MODULE 1: CELLS AS THE BASIS OF LIFE Inquiry question: What distinguishes one cell from another?

What does cell theory state?

Cell Theory states that:

● All organisms are made up of cells ● New cells are produced from existing cells ● The cell is the smallest organisational unit of a living thing.

Describe and list advantages and disadvantages of light microscopes and electron microscopes

Type of microscope

Description Advantages Disadvantages

Light Uses light and system of lenses to magnify the image. One lens is the ocular lens and the other is the objective

● Low costs ● Can be used to

observe living specimens

● Low magnifying power

● Lower resolution

Electron Uses an electron beam to refract then a system of lenses to magnify

● High magnifying power

● High resolution

● High costs ● Only in black

and white

Describe the following different types of cells, including at least one unique feature of each.

Type of cell Description (characteristics and features)

Plant Eukaryotic with membrane bound organelles. Larger than animal cells. Have a rigid cell wall which helps maintain structure of the cell and large central vacuoles.

Animal Eukaryotic with membrane bound organelles. Smaller than plant cells. Animal cells have centrosomes and lysosomes.

Bacteria Prokaryotic with no membrane bound organelles Have very diverse metabolic systems, making them extremely adaptable.

Organelle Function (What it does)

Structure (What it’s made of)

Appearance

Nucleus Contains the genetic instructions for cell replication, growth, repair and function

Membrane-bound: double membrane Contains DNA

Cell wall in plants

Cell structure and protection

External structure of cellulose surrounding cell membrane No membrane

Ribosome Synthesises proteins Made of proteins and rRNA No membrane

Mitochondria Obtains energy from organic molecules - site of aerobic respiration

Membrane-bound: double membrane, inner membrane is folded

Rough endoplasmic reticulum

Processes and modifies proteins

Membrane-bound network of cisternae Ribosomes bind to its membranes

Smooth endoplasmic reticulum

Synthesises lipids Membrane-bound network of cisternae

Golgi apparatus

Processes and packages proteins as well as prepare substances for secretion from cell

Membrane-bound stack of cisternae that aren’t connected to each other

Lysosome Digests cellular waste material and foreign matter

Membrane-bound vesicle containing digestive enzymes

Cytoplasm Gives cells their shape, provides area for chemical reactions

Consists of cytosol and organelles (eukaryotes) Gel-like substance (cytosol) made up of 80% water

Chloroplast Uses light energy, carbon dioxide and water to produce glucose - photosynthesis

Spherical with double membrane Contains DNA and thylakoid sacs

Flagella Allows cells to move. Longer than cilia

Rod like structure

Cilia Movement of substances across cell surface

External structure containing microtubules

Vacuole Stores substances and keeps a variety of substances separate from cell contents

Membrane-bound fluid-filled vesicle

Peroxisomes Key role in the breaking down toxic materials. Digest fatty acids

Small vesicles Single membrane

Cytoskeleton Supports the cell’s structure, allows them to move and helps transport organs and vesicles within cell

Made of microtubules of protein called tubulin, and filaments of actin

Plant Cells Both Animal Cells

Larger than animal cells Both are eukaryotic and have specialised cells

Smaller than plant cells

Have cell wall and chloroplasts

Both have a nucleus, mitochondria, ribosomes, endoplasmic reticulum, golgi apparatus, vacuoles, cilia, flagella and cell membrane

Plant cell: Animal cell:

Describe (provide characteristics and features) the role of the cell wall in plants and identify analogous structures in other organisms.

The role of a cell wall in plants is to provide support, prevent expansion and allow water and dissolved substances of a cell to pass through it.

Describe how to make a wet mount onion slide. Outline the process by listing the materials required and specifying logical, numbered steps. Include numbers/amounts/sizes as required. Materials required:

● Slide ● 1 drop water ● Dropper ● Coverslip ● Onion slice ● Scalpel ● Dissecting needle

Method:

1. Using the scalpel, carefully separate the epidermal skin from the remaining onion 2. Peel off the epidermal skin of the onion 3. Make sure the skin doesn’t wrinkle or fold 4. Place onion on the slide with a dissecting needle 5. Drop one drop of water on the slide to erase any air bubbles 6. Place coverslip so that its bottom edge is in contact with drop of water 7. Gently remove dissecting needle and lower coverslip

Prokaryotic - Bacteria, archaea

Both Eukaryotic - Animalia, fungi, plantae and protista

Very small (0.1-5.0Mm) Large SA:V ratio No membrane bound organelles Single circular chromosome and small circular DNA

Have ribosomes in cytoplasm Bilayer of phospholipid molecules

Larger (10-100Mm) Smaller SA:V ratio Many membrane bound organelles Linear chromosomes Have cell compartments which allow enzymes and reactants of a particular cellular function to be close. Also allow processes which require different environments to happen simultaneously, make cell less vulnerable to environmental changes

Describe the structure and features of the Fluid Mosaic Model of the Cell Membrane. The Fluid Mosaic Model of the Cell Membrane consists of a bilayer of phospholipid molecules consisting of a hydrophobic tail and hydrophilic head. Other molecules, such as proteins, cholesterol and carbohydrates are scattered throughout the bilayer Label the diagram of the Fluid Mosaic Model of the Cell Membrane. Identify a possible ‘channel protein’.

Inquiry question: How do cells coordinate activities within their internal environment and the external environment? Factors that affect the fluidity of a cell membrane:

● Phospholipid composition and structure ● Temperature ● Presence of cholesterol

Term Definition

Concentration gradient

Process in which particles move through a solution or gas from an area with a higher number of particles to an area with a lower number of particles

Semi-permeable A selective membrane which chooses the liquids and materials that are

membrane able to pass between the external and internal environment of the cell

High concentration

An area with a high number of particles per set volume

Low concentration

An area with a low number of particles per set volume

Solute The dissolved component of a solution

Solvent The dissolving component of a solution

Solution A type of homogenous mixture in which the particles of substances (the solute) are distributed uniformly throughout another substance (the solvent).

Permeability of cell membranes to different molecules:

Molecule/ion Examples Permeability

Small, uncharged molecule Oxygen, carbon dioxide Permeable

Non-polar molecule Alcohol, chloroform, steroids Permeable

Small, polar molecule Water, urea Permeable or semipermeable

Small ion K+, Na+ Impermeable (ions pass through protein channels)

Large, polar, water-soluble molecule

Amino acids, glucose Impermeable (passes through protein channels)

Mechanisms of transport into and out of cells. Active transport: Type of transport in which substances move against the concentration gradient and therefore requires energy. Passive transport: Type of transport in which substances move along the concentration gradient and therefore require no energy input.

Transport Method

Define and describe Materials transported

Particle size limitations

Direction c/w concentration gradient

Diffusion Movement of particles from an area of high

Gases, digestive

Smaller the particle,

Across

concentration to an area in low concentration. Very slow process. Affected by the difference in concentration, temperature, particle size

food molecules.

faster diffusion

Facilitated diffusion

Movement of particles from high to low concentration through channel protein

Food molecules

Across

Osmosis The net diffusion of water molecules across a semipermeable membrane. Movement from area of high concentration of free water molecules to area of low concentration of free water molecules

Water Across

Endocytosis In endocytosis, materials are taken in bulk by forming new vesicles. Small area of membrane sinks to form pocket, pocket encloses and forms vesicle - requires input of energy

Molecules which aren’t allowed past the membrane

Against

Exocytosis Secretory vesicle membrane and cell membrane come into contact, fuse and secrete materials in cell

Molecules which cannot pass through membrane

Against

Hypertonic Isotonic Hypotonic

The solution with a lower concentration of solute (higher concentration of water)

The solutions being compared have equal concentration of solutes

The solution with a higher concentration of solute (lower concentration of water)

Factors which affect movement of a molecule across the cell membrane.

Factor Moves easily across cell membrane

Moves across with difficulty or not at all

Size of molecule Small Large

Electrical charge of molecule

Uncharged Charged

Lipid solubility of molecule Insoluble in water Water soluble

Explain (provide the how and the why) the importance of Surface Area to Volume ratio (SA:V) in transport across the cell membrane. What are the implications of this as organisms grow in size? A large surface area to volume ratio is one of the most important features of a cell because they rely on processes like diffusion and osmosis for substance transport and these methods rely on a large SA to efficiently provide the substance. As organisms get larger, their SA:V ratio decreases meaning that they aren’t as efficient getting things into cells. Larger organisms can increase their SA:V ratio by cell compartmentalisation, a flattened shape or cell membrane extensions. Organic compounds: complex compounds containing carbon and hydrogen atoms; proteins, carbohydrates, lipids, vitamins, DNA, RNA Inorganic compounds: compounds without carbon atoms; water, oxygen, carbon dioxide, nitrogen, minerals

Autotrophs Both Heterotrophs

Obtain energy from sunlight Make their own organic compounds from inorganic compounds found in soil and atmosphere (carbon fixation)

Use organic and inorganic compounds to produce the energy required for all biological processes through photosynthesis (autotrophs) and cellular respiration (both autotrophs and heterotrophs)

Obtain organic compounds by consuming other organisms

Substances needed by cells

Substance Types Used how in the body?

Organic Carbohydrates C-H-O : 1:2:1

Important energy sources and structural components of organisms

Lipids C-H-O

Important role in cell membranes, important for energy storage

Proteins C-H-O-N-S (some)

Have many roles, some are enzymes, hormones, antibodies (CHON), structural component of membranes

Nucleic acids C-H-O-N-P

Carry genetic information of cells

Inorganic Water

Important solvent and transport medium. Most reactions take place in cytosol, made mainly of water

Oxygen Needed for efficient energy supply through cellular respiration

Carbon dioxide Source of carbon atoms

Nitrogen Building block of amino acids

Minerals Important for building many enzymes and vitamins that are needed for the structure and function of biological systems Assist in all chemical reactions

Metabolism: total of all the chemical reactions in a living organism Excretion: removal of substances that once formed part of the body of an organism; carbon dioxide and nitrogenous waste

Brown paper test Lipids - translucent Biuret test Protein - green

Benedict’s test Glucose - yellow Silver nitrate Chloride ions - white

Iodine test Starch - blue Iodine + H2SO4 Cellulose - brown

Construct a 2-stage flow chart of photosynthesis and label the reactants and products of the chemical reaction. Clearly identify the light dependent and light independent stages of photosynthesis and where each occurs. Photosynthesis is a biochemical process in which plants and other photoautotrophic organisms obtain energy from sunlight to produce their own organic compounds. Chloroplasts are the sites of photosynthesis. Water + carbon dioxide = glucose + oxygen 6H2O + 6CO2 = C6H12O6 + 6O2 Light dependent stage: chlorophyll captures solar energy and uses it to produce adenosine triphosphate (ATP). Photolysis occurs- water is split into hydrogen ions and oxygen gas. Occurs on thylakoid membranes. Water = hydrogen ions + oxygen + ATP Light independent stage: produce glucose, water and adenine diphosphate (ADP). Don’t require solar energy, use ATP instead. Hydrogen ions + ATP + Carbon dioxide = glucose + water + ADP Things that affect the rate of photosynthesis:

● Light intensity: when light intensity is low, the light dependent stage cannot occur. As light intensity increases so does the rate of photosynthesis up until a certain stage.

● Carbon dioxide concentration: carbon dioxide availability affects the rate of photosynthesis because photosynthesis uses the carbon atoms from carbon dioxide to make glucose. As carbon dioxide concentration increases so does the rate of photosynthesis up to a point

● Temperature: affects rate of photosynthesis because all light dependent and light independent reactions are catalysed by enzymes. Enzyme activity increases with temperature until it is denatured after the optimum temperature at 25 degrees.

Construct a flow chart of the process of cellular respiration and label the reactants and products of the chemical reaction. Where does it occur? Cellular respiration is a biochemical process in which glucose and oxygen are used to produce usable energy such as ATP. Glucose + Oxygen = Carbon dioxide + water + energy (ATP)

1. Glycolysis: Splits glucose molecules into two parts and doesn’t require oxygen 2. Aerobic respiration (oxygen): occurs in mitochondria; converts ADP to ATP. 3. Anaerobic respiration (if there’s insufficient or no oxygen): occurs in the cytosol; provides

no ATP - prevents buildup of pyruvate to let glycolysis continue Pathway of oxygen: Alveoli in lungs - (diffuse) - haemoglobin in red blood cell - (diffuse) - into cells Explain the function, features and importance of enzymes. Enzymes are protein molecules which catalyse their own specific biochemical reactions that would otherwise be very slow and unsuitable for survival. They are formed from long chains of amino acids that fold and can be compacted. They have specificity for a substrate (a molecule which an enzyme reacts upon), aren’t consumed when they catalyse reactions and catalytic power. Catabolic reactions: break down substrates, release energy Anabolic reactions: produce larger molecules from smaller substrates. Are endergonic Factors that affect enzyme activity:

● Temperature: generally increases enzyme activity because heat increases kinetic energy of particles with more collisions. However, are denatured after a point. Optimum for humans is 36-38.

● pH: enzymes have specific pH at which they function best. If they are far above or below optimum range, they may become denatured

● Enzyme and substrate concentration: increases enzyme activity until saturation point

Lock and key model Induced fit model

Describes the active site and substrates as fitting together like lock and key If the substrate doesn’t fit into the active site, no reaction occurs

When substrate binds to the active site of an enzyme, the active site changes shape slightly Active site is flexible

INVESTIGATIONS:

Investigation Describe the investigation Summarise the outcomes of the investigation

Osmosis Used dialysis tubing with starch inside. Poured iodine on the outside beaker

Turned blue, indicated starch had passed through with water

SA:V ratio Cut 3 different sized agar cubes and covered them with HCl.

Very slow process, showed that smaller sized cubes were more able to diffuse efficiently

Food tests Did different tests to figure out what it indicated

Photosynthesis conditions

Collected one leaf that had been in light and another which hadn’t Boiled them until they were limp Covered them with methylated spirits and put iodine on them

Indicated chlorophyll was necessary for photosynthesis

Enzyme reaction conditions

Indicated that certain temperatures were ideal through rate of bubbles and height

pH - optimal Temperature -optimal Substrate concentration - induced