B1 Flashcards
Eukaryotic Cell
A cell with genetic material in a nucleus
Ranges between 10 and 100 nanometers
E.g Animal cells, plant cells
Prokaryotic Cell
Cells with genetic material floating about in the cytoplasm (no nucleus)
Ranges between 1 and 10 nanometers
E.g bacterium
Animal Cell Structure
Nucleus - Controls the activities of the cell, contains genetic material, and contains instructions to make new cells/organisms
Mitochondria - Where respiration occurs
Cell membrane - A selective barrier that controls which substances pass in and out of the cell
Cytoplasm - A jellylike substance which hosts the chemical reactions that keeps the cell alive, and hosts the other sub cellular structures
Plant Cell Structure
Nucleus - Controls the activities of the cell, contains genetic material, and contains instructions to make new cells/organisms
Mitochondria - Where respiration occurs
Cell membrane - A selective barrier that controls which substances pass in and out of the cell
Cytoplasm - A jellylike substance which hosts the chemical reactions that keeps the cell alive, and hosts the other sub cellular structures
AND
Chloroplast - Contain chlorophyll, that transfers energy from the Sun to the plant via light. Chlorophyll causes the chloroplast to be green, causing parts of the plant with chloroplasts to be green
Vacuole - A sac full of cell sap (solution of sugar and salts). It helps keep the cell rigid, and therefore supports the entire plant and keeps it upright
Cell Wall - A tough substance called cellulose that surrounds the cell. It makes the wall rigid and supports the cell
Structure of (most) Prokaryotes
Cell Wall
Cell Membrane
Cytoplasm
Some bacterial (prokaryote) cells also have
Flagellum - A tail-like structure that allows the cell to travel through liquids
Pili - Tiny hairlike structures that enable the cell to attach to other structures, e.g cells in your digestive tract. In bacteria they’re also used to transfer genetic material
Slime capsule - a thin layer outside the cell wall that protects bacteria from drying out, from toxic substances, and allows it to stick to smooth surfaces
Plasmid - a circular piece of DNA that stores extra genes that may be needed in times of stress, e.g. genes for antibiotic resistance
Light microscope
A microscope that uses light to observe small structures in detail
Light microscope method
- Move the stage to its lowest position
- Select the objective lens with the lowest magnification
- Place the slide, with cells on it, on the stage
- Turn the coarse knob slowly until you see a (usually blurred) image of the object
- Turn the fine focus knob slowly until you see a clear image of the object
- To see cells in greater detail, repeat the steps above, but use a different objective lens
Magnification equation
Total magnification = eyepiece lens magnification x objective lens magnification
Stains
Used to make colourless cells easier to observe, or highlight specific sub cellular structure
Common stains:
Methylene blue - nucleus of an animal cell
Iodine solution - nucleus of a plant cell
Crystal violet - cell walls of bacteria
Electron microscope
Uses electrons instead of light to produce an image
Transmission Electron Microscope
Produce the most magnified images
Work like light microscopes, but instead a beam of electrons passes through a very thin slice of an object
Scanning Electron Microscope
These produce a 3D image of a surface by sending a beam of electrons across the surface
Light Microscopes vs Electron Microscopes
Light Microscope: Cheap to buy and easy to operate Small and portable Simple to prepare a sample Specimens can be living or dead (light microscopes need a dead specimen)
Electron microscope:
Gives black and white images, but colour can be added (light microscopes give the natural colour unless a stain is used)
Resolution: 1x10^(-10) vs light microscope - 2x10^(-7)
DNA
Deoxyribonucleic acid. This substance contains all the instructions that determine your characteristics
Chromosome
A long strand of DNA. Half of all your chromosome are inherited from your mother, the other half from your father
Gene
A short section of DNA. The code of a gene contains specific proteins to be made. These proteins determine the cell’s function
DNA is…
Made up of two strands, forming a double helix
Made up of small units called nucleotides
A polymer
Nucleotide Structure
Circle - phosphate
Pentagon - sugar (deoxyribose)
Rectangle - base
There are 4 different types of nucleotide, because there are 4 different bases. These are:
A - adenine
T - thymine
C - cytosine
G - guanine
Complementary Base Pairing
When bases bond together to hold the two strains of DNA together. A base from one strand bonds with the base from another.
A-T, C-G
Transcription
A process through which DNA leaves the nucleus
Transcription Process
DNA can’t leave the nucleus because it’s too big
Instead, a copy of the DNA called mRNA is sent
To create mRNA, the DNA ‘unzips’ so that strands are separated
One of the strands acts as a template for mRNA
Complementary Bases attach to the strand being copied, but there’s no thymine in mRNA so Uracil instead bonds with Adenine
When complete, the DNA strands ‘zip’ back up and the mRNA travels out of the nucleus to ribosomes in the cytoplasm
Translation
A process by which proteins are made
Translation
The ribosome ‘reads’ the nucleotides on the mRNA in groups of three
These groups are called base triplets/codons. Each triplet codes for a specific amino acid
The ribosome continues to ‘read’ the triplet code, adding more and more amino acids
The amino acids join together to form a chain. This is a protein
The order of amino acids is very important, as it determines how the protein will fold. This is significant to the protein’s function
Enzyme
Biological catalyst
Anabolic enzyme
Builds larger molecules from smaller ones, such as in protein synthesis
Catabolic
Breaks down large molecules into smaller ones, such as digestion
Active site
Where substances bind to an enzyme
Substrate
The molecule that bonds to the enzyme
Lock and Key Hypothesis
When enzymes bind to a specific substrate
Factor that affects enzymes: temperature
At higher temperatures the enzyme and substrate move faster and collide, generally meaning that a higher temperature means a faster reaction
Factor that affects enzymes: pH
Each enzyme has its optimum pH, and a change in pH affects the amino acids in a chain
E.g Pepsin is found in the stomach (very acidic optimum pH) whereas pancreatic amylase is found in the small intestines (slightly alkaline pH)
Factor that affects enzymes: enzyme concentration
If no new substrate molecules are added, the reaction will stop
Factor that affects enzymes: substrate concentration
Eventually all the enzyme molecules will be bound to substrate molecules so the rate of reaction will remain constant
Metabolic rate
The rate at which your cells transfer energy from the chemical stores in food
Carbohydrate (enzyme)
Carbohydrase enzyme breaks down carbohydrates
Enzyme that breaks down starch is amylase
Protein (enzyme)
Protease enzyme breaks down proteins into amino acids
Fats/lipids (enzyme)
Lipase enzymes break down lipids into fatty acids and glycerol (3:1)
Aerobic respiration
The transfer of energy from chemical stores in food via a series of reactions that involve oxygen
Glucose + oxygen -> carbon dioxide + water
C(6)H(12)O(6) + 6O(2) -> 6CO(2) + 6H(2)O
ATP
The store for energy from respiration
ATP produced during respiration is used for:
Movement
Staying warm
Synthesising larger molecules from smaller ones to make new cells material
The more active a cell is…
The more mitochondria it has
Anaerobic respiration
Respiration without oxygen
glucose -> lactic acid
Aerobic respiration is used instead of anaerobic respiration normally because…
Aerobic respiration produces more ATP per glucose molecule because glucose is fully broken down
Lactic acid causes fatigue, which is pain in the muscles causing them to stop contracting
Lactic acid has to be broken down with oxygen, known as oxygen debt
Fermentation
Another type of anaerobic respiration in microorganisms and plants
Glucose -> ethanol + carbon dioxide
C(6)H(12)O(6) -> 2C(2)H(5)OH + 2CO(2)
Photosynthesis
The process through which plants make their food
Carbon dioxide - diffuses via the stomata
Water - absorbed by the roots
Carbon dioxide + water -> glucose + oxygen
6CO(2) + 6H(2)O -> C(6)H(12)O(6) + 6O(2)
Respiration in plants takes place in the…
Chloroplast
Stage 1: Light dependent photosynthesis
Energy transferred from light splits water molecules into oxygen gas and hydrogen ions
Stage 2: Light independent
Carbon dioxide gas combines with the hydrogen ions to make glucose
What is glucose used for during photosynthesis?
Fats and oils - food store and growth
Converted into sucrose - stored in fruit
Converted into starch - food store
Converted into cellulose - to form cell walls
Plus nitrogen - proteins (growth and repair)
Light intensity
Light intensity = 1/(Distance from light source)^2
Factor that affects photosynthesis: light intensity
The higher the light intensity the faster the rate of photosynthesis until it reaches its maximum rate
Factor that affects photosynthesis: carbon dioxide
The greater the carbon dioxide concentration the faster the rate of reaction
The atmosphere contains only 0.04% carbon dioxide so it’s commonly the limiting factor
Factor that affects photosynthesis: temperature
The higher the temperature the faster the rate of photosynthesis, but if it’s too high the enzymes will denature
