Cellular Processes

Flashcards for cell biology exam review.

Unicellular Organism

An organism that consists of one independent cell.

Multicellular Organism

An organism that consists of more than one cell. Each cell has different functions and structures.

Prokaryote

A cell type without a nucleus.

Eukaryote

A cell type with a nucleus.

Specialized cells

Cells in multicellular organisms adapted for specific functions.

Plant cells

Eukaryotic cells present in green plants. Plant cells have certain features like chloroplasts, cell walls, and intracellular vacuoles.

Cell Wall

Tough external outer covering. It provides support and strength; prevents excess water uptake

Chloroplast

The site of photosynthesis in plant cells; gives the cell its characteristic green color.

Large Central Vacuole

Assists with storage and structure in plant cells.

Animal Cells

Eukaryotic cells that make up the tissues and organs of animals.

Cell Membrane (Animal Cell)

Surrounds the animal cell and controls the passage of nutrients and chemicals; flexible and allows the cell to change shape.

Enzyme

A biological catalyst that speeds up the rate of reactions or allows reactions to take place.

Enzyme Action

Enzymes speed up chemical reactions because they reduce the stability of bonds in the reactants, providing an alternative energy pathway with lower activation energy.

Substrate

The molecule that fits into an enzyme

Active site

The place on the enzyme that the substrate fits

Enzyme Specificity

Enzymes are specific meaning they only work on one type of reaction due to the shape of their active sites.

Denaturation

Loss of an enzyme's three-dimensional structure, resulting in loss of catalytic activity.

Enzyme Optimum pH

The pH at which an enzyme will work best.

Substrate Concentration

Affects enzyme activity; the greater the substrate concentration, the higher the rate of reaction until all enzyme is 'busy'.

Enzyme Concentration

Affects the rate of reaction; as the amount of enzyme increases, activity will increase if there is sufficient substrate available.

Co-factor

Cannot be made in the body but interacts with enzymes so the substrate can bind better and the enzyme can function (helpful).

Inhibitors

Competitive: Similar shape to substrate so it blocks the active site and alter its shape.

Semipermeable Membrane

Allows small molecules and larger hydrophobic molecules to move through easily by diffusion.

Diffusion

The net movement of particles from an area of high concentration to low concentration, along the concentration gradient until they are equal.

Simple Diffusion

Molecules can freely move through a membrane.

Facilitated Diffusion

for big and charged particles they can pass through protein channels.

Facilitated Diffusion is used when large particles can’t diffuse freely through the phospholipid bilayer 

Osmosis

The diffusion of water molecules through a semipermeable membrane from where water is in higher concentration to where it is in lower concentration.

Active Transport

Moving ions and molecules from an area of low concentration to high concentration using energy, through a protein pump.

Active transport is used when cells need to transport a substance into the cell against it’s concentration gradient. 

Photosynthesis

Carbon Dioxide + Water → Glucose + Oxygen.

Photosynthesis stages

1. The light-dependent reactions (also called the light phase) take place in the grana, which are stacks of thylakoids inside the chloroplast.

2. The light-independent reactions (also called the Calvin cycle or dark phase) occur in the stroma, which is the fluid-filled space surrounding the grana inside the chloroplast.

Chlorophyll

Chlorophyll is the pigment that gives plants their green color. Plants use chlorophyll to trap light needed for photosynthesis

Light Dependent Reaction

It occurs in the thylakoid membranes. Water enters and the energy from light splits water into hydrogen and oxygen. Oxygen is released and ATP (energy) is also produced.

Light Independent Reaction

It occurs in the stroma of chloroplast. Hydrogen from light dependent enter the chloroplast and combine with the Carbon dioxide (CO2) carbon + hydrogen and leave the reaction as glucose, there will be excess Hydrogen and carbon released. ADP is converted to form ATP.

Respiration

Respiration occurs in the mitochondria

Glucose + Oxygen → Carbon Dioxide + Water + ATP + Heat

Aerobic Respiration

This takes place in the mitochondria.

Glucose + Oxygen → Carbon Dioxide + Water + Energy (36ATP)

Glycolysis - Enzyme Controlled reaction that involves Aerobic Respiration.

Occurs in the cytoplasm, it happens in the first stages of both aerobic and anaerobic respiration. One molecule of glucose and 2ATP is used to produce two pyruvate molecules, hydrogen ions, and 4ATP

Krebs Cycle - Enzyme Controlled reaction that involves Aerobic Respiration.

Occurs in the matrix of the mitochondria, it happens in the 2 stage of aerobic respiration. It uses pyruvate from glycolysis and produces Carbon dioxide, ATP, and water

Electrons transfer chain - Enzyme Controlled reaction that involves Aerobic Respiration.

Occurs in the inner mitochondrial membrane – cristae, it happens in the 3rd stage of aerobic respiration and it uses energy from the kerb cycle and oxygen so it can produce ATP and Water.

Anaerobic respiration

It occurs in the cytoplasm

Glucose → Lactic Acid + Energy (2ATP)

Advantages and Disadvantages of Aerobic

Advantages

• More efficient in producing ATP

• No lactic acid build up which can cause muscle fatigue and soreness.

Disadvantages

• Oxygen dependent, so it cannot occur in anaerobic environments

• It’s a slow process that requires multiple steps to produce ATP which is why it cannot meet immediate energy.

Advantages and Disadvantages of Anaerobic

Advantages

• It can produce energy quickly making it useful for short bursts of high-intensity.

• No oxygen needed which makes it useful in anaerobic environments.

Disadvantages

• It is less efficient in producing ATP because it uses small amount of energy from glucose

• Produces lactic acid, which can lead to muscle fatigue, soreness and decreased performance.

Cell Cycle

Is a regulated sequence of events that occur between one cell division and the next. It has two phases: Interphase and Cell division (mitosis)

Interphase

The cell increases in mass and size and carries out its normal cellular functions. Interphase consists of 3 phases G1, S phase, G2 phase

G1 Phase

It occurs prior to DNA replication. During this phase the cell is actively growing and preparing for DNA synthesis.

The cell also checks for damage to its DNA and other cellular components before proceeding to the next phase of the cell cycle. If damage is detected, the cell undergoes repair or cell death

S phase

During the G1 phase a signal is received telling the cell to divide again. DNA in the nucleus replicates resulting in each chromosome consisting of 2 identical sister chromatids

G2 Phase

In this phase, the cell contiues to grow and prepare for cell division. Then the cell undergoes a final check for DNA damage and makes any necessary repairs before entering mitosis

Chloroplast Diagram

Outer Membrane - Is clear and allows light to pass through. Controls what goes in and out of chloroplast.

Thylakoids - Stacks within the chloroplast.

Grana - Stacks of thylakoids.

Inner Membrane - Inside of chloroplast

Stroma - Liquid filled space where CO2 is captured and is used to make sugars (food for plants).

Mitochondria Diagram

Outer Membrane - Is smooth

Inner Membrane - Is folded

Cristae - Inside Folds, the wiggles of the cristae increase the surface area of the inner membrane, where lots of reactions happen.

Which means mitochondria can convert more sugar into ATP energy the same amount of time.

Matrix - Liquid filled space inside the inner membrane which contains many enzymes for respiration.

DNA Replication

DNA replication is when DNA replicates itself so that chromosomes can be replicated prior to cell division

Replication ensues that all cells formed have a copy of the genetic code which gives them the instructions needed to grow and carry out their essential cell process.

STEPS of DNA REPLICATION

• Unwinding

  • The enzyme helicase unwinds the DNA double helix and separates the two strands.

• Base Pairing

  • DNA polymerase adds complementary nucleotides (A with T, C with G) to each original strand.

• Bond Formation

  • The sugar-phosphate backbone is sealed by DNA ligase, forming two new DNA strands.

• Result

  • Two identical DNA molecules are formed, each with one original strand and one new strand (semi-conservative replication).

Mitosis

Mitosis produces two identical daughter cells that are genetically identical to each other - these news cells thus can continue essential life processes.

Rate of Mitosis can be influenced by:

Cell type - Each has different rates of mitosis e.g. skin cell divide faster than nerve cells

Age - Mitosis rates are generally higher in younger organisms and tend to decline with age.

Hormones - Oestrogen can increase the rate of mitosis in breast tissues.

Growth Factors - Can stimulate cell division and increase the rate of mitosis.

Environmental Factors - Such as temperature, pH, and availability of nutrients can also affect the rate of mitosis.

Genetic Factors - Leading to conditions such as cancer

Surface area:volume ratio

Cells may increase their surface area to volume ratio by:

• having a long thin shape

• folding the surface of an object (cell membrane)

Cells need to be small because they rely on diffusion for getting substances into and out of their cells.

As cells grow, the volume increases more than the surface area.

smaller SA:Vol ratios are not effective at transporting key material

Key takeaway: Small cells are more efficient at diffusion as they have a HIGH SA:V ratio