Exam 2

Cellular Respiration

metabolic reactions convert food molecules into ATP

Metabolism

all of the chemical reactions occurring in the body

Metabolic Rates

the measure of a person’s energy use

• Depends on speed and efficiency of different enzymes

• Changes according to activity levels

• Influenced by exercise, biological sex, and genetics

Basal Metabolic Rate (BMR)

the energy use of a resting, wakeful person

• Average BMR: 70 cals/hr or 1680 cals/day

Adenosine Triphosphate (ATP)

consists of adenine, a ribose sugar, and 3 negatively charged phosphate groups

• Energy stored in chemical bonds of ATP

Phosphorylation

phosphate group is transferred (removed) from ATP to an enzyme to generate energy (ADP)

• Energy is transferred

Regenerating ATP

cellular respiration replenishes ATP when used in the cell

Breathing and Cellular Respiration

Cellular respiration requires oxygen from breathing as part of the metabolic process; carbon dioxide waste is returned to the lungs

Aerobic Cellular Respiration

cells generate energy with oxygen

• Occurs mostly in the mitochondria

• Glucose (C₆H₁₂O₆) + 6O₂ → 6H₂O + 6CO₂

  • Simplified Equation: Glucose + oxygen = carbon dioxide + water

Anaerobic Respiration

cells generate energy without oxygen

• Occurs during intense exercise: muscles run low on oxygen

• ATP comes from glycolysis only

• NAD⁺ level decrease

• Muscle cells use fermentation to regenerate NAD⁺

Fermentation

microbes transform milk sugars into lactic acid

• Yeast cells convert glucose to ethyl alcohol

Stages of Cellular Respiration

1. Glycolysis

2. Citric Acid Cycle

3. Electron Transport Chain and ATP Synthesis

Glycolysis

6-carbon glucose molecule is broken down into two 3-carbon pyruvic acid molecules

• Occurs in cytosol

• Doesn’t require oxygen

• Spend 2 ATP, output 4 ATP: Produces 2 ATP

Glycolysis Steps

1. Empty taxicab (NAD⁺) picks up electrons and hydrogen ions (H⁺)

2. Becomes full taxicab (NADH) that carries electrons to final destination

3. After Glycolysis: 

   1. Pyruvic acid loses a carbon dioxide (decarboxylated)

   2. 2-carbon fragment is metabolized inside mitochondrion

Citric Acid Cycle

series of enzyme-catalyzed reactions in the matrix of the mitochondria

• Produces 2 ATP

• Releases carbon dioxide and NADH

Electronic Transport Chain

series of proteins in the mitochondrion acting like a conveyor belt for electrons

Electron Transport Chain Steps

1. NADH drops off electrons and H⁺ ions

2. Electrons move through the chain

3. H⁺ concentration increases as the ions are moved into the intermembrane space

4. Charged H⁺ ions can’t diffuse across the membrane

   1. Pass through ATP synthase protein channels

   2. Sythesize 26 ATP molecules

5. Electrons eventually combine with oxygen to produce water

Results of the Electron Transport Chain

1. 26 ATP

2. Water

Global Climate Change

local changes in average temperature, precipitation, and sea level

• Relative to historical conditions

Global Warming

the progressive increase of Earth’s average temperature

• Contributes to global climate change

• Mostly attributed to human activities

What is the cause of Global Warming?

Increases in concentration of greenhouse gases:

• Water vapor

• Carbon dioxide (CO₂)

• Methane (CH₄)

• Ozone (O₃)

The Greenhouse Effect

atmospheric greenhouse gases trap energy from the sun

The Greenhouse Effect and Bodies of Water

Bodies of water absorb heat energy and help maintain stable temperatures

• Hydrogen bonds allow water to absorb and release heat

• Bonds break and release as needed

• Prevents large changes in temperature

Heat

the total amount of energy associated with movement of atoms and molecules

Temperature

measures the intensity of heat, how fast molecules move

Fossil Fuels

concentrated energy forms produced from the stored carbohydrates of ancient, buried organisms

• Petroleum, coal, natural gas

What has the use of fossil fuels led to?

an increase in the levels of atmospheric carbon dioxide

Where is the scientific proof of the increase of fossil fuels in the atmosphere from?

ice cores

Photosynthesis

process that plants use to trap light energy

• Uses light energy to convert carbon dioxide and water into sugar and oxygen

• Opposite of respiration: the inputs of one are the outputs of the other

Chloroplasts

organelles where photosynthesis occurs

Chloroplast Envelope

inner and outer membranes of the chloroplast

Stroma

thick fluid in chloroplast

Thylakoids

disk-like membranous structures in chloroplasts

• stacked in piles

Chlorophyll

covers surface of thylakoid membranes

• Absorbs light energy from the sun: absorbs blue and red wavelengths, reflects green wavelengths

Photosynthesis Chemical Reaction

6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂

• Carbon + Water + Light → Glucose + Oxygen

Photosynthesis Steps

1. The Light Reactions

2. Calvin Cycle

Photosynthesis: The Light Reactions

sunlight excites chlorophyll electrons in thylakoid

• Produces oxygen, ATP, and NADPH

Photosynthesis: The Light Reaction Steps

1. Light energy is absorbed by chlorophyll, which releases electrons to step 2

2. Electron transport chain pumps hydrogen ions into thylakoid

3. Water is split to provide replacement electrons to chlorophyll

4. Hydrogen ions power ATP production and combine with electrons to produce NADPH

Photosynthesis: The Calvin Cycle

series of reactions that occur in the stroma

• Produces glucose using ATP and NADPH

Photosynthesis: The Calvin Cycle Steps

1. Carbon Fixation

2. Reduction

3. Regeneration

The Calvin Cycle: Carbon Fixation

Carbon dioxide is added to RuBP (a 5 carbon sugar)

Result: The 6-carbon product is unstable, splits into two 3-carbon molecules of 3-PGA

The Calvin Cycle: Reduction

Energy from ATP and electrons from NADPH (both from the light-dependent reactions) convert 3-PGA into G3P (result)

The Calvin Cycle: Regeneration

Out of every 6 molecules of G3P, 5 are recycled to regenerate 3 molecules of RuBP

• Remaining G3P used for glucose and carbs

Stomata

openings in leaves for entrance of gases

Guard Cells

Regulate stomata openings

Transpiration

movement of water through a plant’s stomata

• Stomata open: plenty of carbon dioxide, loss of water

• Stomata closed: conserves water, limits photosynthesis

Photorespiration

series of reactions that counteract photosynthesis

• Closed stomata limit carbon dioxide levels

• Oxygen is used instead of carbon dioxide to react with RuBP

• Plants will release carbon dioxide instead of oxygen

Tumors

unregulated cell division forming a lump of cells with no function

Benign Tumor

doesn’t affect surrounding tissues, not cancer

Malignant Tumor

invades surrounding tissues; cancerous

Metastasis

cells break away from a malignant tumor and start new cancers at distant locations

How do cancer cells travel through the body?

Through the circulatory and or lymphatic system

How are cancer cells different than normal cells?

• Replicate when they shouldn’t

• Invade surrounding tissues

• Move to other locations in the body

Risk factors for cancer

• Inherited through genes

• Environmental exposures: carcinogens

Synergistic Risk Factors

enhance the activity of other carcinogens

• Tobacco

• Alcohol

  • Together, they have a greater cancer risk than either alone

How to decrease cancer risk

• Don’t consume alcohol or tobacco

• Low fat, high fiber diet

• Exercise

• Healthy weight

Types of Reproduction

1. Asexual

2. Sexual

Asexual Reproduction

one parent

• Offspring are genetically identical to parent

• Efficient: only need one parent

Sexual Reproduction

gametes combine from two parents

• offspring are genetically different from one another and from the parents

• Requires gametes made by meiosis

• Increase variability by having 2 parents

Types of Genetic Materials

1. Genes

2. Chromosomes

Genes

section of DNA with instructions for building all cell proteins

What carries genes?

DNA

• must be copied before cells divide

Chromosomes

made of DNA wrapped around proteins

• In uncondensed, string-like form before cell division

• Carry hundreds of genes

• Sister chromatids: duplicated chromosomes, attached at the centromere

DNA Structure

double stranded

• Sides of ladder: sugar-phosphate backbone

• “Rungs” of ladder: nitrogen bases connected by hydrogen bonds

  • Adenine (A) pairs with thymine (T)

  • Cytosine (C) pairs with guanine (G)

DNA Replication

Occurs before cell division

• Begins by splitting helix in half down the middle

• Semiconservative Replication: Newly formed DNA strand has one-half new daughter DNA and one-half conserved parental DNA

DNA polymerase

enzyme that replicates DNA

• moves along the unwound DNA to form the new strands

Where does the cell cycle occur?

In all somatic (body cells)

• NOT sexual reproduction cells

Cell Cycle Steps

1. Interphase: DNA replicates

2. Mitosis: DNA separates

3. Cytokinesis: cells separate

Interphase Steps

1. G₁: cell grows, organelles duplicate

2. S: DNA replicates

3. G₂: cell makes proteins needed to complete mitosis

In what phase of the cell cycle do cells spend most of their time?

Interphase

Mitosis

Movement of chromosomes from original eukaryotic parent cell into two genetically identical daughter cells

• Cells spend about 10% of their time here

Stages of Mitosis

1. Prophase: plump

2. Metaphase: middle

3. Anaphase: apart

4. Telophase: the end

Mitosis: Prophase

• Nuclear membrane breaks down

• Sister chromatids/Chromosomes condense

• Spindle begins to form

Mitosis: Metaphase

Chromosomes line up in MIDDLE of cell

• Spindle fully formed

• Chromosomes attach to spindle

Mitosis: Anaphase

spindle contracts and pulls chromosomes APART to opposite sides of cell

Mitosis: Telophase

nuclear membrane is reassembled and cell begins to split

• Two individual nuclei

  • Each have same # of chromosomes as you started with

Is cytokinesis a part of mitosis?

NO!

Cytokinesis

cell splits into two independent cells

• Cytoplasm and organelles duplicate and separate

• Cytokinesis: cut

Cytokinesis in animal cells

Cell membrane forms at or near the place once occupied by the chromosomes

• Contractile ring pinches the cell in two form the outside

• Spot where is splits is called the cleavage furrow

• Easier than in plant cells: animal cells have just a cell membrane, no cell wall

Cytokinesis in plant cells

Different than animal cells bc plant cells also have a cell wall, which is thicker than the cell membrane

• Divide from outside in

• Cell wall precursors collect at center of cell, forming a cell plate between the two plasma membranes

Cell Cycle Control

Normal cells pass checkpoints to determine if they are ready to proceed with cell division

• Proteins determine condition of the cell

• Three Checkpoints:

  1. G₁

  2. G₂

  3. Metaphase

Cell Cycle Checkpoint: G₁

• Is cell division necessary

• Is the cell large enough for G₂?

Cell Cycle Checkpoint: G₂

Was DNA replicated correctly?

Cell Cycle Checkpoint: Metaphase

Are all the chromosomes attached to microtubules?

Mutation

a change in sequence of DNA

• May change the structure and function of the protein coded by the DNA

• May be inherited or caused by carcinogens

• Mutated tumor suppressor genes can increase the likelihood of cancer: protein fails to stop tumor growth

Proto-oncogenes

Genes that code for the cell cycle control proteins

Oncogenes

formed from mutated proto-oncogenes

• Proteins no longer regulate cell division properly

• Usually overstimulate cell division

Cancer

• Usually related to changes in a cell’s DNA

  • Changes can be caused by substances from the environment or viruses

  • Changes affect growth factors and receptors for the growth factors

Biopsy

Surgical removal of cells or fluid for analysis

• Fluid: typically a benign cyst

• Solid mass of cells:

  • Benign tumors resemble other cells

  • Malignant tumors do not resemble other tissue cells from the same sample

Chemotherapy

chemicals that selectively kill dividing cells

• Combo of different drugs used

  • Interrupts cell division in different ways

  • Helps prevent resistance to the drugs

• Normal dividing cells are also killed (bone marrow, hair follicles, stomach lining)

Radiation Therapy

use of high-energy particles to destroy cancer cells

• Damages DNA of cancer cells to prevent cell division

• Usually for cancers close to the surface

• After surgical removal of tumor

Meiosis

specialized form of cell division in gonads to produce gametes

• Reduces number of chromosomes in each cell by one-half

  • Chromosomes come in homologous pairs: chromosomes that match each other that were in the egg and sperm that made you

  • Gamete gets one of each pair

Diploid Cells

have two copies of each chromosome

Haploid Cells

have one copy of each chromosome

• Gametes, only in meiosis

Meiosis Cell Types

Adult form (diploid cells) —> Meiosis (haploid cells) —> Fertilization (diploid cells)

Meiosis: Chromosome Sets

Body cells of all eukaryotes occur in pairs

• Homologous chromosomes are similar in size, shape, and gene order

Gametes

Specialized sex cells (egg, sperm)

• produced by meiosis in the gonads (sex organs)

• Haploid cells, with one set of the 23 chromosomes in humans

Fused Gametes

Form a diploid zygote

• Occur during fertilization

Meiosis Process

Uses the DNA that was duplicated during interphase

• Two Phases

  1. Meiosis 1

  2. Meiosis 2

Meiosis 1

Separating out the homologous pairs into two separate cells