate sugarcane

Cane Toad selection pressures

No natural diseases - Biotic - Increase in population due to lack of disease

High reproductive rate - Biotic - Faster population growth (more eggs)

High rainfall - Abiotic - Population increase due to need for moisture

Why were prickly pears introduced?

To use the insects that feed on them for dye